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Metals, Volume 7, Issue 10 (October 2017)

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Editorial

Jump to: Research, Review

Open AccessEditorial Fatigue Damage
Metals 2017, 7(10), 394; doi:10.3390/met7100394
Received: 22 September 2017 / Revised: 24 September 2017 / Accepted: 25 September 2017 / Published: 26 September 2017
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Abstract
Prevention of unexpected failures is a fundamental design objective in any engineering structure or system subjected to fatigue.[...] Full article
(This article belongs to the Special Issue Fatigue Damage)
Open AccessEditorial 3D Printing of Metals
Metals 2017, 7(10), 403; doi:10.3390/met7100403
Received: 26 September 2017 / Revised: 27 September 2017 / Accepted: 28 September 2017 / Published: 29 September 2017
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Abstract
The potential benefits that could be derived if the science and technology of 3D printing were to be established have been the crux behind monumental efforts by governments, in most countries, that invest billions of dollars to develop this manufacturing technology.[...] Full article
(This article belongs to the Special Issue 3D Printing of Metals)
Open AccessEditorial Laser Shock Processing on Metal
Metals 2017, 7(10), 409; doi:10.3390/met7100409
Received: 28 September 2017 / Revised: 28 September 2017 / Accepted: 28 September 2017 / Published: 1 October 2017
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(This article belongs to the Special Issue Laser Shock Processing on Metal)
Open AccessEditorial Metals Are Main Actors in the Biological World
Metals 2017, 7(10), 422; doi:10.3390/met7100422
Received: 25 September 2017 / Revised: 2 October 2017 / Accepted: 3 October 2017 / Published: 11 October 2017
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Abstract
The word “metallomics” was introduced for the first time in 2004 [1] to describe the emerging scientific field of investigation addressing the role that metal ions have in the biological world, including their trafficking, uptake, transport, and storage.[...]
Full article
(This article belongs to the Special Issue Metallomics)
Open AccessEditorial Non-Destructive Metallic Materials Testing—Recent Research and Future Perspectives
Metals 2017, 7(10), 430; doi:10.3390/met7100430
Received: 9 October 2017 / Revised: 10 October 2017 / Accepted: 10 October 2017 / Published: 16 October 2017
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Abstract
Non-destructive testing (NDT) has become extremely important formicrostructural characterization, mainly by allowing the assessment of metallic material properties in an effective and reasonable manner, in addition to maintaining the integrity of the evaluated metallic samples and applicability in service in many cases [...]
[...] Read more.
Non-destructive testing (NDT) has become extremely important formicrostructural characterization, mainly by allowing the assessment of metallic material properties in an effective and reasonable manner, in addition to maintaining the integrity of the evaluated metallic samples and applicability in service in many cases [...]
Full article
Open AccessEditorial Intermetallics
Metals 2017, 7(10), 446; doi:10.3390/met7100446 (registering DOI)
Received: 10 October 2017 / Revised: 17 October 2017 / Accepted: 18 October 2017 / Published: 20 October 2017
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Abstract
The combination of low density, high strength, and good corrosion resistance makes intermetallics promising for structural applications, especially at high temperatures and under severe environments [...] Full article
(This article belongs to the Special Issue Intermetallics 2016)

Research

Jump to: Editorial, Review

Open AccessArticle RBF-Neural Network Applied to the Quality Classification of Tempered 100Cr6 Steel Cams by the Multi-Frequency Nondestructive Eddy Current Testing
Metals 2017, 7(10), 385; doi:10.3390/met7100385
Received: 18 August 2017 / Revised: 13 September 2017 / Accepted: 15 September 2017 / Published: 21 September 2017
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Abstract
This article proposes a Radial Basis Function Artificial Neural Network (RBF-ANN) to classify tempered steel cams as correctly or incorrectly treated pieces by using multi-frequency nondestructive eddy current testing. Impedances at five frequencies between 10 kHz and 300 kHz were employed to perform
[...] Read more.
This article proposes a Radial Basis Function Artificial Neural Network (RBF-ANN) to classify tempered steel cams as correctly or incorrectly treated pieces by using multi-frequency nondestructive eddy current testing. Impedances at five frequencies between 10 kHz and 300 kHz were employed to perform the binary sorting. The ANalysis Of VAriance (ANOVA) test was employed to check the significance of the differences between the impedance samples for the two classification groups. Afterwards, eleven classifiers were implemented and compared with one RBF-ANN classifier: ten linear discriminant analysis classifiers and one Euclidean distance classifier. When employing the proposed RBF-ANN, the best performance was achieved with a precision of 95% and an area under the Receiver Operating Characteristic (ROC) curve of 0.98. The obtained results suggest RBF-ANN classifiers processing multi-frequency impedance data could be employed to classify tempered steel DIN 100Cr6 cams with a better performance than other classical classifiers. Full article
(This article belongs to the Special Issue Advanced Non-Destructive Testing in Steels)
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Open AccessArticle Analytical Investigation of the Cyclic Behavior of Smart Recentering T-Stub Components with Superelastic SMA Bolts
Metals 2017, 7(10), 386; doi:10.3390/met7100386
Received: 16 July 2017 / Revised: 10 September 2017 / Accepted: 12 September 2017 / Published: 21 September 2017
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Abstract
Partially restrained (PR) bolted T-stub connections have been widely used in replacement of established fully restrained (FR) welded connections, which are susceptible to sudden brittle failure. These bolted T-stub connections can permit deformation, easily exceeding the allowable limit without any fracture because they
[...] Read more.
Partially restrained (PR) bolted T-stub connections have been widely used in replacement of established fully restrained (FR) welded connections, which are susceptible to sudden brittle failure. These bolted T-stub connections can permit deformation, easily exceeding the allowable limit without any fracture because they are constructed with a design philosophy whereby the plastic deformation concentrates on bolt fasteners made of ductile steel materials. Thus, the PR bolted connections take advantage of excellent energy dissipation capacity in their moment and rotation behavior. However, a considerable amount of residual deformation may occur at the bolted connection subjected to excessive plastic deformation, thereby requiring additional costs to recover the original configuration. In this study, superelastic shape memory alloy (SMA) bolts, which have a recentering capability upon unloading, are fabricated so as to solve these drawbacks, and utilized by replacing conventional steel bolts in the PR bolted T-stub connection. Instead of the full-scale T-stub connection, simplified T-stub components subjected to axial force are designed on the basis of a basic equilibrium theory that transfers the bending moment from the beam to the column and can be converted into equivalent couple forces acting on the beam flange. The feasible failure modes followed by corresponding response mechanisms are taken into consideration for component design with superelastic SMA bolts. The inelastic behaviors of such T-stub components under cyclic loading are simulated by advanced three-dimensional (3D) finite element (FE) analysis. Finally, this study suggests an optimal design for smart recentering T-stub components with respect to recentering and energy dissipation after observing the FE analysis results. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2017)
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Open AccessArticle Study of the Precipitation Hardening Behaviour and Intergranular Corrosion of Al-Mg-Si Alloys with Differing Si Contents
Metals 2017, 7(10), 387; doi:10.3390/met7100387
Received: 10 August 2017 / Revised: 16 September 2017 / Accepted: 17 September 2017 / Published: 21 September 2017
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Abstract
The effects of Si addition on the precipitation hardening behaviour and evolution of intergranular corrosion (IGC) of Al-Mg-Si alloys were investigated using hardness tests, scanning electron microscopy (SEM), potentiodynamic polarization measurements, and high-resolution transmission electron microscopy (HRTEM). With an increase of the Si
[...] Read more.
The effects of Si addition on the precipitation hardening behaviour and evolution of intergranular corrosion (IGC) of Al-Mg-Si alloys were investigated using hardness tests, scanning electron microscopy (SEM), potentiodynamic polarization measurements, and high-resolution transmission electron microscopy (HRTEM). With an increase of the Si content, the peak hardness of the Al-Mg-Si alloys considerably increased by enhancing the density of the β″ (Mg5Si6) phase inside the grains. The microstructures affecting the IGC performance consisted of MgSi particles, Si particles, Al-Fe-Mn-Si intermetallics, and the precipitate-free zone (PFZ). The IGC susceptibility of the Al-Mg-Si alloys was mainly attributed to the high electrochemical potential difference between the MgSi particles and solute-depleted zones. Excess Si improved the IGC susceptibility of the alloys, mainly due to an increase of the grain boundary MgSi precipitates. Furthermore, the evolution of the IGC process was discussed in detail. Full article
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Open AccessArticle Ultrasound Assisted Casting of an AM60 Based Metal Matrix Nanocomposite, Its Properties, and Recyclability
Metals 2017, 7(10), 388; doi:10.3390/met7100388
Received: 16 August 2017 / Revised: 18 September 2017 / Accepted: 19 September 2017 / Published: 22 September 2017
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Abstract
An AM60 magnesium alloy nanocomposite reinforced with 1 wt % of AlN nanoparticles was prepared using an ultrasound (US) assisted permanent-mould indirect-chill casting process. Ultrasonically generated cavitation and acoustic streaming promoted de-agglomeration of particle clusters and distributed the particles throughout the melt. Significant
[...] Read more.
An AM60 magnesium alloy nanocomposite reinforced with 1 wt % of AlN nanoparticles was prepared using an ultrasound (US) assisted permanent-mould indirect-chill casting process. Ultrasonically generated cavitation and acoustic streaming promoted de-agglomeration of particle clusters and distributed the particles throughout the melt. Significant grain refinement due to nucleation on the AlN nanoparticles was accompanied by an exceptional improvement in properties: yield strength increased by 103%, ultimate tensile strength by 115%, and ductility by 140%. Although good grain refinement was observed, the large nucleation undercooling of 14 K limits further refinement because nucleation is prevented by the formation of a nucleation-free zone around each grain. To assess the industrial applicability and recyclability of the nanocomposite material in various casting processes, tests were performed to determine the effect of remelting on the microstructure. With each remelting, a small percentage of effective AlN nanoparticles was lost, and some grain growth was observed. However, even after the third remelting, excellent strength and ductility was retained. According to strengthening models, enhanced yield strength is mainly attributed to Hall-Petch strengthening caused by the refined grain size. A small additional contribution to strengthening is attributed to Orowan strengthening. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
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Open AccessArticle Structure and Formation Model of Ag/TiO2 and Au/TiO2 Nanoparticles Synthesized through Ultrasonic Spray Pyrolysis
Metals 2017, 7(10), 389; doi:10.3390/met7100389
Received: 31 July 2017 / Revised: 31 August 2017 / Accepted: 18 September 2017 / Published: 25 September 2017
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Abstract
This article explains the mechanism of the metal/oxide core-shell Ag/TiO2 and Au/TiO2 nanoparticle formation via one-step ultrasonic spray pyrolysis (USP) by establishing a new model. The general knowledge on the standard “droplet-to-particle” (DTP) mechanism, nucleation, and growth processes of noble metals,
[...] Read more.
This article explains the mechanism of the metal/oxide core-shell Ag/TiO2 and Au/TiO2 nanoparticle formation via one-step ultrasonic spray pyrolysis (USP) by establishing a new model. The general knowledge on the standard “droplet-to-particle” (DTP) mechanism, nucleation, and growth processes of noble metals, as well as physical and chemical properties of core and shell materials and experimental knowledge, were utilized with the purpose of the construction of this new model. This hypothesis was assessed on silver (Ag)/titanium oxide (TiO2) and gold (Au) TiO2 binary complex nanoparticles’ experimental findings revealed by scanning electron microscopy (SEM), focused ion beam (FIB), high-resolution transmission electron microscopy (HRTEM), and simulation of crystal lattices. It was seen that two mechanisms run as proposed in the new model. However, there were some variations in size, morphology, and distribution of Ag and Au through the TiO2 core particle and these variations could be explained by the inherent physical and chemical property differences of Ag and Au. Full article
(This article belongs to the Special Issue Powder Synthesis and Processing)
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Open AccessArticle Environmental Compatibility of Lightweight Aggregates from Mine Tailings and Industrial Byproducts
Metals 2017, 7(10), 390; doi:10.3390/met7100390
Received: 9 August 2017 / Revised: 7 September 2017 / Accepted: 18 September 2017 / Published: 25 September 2017
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Abstract
A lightweight aggregate was produced by sintering the mixture of gold mine tailings, red mud, and limestone at 1150 °C. The physical (i.e., skid resistance, abrasion resistance, and bond strength) and environmental (i.e., leachability) feasibility of this aggregate was assessed to consider its
[...] Read more.
A lightweight aggregate was produced by sintering the mixture of gold mine tailings, red mud, and limestone at 1150 °C. The physical (i.e., skid resistance, abrasion resistance, and bond strength) and environmental (i.e., leachability) feasibility of this aggregate was assessed to consider its potential use as a construction material for bicycle lanes. The skid resistance (British pendulum number of 71) and bond strength (1.5 N·mm−2) of the aggregate were found to be appropriate for this use. However, the abrasion loss value of the aggregate was found to be 290 mg, which exceeds the limit of Korean Standard KS F 281 (200 mg). Heavy metals were found to not leach from the aggregate in various leaching tests. These include Korean (Korea Standard Method for Solid Waste), American (Toxic Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP)), and European (BS EN 12457-1) leaching tests, despite the raw materials containing significant amounts of Pb, As, and F. However, leachate extracted from the aggregate exhibited an aquatic toxicity to Daphnia magna of 13.94 TU24hr and 14.25 TU48hr, most likely due to a high pH and Ca concentration originating from the free CaO present in the aggregate. The data suggests that the physical properties of the reconstructed aggregate are appropriate for use in bicycle lane construction, however the dissolution of Ca and the pH level of the leachate need to be controlled to protect aquatic ecosystems. Full article
(This article belongs to the Special Issue Valuable Metal Recycling)
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Open AccessFeature PaperArticle Formation of Light-Weight Ferroalloys in the Fe2O3-Al2O3-C System at 1550 °C: Influence of Silica Impurities
Metals 2017, 7(10), 391; doi:10.3390/met7100391
Received: 16 August 2017 / Revised: 31 August 2017 / Accepted: 19 September 2017 / Published: 25 September 2017
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Abstract
Light-weight ferro-aluminium alloys are finding increasing application in the transport sector to reduce overall weights, energy costs and CO2 emissions. As the primary production processes of both Fe and Al are among the most energy-intensive industrial processes in the world, there is
[...] Read more.
Light-weight ferro-aluminium alloys are finding increasing application in the transport sector to reduce overall weights, energy costs and CO2 emissions. As the primary production processes of both Fe and Al are among the most energy-intensive industrial processes in the world, there is an urgent need to develop alternate routes for producing Fe-Al alloys. Our group has successfully produced these alloys in the Fe2O3-Al2O3-C system by producing molten iron in situ, followed by the reduction of alumina at 1550 °C and pick-up of Al by Fe. In this article, we report on the influence of silica, a typical impurity present in iron oxide and reductant carbon, on the reduction reactions in this system, and on the formation of ferroalloys. In-depth investigations were carried out on the Fe2O3-SiO2-C and Fe2O3-Al2O3-SiO2-C systems at 1550 °C for times of up to 60 min. Detailed HRSEM/EDS and XRD analysis was carried on the quenched reaction products recovered after various heat treatments. A complete reduction of silica and alumina was observed in the Fe2O3-SiO2-C system, along with the formation of FeSi and SiC. The reduction reactions were relatively slow in the Fe2O3-Al2O3-SiO2-C system. While the formation of SiC, FeSi and mullite (Al6Si2O13) was observed, even small amounts of Fe-Al alloys could not be detected. The presence of silica impurities reduced the formation of Fe-Al to negligible levels by depleting molten iron from the reaction zone, a key ingredient for the low-temperature carbothermic reduction of alumina. This study shows that some impurities can be highly detrimental to the reaction kinetics and the formation of ferroalloys, and great care needs to be exercised during the choice of reaction constituents. Full article
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Open AccessArticle Microstructural Evolution of Intermetallic Compound Formed in Boron Steel Hot-Dipped in Al–7%Ni Alloy
Metals 2017, 7(10), 393; doi:10.3390/met7100393
Received: 24 August 2017 / Revised: 14 September 2017 / Accepted: 19 September 2017 / Published: 26 September 2017
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Abstract
The microstructural evolution of the intermetallic compound (IMC) layer formed on and in boron steel that was hot dipped in an Al–7Ni (wt %) bath at 690 °C for 30–180 s was investigated, and the growth mechanism of the IMC was identified. Except
[...] Read more.
The microstructural evolution of the intermetallic compound (IMC) layer formed on and in boron steel that was hot dipped in an Al–7Ni (wt %) bath at 690 °C for 30–180 s was investigated, and the growth mechanism of the IMC was identified. Except for the solidification structure of Al, the reaction layer consisted of one layer on the steel surface and two layers in the steel interior. The reaction phase formed on the original surface of the steel was the Al9FeNi (T) phase, which has a monoclinic (space group: P21/c) crystal structure. The reaction phase formed from the T phase was the Fe2Al5 (η) phase, which is orthorhombic (space group: Cmcm). The variation in thickness of the η phase increased linearly with increasing dipping time, which is in accordance with the diffusion growth, a growth mechanism of the η phase in Al-coated pure Fe and low-carbon steels. The Fe3AlC (κ) phase (which had a band shape with a width of 100 nm) and a cubic system were formed along the interface between the Fe2Al5 (η) phase and the steel. Full article
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Open AccessArticle The Effects of Incorporated Sn in Resynthesized Ni-Rich Cathode Materials on Their Lithium-Ion Battery Performance
Metals 2017, 7(10), 395; doi:10.3390/met7100395
Received: 29 August 2017 / Revised: 16 September 2017 / Accepted: 21 September 2017 / Published: 26 September 2017
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Abstract
LiNixCoyMnz (NCM), one of the most promising candidates for high-capacity cathode materials in Li-ion batteries (LIBs), is synthesized with various amounts of Sn. Sn-incorporated NCM from the resynthesis of NMC in leach liquor containing Sn from spent LIBs
[...] Read more.
LiNixCoyMnz (NCM), one of the most promising candidates for high-capacity cathode materials in Li-ion batteries (LIBs), is synthesized with various amounts of Sn. Sn-incorporated NCM from the resynthesis of NMC in leach liquor containing Sn from spent LIBs is characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, particle strength tests, and electrochemical tests. Sn-incorporated NCM has a globular form, and the uniform distribution of Sn inside cathode materials is confirmed. As Sn is introduced, the (003) diffraction peak tends to shift to a smaller angle and particle breaking strength increases. It is found that Sn-incorporated cathode active materials have better cycle performance and rate capability than pristine cathode active material although the discharge capacity slightly decreases. Because there is a trade-off between decreased discharge capacity and improved cycling and rate performance, the incorporation of Sn in resynthesized NCM should be carefully designed and conducted. Full article
(This article belongs to the Special Issue Valuable Metal Recycling)
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Open AccessArticle Preparation and Characterization of Zinc Materials Prepared by Powder Metallurgy
Metals 2017, 7(10), 396; doi:10.3390/met7100396
Received: 30 August 2017 / Revised: 18 September 2017 / Accepted: 22 September 2017 / Published: 27 September 2017
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Abstract
The use of zinc-based materials as biodegradable materials for medical purposes is offered as a possible alternative to corrosion-less resistant magnesium-based materials. Zinc powders with two different particle sizes (7.5 µm and 150 µm) were processed by the methods of powder metallurgy: cold
[...] Read more.
The use of zinc-based materials as biodegradable materials for medical purposes is offered as a possible alternative to corrosion-less resistant magnesium-based materials. Zinc powders with two different particle sizes (7.5 µm and 150 µm) were processed by the methods of powder metallurgy: cold pressing, cold pressing followed by sintering and hot pressing. The microstructure of prepared materials was evaluated in terms of light optical microscopy, and the mechanical properties were analyzed with Vickers microhardness testing and three-point bend testing. Fractographic analysis of broken samples was performed with scanning electron microscopy. Particle size was shown to have a significant effect on compacts mechanical properties. The deformability of 7.5 µm particle size powder was improved by increased temperature during the processing, while in the case of larger powder, no significant influence of temperature was observed. Bending properties of prepared materials were positively influenced by elevated temperature during processing and correspond to the increasing compacting pressures. Better properties were achieved for pure zinc prepared from 150 µm particle size powder compared to materials prepared from 7.5 µm particle size powder. Full article
(This article belongs to the Special Issue Biodegradable Metals)
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Open AccessArticle Damping Characteristics of Inherent and Intrinsic Internal Friction of Cu-Zn-Al Shape Memory Alloys
Metals 2017, 7(10), 397; doi:10.3390/met7100397
Received: 28 August 2017 / Revised: 18 September 2017 / Accepted: 22 September 2017 / Published: 28 September 2017
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Abstract
Damping properties of the inherent and intrinsic internal friction peaks (IFPT + IFI) of Cu-xZn-11Al (x = 7.0, 7.5, 8.0, 8.5, and 9.0 wt. %) shape memory alloys (SMAs) were investigated by using dynamic mechanical analysis. The Cu-7.5Zn-11Al, Cu-8.0Zn-11Al, and
[...] Read more.
Damping properties of the inherent and intrinsic internal friction peaks (IFPT + IFI) of Cu-xZn-11Al (x = 7.0, 7.5, 8.0, 8.5, and 9.0 wt. %) shape memory alloys (SMAs) were investigated by using dynamic mechanical analysis. The Cu-7.5Zn-11Al, Cu-8.0Zn-11Al, and Cu-8.5Zn-11Al SMAs with ( IF PT + IF I ) β 3 ( L 2 1 ) γ 3 ( 2 H ) peaks exhibit higher damping capacity than the Cu-7.0Zn-11Al SMA with a ( IF PT + IF I ) β 3 ( L 2 1 ) γ 3 ( 2 H ) peak, because the γ 3 martensite phase possesses a 2H type structure with abundant movable twin boundaries, while the β 3 phase possesses an 18R structure with stacking faults. The Cu-9.0Zn-11Al SMA also possesses a ( IF PT + IF I ) β 3 ( L 2 1 ) γ 3 ( 2 H ) peak but exhibits low damping capacity because the formation of γ phase precipitates inhibits martensitic transformation. The Cu-8.0Zn-11Al SMA was found to be a promising candidate for practical high-damping applications because of its high (IFPT + IFI) peak with tan δ > 0.05 around room temperature. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2017)
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Open AccessArticle Preparation, Microstructure Evolutions, and Mechanical Property of an Ultra-Fine Grained Mg-10Gd-4Y-1.5Zn-0.5Zr Alloy
Metals 2017, 7(10), 398; doi:10.3390/met7100398
Received: 30 August 2017 / Revised: 14 September 2017 / Accepted: 25 September 2017 / Published: 28 September 2017
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Abstract
In this work, the microstructural evolutions and mechanical properties of an as-cast Mg-10Gd-4Y-1.5Zn-0.5Zr (wt %) alloy during successive multi-pass equal channel angular pressing (ECAP) were systematically investigated by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and compression test. The obtained results show
[...] Read more.
In this work, the microstructural evolutions and mechanical properties of an as-cast Mg-10Gd-4Y-1.5Zn-0.5Zr (wt %) alloy during successive multi-pass equal channel angular pressing (ECAP) were systematically investigated by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and compression test. The obtained results show that the microstructure of as-cast alloy consists of α-Mg grains, Mg3Gd island phase, few Y-rich particles, and lamellar 14H LPSO (long period stacking ordered) phase located at the grain boundaries. During ECAP, the Mg3Gd-type phase is crushed and refined gradually. However, the refined Mg3Gd particles are not distributed uniformly in the matrix, but still aggregated at the interdendritic area. The 14H phase becomes kinked during the early passes of ECAP and then broken at the kinking bands with more severe deformation. Dynamic recrystallization of α-Mg is activated during ECAP, and their average diameter decreases to around 1 μm, which is stabilized in spite of increasing ECAP passes. Moreover, nano-scale γ′ phases were dynamically precipitated in 16p ECAP alloy. Compression tests indicate that 16p ECAP alloy exhibits excellent mechanical property with compressive strength of 548 MPa and fracture strain of 19.1%. The significant improvement for both strength and ductility of deformed alloy could be ascribed to dynamic recrystallization (DRX) grains, refined Mg3Gd-type and 14H particles, and dynamically precipitated γ′ plates. Full article
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Open AccessArticle Effect of Weld Bead Shape on the Fatigue Behavior of GMAW Lap Fillet Joint in GA 590 MPa Steel Sheets
Metals 2017, 7(10), 399; doi:10.3390/met7100399
Received: 21 August 2017 / Revised: 23 September 2017 / Accepted: 24 September 2017 / Published: 28 September 2017
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Abstract
In this study, the effect of weld bead shape on the fatigue strength of lap fillet joints using the gas metal arc welding (GMAW) process was investigated. The base material used in the experiment was 590 MPa grade galvanealed steel sheet with 2.3
[...] Read more.
In this study, the effect of weld bead shape on the fatigue strength of lap fillet joints using the gas metal arc welding (GMAW) process was investigated. The base material used in the experiment was 590 MPa grade galvanealed steel sheet with 2.3 mm and 2.6 mm thickness. In order to make the four types of weld beads with different shapes by factors such as length, angle, and area, the welding process, wire feeding speed, and joint shape were changed. The stress-number of cycles to failure (S–N) curve and fatigue strength were obtained from the fatigue test for four types of weld bead, and the cause of the fatigue strength difference was clarified through the analysis of the geometrical factors, such as length, angle, and area of the weld bead. In addition, the relationship between weld bead shape and fatigue strength was discussed. Full article
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Open AccessArticle The Mechanism of Inhomogeneous Grain Refinement in a NiTiFe Shape Memory Alloy Subjected to Single-Pass Equal-Channel Angular Extrusion
Metals 2017, 7(10), 400; doi:10.3390/met7100400
Received: 6 September 2017 / Revised: 20 September 2017 / Accepted: 26 September 2017 / Published: 29 September 2017
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Abstract
Based on electron backscattered diffraction analysis and transmission electron microscopy observation, the mechanism of inhomogeneous grain refinement in a NiTiFe shape memory alloy (SMA) subjected to single-pass equal-channel angular extrusion (ECAE) was investigated. The results show that refined grains are mainly nucleated near
[...] Read more.
Based on electron backscattered diffraction analysis and transmission electron microscopy observation, the mechanism of inhomogeneous grain refinement in a NiTiFe shape memory alloy (SMA) subjected to single-pass equal-channel angular extrusion (ECAE) was investigated. The results show that refined grains are mainly nucleated near grain boundaries and a small fraction of them emerges in the grain interior. The size of refined grains increases as deformation temperature increases, which indicates that a higher deformation temperature is adverse to grain refinement in the ECAE of NiTiFe SMAs. It is the accumulation and rearrangement of geometrically necessary dislocations as plastic strain increases that leads to the transition of lower angle subgrain boundaries, and finally higher angle subgrain boundaries are induced and finer grains are formed. Due to the limitation of slip systems, the mechanism of grain refinement in a NiTiFe SMA subjected to ECAE is different from that in face-centered cubic and body-centered cubic crystals. Dislocation cells and shear bands are two transition microstructures of grain refinement in the ECAE of NiTiFe SMAs. The nucleation of fine grains mainly occurs along shear bands or grain boundaries, which leads to the inhomogeneity of grain refinement. Full article
(This article belongs to the Special Issue Advances in Plastic Forming of Metals)
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Open AccessCommunication Novel Recycling Method for Boron Removal from Silicon by Thermal Plasma Treatment Coupled with Steam and Hydrogen Gases
Metals 2017, 7(10), 401; doi:10.3390/met7100401
Received: 31 August 2017 / Revised: 23 September 2017 / Accepted: 27 September 2017 / Published: 29 September 2017
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Abstract
Boron (B) separation from photovoltaic silicon (Si) remains a research challenge in the recycling field. In this study, a novel B-removal process was developed using thermal plasma treatment coupled with steam and hydrogen gases. Experiments were performed on artificially B-doped Si using various
[...] Read more.
Boron (B) separation from photovoltaic silicon (Si) remains a research challenge in the recycling field. In this study, a novel B-removal process was developed using thermal plasma treatment coupled with steam and hydrogen gases. Experiments were performed on artificially B-doped Si using various plasma conditions of mixed argon (Ar)/steam/hydrogen gases and varied refining time. The B concentration in all of the samples decreased with increasing refining time. The use of the plasma mixed with Ar/steam/hydrogen gases resulted in a significant improvement of the efficiency of B removal compared with the Ar/steam plasma refining. In addition, with increasing steam content in the plasma with mixed Ar/steam/hydrogen gases, the B-removal rates increased. Full article
(This article belongs to the Special Issue Valuable Metal Recycling)
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Open AccessArticle Microwave Pretreatment for Thiourea Leaching for Gold Concentrate
Metals 2017, 7(10), 404; doi:10.3390/met7100404
Received: 4 September 2017 / Revised: 21 September 2017 / Accepted: 27 September 2017 / Published: 1 October 2017
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Abstract
In this research, we studied the use of microwave pretreatment to enhance the efficiency of Au leaching from gold concentrate. The gold concentrate was pretreated using microwaves with different irradiation time. The sample temperature was increased up to 950 °C by the microwave
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In this research, we studied the use of microwave pretreatment to enhance the efficiency of Au leaching from gold concentrate. The gold concentrate was pretreated using microwaves with different irradiation time. The sample temperature was increased up to 950 °C by the microwave irradiation. A scanning electron microscope-energy dispersive spectrometer showed the evolution of microcracks and the reduction of sulfur on the mineral surface. X-ray diffraction data also showed the mineral phase shift from pyrite to hematite or pyrrhotite. A leaching test was conducted for the microwave-treated and untreated gold concentrates using thiourea. Although the thiourea leaching recovered 80% of Au from the untreated concentrate, from the treated concentration, the Au could be recovered completely. Au leaching efficiency increased as the microwave irradiation time increased, as well as with a higher composition of thiourea. Full article
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Open AccessFeature PaperArticle High Temperature Strength and Hot Working Technology for As-Cast Mg–1Zn–1Ca (ZX11) Alloy
Metals 2017, 7(10), 405; doi:10.3390/met7100405
Received: 18 August 2017 / Revised: 14 September 2017 / Accepted: 20 September 2017 / Published: 1 October 2017
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Abstract
Cast Mg–1Zn–1Ca alloy (ZX11) has been tested to evaluate its compressive strength between 25 °C and 250 °C, and workability in the range of 260–500 °C. The ultimate compressive strength of this alloy is about 30% higher than that of creep-resistant alloy Mg–3Sn–2Ca
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Cast Mg–1Zn–1Ca alloy (ZX11) has been tested to evaluate its compressive strength between 25 °C and 250 °C, and workability in the range of 260–500 °C. The ultimate compressive strength of this alloy is about 30% higher than that of creep-resistant alloy Mg–3Sn–2Ca (TX32) between 25 °C and 200 °C, and exhibits a plateau between 100 °C and 175 °C, similar to TX32. This is attributed to Mg2Ca particles present at grain boundaries that reduce their sliding. The processing map, developed between 260 and 420 °C in the strain rate limits of 0.0003 s−1 to 1 s−1, exhibited two domains in the ranges: (1) 280–330 °C and 0.0003–0.01 s−1 and (2) 330–400 °C and 0.0003–0.1 s−1. In these domains, dynamic recrystallization occurs, with basal slip dominating in the first domain and prismatic slip in the second, while the recovery mechanism being climb of edge dislocations in both. The activation energy estimated using standard kinetic rate equation is 191 kJ/mol, which is higher than the value for lattice self-diffusion in magnesium indicating that a large back stress is created by the presence of Ca2Mg6Zn3 intermetallic particles in the matrix. It is recommended that the alloy be best processed at 380 °C and 0.1 s−1 at which prismatic slip is favored due to Zn addition. At higher strain rates, the alloy exhibits flow instability and adiabatic shear band formation at <340 °C while flow localization and cracking at grain boundaries occurs at temperatures >400 °C. Full article
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Open AccessFeature PaperCommunication In-Situ TEM Study of a Nanoporous Ni–Co Catalyst Used for the Dry Reforming of Methane
Metals 2017, 7(10), 406; doi:10.3390/met7100406
Received: 24 August 2017 / Revised: 21 September 2017 / Accepted: 28 September 2017 / Published: 1 October 2017
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Abstract
We performed in-situ transmission electron microscopy (TEM) on a dealloyed nanoporous NiCo catalyst used for the dry reforming of methane (DRM) to investigate the origin of the catalytic activity and structural durability. The in-situ observations and local chemical analysis indicated that the DRM
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We performed in-situ transmission electron microscopy (TEM) on a dealloyed nanoporous NiCo catalyst used for the dry reforming of methane (DRM) to investigate the origin of the catalytic activity and structural durability. The in-situ observations and local chemical analysis indicated that the DRM induced chemical demixing of Ni and Co accompanied by grain refinement, implying possible “synergic effects” in a general bimetallic NiCo catalyst when used for the DRM. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessArticle Numerical Simulation of Ti/Al Bimetal Composite Fabricated by Explosive Welding
Metals 2017, 7(10), 407; doi:10.3390/met7100407
Received: 17 August 2017 / Revised: 20 September 2017 / Accepted: 25 September 2017 / Published: 1 October 2017
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Abstract
In this paper, a 2D numerical model that is more physically realistic was established to simulate the complete process of Ti/Al explosive welding. Basing on the ANSYS/AUTODYN software package, the smoothed particle hydrodynamics (SPH) and arbitrary Lagrangian-Eulerian (ALE) were used for running this
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In this paper, a 2D numerical model that is more physically realistic was established to simulate the complete process of Ti/Al explosive welding. Basing on the ANSYS/AUTODYN software package, the smoothed particle hydrodynamics (SPH) and arbitrary Lagrangian-Eulerian (ALE) were used for running this simulation. The numerical model can capture the typical physics in the explosive welding process, including the expansion of explosives, flyer plate bending, the impact of metal plates, jetting, and the wavy interface. The variable physical parameters during the explosive welding process were discussed. Most parts of the jet originated from the aluminum plate. According to the model, the jet velocity reached 7402 m/s. The pressure at the detonation point was too small to make the two plates to bond. The pressure could reach an order of magnitude of 107 kPa when the detonation energy tended to be stable and was far more than the yield strength of both materials, which resulted in an obvious narrow region of plastic strain emerging close to the collision zone. The signs of shear stresses between the two plates were the opposite. The interface morphology changed from straight to wave along the propagation of the detonation wave in the simulation, which was consistent with the experimental results. Full article
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Open AccessArticle Tensile Properties and Fracture Behavior of a Powder-Thixoformed 2024Al/SiCp Composite at Elevated Temperatures
Metals 2017, 7(10), 408; doi:10.3390/met7100408
Received: 23 August 2017 / Revised: 7 September 2017 / Accepted: 28 September 2017 / Published: 1 October 2017
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Abstract
In the present work, the tensile properties and fracture behavior of a 2024Al composite reinforced with 10 vol % SiCp and fabricated via powder thixoforming (PT) were studied at temperatures ranging from 25 °C to 300 °C with a strain rate of
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In the present work, the tensile properties and fracture behavior of a 2024Al composite reinforced with 10 vol % SiCp and fabricated via powder thixoforming (PT) were studied at temperatures ranging from 25 °C to 300 °C with a strain rate of 0.05 s−1, as well as the PT 2024 alloy. The results indicated that the tensile strengths of both the PT materials were all decreased with increasing the temperature, but the decrease rate of the composite was smaller than that of the 2024 alloy, and the composite exhibited higher tensile strength than that of the 2024 alloy at all of the employed testing temperatures due to the strengthening role of SiCp. Increasing temperature was beneficial for enhancing the ductility of materials, and the maximum elongation was reached at 250 °C. The elongation decrease over 250 °C was attributed to the cavity formation due to the debonding of the SiCp/Al interface and the fracturing of the matrix between SiCp. The fracture of the composite at room temperature initiated from the fracture of SiCp and the debonding of the SiCp/Al interface, but that at high temperatures was dominated by void nucleation and growth in the matrix besides the interface debonding. Full article
(This article belongs to the Special Issue Powder Synthesis and Processing)
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Open AccessFeature PaperArticle Magnetostriction of Ni2Mn1−xCrxGa Heusler Alloys
Metals 2017, 7(10), 410; doi:10.3390/met7100410
Received: 12 August 2017 / Revised: 25 September 2017 / Accepted: 28 September 2017 / Published: 1 October 2017
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Abstract
Among the functionalities of magnetic Heusler alloys, magnetostriction is attracting considerable attention. The alloy Ni2MnGa has a premartensite phase, which is a precursor state to the martensitic transition. Some researchers have observed magnetostriction in this alloy in the premartensite phase. We
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Among the functionalities of magnetic Heusler alloys, magnetostriction is attracting considerable attention. The alloy Ni2MnGa has a premartensite phase, which is a precursor state to the martensitic transition. Some researchers have observed magnetostriction in this alloy in the premartensite phase. We performed magnetostriction studies on the premartensite phase of related Cr-substituted Ni2Mn1−xCrxGa alloys and measured the thermal strain, permeability, magnetisation, and magnetostriction of polycrystals. Our thermal expansion measurements show an anomaly that indicates the occurrence of lattice deformation below the premartensitic transition temperature TP. Our permeability measurements also showed an anomaly at the premartensitic transition. From our magnetisation results, we obtained the magnetic-anisotropy constant K1. In the martensite phase, we found that the magnetic-anisotropy constant of the x = 0.00 alloy is larger than that of the x = 0.15 alloy. At 0.24 MA/m, we obtained a magnetostriction of −120 ppm for the x = 0.15 alloy. Magnetostriction in the premartensite phase is larger than that in the austenite and martensite phases at low magnetic-field strength, thus indicating that it is related to lattice softening in the premartensite phase. The e/a is proportional to the magnetostriction and TP, which indicates that the electron energy, the magnetostriction, and the Tp are correlative each other. Full article
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Open AccessArticle Kinetic Study of Ag Leaching from Arsenic Sulfosalts in the S2O32-O2-NaOH System
Metals 2017, 7(10), 411; doi:10.3390/met7100411
Received: 12 August 2017 / Revised: 27 September 2017 / Accepted: 30 September 2017 / Published: 3 October 2017
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Abstract
In Zimapan, Mexico abundant mineral species have been identified. However, a significant number of these precious metals appear to be related to complex sulfides, as is the case of silver (Ag) in sulfosalts. In this work, a kinetic study of the formation of
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In Zimapan, Mexico abundant mineral species have been identified. However, a significant number of these precious metals appear to be related to complex sulfides, as is the case of silver (Ag) in sulfosalts. In this work, a kinetic study of the formation of Ag complexes in the AgAsS2-S2O32-O2-NaOH system from a Zn concentrate found in the Zimapan mining district was conducted. The kinetic model application on Ag leaching shows a linear adjustment in the valuation of the particle size effect. The rate of formation of Ag complexes is dependent of temperature, leaching agent concentration and OH concentration. Furthermore, graphical verification of the kinetic models indicates that the kinetics of the formation of Ag complexes correspond to the shrinking core model with chemical controls as the controlling stage. The formation of Ag complexes was confirmed by Fourier transform infrared (FTIR) spectroscopy. Full article
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Open AccessArticle The Formation of Strong {100} Texture by Dynamic Strain-Induced Boundary Migration in Hot Compressed Ti-5Al-5Mo-5V-1Cr-1Fe Alloy
Metals 2017, 7(10), 412; doi:10.3390/met7100412
Received: 6 September 2017 / Revised: 23 September 2017 / Accepted: 26 September 2017 / Published: 3 October 2017
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Abstract
The microstructure and texture evolution of Ti-5Al-5Mo-5V-1Cr-Fe alloy during hot compression were investigated by the electron backscatter diffraction technique. The results reveal that two main texture components containing <100> and <111> fiber textures form after the hot compression. The fraction of each component
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The microstructure and texture evolution of Ti-5Al-5Mo-5V-1Cr-Fe alloy during hot compression were investigated by the electron backscatter diffraction technique. The results reveal that two main texture components containing <100> and <111> fiber textures form after the hot compression. The fraction of each component is mainly controlled by deformation and strain rate. Dynamic strain-induced boundary migration (D-SIBM) is proved to be the reason that <100>-oriented grains grow towards <111>-oriented grains. The <100>-oriented grains coarsen with the increasing <100> texture intensity. Dynamic recrystallization (DRX) occurs under a low strain rate and large deformation. The DRX grains were detected by the method of grain orientation spread. The DRX grains reserve a <100> fiber texture similar to the deformation texture; however, DRX is not the main reason causing the formation of a strong <100> texture, due to its low volume fraction. Full article
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Open AccessFeature PaperArticle Temperature Dependences of the Electrical Resistivity on the Heusler Alloy System Ni2MnGa1−xFex
Metals 2017, 7(10), 413; doi:10.3390/met7100413
Received: 10 August 2017 / Revised: 22 September 2017 / Accepted: 28 September 2017 / Published: 3 October 2017
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Abstract
Temperature dependences of the electrical resistivity have been measured on the Heusler alloy system Ni2MnGa1−xFex. The phase diagram of Ni2MnGa1−xFex was constructed on the basis of the experimental results. The structural and
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Temperature dependences of the electrical resistivity have been measured on the Heusler alloy system Ni2MnGa1−xFex. The phase diagram of Ni2MnGa1−xFex was constructed on the basis of the experimental results. The structural and magnetic transition temperatures are consistent with those previously determined by magnetic measurements. The changes of the electrical resistivity at the martensitic transition temperature, ∆ρ, were studied as a function of Fe concentration x. The ∆ρ abruptly increased in the concentration range between x = 0.15 and 0.20. The magnetostructural transitions were observed at x = 0.275, 0.30, and 0.35. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2017)
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Open AccessFeature PaperArticle Evidence of Change in the Density of States during the Martensitic Phase Transformation of Ni-Mn-In Metamagnetic Shape Memory Alloys
Metals 2017, 7(10), 414; doi:10.3390/met7100414
Received: 11 August 2017 / Revised: 15 September 2017 / Accepted: 27 September 2017 / Published: 4 October 2017
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Abstract
Specific heat measurements were performed at low temperatures for Ni50Mn50xInx alloys to determine their Debye temperatures (θD) and electronic specific heat coefficients (γ). For x ≤ 15, where the ground state
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Specific heat measurements were performed at low temperatures for Ni50Mn50xInx alloys to determine their Debye temperatures (θD) and electronic specific heat coefficients (γ). For x ≤ 15, where the ground state is the martensite (M) phase, θD decreases linearly and γ increases slightly with increasing In content. For x ≥ 16.2, where the ground state is the ferromagnetic parent (P) phase, γ increases with decreasing In content. Extrapolations of the composition dependences of θD and γ in both the phases suggest that these values change discontinuously during the martensitic phase transformation. The value of θD in the M phase is larger than that in the P phase. The behavior is in accordance with the fact that the volume of the M phase is more compressive than that of the P phase. On the other hand, γ is slightly larger in the P phase, in good agreement with the reported density of states around the Fermi energy obtained by the first-principle calculations. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2017)
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Open AccessArticle Optimizing Gear Performance by Alloy Modification of Carburizing Steels
Metals 2017, 7(10), 415; doi:10.3390/met7100415
Received: 30 August 2017 / Revised: 24 September 2017 / Accepted: 26 September 2017 / Published: 6 October 2017
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Abstract
Both the tooth root and tooth flank load carrying capacity are characteristic parameters that decisively influence gear size, as well as gearbox design. The principal requirements towards all modern gearboxes are to comply with the steadily-increasing power density and to simultaneously offer a
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Both the tooth root and tooth flank load carrying capacity are characteristic parameters that decisively influence gear size, as well as gearbox design. The principal requirements towards all modern gearboxes are to comply with the steadily-increasing power density and to simultaneously offer a high reliability of their components. With increasing gear size, the load stresses at greater material depth increase. Thus, the material and particularly the strength properties also at greater material depth gain more importance. The present paper initially gives an overview of the main failure modes of case carburized gears resulting from material fatigue. Furthermore, the underlying load and stress mechanisms, under particular contemplation of the gear size, will be discussed, as these considerations principally define the required material properties. Subsequently, the principles of newly developed, as well as modified alloy concepts for optimized gear steels with high load carrying capacity are presented. In the experimental work, the load carrying capacity of the tooth root and tooth flank was determined using a pulsator, as well as an FZG back-to-back test rig. The results demonstrate the suitability of these innovative alloy concepts. Full article
(This article belongs to the Special Issue Fatigue and Wear for Steels)
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Open AccessArticle Effect of Y Addition on the Semi-Solid Microstructure Evolution and the Coarsening Kinetics of SIMA AZ80 Magnesium Alloy
Metals 2017, 7(10), 416; doi:10.3390/met7100416
Received: 18 July 2017 / Revised: 21 August 2017 / Accepted: 3 October 2017 / Published: 6 October 2017
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Abstract
Semi-solid feedstock of AZ80 magnesium alloy modified by trace rare-earth Y element (0, 0.2, 0.4, 0.8 wt. %) was fabricated by strain-induced melting activation (SIMA) in the form of extrusion and partial remelting. The effect of Y addition on the microstructure evolution of
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Semi-solid feedstock of AZ80 magnesium alloy modified by trace rare-earth Y element (0, 0.2, 0.4, 0.8 wt. %) was fabricated by strain-induced melting activation (SIMA) in the form of extrusion and partial remelting. The effect of Y addition on the microstructure evolution of the extruded and isothermally heat treated alloy was observed by using an optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and quantitative analysis. The results show that the Y addition can refine the microstructure and make the β-Mg17Al12 phases agglomerate. During the subsequent isothermal treatment at 570 °C, the average solid grain size, shape factor and liquid fractions increased with the prolonged soaking time. The smaller spheroidal solid grains and larger shape factor were obtained in the semi-solid microstructure due to Y addition. The coalescence and Ostwald ripening mechanism operated the coarsening process of solid grains simultaneously. The coarsening rate constants of AZ80M1 (0.2 wt. % Y addition) of 164.22 μm3 s−1 was approximately four times less than the un-modified AZ80 alloy of 689.44 μm3 s−1. In contrast, the desirable semi-solid structure featured, with fine and well globular solid grains, an appropriate liquid fraction, and shape factor was achieved in AZ80M1 alloy treated at 570 °C for 20–30 min. Full article
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Open AccessArticle Quantitative Analysis of Weld-Pore Size and Depth and Effect on Fatigue Life of Ti-6Al-2Zr-1Mo-1V Alloy Weldments
Metals 2017, 7(10), 417; doi:10.3390/met7100417
Received: 8 September 2017 / Revised: 3 October 2017 / Accepted: 5 October 2017 / Published: 7 October 2017
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Abstract
Titanium-alloy weldments have been extensively used in engineering structures, and accurate estimation of the fatigue life is beneficial for avoiding catastrophic failures in titanium-alloy structures. The weld pore is a common defect in these weldments that significantly influences the fatigue process. In this
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Titanium-alloy weldments have been extensively used in engineering structures, and accurate estimation of the fatigue life is beneficial for avoiding catastrophic failures in titanium-alloy structures. The weld pore is a common defect in these weldments that significantly influences the fatigue process. In this study, the weld-pore size and depth and its effect on the fatigue life of Ti-6Al-2Zr-1Mo-1V (TA15) alloy weldments are investigated by adopting fatigue tests and fracture observations. The results show that fatigue crack initiations occurred at the weld pores for all specimens. The diameter and depth of all weld pores on fracture surfaces were then measured, and an indicator, P, was proposed, defined as a combination of pore diameter and depth. It was found that all the fatigue cracks initiated from the pore have the smallest P indicator, which suggests that P can be used to judge the location of crack initiation in an individual sample. Moreover, a model was developed based on P to estimate the fatigue life of weldments, considering the effects of weld-pore size and depth. Finally, analogous fatigue tests were carried out for model verification, and results show that the proposed model has a higher accuracy compared with several typical models. The findings of this study can be helpful in estimating the fatigue life and fatigue design of titanium-alloy weldments. Full article
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Open AccessArticle Preparation of Chitosan/Poly‐γ‐Glutamic Acid Polyelectrolyte Multilayers on Biomedical Metals for Local Antibiotic Delivery
Metals 2017, 7(10), 418; doi:10.3390/met7100418
Received: 14 September 2017 / Revised: 2 October 2017 / Accepted: 5 October 2017 / Published: 7 October 2017
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Abstract
Polyelectrolyte multilayer assembly is one of the most widely applied biomaterial coatings for applications from surface modification, drug delivery, tissue engineering to biomimetic extracellular environment. In this research, we propose a simple layer-wise spin coating technique to prepare chitosan/poly-γ-glutamic acid (C/PGA) polyelectrolyte multilayers
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Polyelectrolyte multilayer assembly is one of the most widely applied biomaterial coatings for applications from surface modification, drug delivery, tissue engineering to biomimetic extracellular environment. In this research, we propose a simple layer-wise spin coating technique to prepare chitosan/poly-γ-glutamic acid (C/PGA) polyelectrolyte multilayers (PEMs) on two different biomedical metals, 316L stainless steel (316LSS) and titanium alloy (Ti6Al4V). The multilayer coating was fabricated using oppositely charged chitosan and poly--glutamic acid to deposit a total of 10, 20, or 30 multilayered films. Afterward, tetracycline was loaded by soaking the coated metals for 12 hours. The microstructure, mechanical properties, biocompatibility and drug release rate were investigated by scanning electron microscopy, contact angle measurement, MG63 cell viability and inhibition of Escherichia coli (E. coli) growth. Lastly, MG63 cell attachment was detected by fluorescence microscopy after staining with Hoechst 33258. This coating technique can prepare a layer of 2.2–6.9 m C/PGA PEMs favoring cell attachment and growth. Moreover, tetracycline was released from C/PGA PEMs and inhibited the growth of E. coli. The results suggest that C/PGA PEMs provide a useful platform for modulating the micro-environment for better cell adhesion and antibiotic delivery, which hold great potential for surface modification and drug loading for biomimetic materials. Full article
(This article belongs to the Special Issue Nanostructured Surfaces in Metallic Biomaterials)
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Open AccessArticle Microstructure and Wear Resistance of Laser-Clad (Co, Ni)61.2B26.2Si7.8Ta4.8 Coatings
Metals 2017, 7(10), 419; doi:10.3390/met7100419
Received: 12 August 2017 / Revised: 22 September 2017 / Accepted: 25 September 2017 / Published: 7 October 2017
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Abstract
It has been reported that a quaternary Co61.2B26.2Si7.8Ta4.8 alloy is a good glass former and can be laser-clad to an amorphous composite coating with superior hardness and wear resistance. In this paper, alloys with varying Ni
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It has been reported that a quaternary Co61.2B26.2Si7.8Ta4.8 alloy is a good glass former and can be laser-clad to an amorphous composite coating with superior hardness and wear resistance. In this paper, alloys with varying Ni contents to substitute for Co are coated on the surface of #45 carbon steel using a 5-kW CO2 laser source for the purpose of obtaining protective coatings. In contrast to the quaternary case, the clad layers are characterized by a matrix of α-(Fe, Co, Ni) solid solution plus CoB, Co3B, and Co3Ta types of precipitates. The cladding layer is divided into four regions: Near-surface dendrites, α-(Fe, Co, Ni) solid solution plus dispersed particles in the middle zone, columnar bonding zone, and heat-affected area that consists of martensite. The hardness gradually decreases with increasing Ni content, and the maximum hardness occurs in the middle zone. Both the friction coefficient and wear volume are minimized in the alloy containing 12.2% Ni. Compared with the previous cobalt-based quaternary alloy Co61.2B26.2Si7.8Ta4.8, the addition of the Ni element reduces the glass-forming ability and henceforth the hardness and wear resistance of the clad layers. Full article
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Open AccessArticle The Effect of Rolling Temperature on the Microstructure and Mechanical Properties of Surface-Densified Powder Metallurgy Fe-Based Gears Prepared by the Surface Rolling Process
Metals 2017, 7(10), 420; doi:10.3390/met7100420
Received: 7 August 2017 / Revised: 14 September 2017 / Accepted: 25 September 2017 / Published: 10 October 2017
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Abstract
In this investigation, the surface-rolling process was performed to improve the performance of PM (powder metallurgy) parts. Different rolling temperatures were applied and the effect of rolling temperature on the microstructure and mechanical properties of the surface dense layers in the samples were
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In this investigation, the surface-rolling process was performed to improve the performance of PM (powder metallurgy) parts. Different rolling temperatures were applied and the effect of rolling temperature on the microstructure and mechanical properties of the surface dense layers in the samples were investigated. In the study, room temperature and temperatures of 100 °C, 200 °C, 300 °C were studied during the rolling process. The results confirmed that the sample prepared with a pre-heated temperature of 200 °C had the lowest porosity at the surface area. It also exhibited the highest surface hardness and wear resistance. The optimum rolling temperature was determined to be 200 °C and the related mechanism was discussed. Full article
(This article belongs to the Special Issue Powder Synthesis and Processing)
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Open AccessArticle The Effect of Vibration during Friction Stir Welding on Corrosion Behavior, Mechanical Properties, and Machining Characteristics of Stir Zone
Metals 2017, 7(10), 421; doi:10.3390/met7100421
Received: 10 July 2017 / Revised: 18 September 2017 / Accepted: 26 September 2017 / Published: 10 October 2017
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Abstract
Different methods have been applied to refine various characteristics of the zone (or nugget) obtained by friction stir welding (FSW). In the current research, joining components are vibrated normal to the weld line during FSW to refine the zone microstructure. This process is
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Different methods have been applied to refine various characteristics of the zone (or nugget) obtained by friction stir welding (FSW). In the current research, joining components are vibrated normal to the weld line during FSW to refine the zone microstructure. This process is described as friction stir vibration welding (FSVW). The effect of FSVW on mechanical properties, corrosion behavior, and machining characteristics of the zone are investigated. Al5052 alloy specimens are welded using FSW and FSVW processes and their different characteristics are compared and discussed. The results show that the strength and ductility of the welded parts increase when the vibration is applied. The outcomes also show that corrosion resistance of the nugget for FSV-welded specimens is lower than FS welded samples, and machining force of the former specimens is higher than the latter ones. These are related to smaller grain size in the zone of FSV-welded specimens compared to FS welded parts. Smaller grain size leads to a greater volume fraction of grain boundaries and, correspondingly, higher strength and hardness, as well as lower corrosion resistance. Full article
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Open AccessArticle Development of Metallographic Etchants for the Microstructure Evolution of A6082-T6 BFSW Welds
Metals 2017, 7(10), 423; doi:10.3390/met7100423
Received: 4 September 2017 / Revised: 3 October 2017 / Accepted: 6 October 2017 / Published: 11 October 2017
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Abstract
BACKGROUND—The solid-phase joining of A6082-T6 plates by bobbin friction stir welding (BFSW) is problematic. Better methods are needed to evaluate the microstructural evolution of the weld. However, conventional Al reagents (e.g., Keller’s and Kroll’s) do not elucidate the microstructure satisfactorily, specifically regarding grain
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BACKGROUND—The solid-phase joining of A6082-T6 plates by bobbin friction stir welding (BFSW) is problematic. Better methods are needed to evaluate the microstructural evolution of the weld. However, conventional Al reagents (e.g., Keller’s and Kroll’s) do not elucidate the microstructure satisfactorily, specifically regarding grain size and morphology within the weld region. APPROACH—We developed innovative etchants for metallographic observations for optical microscopy. RESULTS—The macrostructure and microstructure of A6082-T6 BFSW welds were clearly demonstrated by optical microscopy analysis. The microetching results demonstrated different microstructures of the Stir Zone (S.Z) distinct from the Base Metal (B.M) and Heat Affected Zone (HAZ) & Thermo-mechanical Affected Zone (TMAZ). The micrographs showed a significant decrease in grain size from 100 μm in B.M to ultrafine 4–10 μm grains for the S.Z. Also, the grain morphology changed from directional columnar in the B.M to equiaxed in the S.Z. Furthermore, thermomechanical recrystallization was observed by the morphological flow of the grain distortion in HAZ and TMAZ. The etchants also clearly show the polycrystalline structure, microflow patterns, and the incoherent interface around inclusion defects. ORIGINALITY—Chemical compositions are identified for a suite of etchant reagents for metallographic examination of the friction-stir welded A6082-T6 alloy. The reagents have made it possible to reveal microstructures not previously evident with optical microscopy. Full article
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Open AccessArticle Characteristics of Resistance Spot Welded Ti6Al4V Titanium Alloy Sheets
Metals 2017, 7(10), 424; doi:10.3390/met7100424
Received: 4 September 2017 / Revised: 30 September 2017 / Accepted: 3 October 2017 / Published: 12 October 2017
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Abstract
Ti6Al4V titanium alloy is applied extensively in the aviation, aerospace, jet engine, and marine industries owing to its strength-to-weight ratio, excellent high-temperature properties and corrosion resistance. In order to extend the application range, investigations on welding characteristics of Ti6Al4V alloy using more welding
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Ti6Al4V titanium alloy is applied extensively in the aviation, aerospace, jet engine, and marine industries owing to its strength-to-weight ratio, excellent high-temperature properties and corrosion resistance. In order to extend the application range, investigations on welding characteristics of Ti6Al4V alloy using more welding methods are required. In the present study, Ti6Al4V alloy sheets were joined using resistance spot welding, and the weld nugget formation, mechanical properties (including tensile strength and hardness), and microstructure features of the resistance spot-welded joints were analyzed and evaluated. The visible indentations on the weld nugget surfaces caused by the electrode force and the surface expulsion were severe due to the high welding current. The weld nugget width at the sheets’ faying surface was mainly affected by the welding current and welding time, and the welded joint height at weld nugget center was chiefly associated with electrode force. The maximum tensile load of welded joint was up to 14.3 kN in the pullout failure mode. The hardness of the weld nugget was the highest because of the coarse acicular α′ structure, and the hardness of the heat-affected zone increased in comparison to the base metal due to the transformation of the β phase to some fine acicular α′ phase. Full article
(This article belongs to the Special Issue Light Weight Alloys: Processing, Properties and Their Applications)
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Open AccessArticle Formation of Nanoscale Metallic Glassy Particle Reinforced Al-Based Composite Powders by High-Energy Milling
Metals 2017, 7(10), 425; doi:10.3390/met7100425
Received: 8 September 2017 / Revised: 1 October 2017 / Accepted: 9 October 2017 / Published: 12 October 2017
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Abstract
The initial microstructure and mechanical properties of composite powders have a vital role in determining the microstructure and mechanical properties of the subsequent consolidated bulk composites. In this work, Al-based matrix composite powders with a dense and uniform distribution of metallic glass nanoparticles
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The initial microstructure and mechanical properties of composite powders have a vital role in determining the microstructure and mechanical properties of the subsequent consolidated bulk composites. In this work, Al-based matrix composite powders with a dense and uniform distribution of metallic glass nanoparticles were obtained by high-energy milling. The results show that high-energy milling is an effective method for varying the microstructure and mechanical properties of the composite powders, thereby offering the ability to control the final microstructure and properties of the bulk composites. It was found that the composite powders show a deformed layer combined with an undeformed core after milling. The reinforcements, metallic glass microparticles, are fractured into dense distributed nanoparticles in the deformed layer, owing to the severe plastic deformation, while in the undeformed core, the metallic glass microparticles are maintained. Therefore, a bimodal structure was obtained, showing a mechanical bimodal structure that has much higher hardness in the outer layer than the center core. The hardness of the composite particles increases significantly with increasing milling time, due to dispersion strengthening and work hardening. Full article
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Open AccessArticle Evaluation of Tool Path Strategy and Cooling Condition Effects on the Cutting Force and Surface Quality in Micromilling Operations
Metals 2017, 7(10), 426; doi:10.3390/met7100426
Received: 22 August 2017 / Revised: 15 September 2017 / Accepted: 9 October 2017 / Published: 13 October 2017
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Abstract
Compared to milling on a macro scale, the micromilling process has several cumbersome points that need to be addressed. Rapid tool wear and fracture, severe burr formation, and poor surface quality are the major problems encountered in the micromilling process. This study aimed
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Compared to milling on a macro scale, the micromilling process has several cumbersome points that need to be addressed. Rapid tool wear and fracture, severe burr formation, and poor surface quality are the major problems encountered in the micromilling process. This study aimed to reveal the effect of cutting path strategies on the cutting force and surface quality in the micromilling of a pocket. The hatch zigzag tool path strategy and the contour climb tool path strategy under different cooling conditions (e.g., dry, air blow, and flood coolant) at fixed cutting parameters. The micromilling tests revealed that better results were obtained with the use of the contour tool path strategy in terms of cutting forces (by up to ~43% compared to the dry condition) and surface quality (by up to ~44% compared to the air blow condition) when compared to the hatch tool path strategy. In addition, the flood coolant reduces the cutting temperature and eliminates chips to significantly enhance the quality of the micro milled surface. Full article
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Open AccessArticle The Effect of Deep Cryogenic Treatment on the Corrosion Behavior of Mg-7Y-1.5Nd Magnesium Alloy
Metals 2017, 7(10), 427; doi:10.3390/met7100427
Received: 28 August 2017 / Revised: 27 September 2017 / Accepted: 10 October 2017 / Published: 13 October 2017
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Abstract
The effect of quenching on the corrosion resistance of Mg-7Y-1.5Nd alloy was investigated. The as-cast alloy was homogenized at 535 °C for 24 h, followed by quenching in air, water, and liquid nitrogen. Then, all of the samples were peak-aged at 225 °C
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The effect of quenching on the corrosion resistance of Mg-7Y-1.5Nd alloy was investigated. The as-cast alloy was homogenized at 535 °C for 24 h, followed by quenching in air, water, and liquid nitrogen. Then, all of the samples were peak-aged at 225 °C for 14 h. The microstructures were studied by scanning electron microscopy, energy-dispersive spectrometry, and X-ray diffraction. Corrosion behavior was analyzed by using weight loss rate and gas collection. Electrochemical characterizations revealed that the T4-deep cryogenic sample displayed the strongest corrosion resistance among all of the samples. A new square phase was discovered in the microstructure of the T6-deep cryogenic sample; this phase was hugely responsible for the corrosion property. Cryogenic treatment significantly improved the corrosion resistance of Mg-7Y-1.5Nd alloy. Full article
(This article belongs to the Special Issue Corrosion of Magnesium Alloys)
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Open AccessArticle Microstructure and Mechanical Properties of Al-5Mg-0.8Mn Alloys with Various Contents of Fe and Si Cast under Near-Rapid Cooling
Metals 2017, 7(10), 428; doi:10.3390/met7100428
Received: 13 September 2017 / Revised: 29 September 2017 / Accepted: 29 September 2017 / Published: 13 October 2017
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Abstract
Al-5Mg-0.8Mn alloys (AA5083) with various iron and silicon contents were cast under near-rapid cooling and rolled into sheets. The aim was to study the feasibility of minimizing the deteriorating level of the harmful Fe-rich phases on the mechanical properties through refining the intermetallics
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Al-5Mg-0.8Mn alloys (AA5083) with various iron and silicon contents were cast under near-rapid cooling and rolled into sheets. The aim was to study the feasibility of minimizing the deteriorating level of the harmful Fe-rich phases on the mechanical properties through refining the intermetallics by significantly increasing the casting rate. The results showed that the size and density of the intermetallic particles that remained in the hot bands and the cold rolled sheets increased as the contents of iron and silicon in the alloys were increased. However, the increment of the particle sizes was limited due to the significant refinement of the intermetallics formed during casting under near-rapid cooling. The mechanical properties of the alloys reduced as the contents of iron and silicon in the alloys increased. However, the decrement of tensile strengths and ductility was quite small. Therefore, higher contents of iron and silicon could be used in the Al-5Mg-0.8Mn alloy (AA5083 alloy) when the material is cast under near-rapid cooling, such as in the continuous strip casting process. Full article
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Open AccessArticle Phase Diagram of Al-Ca-Mg-Si System and Its Application for the Design of Aluminum Alloys with High Magnesium Content
Metals 2017, 7(10), 429; doi:10.3390/met7100429
Received: 28 August 2017 / Revised: 29 September 2017 / Accepted: 9 October 2017 / Published: 13 October 2017
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Abstract
The phase transformations in the Al-Ca-Mg-Si system have been studied using thermodynamic calculations and experimental methods. We show that at 10% Magnesium (Mg), depending on the concentrations of calcium (Ca) and silicon (Si), the following phases crystallize first (apart from the aluminum (Al)
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The phase transformations in the Al-Ca-Mg-Si system have been studied using thermodynamic calculations and experimental methods. We show that at 10% Magnesium (Mg), depending on the concentrations of calcium (Ca) and silicon (Si), the following phases crystallize first (apart from the aluminum (Al) solid solution): Al4Ca, Mg2Si, and Al2CaSi2. We have found that the major part of the calculated concentration range is covered by the region of the primary crystallization of the Al2CaSi2 phase. Regardless of the Ca and Si content, the solidification of the aluminum-magnesium alloys ends with the following nonvariant eutectic reaction: L → (Al) + Al4Ca + Mg2Si + Al3Mg2. With respect to the temperature and composition of the liquid phase, this reaction is close to the eutectic reaction in the Al-Mg binary system. The addition of Ca and Si to the Al-10% Mg base alloy increases its hardness, reduces its density, and has no negative influence on its corrosion resistance. We have also established that the near-eutectic alloy containing about 3% Ca and 1% Si has the optimum structure. Full article
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Open AccessArticle Development and Application of SKSSIM Simulation Software for the Oxygen Bottom Blown Copper Smelting Process
Metals 2017, 7(10), 431; doi:10.3390/met7100431
Received: 16 September 2017 / Revised: 2 October 2017 / Accepted: 3 October 2017 / Published: 16 October 2017
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Abstract
The oxygen bottom blown copper smelting process (SKS process) is a newly developed intense smelting process, which has been widely applied to copper production in China. A multiphase equilibrium model for the SKS process was established based on its mechanism characteristics and the
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The oxygen bottom blown copper smelting process (SKS process) is a newly developed intense smelting process, which has been widely applied to copper production in China. A multiphase equilibrium model for the SKS process was established based on its mechanism characteristics and the principle of Gibbs energy minimization, and an efficient simulation software—SKSSIM (SKS Simulation)—was developed based on the model. Industrial data from the SKS process were used to compare with the calculated data from the SKSSIM software. The calculated data on the compositions of slag and matte as well as the distribution ratios of minor elements (such as Pb, Zn, As, Sb and Bi) among the slags, mattes and off-gases were in good agreement with the actual plant data. Accordingly, the SKSSIM simulation software has the potentail to be used for the prediction of smelting production and for optimizing the operating parameters of the SKS process. Full article
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Open AccessArticle Molecular Dynamics Simulation of Crack Propagation in Nanoscale Polycrystal Nickel Based on Different Strain Rates
Metals 2017, 7(10), 432; doi:10.3390/met7100432
Received: 11 September 2017 / Revised: 30 September 2017 / Accepted: 3 October 2017 / Published: 16 October 2017
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Abstract
Based on the strain rates of 2 × 108 s−1 and 2 × 1010 s−1, molecular dynamics simulation was conducted so as to study mechanisms of crack propagation in nanoscale polycrystal nickel. The strain rate has an important effect on the mechanism of
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Based on the strain rates of 2 × 108 s−1 and 2 × 1010 s−1, molecular dynamics simulation was conducted so as to study mechanisms of crack propagation in nanoscale polycrystal nickel. The strain rate has an important effect on the mechanism of crack propagation in nanoscale polycrystal nickel. In the case of a higher strain rate, local non-3D-crystalline atoms are induced and Lomer-Cottrell locks are formed, which plays a critical role in crack initiation and propagation. Orientation difference between adjacent grains leads to the slipping of dislocations along the different directions, which results in the initiation of a void near the triple junction of grain boundaries and further contributes to accelerating the crack propagation. Full article
(This article belongs to the Special Issue First-Principles Approaches to Metals, Alloys, and Metallic Compounds)
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Open AccessArticle Amplitude Dependent Internal Friction in a Mg-Al-Zn Alloy Studied after Thermal and Mechanical Treatment
Metals 2017, 7(10), 433; doi:10.3390/met7100433
Received: 11 July 2017 / Revised: 3 October 2017 / Accepted: 12 October 2017 / Published: 17 October 2017
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Abstract
The amplitude-dependent internal friction of continuously-cast and rolled AZ31 magnesium alloy was measured in this study. Samples were annealed and quenched step by step; immediately after the treatment, the amplitude dependence of the logarithmic decrement was measured. Changes in the microstructure due to
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The amplitude-dependent internal friction of continuously-cast and rolled AZ31 magnesium alloy was measured in this study. Samples were annealed and quenched step by step; immediately after the treatment, the amplitude dependence of the logarithmic decrement was measured. Changes in the microstructure due to thermomechanical treatment were reflected in changes in the damping. Internal friction is influenced by the dislocation substructure and its modification due to solute atoms migration, microplastic deformation, and twins’ formation. Internal friction in the rolled sheets is affected by the rolling texture. Full article
Open AccessArticle Trajectory Analysis of Copper and Glass Particles in Electrostatic Separation for the Recycling of ASR
Metals 2017, 7(10), 434; doi:10.3390/met7100434
Received: 6 September 2017 / Revised: 7 October 2017 / Accepted: 13 October 2017 / Published: 17 October 2017
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Abstract
Automobile-shredder-residue (ASR) recycling techniques have been widely applied for improving the total recycling rate of end-of-life vehicles. In this study, to obtain useful information for predicting or improving ASR-separation efficiency, trajectory analyses of conductors (copper) and non-conductors (glass) were performed using a lab-scale
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Automobile-shredder-residue (ASR) recycling techniques have been widely applied for improving the total recycling rate of end-of-life vehicles. In this study, to obtain useful information for predicting or improving ASR-separation efficiency, trajectory analyses of conductors (copper) and non-conductors (glass) were performed using a lab-scale induction electrostatic separator. The copper-wire trajectories obtained showed a good agreement depending significantly on the electric field strength and particle size. The observed copper-wire trajectories showed consistent congruity with the coarse-particles simulation (0.5 and 0.25 mm). The observed fine-particles (0.06 mm) trajectory was deflected toward the (−) attractive electrode, owing to the charge density effects due to the particle characteristics and relative humidity. This results in superior separation performance because more copper enters the conductor products bin. The actual dielectric-glass trajectory was deflected toward the (−) attractive electrode, thus showing characteristics similar to conductive-particle characteristics. Through analyses conducted using a stereoscopic microscope, scanning electron microscope, and energy dispersive spectroscope, we found heterogeneous materials (fine ferrous particles and conductive organics) on the glass surface. This demonstrates the separation-efficiency decrease for non-ferrous metals during electrostatic separation in the recycling of ASR. Future work should include a pretreatment process for eliminating impurities from the glass and advanced trajectory-simulation processes. Full article
(This article belongs to the Special Issue Valuable Metal Recycling)
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Open AccessArticle Microscopic Analysis and Electrochemical Behavior of Fe-Based Coating Produced by Laser Cladding
Metals 2017, 7(10), 435; doi:10.3390/met7100435
Received: 16 September 2017 / Revised: 11 October 2017 / Accepted: 13 October 2017 / Published: 18 October 2017
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Abstract
The effect of laser cladding on the surface microstructure and corrosion properties of coated/uncoated specimens were investigated. Fe-based alloy coating was produced on 35CrMo steel by laser cladding. The phase composition, microstructure, interface element distribution, microhardness and corrosion resistance of the cladding coating
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The effect of laser cladding on the surface microstructure and corrosion properties of coated/uncoated specimens were investigated. Fe-based alloy coating was produced on 35CrMo steel by laser cladding. The phase composition, microstructure, interface element distribution, microhardness and corrosion resistance of the cladding coating were measured. The results show that the cladding layer is mainly composed of α-Fe phases, the microstructure presents a gradient distribution, and a good metallurgical bond is formed at the boundary with the substrate. Microhardness profiles show that the average microhardness of the cladding coating is about 2.1 times higher than that of the uncoated specimen. In addition, the electrochemical results show that the coated specimen exhibits far better corrosion resistance than to the uncoated specimen. Full article
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Open AccessArticle Carbides Evolution and Tensile Property of 4Cr5MoSiV1 Die Steel with Rare Earth Addition
Metals 2017, 7(10), 436; doi:10.3390/met7100436
Received: 17 September 2017 / Revised: 6 October 2017 / Accepted: 13 October 2017 / Published: 18 October 2017
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Abstract
Studies of 4Cr5MoSiV1 die steel suggest that under appropriate conditions, additions of rare earth (RE) can enhance tensile property. This improvement is apparently due to the more uniform distribution of carbides and the enhancement of precipitation strengthening after RE additions. In this present
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Studies of 4Cr5MoSiV1 die steel suggest that under appropriate conditions, additions of rare earth (RE) can enhance tensile property. This improvement is apparently due to the more uniform distribution of carbides and the enhancement of precipitation strengthening after RE additions. In this present work, the effect of the RE addition on the carbides evolution and tensile property of 4Cr5MoSiV1 steel with various RE contents (0, 0.018, 0.048 and 0.15 wt %) were systematically investigated. The two-dimensional detection techniques such as optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to investigate the carbides evolution of as-cast, annealed and tempered with RE addition. The results indicated that the carbides in 4Cr5MoSiV1 steels were modified by adding the suitable amount of RE. The eutectic structure and coarse eutectic carbides were all refining and the morphology of the annealed carbides initiated change from strip shape to ellipsoidal shape compared with the unmodified test steel (0RE). In addition, the amount of the tempered M8C7 carbides increased initially and then decreased with the alteration of RE addition from 0.018 to 0.15 wt %. Notably, the tensile test indicated that the average value of ultimate tensile strength (UTS) and elongation rate of 0.048RE steel increased slightly to 1474 MPa and 15%, higher than the 1452 MPa and 12% for the unmodified test steel (0RE), respectively. Such an addition of RE (0.048 wt %) would have a significant effect on the carbides evolution of as-cast, annealed and tempered and resulting in the tensile property of 4Cr5MoSiV1 die steel. Full article
(This article belongs to the Special Issue Alloy Steels)
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Open AccessArticle Effect of Compression Process of MWCNT-Reinforced Al6061 Powder on Densification Characteristics and Its Mechanical Properties
Metals 2017, 7(10), 437; doi:10.3390/met7100437
Received: 13 July 2017 / Revised: 26 September 2017 / Accepted: 10 October 2017 / Published: 18 October 2017
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Abstract
In this paper, aluminium-based (Al6061) composites with 1, 3, 5, 7, and 10 vol % of multi-walled carbon nanotubes (MWCNTs) are investigated. The composites are fabricated by high-energy ball milling, cold-compacting at room temperature under compacting pressures of 400–1600 MPa, and sintering at
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In this paper, aluminium-based (Al6061) composites with 1, 3, 5, 7, and 10 vol % of multi-walled carbon nanotubes (MWCNTs) are investigated. The composites are fabricated by high-energy ball milling, cold-compacting at room temperature under compacting pressures of 400–1600 MPa, and sintering at 620 °C in an argon gas atmosphere. Thereafter, the hardness and microstructure of MWCNTs/Al6061 composites are examined. Further, to improve the relative density and hardness level of the complex material, open-die forging is performed after cold-compacting under 1 GPa pressure at room temperature and sintering at 620 °C. The open-die forging parameters include 1, 3, 5, 7, and 10 vol % MWCNTs/Al6061, and Al6061. The experimental results show that the mechanical properties of the composites are significantly superior to that of the Al6061 alloy after undergoing cold-compacting, sintering, and open-die forging. Full article
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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Open AccessArticle Size Effect and Deformation Mechanism in Twinned Copper Nanowires
Metals 2017, 7(10), 438; doi:10.3390/met7100438
Received: 30 August 2017 / Revised: 5 October 2017 / Accepted: 16 October 2017 / Published: 18 October 2017
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Abstract
Molecular dynamics simulations were performed to demonstrate the synergistic effects of the extrinsic size (nanowire length) and intrinsic size (twin boundary spacing) on the failure manner, yield strength, ductility and deformation mechanism of the twinned nanowires containing high density coherent twin boundaries CTBs
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Molecular dynamics simulations were performed to demonstrate the synergistic effects of the extrinsic size (nanowire length) and intrinsic size (twin boundary spacing) on the failure manner, yield strength, ductility and deformation mechanism of the twinned nanowires containing high density coherent twin boundaries CTBs paralleled to the nanowires’ axis. The twinned nanowires show an intense extrinsic size effect, i.e., shorter is stronger and more ductile, and an intense intrinsic size effect, i.e., thinner is stronger. Notably, the strengthening effect degradation of CTBs in the twinned nanowires is observed with an increase in nanowire length: remarkable strengthening effect can be obtained for the short nanowires, but the strengthening effect becomes less pronounced for the long nanowires. The twinned nanowires fail via a ductile manner or via a brittle manner depending on the synergistic effect of the nanowire length and twin boundary spacing. By atomic-level observation of the plastic deformation, we found that the emission of a trailing 30° partial from the free surface controls the yield behavior of the twinned nanowires. We also found that the special zigzag extended dislocations are formed by the dislocation–CTBs interactions, and propagate to sustain the plastic deformation. Full article
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Open AccessArticle Application of Co and Mn for a Co-Mn-Br or Co-Mn-C2H3O2 Petroleum Liquid Catalyst from the Cathode Material of Spent Lithium Ion Batteries by a Hydrometallurgical Route
Metals 2017, 7(10), 439; doi:10.3390/met7100439
Received: 30 August 2017 / Revised: 29 September 2017 / Accepted: 11 October 2017 / Published: 18 October 2017
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Abstract
We investigated the preparation of CMB (cobalt-manganese-bromide) and CMA (cobalt-manganese-acetate) liquid catalysts as petroleum liquid catalysts by simultaneously recovering Co and Mn from spent Li-ion battery cathode material. To prepare the liquid catalysts, the total preparation process for the liquid catalysts consisted of
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We investigated the preparation of CMB (cobalt-manganese-bromide) and CMA (cobalt-manganese-acetate) liquid catalysts as petroleum liquid catalysts by simultaneously recovering Co and Mn from spent Li-ion battery cathode material. To prepare the liquid catalysts, the total preparation process for the liquid catalysts consisted of physical pre-treatments, such as grinding and sieving, and chemical processes, such as leaching, solvent extraction, and stripping. In the physical pre-treatment process, over 99% of Al was removed from material with a size of less than 0.42 mm. In the chemical process, the leaching solution as obtained under the following conditions: 2 mol/L sulfuric acid, 10 vol % H2O2, 0.1 of solid/liquid ratio, and 60 °C. In the solvent extraction process, the optimum concentration of bis (2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), the equilibrium pH, the degree of saponification, the organic phase/aqueous phase ratio isotherm, and the stripping study for the extraction of Co and Mn were investigated. As a result, Co and Mn were recovered by 0.85 M Cyanex 272 with 50% saponification in counter current two extraction stages. Finally, a CMB and CMA liquid catalyst containing 33.1 g/L Co, 29.8 g/L Mn, and 168 g/L Br and 12.67 g/L Co, 12.0 g/L Mn, and 511 g/L C2H3O2, respectively, was produced by 2 M hydrogen bromide and 50 vol % acetic acid; it was also found that a shortage in the concentration can be compensated with cobalt and manganese salts. Full article
(This article belongs to the Special Issue Valuable Metal Recycling)
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Open AccessArticle Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid
Metals 2017, 7(10), 440; doi:10.3390/met7100440
Received: 26 September 2017 / Revised: 7 October 2017 / Accepted: 11 October 2017 / Published: 18 October 2017
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Abstract
The effect of ultrasonic nanocrystal surface modification (UNSM) on the fatigue behavior of Ti6Al4V (TC4) in simulated body fluid (SBF) was investigated. UNSM with the condition of a static load of 25 N, vibration amplitude of 30 μm and 36,000 strikes per unit
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The effect of ultrasonic nanocrystal surface modification (UNSM) on the fatigue behavior of Ti6Al4V (TC4) in simulated body fluid (SBF) was investigated. UNSM with the condition of a static load of 25 N, vibration amplitude of 30 μm and 36,000 strikes per unit produced about 35 μm surface severe plastic deformation (SPD) layers on the TC4 specimens. One group was treated with a hybrid surface treatment (UNSM + TiN film). UNSM technique improves the micro hardness and the compressive residual stress. The surface roughness is increased slightly, but it can be remarkably improved by the TiN film. The fatigue strength of TC4 is improved by about 7.9% after UNSM. Though the current density of corrosion is increased and the pitting corrosion is accelerated, UNSM still improved the fatigue strength of TC4 after pre-soaking in SBF by 10.8%. Interior cracks initiate at the deformed carbide and oxide inclusions due to the ultrasonic impacts of UNSM. Corrosion products are always observed at the edge of fracture surface to both interior cracks and surface cracks. Coating a TiN film on the UNSMed surface helps to improve the whole properties of TC4 further. Full article
Open AccessArticle Effects of Increasing Feed Rate on Tool Deterioration and Cutting Force during End Milling of 718Plus Superalloy Using Cemented Tungsten Carbide Tool
Metals 2017, 7(10), 441; doi:10.3390/met7100441
Received: 30 September 2017 / Revised: 17 October 2017 / Accepted: 17 October 2017 / Published: 19 October 2017
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Abstract
Understanding how feed rate (ft) affects tool deterioration during milling of Ni-based superalloys is practically important, but this understanding is currently insufficient. In the present study using a 718Plus Ni-based alloy and cemented tungsten carbide tool inserts, milling experiments were
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Understanding how feed rate (ft) affects tool deterioration during milling of Ni-based superalloys is practically important, but this understanding is currently insufficient. In the present study using a 718Plus Ni-based alloy and cemented tungsten carbide tool inserts, milling experiments were conducted with ft = 0.10 mm/tooth under either dry or wet (with coolant) conditions. The results are compared to those based on using ft = 0.05 mm/tooth from previous studies. The milling force (F) was monitored, the cutting tool edge was examined and the flank wear (VBmax) was measured. As would be expected, an increase in ft increased F. It was found that F correlated well with VBmax for the high ft (0.1 mm/tooth) experiments, as opposed to the previously observed poor F-VBmax relationship for the lower ft (0.05 mm/tooth) value. This is explained, supported by detailed failure analysis of the cutting tool edges, by the deterioration mode to be dominantly edge chipping with a low occurrence of fracturing along the flank face when the high ft was used. This dominancy of the deterioration mode means that the tool edge and workpiece contact was consistent and thus resulted in a clear F-VBmax relationship. A clear F-VBmax relationship should then mean monitoring VBmax through monitoring F is possible. Full article
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Open AccessArticle Hydrogen Reduction in MEP Niobium Studied by Secondary Ion Mass Spectrometry (SIMS)
Metals 2017, 7(10), 442; doi:10.3390/met7100442 (registering DOI)
Received: 4 September 2017 / Revised: 10 October 2017 / Accepted: 10 October 2017 / Published: 20 October 2017
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Abstract
Niobium, as pure metal and alloying element, is used in a variety of applications, among them in nuclear industries. Niobium is incorporated into nuclear fission reactors due to its enormous strength and low density. Surface finishing of niobium is often performed in electrochemical
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Niobium, as pure metal and alloying element, is used in a variety of applications, among them in nuclear industries. Niobium is incorporated into nuclear fission reactors due to its enormous strength and low density. Surface finishing of niobium is often performed in electrochemical polishing processes in view of improving its smoothness, corrosion resistance and its surface cleanability. However, the presently used electropolishing process (EP) is intrinsically linked to the subsurface hydrogenation of niobium, which measurably degrades its properties. This is why the annealing operation is used to remove hydrogen from electropolished niobium that is a costly and time-consuming process. The traditional electrolyte consisting of a mixture of 96% H2SO4/49% HF acids by volume in a 9:1 ratio has been substituted for the new one, being a mixture of 70% methanesulfonic acid with 49% hydrofluoric acid by volume in a 3:1 ratio. Moreover, the additional imposition of a magnetic field during the electropolishing process (MEP) further increases hydrogen removal, when compared to the hydrogen content achieved by the electropolishing process alone. The aim of the study is to reveal a methodic approach and showing decreasing hydrogenation of niobium samples after consecutive steps of electrochemical polishing. Secondary ion mass spectrometry (SIMS) was used to measure the hydrogen content in the surface layer of as-received AR niobium and in the samples after EP and MEP processes. Full article
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Open AccessFeature PaperArticle The Influence of the Powder Stream on High-Deposition-Rate Laser Metal Deposition with Inconel 718
Metals 2017, 7(10), 443; doi:10.3390/met7100443 (registering DOI)
Received: 1 September 2017 / Revised: 10 October 2017 / Accepted: 12 October 2017 / Published: 20 October 2017
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Abstract
For the purpose of improving the productivity of laser metal deposition (LMD), the focus of current research is set on increasing the deposition rate, in order to develop high-deposition-rate LMD (HDR-LMD). The presented work studies the effects of the powder stream on HDR-LMD
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For the purpose of improving the productivity of laser metal deposition (LMD), the focus of current research is set on increasing the deposition rate, in order to develop high-deposition-rate LMD (HDR-LMD). The presented work studies the effects of the powder stream on HDR-LMD with Inconel 718. Experiments have been designed and conducted by using different powder feeding nozzles—a three-jet and a coaxial powder feeding nozzle—since the powder stream is mainly determined by the geometry of the powder feeding nozzle. After the deposition trials, metallographic analysis of the samples has been performed. The laser intensity distribution (LID) and the powder stream intensity distribution (PID) have been characterized, based on which the processes have been simulated. Finally, for verifying and correcting the used models for the simulation, the simulated results have been compared with the experimental results. Through the conducted work, suitable boundary conditions for simulating the process with different powder streams has been determined, and the effects of the powder stream on the process have also been determined. For a LMD process with a three-jet nozzle a substantial part of the powder particles that hit the melt pool surface are rebounded; for a LMD process with a coaxial nozzle almost all the particles are caught in the melt pool. This is due to the different particle velocities achieved with the two different nozzles. Moreover, the powder stream affects the heat exchange between the heated particles and the melt pool: a surface boundary condition applies for a powder stream with lower particle velocities, in the experiment provided by a three-jet nozzle, and a volumetric boundary condition applies for a powder stream with higher particle velocities, provided by a coaxial nozzle. Full article
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Open AccessArticle Free Volume Contributing to the Different Yield Behaviors between Tension and Compression Deformations in Metallic Glasses
Metals 2017, 7(10), 444; doi:10.3390/met7100444 (registering DOI)
Received: 13 September 2017 / Revised: 13 October 2017 / Accepted: 16 October 2017 / Published: 20 October 2017
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Abstract
The different deformation behaviors in the yield stage, in particular, of metallic glasses under uniaxial tension and compression are investigated from an atomic structural perspective, by applying both experimental and simulation methods. A new computational approach for quantitatively calculating free volumes (FVs) in
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The different deformation behaviors in the yield stage, in particular, of metallic glasses under uniaxial tension and compression are investigated from an atomic structural perspective, by applying both experimental and simulation methods. A new computational approach for quantitatively calculating free volumes (FVs) in structural models is developed, based on which the manner in which FVs contribute to deformation is studied. It is found that FVs have different expansion behaviors in terms of their saturation sizes and corresponding strain values, which are essential structural causes of different yield behaviors in these two deformations in metallic glasses. Full article
(This article belongs to the Special Issue Metallic Glasses: Pathways to Viable Applications)
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Open AccessArticle The Effect of Strain on the Formation of an Intermetallic Layer in an Al-Ni Laminated Composite
Metals 2017, 7(10), 445; doi:10.3390/met7100445 (registering DOI)
Received: 5 September 2017 / Revised: 9 October 2017 / Accepted: 16 October 2017 / Published: 20 October 2017
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Abstract
In the present work, the influence of strain on phase formation at the Al/Ni interface was investigated during cold roll bonding and annealing. A sandwich sample composed of an Al-Ni-Al stack was cold rolled with reductions in the range of 50% to 90%,
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In the present work, the influence of strain on phase formation at the Al/Ni interface was investigated during cold roll bonding and annealing. A sandwich sample composed of an Al-Ni-Al stack was cold rolled with reductions in the range of 50% to 90%, followed by annealing at 450 °C for 60 min. The crystallography of the annealed sandwich samples was analyzed by XRD (X-ray diffraction), whereas the microstructure was studied by scanning electron microscopy, equipped with EDS (energy dispersive spectrometer) analysis, and optical microscope. In the annealed samples, the intermetallic phase Al3Ni has formed at the Ni/Al interface, preferentially on the Al side of the interface. It is found that the applied strains did not have an effect on the type of intermetallic phase that was formed. However, the rolling reduction has a significant effect on the morphology of the intermetallic layer, as it was observed that after the lowest reduction of 50% only some scattered intermetallic nuclei were present, whereas at the highest rolling reduction of 90% a continuous intermetallic layer of 4.1 μm was exhibited. The formation of the intermetallic layer is discussed in terms of Al and Ni diffusion at the interface and irregular nature of the Al/Ni bonded interface after rolling reductions. Full article
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Open AccessArticle High Power Diode Laser (HPDL) for Fatigue Life Improvement of Steel: Numerical Modelling
Metals 2017, 7(10), 447; doi:10.3390/met7100447 (registering DOI)
Received: 18 September 2017 / Revised: 5 October 2017 / Accepted: 18 October 2017 / Published: 21 October 2017
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Abstract
This paper deals with the improvement of fatigue life of AISI 1040 steel components by using a High Power Diode Laser (HPDL). First, the meaningfulness of each operational parameter was assessed by varying the experimental laser power and scan speed. After laser treatment,
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This paper deals with the improvement of fatigue life of AISI 1040 steel components by using a High Power Diode Laser (HPDL). First, the meaningfulness of each operational parameter was assessed by varying the experimental laser power and scan speed. After laser treatment, fatigue tests were performed to investigate the influence of laser processing parameters on the material resistance. The fatigue tests were carried out by using a rotating bending machine. Wöhler curves were obtained from the analysis of experimental results. Second, in the light of experimental findings, a 3D transient finite element method for a laser heat source, with Gaussian energy distribution, was developed to predict the temperature and the depth of the heat affected zone on the workpiece. The model allows us to understand the relationship between the laser treatment parameters and the fatigue enhancement of the components. HPDL was found to significantly increase the fatigue life of the irradiated workpieces, thus revealing its suitability for industrial applications. Full article
Open AccessArticle Microstructure and Fatigue Properties of AlZn6Mg0.8Zr Alloy Subjected to Low-Temperature Thermomechanical Processing
Metals 2017, 7(10), 448; doi:10.3390/met7100448 (registering DOI)
Received: 22 August 2017 / Revised: 10 October 2017 / Accepted: 12 October 2017 / Published: 21 October 2017
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Abstract
The paper presents results of the investigations on the effect of the low-temperature thermomechanical treatment on the microstructure of AlZn6Mg0.8Zr alloy (7003 alloy) and the relationships between microstructure and fatigue properties and fractography of fractured samples. Fatigue life has been determined in a
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The paper presents results of the investigations on the effect of the low-temperature thermomechanical treatment on the microstructure of AlZn6Mg0.8Zr alloy (7003 alloy) and the relationships between microstructure and fatigue properties and fractography of fractured samples. Fatigue life has been determined in a mechanical test at a simple state of loading under conditions of bending as well as torsion. The development of fatigue cracking has been described based on fractography investigations of the fractured samples making use of a scanning electron microscope (SEM). It was found that the factors determining the fatigue strength of the tested alloy are the microstructure as well as the type and size of the cyclic stresses. These factors determine the fractography of fatigue samples. Full article
(This article belongs to the Special Issue Light Weight Alloys: Processing, Properties and Their Applications)
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Open AccessArticle 3D Modelling of Flash Formation in Linear Friction Welded 30CrNiMo8 Steel Chain
Metals 2017, 7(10), 449; doi:10.3390/met7100449 (registering DOI)
Received: 20 September 2017 / Revised: 17 October 2017 / Accepted: 18 October 2017 / Published: 21 October 2017
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Abstract
Linear friction welding (LFW) is a solid-state welding process that has been thoroughly investigated for chain welding in recent years in order to replace the currently in use Flash Butt Welding (FBW) process. Modelling has proven to be an indispensable tool in LFW,
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Linear friction welding (LFW) is a solid-state welding process that has been thoroughly investigated for chain welding in recent years in order to replace the currently in use Flash Butt Welding (FBW) process. Modelling has proven to be an indispensable tool in LFW, thus providing necessary insight to the process, regardless of its final application. This article describes a 3D model developed in the commercial software DEFORM to study the LFW process of 30CrNiMo8 high strength steel in the Hero chain. Hence, a weakly coupled thermal and mechanical model were used, by means of the process experimental input such as displacement histories. The flash morphology and intervening mechanisms were analyzed. A thermal evaluation of different regions in the studied geometry was considered, and a correlation of the modeled and experimental width of the extrusion zone was established. Full article
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Open AccessFeature PaperReview Metallurgical Challenges in Carbon Nanotube-Reinforced Metal Matrix Nanocomposites
Metals 2017, 7(10), 384; doi:10.3390/met7100384
Received: 14 July 2017 / Revised: 14 August 2017 / Accepted: 11 September 2017 / Published: 22 September 2017
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Abstract
The inclusion of carbon nanotubes (CNTs) into metallic systems has been the main focus of recent literature. The aim behind this approach has been the development of a new property or improvement of an inferior one in CNT-dispersed metal matrix nanocomposites. Although it
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The inclusion of carbon nanotubes (CNTs) into metallic systems has been the main focus of recent literature. The aim behind this approach has been the development of a new property or improvement of an inferior one in CNT-dispersed metal matrix nanocomposites. Although it has opened up new possibilities for promising engineering applications, some practical challenges have restricted the full exploitation of CNTs’ unique characteristics. Non-uniform dispersion of CNTs in the metallic matrix, poor interfacial adhesion at the CNT/metal interface, the unfavorable chemical reaction of CNTs with the matrix, and low compactability are the most significant challenges, requiring more examination. The present paper provides a broad overview of the mentioned challenges, the way they occur, and their adverse influences on the physicomechanical properties of CNT-reinforced metal matrix nanocomposites. The suggested solutions to these issues are fully addressed. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
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Open AccessReview Overview of Intergranular Fracture of Neutron Irradiated Austenitic Stainless Steels
Metals 2017, 7(10), 392; doi:10.3390/met7100392
Received: 10 August 2017 / Revised: 8 September 2017 / Accepted: 16 September 2017 / Published: 25 September 2017
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Abstract
Austenitic stainless steels are normally ductile and exhibit deep dimples on fracture surfaces. These steels can, however, exhibit brittle intergranular fracture under some circumstances. The occurrence of intergranular fracture in the irradiated steels is briefly reviewed based on limited literature data. The data
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Austenitic stainless steels are normally ductile and exhibit deep dimples on fracture surfaces. These steels can, however, exhibit brittle intergranular fracture under some circumstances. The occurrence of intergranular fracture in the irradiated steels is briefly reviewed based on limited literature data. The data are sorted according to the irradiation temperature. Intergranular fracture may occur in association with a high irradiation temperature and void swelling. At low irradiation temperature, the steels can exhibit intergranular fracture at low or even at room temperatures during loading in air and in high temperature water (~300 °C). This paper deals with the similarities and differences for IG fractures and discusses the mechanisms involved. The intergranular fracture occurrence at low temperatures might be correlated with decohesion or twinning and strain martensite transformation in local narrow areas around grain boundaries. The possibility of a ductile-to-brittle transition is also discussed. In case of void swelling higher than 3%, quasi-cleavage at low temperature might be expected as a consequence of ductile-to-brittle fracture changes with temperature. Any existence of the change in fracture behavior in the steels of present thermal reactor internals with increasing irradiation dose should be clearly proven or disproven. Further studies to clarify the mechanism are recommended. Full article
(This article belongs to the Special Issue Radiation Effects in Metals)
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Open AccessReview The Prospects of Zinc as a Structural Material for Biodegradable Implants—A Review Paper
Metals 2017, 7(10), 402; doi:10.3390/met7100402
Received: 31 August 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 1 October 2017
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Abstract
In the last decade, iron and magnesium, both pure and alloyed, have been extensively studied as potential biodegradable metals for medical applications. However, broad experience with these material systems has uncovered critical limitations in terms of their suitability for clinical applications. Recently, zinc
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In the last decade, iron and magnesium, both pure and alloyed, have been extensively studied as potential biodegradable metals for medical applications. However, broad experience with these material systems has uncovered critical limitations in terms of their suitability for clinical applications. Recently, zinc and zinc-based alloys have been proposed as new additions to the list of degradable metals and as promising alternatives to magnesium and iron. The main byproduct of zinc metal corrosion, Zn2+, is highly regulated within physiological systems and plays a critical role in numerous fundamental cellular processes. Zn2+ released from an implant may suppress harmful smooth muscle cells and restenosis in arteries, while stimulating beneficial osteogenesis in bone. An important limitation of pure zinc as a potential biodegradable structural support, however, lies in its low strength (σUTS ~ 30 MPa) and plasticity (ε < 0.25%) that are insufficient for most medical device applications. Developing high strength and ductility zinc with sufficient hardness, while retaining its biocompatibility, is one of the main goals of metallurgical engineering. This paper will review and compare the biocompatibility, corrosion behavior and mechanical properties of pure zinc, as well as currently researched zinc alloys. Full article
(This article belongs to the Special Issue Biodegradable Metals)
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Open AccessReview A Comparison of Different Finite Element Methods in the Thermal Analysis of Friction Stir Welding (FSW)
Metals 2017, 7(10), 450; doi:10.3390/met7100450 (registering DOI)
Received: 28 August 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 21 October 2017
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Abstract
Friction Stir Welding (FSW) is a novel kind of welding for joining metals that are impossible or difficult to weld by conventional methods. Three-dimensional nature of FSW makes the experimental investigation more complex. Moreover, experimental observations are often costly and time consuming, and
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Friction Stir Welding (FSW) is a novel kind of welding for joining metals that are impossible or difficult to weld by conventional methods. Three-dimensional nature of FSW makes the experimental investigation more complex. Moreover, experimental observations are often costly and time consuming, and usually there is an inaccuracy in measuring the data during experimental tests. Thus, Finite Element Methods (FEMs) has been employed to overcome the complexity, to increase the accuracy and also to reduce costs. It should be noted that, due to the presence of large deformations of the material during FSW, strong distortions of mesh might be happened in the numerical simulation. Therefore, one of the most significant considerations during the process simulation is the selection of the best numerical approach. It must be mentioned that; the numerical approach selection determines the relationship between the finite grid (mesh) and deforming continuum of computing zones. Also, numerical approach determines the ability of the model to overcome large distortions of mesh and provides an accurate resolution of boundaries and interfaces. There are different descriptions for the algorithms of continuum mechanics include Lagrangian and Eulerian. Moreover, by combining the above-mentioned methods, an Arbitrary Lagrangian–Eulerian (ALE) approach is proposed. In this paper, a comparison between different numerical approaches for thermal analysis of FSW at both local and global scales is reviewed and the applications of each method in the FSW process is discussed in detail. Observations showed that, Lagrangian method is usually used for modelling thermal behavior in the whole structure area, while Eulerian approach is seldom employed for modelling of the thermal behavior, and it is usually employed for modelling the material flow. Additionally, for modelling of the heat affected zone, ALE approach is found to be as an appropriate approach. Finally, several significant challenges and subjects remain to be addressed about FSW thermal analysis and opportunities for the future work are proposed. Full article
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