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Metals, Volume 7, Issue 10 (October 2017)

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Cover Story (view full-size image) The technological and industrial needs for the development of high-strength bulk materials have led [...] Read more.
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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; https://doi.org/10.3390/met7100450
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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Open AccessArticle 3D Modelling of Flash Formation in Linear Friction Welded 30CrNiMo8 Steel Chain
Metals 2017, 7(10), 449; https://doi.org/10.3390/met7100449
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 AccessArticle Microstructure and Fatigue Properties of AlZn6Mg0.8Zr Alloy Subjected to Low-Temperature Thermomechanical Processing
Metals 2017, 7(10), 448; https://doi.org/10.3390/met7100448
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 High Power Diode Laser (HPDL) for Fatigue Life Improvement of Steel: Numerical Modelling
Metals 2017, 7(10), 447; https://doi.org/10.3390/met7100447
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
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Open AccessEditorial Intermetallics
Metals 2017, 7(10), 446; https://doi.org/10.3390/met7100446
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) Printed Edition available
Open AccessArticle The Effect of Strain on the Formation of an Intermetallic Layer in an Al-Ni Laminated Composite
Metals 2017, 7(10), 445; https://doi.org/10.3390/met7100445
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 Free Volume Contributing to the Different Yield Behaviors between Tension and Compression Deformations in Metallic Glasses
Metals 2017, 7(10), 444; https://doi.org/10.3390/met7100444
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
[...] Read more.
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 AccessFeature PaperArticle The Influence of the Powder Stream on High-Deposition-Rate Laser Metal Deposition with Inconel 718
Metals 2017, 7(10), 443; https://doi.org/10.3390/met7100443
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
[...] Read more.
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 Hydrogen Reduction in MEP Niobium Studied by Secondary Ion Mass Spectrometry (SIMS)
Metals 2017, 7(10), 442; https://doi.org/10.3390/met7100442
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 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; https://doi.org/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 Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid
Metals 2017, 7(10), 440; https://doi.org/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
[...] Read more.
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
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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; https://doi.org/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
[...] Read more.
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 Size Effect and Deformation Mechanism in Twinned Copper Nanowires
Metals 2017, 7(10), 438; https://doi.org/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 Effect of Compression Process of MWCNT-Reinforced Al6061 Powder on Densification Characteristics and Its Mechanical Properties
Metals 2017, 7(10), 437; https://doi.org/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
[...] Read more.
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 Carbides Evolution and Tensile Property of 4Cr5MoSiV1 Die Steel with Rare Earth Addition
Metals 2017, 7(10), 436; https://doi.org/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) Printed Edition available
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