Metals

21 pages, 3944 KiB

Open AccessFeature PaperReview

Solidification of Immiscible Alloys under High Magnetic Field: A Review

by Chen Wei, Jun Wang, Yixuan He, Jinshan Li and Eric Beaugnon

Metals 2021, 11(3), 525; https://doi.org/10.3390/met11030525 - 23 Mar 2021

Cited by 10 | Viewed by 3813

Immiscible alloy is a kind of functional metal material with broad application prospects in industry and electronic fields, which has aroused extensive attention in recent decades. In the solidification process of metallic material processing, various attractive phenomena can be realized by applying a [...] Read more.

Immiscible alloy is a kind of functional metal material with broad application prospects in industry and electronic fields, which has aroused extensive attention in recent decades. In the solidification process of metallic material processing, various attractive phenomena can be realized by applying a high magnetic field (HMF), including the nucleation and growth of alloys and microstructure evolution, etc. The selectivity provided by Lorentz force, thermoelectric magnetic force, and magnetic force or a combination of magnetic field effects can effectively control the solidification process of the melt. Recent advances in the understanding of the development of immiscible alloys in the solidification microstructure induced by HMF are reviewed. In this review, the immiscible alloy systems are introduced and inspected, with the main focus on the relationship between the migration behavior of the phase and evolution of the solidification microstructure under HMF. Special attention is paid to the mechanism of microstructure evolution caused by the magnetic field and its influence on performance. The ability of HMF to overcome microstructural heterogeneity in the solidification process provides freedom to design and modify new functional immiscible materials with desired physical properties. This review aims to offer an overview of the latest progress in HMF processing of immiscible alloys. Full article

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18 pages, 6668 KiB

Open AccessFeature PaperArticle

Strategies to Reduce Porosity in Al-Mg WAAM Parts and Their Impact on Mechanical Properties

by Maider Arana, Eneko Ukar, Iker Rodriguez, Amaia Iturrioz and Pedro Alvarez

Metals 2021, 11(3), 524; https://doi.org/10.3390/met11030524 - 23 Mar 2021

Cited by 32 | Viewed by 4865

Abstract

With the advent of disruptive additive manufacturing (AM), there is an increasing interest and demand of high mechanical property aluminium parts built directly by these technologies. This has led to the need for continuous improvement of AM technologies and processes to obtain the [...] Read more.

With the advent of disruptive additive manufacturing (AM), there is an increasing interest and demand of high mechanical property aluminium parts built directly by these technologies. This has led to the need for continuous improvement of AM technologies and processes to obtain the best properties in aluminium samples and develop new alloys. This study has demonstrated that porosity can be reduced below 0.035% in area in Al-Mg samples manufactured by CMT-based WAAM with commercial filler metal wires by selecting the correct shielding gas, gas flow rate, and deposition strategy (hatching or circling). Three phase Ar+O₂+N₂O mixtures (Stargold^®) are favourable when the hatching deposition strategy is applied leading to wall thickness around 6 mm. The application of circling strategy (torch movement with overlapped circles along the welding direction) enables the even build-up of layers with slightly thicker thickness (8 mm). In this case, Ar shielding gas can effectively reduce porosity if proper flow is provided through the torch. Reduced gas flows (lower than 30 Lmin) enhance porosity, especially in long tracks (longer than 90 mm) due to local heat accumulation. Surprisingly, rather high porosity levels (up to 2.86 area %) obtained in the worst conditions, had a reduced impact on the static tensile test mechanical properties, and yield stress over 110 MPa, tensile strength over 270 MPa, and elongation larger than 27% were achieved either for Ar circling, Ar hatching, or Stargold^® hatching building conditions. In all cases anisotropy was lower than 11%, and this was reduced to 9% for the most appropriate shielding conditions. Current results show that due to the selected layer height and deposition parameters there was a complete re-melting of the previous layer and a thermal treatment on the prior bottom layer that refined the grain size removing the original dendritic and elongated structure. Under these conditions, the minimum reported anisotropy levels can be achieved. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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14 pages, 4863 KiB

Open AccessFeature PaperArticle

The Significance of Optimizing Mn-Content in Tuning the Microstructure and Mechanical Properties of δ-TRIP Steels

by Baoyu Xu, Peng Chen, Zhengxian Li, Di Wu, Guodong Wang, Jinyu Guo, Rendong Liu, R. D. K. Misra and Hongliang Yi

Metals 2021, 11(3), 523; https://doi.org/10.3390/met11030523 - 23 Mar 2021

Cited by 4 | Viewed by 2396

Abstract

The δ-TRIP steel has attracted a lot of attention for its potential application in automotive components, owing to the low density, good combination of strength, and ductility. As the difficulty in yield strength further increasement is caused by large fraction ferrite, the work [...] Read more.

The δ-TRIP steel has attracted a lot of attention for its potential application in automotive components, owing to the low density, good combination of strength, and ductility. As the difficulty in yield strength further increasement is caused by large fraction ferrite, the work hardening ability was enhanced by optimizing the manganese (Mn)-content in this study. Three δ-TRIP steels with different manganese (Mn)-content were designed to explore the significant effect of Mn content on the work hardening behavior in order to develop high strength steel suitable for the industrial continuous annealing process. The detailed effect of Mn on microstructure evolution and deformation behavior was studied by scanning electron microscope (SEM), interrupted tensile tests, X-ray diffraction (XRD), and in-situ electron backscattered diffraction (EBSD). The study suggested that 2 Mn steel has the lowest degree of bainitic transformation, as a result of fine grain size of prior austenite. The large TRIP effect and dislocation strengthening improve the work hardening rate, resulting in 2 Mn steel exhibiting comparable mechanical properties with the QP980 steels. The retained austenite in 1.5 Mn steel progressively transformed into martensite and sustained the strain to a high strain value of 0.40, showing a good strength-ductility balance. Full article

(This article belongs to the Special Issue Advanced Multiphase Steels)

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10 pages, 3106 KiB

Open AccessArticle

Influence of Surface Preparation and Heat Treatment on Mechanical Behavior of Hybrid Aluminum Parts Manufactured by a Combination of Laser Powder Bed Fusion and Conventional Manufacturing Processes

by Alessio Tommasi, Nathalie Maillol, Andrea Bertinetti, Pavel Penchev, Julien Bajolet, Flavia Gili, Daniele Pullini and David Busquets Mataix

Metals 2021, 11(3), 522; https://doi.org/10.3390/met11030522 - 23 Mar 2021

Cited by 10 | Viewed by 2585

Abstract

Today, in industry, laser-based additive manufacturing (LAM) is used to produce high-value parts of very complex designs that are not manufacturable by conventional technologies; this process’ low production throughput and high cost prevent it from being used more extensively. One way to exploit [...] Read more.

Today, in industry, laser-based additive manufacturing (LAM) is used to produce high-value parts of very complex designs that are not manufacturable by conventional technologies; this process’ low production throughput and high cost prevent it from being used more extensively. One way to exploit the benefits of LAM in industry is to have it combined with lower-cost manufacturing technologies. In a hybrid approach, LAM can be integrated within an assembly line’s welding station to complete the manufacturing of a product by depositing a foreign material on a substrate only where needed, or by building structures of complex 3D geometries (e.g., lattice structures) directly onto inexpensive preforms. To pave the way for using a hybrid approach design in real applications, as a prime requirement, the chosen technology must grant comparable structural integrity to its products with respect to its conventional counterparts. In this work, different types of surface pretreatments for substrates were investigated as a key enabling factor to tailor the bi-material system’s mechanical properties in use. Hybrid samples were made by depositing AlSi10Mg by direct metal laser sintering onto A356-T6 aluminum bases prefabricated by casting and forging, and their properties were compared with fully homogeneous samples that were conventionally produced. Specifically referring to the automotive use case, both these alloy grades were chosen for their extensive use in the production of motor vehicles. The testing campaign, characterized by microscopy, mechanical testing, and fatigue, revealed that the structural integrity of the hybrid samples is comparable with the benchmarks when standard heat treatments are adopted. This result makes the prospect of the exploitation of the hybridization concept as conceived very promising for the future. Full article

(This article belongs to the Section Additive Manufacturing)

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9 pages, 3326 KiB

Open AccessArticle

Modification of Liquid Steel Viscosity and Surface Tension for Inert Gas Atomization of Metal Powder

by Iurii Korobeinikov, Anton Perminov, Tobias Dubberstein and Olena Volkova

Metals 2021, 11(3), 521; https://doi.org/10.3390/met11030521 - 23 Mar 2021

Cited by 6 | Viewed by 3143

Abstract

Inert gas atomization is one of the main sources for production of metal powder for powder metallurgy and additive manufacturing. The obtained final powder size distribution is controlled by various technological parameters: gas flow rate and pressure, liquid metal flow rate, gas type, [...] Read more.

Inert gas atomization is one of the main sources for production of metal powder for powder metallurgy and additive manufacturing. The obtained final powder size distribution is controlled by various technological parameters: gas flow rate and pressure, liquid metal flow rate, gas type, temperature of spraying, configuration of nozzles, etc. This work explores another dimension of the atomization process control: modifications of the liquid metal properties and their effect on the obtained powder size. Series of double-alloyed Cr-Mn-Ni steels with sulfur and phosphorus were atomized with argon at 1600 °C. The results indicate that surface tension and viscosity modifications lead to yielding finer powder fractions. The obtained correlation is compared with the individual modification of surface tension with S and Se and modification of viscosity with phosphorus. Discrepancy of the results is discussed. Additives of surfactants and viscosity modifiers can be a useful measure for powder fractions control. Full article

(This article belongs to the Section Powder Metallurgy)

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16 pages, 17762 KiB

Open AccessReview

High Speed Roll Caster for Aluminum Alloy

by Toshio Haga

Metals 2021, 11(3), 520; https://doi.org/10.3390/met11030520 - 22 Mar 2021

Cited by 19 | Viewed by 4990

Abstract

Two types of high-speed twin-roll casters and a single-roll caster equipped with a scraper were proposed. One of the twin-roll casters is a vertical-type high-speed twin-roll caster, and the other twin-roll caster is an unequal-diameter twin-roll caster. The vertical-type high-speed twin-roll caster can [...] Read more.

Two types of high-speed twin-roll casters and a single-roll caster equipped with a scraper were proposed. One of the twin-roll casters is a vertical-type high-speed twin-roll caster, and the other twin-roll caster is an unequal-diameter twin-roll caster. The vertical-type high-speed twin-roll caster can cast strip at speeds of up to 120 m/min. The unequal-diameter twin-roll caster casts strip at speeds up to 60 m/min. The unequal-diameter twin-roll caster is superior to the vertical-type high-speed twin-roll caster at the point of conveyance of the cast strip. A single-roll caster equipped with a scraper can cast strip without center-line segregation at speeds of up to 40 m/min. The use of a copper alloy roll and the non-use of a parting material enable high-speed roll casting. Since the roll loads of these casters are smaller than 0.1 kN/mm, soft copper alloy roll can be used. The strip does not stick to the roll without the parting material because of the use of the copper alloy roll with high thermal conductivity and the small roll load. The cooling rate near the surface is higher than 2000 °C/s. Full article

(This article belongs to the Special Issue Strip Casting of Metals and Alloys)

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16 pages, 5517 KiB

Open AccessArticle

Corrosion Behavior, Microstructure and Mechanical Properties of Novel Mg-Zn-Ca-Er Alloy for Bio-Medical Applications

by Devadas Bhat Panemangalore, Rajashekhara Shabadi and Manoj Gupta

Metals 2021, 11(3), 519; https://doi.org/10.3390/met11030519 - 22 Mar 2021

Cited by 7 | Viewed by 3772

Abstract

In this study, the effect of calcium (Ca) and erbium (Er) on the microstructure, mechanical properties, and corrosion behavior of magnesium-zinc alloys is reported. The alloys were prepared using disintegrated melt deposition (DMD) technique using the alloying additions as Zn, Ca, and Mg-Er [...] Read more.

In this study, the effect of calcium (Ca) and erbium (Er) on the microstructure, mechanical properties, and corrosion behavior of magnesium-zinc alloys is reported. The alloys were prepared using disintegrated melt deposition (DMD) technique using the alloying additions as Zn, Ca, and Mg-Er master alloys and followed by hot extrusion. Results show that alloying addition of Er has significantly reduced the grain sizes of Mg-Zn alloys and also when compared to pure magnesium base material. It also has substantially enhanced both the tensile and the compressive properties by favoring the formation of MgZn₂ type secondary phases that are uniformly distributed during hot-extrusion. The quaternary Mg-Zn-Ca-Er alloy exhibited the highest strength due to lower grain size and particle strengthening due to the influence of the rare earth addition Er. The observed elongation was a result of extensive twinning observed in the alloys. Also, the degradation rates have been substantially reduced as a result of alloying additions and it is attributed to the barrier effect caused by the secondary phases. Full article

(This article belongs to the Special Issue Design, Development and Characterization of Advanced Metallic Materials)

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13 pages, 4826 KiB

Open AccessArticle

Tailoring Extra-Strength of a TWIP Steel by Combination of Multi-Pass Equal-Channel Angular Pressing and Warm Rolling

by Marina Abramova, Arseniy Raab, Ruslan Z. Valiev, Anna Khannanova, Chong Soo Lee, Jae Nam Kim, Gyeong Hyeon Jang, Jung Gi Kim, Hyoung Seop Kim, Oliver Renk and Nariman Enikeev

Metals 2021, 11(3), 518; https://doi.org/10.3390/met11030518 - 22 Mar 2021

Cited by 14 | Viewed by 2816

Abstract

Increasing the yield stress of twinning-induced plasticity (TWIP) steels is a demanding task for modern materials science. This aim can be achieved by microstructure refinement induced by heavy straining. We feature the microstructural evolution and mechanical performance of a high-manganese TWIP steel subjected [...] Read more.

Increasing the yield stress of twinning-induced plasticity (TWIP) steels is a demanding task for modern materials science. This aim can be achieved by microstructure refinement induced by heavy straining. We feature the microstructural evolution and mechanical performance of a high-manganese TWIP steel subjected to deformation treatment by different combinations of equal channel angular pressing (ECAP) and rolling at different temperatures. The effect of microstructure on the tensile properties of the steel subjected to the multi-pass ECAP process and to subsequent rolling is reported as well. We show that the combined deformation procedure allows us to further increase the strength of the processed workpieces due to a gradual transition from a banded structure to a heterogeneous hierarchical microstructure consisting of fragments, dislocation configurations and nano- and micro-twins colonies. Rolling of multi-pass ECAP specimens at 375 °C allowed us to achieve an extraordinary strength, the highest among all the investigated cases, while the best trade-off between yield strength and elongation to failure was reached using multi-pass ECAP followed by rolling at 500 °C. This study shows a great potential of using combined deformation techniques to enhance the mechanical performance of TWIP steels. Full article

(This article belongs to the Special Issue Microstructural Evolution and Phase Transformation in TWIP Steel)

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17 pages, 14045 KiB

Open AccessFeature PaperArticle

The Effects of Heat Treatment on the Microstructure and Tensile Properties of an HPDC Marine Transmission Gearcase

by Joshua Stroh, Dimitry Sediako, Ted Hanes, Kevin Anderson and Alex Monroe

Metals 2021, 11(3), 517; https://doi.org/10.3390/met11030517 - 22 Mar 2021

Cited by 6 | Viewed by 2302

Abstract

The drive for continuously improving the performance and increasing the efficiencies of marine transportation has resulted in the development of a new alloy, Mercalloy A362™. This alloy was designed to lighten Mercury Marine’s lower transmission gearcase while also improving the alloy’s recyclability. The [...] Read more.

The drive for continuously improving the performance and increasing the efficiencies of marine transportation has resulted in the development of a new alloy, Mercalloy A362™. This alloy was designed to lighten Mercury Marine’s lower transmission gearcase while also improving the alloy’s recyclability. The new prototype gearcase was subjected to Mercury Marine’s standard service conditions, which resulted in the premature failure of the prototype. A previous study revealed that a large accumulation of unwanted residual stress (~120 MPa) was present in the gearcase following the high pressure die casting process. Fortunately, the T5 heat treatment reduced the magnitude of stress by approximately 50%. However, the effects that the T5 heat treatment had on the microstructure and mechanical properties of the alloy were not discussed. Thus, this research article characterizes the effects that the T5 heat treatment has on the volume fraction and morphology of the intermetallics, as well as the tensile performance of the alloy. It was found that the T5 heat treatment led to only minor increases in the volume fraction of Fe-bearing intermetallics, leading to similar tensile properties in both the as-cast and T5 condition. These results suggest that the T5 heat treatment can alleviate residual stress without significantly altering the mechanical properties of the alloy. The results from the previous stress analysis and the current study were used to optimize the manufacturing process which led to the successful introduction of the gearcase into the competitive marine industry. Full article

(This article belongs to the Special Issue Material Properties—Superalloys, Ferrous and Lightweight Alloys and Metal Matrix Composites)

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21 pages, 4608 KiB

Open AccessReview

The Corrosion of Stainless Steel Made by Additive Manufacturing: A Review

by Gyeongbin Ko, Wooseok Kim, Kyungjung Kwon and Tae-Kyu Lee

Metals 2021, 11(3), 516; https://doi.org/10.3390/met11030516 - 21 Mar 2021

Cited by 56 | Viewed by 8358

Abstract

The advantages of additive manufacturing (AM) of metals over traditional manufacturing methods have triggered many relevant studies comparing the mechanical properties, corrosion behavior, and microstructure of metals produced by AM or traditional manufacturing methods. This review focuses exclusively on the corrosion property of [...] Read more.

The advantages of additive manufacturing (AM) of metals over traditional manufacturing methods have triggered many relevant studies comparing the mechanical properties, corrosion behavior, and microstructure of metals produced by AM or traditional manufacturing methods. This review focuses exclusively on the corrosion property of AM-fabricated stainless steel by comprehensively analyzing the relevant literature. The principles of various AM processes, which have been adopted in the corrosion study of stainless steel, and the corrosion behaviors of stainless steel depending on the AM process, the stainless steel type, and the corrosion environment are summarized. In this comprehensive analysis of relevant literature, we extract dominant experimental factors and the most relevant properties affecting the corrosion of AM-fabricated stainless steel. In selective laser melting, the effects of the scan speed, laser power, energy density, and the post-treatment technologies are usually investigated. In direct laser deposition, the most relevant papers focused on the effect of heat treatments on passive films and the Cr content. There has been no specific trend in the corrosion study of stainless steel that is fabricated by other AM processes, such as wire arc additive manufacturing. Given the rising utilization of AM-produced metal parts, the corrosion issue will be more important in the future, and this review should provide a worthwhile basis for future works. Full article

(This article belongs to the Section Corrosion and Protection)

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11 pages, 2783 KiB

Open AccessArticle

Separation of Sn, Sb, Bi, and Cu from Tin Anode Slime by Solvent Extraction and Chemical Precipitation

by Wei-Sheng Chen, Shota Mesaki and Cheng-Han Lee

Metals 2021, 11(3), 515; https://doi.org/10.3390/met11030515 - 21 Mar 2021

Cited by 1 | Viewed by 3214

Abstract

Tin anode slime is a by-product of the tin electrolytic refining process. This study investigated a route to separate Sn, Sb, Bi, and Cu from tin anode slime after leaching with hydrochloric acid. In the solvent extraction process with tributyl phosphate, Sb and [...] Read more.

Tin anode slime is a by-product of the tin electrolytic refining process. This study investigated a route to separate Sn, Sb, Bi, and Cu from tin anode slime after leaching with hydrochloric acid. In the solvent extraction process with tributyl phosphate, Sb and Sn were extracted into the organic phase. Bi and Cu were unextracted and remained in the liquid phase. In the stripping experiment, Sb and Sn were stripped and separated with HCl and HNO₃. Bi and Cu in the aqueous phase were also separated with chemical precipitation procedure by controlling pH value. The purities of Sn, Sb, Cu solution and the Bi-containing solid were 96.25%, 83.65%, 97.51%, and 92.1%. The recovery rates of Sn, Sb, Cu, and Bi were 76.2%, 67.1%, and 96.2% and 92.4%. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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10 pages, 4048 KiB

Open AccessArticle

Effects of Al on Precipitation Behavior of Ti-Nb-Ta-Zr Refractory High Entropy Alloys

by Jing Wen, Xin Chu, Yuankui Cao and Na Li

Metals 2021, 11(3), 514; https://doi.org/10.3390/met11030514 - 20 Mar 2021

Cited by 12 | Viewed by 3100

Abstract

Addition of Al can decrease density and improve oxidation resistance of refractory high entropy alloys (RHEAs), but may cause complicated precipitation and further affect mechanical properties. The present work studied the microstructural evolution of Al-contained RHEAs at elevated temperatures. The effects of Al [...] Read more.

Addition of Al can decrease density and improve oxidation resistance of refractory high entropy alloys (RHEAs), but may cause complicated precipitation and further affect mechanical properties. The present work studied the microstructural evolution of Al-contained RHEAs at elevated temperatures. The effects of Al on precipitation behavior were discussed. Results show that, TiNbTa_0.5ZrAl_x alloys (x ≤ 0.5) have single BCC (Body Centered Cubic) structure, but the primary BCC phase is supersaturated. Precipitation of BCC2_(Nb,Ta)-rich solid solution phase, HCP_(Zr,Al)-rich intermetallic phase, and ordered B2 phase can occur during heat treatment at 600~1200 °C. The precipitation of BCC2 phase mainly exists in RHEAs with low content of Al, while HCP (Hexagonal Close Packed) precipitates prefer to form in RHEAs with high content of Al. Interestingly, ordered B2 precipitates with fine and basket-weave structure can form in TiNbTa_0.5ZrAl_0.5 alloy after annealing at 800 °C, producing significant precipitation hardening effect. Full article

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11 pages, 8230 KiB

Open AccessArticle

Effect of Filler Metal Type on Microstructure and Mechanical Properties of Fabricated NiAl Bronze Alloy Using Wire Arc Additive Manufacturing System

by Jaewon Kim, Jaedeuk Kim, Jooyoung Cheon and Changwook Ji

Metals 2021, 11(3), 513; https://doi.org/10.3390/met11030513 - 19 Mar 2021

Cited by 7 | Viewed by 2606

Abstract

This study observed the effect of filler metal type on mechanical properties of NAB (NiAl-bronze) material fabricated using wire arc additive manufacturing (WAAM) technology. The selection of filler metal type is must consider the field condition, mechanical properties required by customers, and economics. [...] Read more.

This study observed the effect of filler metal type on mechanical properties of NAB (NiAl-bronze) material fabricated using wire arc additive manufacturing (WAAM) technology. The selection of filler metal type is must consider the field condition, mechanical properties required by customers, and economics. This study analyzed the bead shape for representative two kind of filler metal types use to maintenance and fabricated a two-dimensional bulk NAB material. The cold metal transfer (CMT) mode of gas metal arc welding (GMAW) was used. For a comparison of mechanical properties, the study obtained three specimens per welding direction from the fabricated bulk NAB material. In the tensile test, the NAB material deposited using filler metal wire A showed higher tensile strength and lower elongation (approx. +71 MPa yield strength, +107.1 MPa ultimate tensile strength, −12.4% elongation) than that deposited with filler metal wire B. The reason is that, a mixture of tangled fine α platelets and dense lamellar eutectoid α + κ_III structure with β′ phases was observed in the wall made with filler metal wire A. On the other hand, the wall made with filler metal wire B was dominated by coarse α phases and lamellar eutectoid α + κ_III structure in between. Full article

(This article belongs to the Special Issue Additive Manufacturing of Non-ferrous Alloys)

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12 pages, 5278 KiB

Open AccessFeature PaperArticle

Surface Modification of the EBM Ti-6Al-4V Alloy by Pulsed Ion Beam

by Natalia Pushilina, Ekaterina Stepanova, Andrey Stepanov and Maxim Syrtanov

Metals 2021, 11(3), 512; https://doi.org/10.3390/met11030512 - 19 Mar 2021

Cited by 11 | Viewed by 2658

Abstract

The effect of surface modification of Ti-6Al-4V samples manufactured by electron beam melting (EBM) using a pulsed carbon ion beam is studied in the present work. Based on the results of XRD, SEM, and TEM analysis, patterns of changes in the microstructure and [...] Read more.

The effect of surface modification of Ti-6Al-4V samples manufactured by electron beam melting (EBM) using a pulsed carbon ion beam is studied in the present work. Based on the results of XRD, SEM, and TEM analysis, patterns of changes in the microstructure and phase composition of the EBM Ti-6Al-4V alloy, depending on the number of pulses of pulsed ion beam exposure, are revealed. It was found that gradient microstructure is formed as a result of pulsed ion beam irradiation of the EBM Ti-6Al-4V samples. The microstructure of the surface layer up to 300 nm thick is represented by the (α + α”) phase. At depths of 0.3 μm, the microstructure is mixed and contains alpha-phase plates and needle-shaped martensite. The mechanical properties were investigated using methods of uniaxial tensile tests, micro- and nanohardness measurements, and tribological tests. It was shown that surface modification by a pulsed ion beam at an energy density of 1.92 J/cm² and five pulses leads to an increase in the micro- and nanohardness of the surface layers, a decrease in the wear rate, and a slight rise in the plasticity of EBM Ti-6Al-4V alloy. Full article

(This article belongs to the Special Issue Additive Manufacturing of Architected Metallic Materials)

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13 pages, 2567 KiB

Open AccessFeature PaperArticle

Decrease in Pitting Corrosion Resistance of Extra-High-Purity Type 316 Stainless-Steel by Cu²⁺ in NaCl

by Takahito Aoyama, Hiroaki Ogawa, Chiaki Kato and Fumiyoshi Ueno

Metals 2021, 11(3), 511; https://doi.org/10.3390/met11030511 - 19 Mar 2021

Cited by 4 | Viewed by 2548

Abstract

The effect of Cu²⁺ in bulk solution on pitting corrosion resistance of extra-high-purity type 316 stainless-steel was investigated. Pitting occurred in 0.1 M NaCl-1 mM CuCl₂, whereas pitting was not initiated in 0.1 M NaCl. Although deposition of Cu²⁺ [...] Read more.

The effect of Cu²⁺ in bulk solution on pitting corrosion resistance of extra-high-purity type 316 stainless-steel was investigated. Pitting occurred in 0.1 M NaCl-1 mM CuCl₂, whereas pitting was not initiated in 0.1 M NaCl. Although deposition of Cu²⁺ on the surface occurred regardless of a potential region in 0.1 M NaCl-1 mM CuCl₂, Cu²⁺ in bulk solution had no influence on the passive film formation. The decrease in pitting corrosion resistance in 0.1 M NaCl-1 mM CuCl₂ resulted from the deposited Cu or Cu compound and continuous supply of Cu²⁺ on the surface. Full article

(This article belongs to the Special Issue Soil and Pitting Corrosion of Steel)

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20 pages, 3046 KiB

Open AccessFeature PaperArticle

The Effects of Chemical Etching and Ultra-Fine Grain Structure of Titanium on MG-63 Cells Response

by Denis Nazarov, Elena Zemtsova, Vladimir Smirnov, Ilya Mitrofanov, Maxim Maximov, Natalia Yudintceva and Maxim Shevtsov

Metals 2021, 11(3), 510; https://doi.org/10.3390/met11030510 - 19 Mar 2021

Cited by 7 | Viewed by 3359

Abstract

In this work, we study the influence of the surface properties of ultrafine grained (UFG) and coarse grained (CG) titanium on the morphology, viability, proliferation and differentiation of osteoblast-like MG-63 cells. Wet chemical etching in H₂SO₄/H₂O₂ [...] Read more.

In this work, we study the influence of the surface properties of ultrafine grained (UFG) and coarse grained (CG) titanium on the morphology, viability, proliferation and differentiation of osteoblast-like MG-63 cells. Wet chemical etching in H₂SO₄/H₂O₂ and NH₄OH/H₂O₂ solutions was used for producing surfaces with varying morphology, topography, composition and wettability. The topography and morphology have been studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The composition was determined by time of flight mass-spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). The results showed that it is possible to obtain samples with different compositions, hydrophilicity, topography and nanoscale or/and microscale structures by changing the etching time and the type of etching solution. It was found that developed topography and morphology can improve spreading and proliferation rate of MG-63 cells. A significant advantage of the samples of the UFG series in comparison with CG in adhesion, proliferation at later stages of cultivation (7 days), higher alkaline phosphatase (ALP) activity and faster achievement of its maximum values was found. However, there is no clear benefit of the UFG series on osteopontin (OPN) expression. All studied samples showed no cytotoxicity towards MG-63 cells and promoted their osteogenic differentiation. Full article

(This article belongs to the Special Issue Surface Modification of Metallic Biomaterials)

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16 pages, 5696 KiB

Open AccessArticle

Active Brazing of Alumina and Copper with Multicomponent Ag-Cu-Sn-Zr-Ti Filler

by Sri Harini Rajendran, Seung Jun Hwang and Jae Pil Jung

Metals 2021, 11(3), 509; https://doi.org/10.3390/met11030509 - 19 Mar 2021

Cited by 11 | Viewed by 4360

Abstract

The study was designed to investigate the synergic effect of Ti and Sn in the active metal brazing of Al₂O₃ ceramic to copper brazed, using the multicomponent Ag-Cu-Zr filler alloy. Numerous fine and hexagonal-shaped rod-like ternary intermetallic (Zr, Ti)₅ [...] Read more.

The study was designed to investigate the synergic effect of Ti and Sn in the active metal brazing of Al₂O₃ ceramic to copper brazed, using the multicomponent Ag-Cu-Zr filler alloy. Numerous fine and hexagonal-shaped rod-like ternary intermetallic (Zr, Ti)₅Sn₃ phase (L/D = 5.1 ± 0.8, measured in microns) were found dispersed in the Ag-Cu matrix of Ag-18Cu-6Sn-3Zr-1Ti alloy, along with the ternary CuZrSn intermetallic phases. An approximate 15° reduction in contact angle and 3.1 °C reduction in melting point are observed upon the incorporation of Ti and Sn in Ag-18Cu-3Zr filler. Interestingly, the interface microstructure of Al₂O₃/Cu joints brazed by using Ag-18Cu-6Sn-3Zr-1Ti filler shows a double reaction layer: a discontinuous Ti-rich layer consisting of (Cu, Al)₃(Ti, Zr)₃O, TiO, and in-situ Cu-(Ti, Zr) precipitates on the Al₂O₃ side and continuous Zr-rich layer consisting of ZrO₂ on the filler side. The shear strength achieved in Al₂O₃/Cu joints brazed with Ag-18Cu-6Sn-3Zr-1Ti filler is 31% higher, compared to the joints brazed with Ag-18Cu-6Sn-3Zr filler. Failure analysis reveals a composite fracture mode indicating a strong interface bonding in Al₂O₃/Ag-18Cu-6Sn-3Zr-1Ti filler/Cu joints. The findings will be helpful towards the development of high entropy brazing fillers in the future. Full article

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11 pages, 6648 KiB

Open AccessArticle

Influence of Duty Ratio and Current Mode on Robot 316L Stainless Steel Arc Additive Manufacturing

by Ping Yao, Hongyan Lin, Wei Wu and Heqing Tang

Metals 2021, 11(3), 508; https://doi.org/10.3390/met11030508 - 19 Mar 2021

Cited by 6 | Viewed by 2535

Abstract

Wire and arc additive manufacturing (WAAM) is usually for fabricating components due to its low equipment cost, high material utilization rate and cladding efficiency. However, its applications are limited by the large heat input decided by process parameters. Here, four 50-layer stainless steel [...] Read more.

Wire and arc additive manufacturing (WAAM) is usually for fabricating components due to its low equipment cost, high material utilization rate and cladding efficiency. However, its applications are limited by the large heat input decided by process parameters. Here, four 50-layer stainless steel parts with double-pulse and single-pulse metal inert gas (MIG) welding modes were deposited, and the effect of different duty ratios and current modes on morphology, microstructure, and performance was analyzed. The results demonstrate that the low frequency of the double-pulse had the effect of stirring the molten pool; therefore, the double-pulse mode parts presented a bigger width and smaller height, finer microstructure and better properties than the single-pulse mode. Furthermore, increasing the duty ratio from 35% to 65% enlarged the heat input, which then decreased the specimen height, increased the width, and decreased the hardness and the tensile strength. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Structures, Properties, and Methodologies)

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30 pages, 22949 KiB

Open AccessFeature PaperArticle

Investigation of the Intermetallic Compounds Fragmentation Impact on the Formation of Texture during the as Cast Structure Thermomechanical Treatment of Aluminum Alloys

by Evgenii Aryshenskii, Jurgen Hirsch and Sergey Konovalov

Metals 2021, 11(3), 507; https://doi.org/10.3390/met11030507 - 19 Mar 2021

Cited by 12 | Viewed by 3481

Abstract

In this work, the influence of the intermetallic particle fragmentation during hot rolling of the as cast structure on the evolution of textures in aluminum alloys 8011, 5182 and 1565 was investigated. For this purpose, laboratory multi-pass rolling of the cast material was [...] Read more.

In this work, the influence of the intermetallic particle fragmentation during hot rolling of the as cast structure on the evolution of textures in aluminum alloys 8011, 5182 and 1565 was investigated. For this purpose, laboratory multi-pass rolling of the cast material was carried out. At various degrees of hot rolling deformation, the process was stopped, and the metal was quenched and sent for optical and electron microscopy to investigate the large intermetallic particles. In addition, the grain structure was studied and an X-ray analysis was carried out in order to determine the main texture components. Some of the samples were held at a temperature above the recrystallization threshold and then cooled in air; the grain structure and texture composition were also studied. In addition, the simulation of the texture evolution was carried out under various modes of rolling of aluminum alloys, taking into account the process of fragmentation of intermetallic particles. The investigation showed that intermetallic compounds with a deformation degree of 1.8, on average, decrease the particle size by 5–7 times. The large eutectic particles remaining after homogenization are drawn out in the direction of deformation and are crushed, increasing their number accordingly. Therefore, the most favorable stage for the formation of recrystallization nuclei on particles is the moment when they are already numerous and their sizes are much larger than subgrains. Simulation of hot rolling of the investigated alloys showed that considering the factor of fragmentation of intermetallic particles during hot deformation of the as-cast structure significantly increases the accuracy of the results. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Aluminum Alloys)

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11 pages, 5429 KiB

Open AccessArticle

Laser Beam Welding of a Ti-15Mo/TiB Metal–Matrix Composite

by Maxim Ozerov, Elizaveta Povolyaeva, Nikita Stepanov, Volker Ventzke, René Dinse, Nikolai Kashaev and Sergey Zherebtsov

Metals 2021, 11(3), 506; https://doi.org/10.3390/met11030506 - 18 Mar 2021

Cited by 16 | Viewed by 2577

Abstract

A Ti-15Mo/TiB metal–matrix composite was produced by spark plasma sintering at 1400 °C. The fractions of the elements in the initial powder mixture were 80.75 wt.% Ti, 14.25 wt.% Mo, and 5 wt.% TiB₂. The initial structure of the synthesized composite [...] Read more.

A Ti-15Mo/TiB metal–matrix composite was produced by spark plasma sintering at 1400 °C. The fractions of the elements in the initial powder mixture were 80.75 wt.% Ti, 14.25 wt.% Mo, and 5 wt.% TiB₂. The initial structure of the synthesized composite was composed of bcc β titanium matrix and needle-like TiB reinforcements with an average thickness of 500 ± 300 nm. Microstructure and mechanical properties of the composite were studied after laser beam welding (LBW) was carried out at room temperature or various pre-heating temperatures: 200, 400, or 600 °C. The quality of laser beam welded joints was not found to be dependent noticeably on the pre-heating temperature; all welds consisted of pores the size of which reached 200–300 µm. In contrast to acicular individual particles in the base material, TiB whiskers in the weld zone were found to have a form of bunches. The maximum microhardness in the weld zone (~700 HV) was obtained after welding at room temperature or at 200 °C; this value was ~200 HV higher than that in the base material. Full article

(This article belongs to the Special Issue Advances in Lightweight Metal Matrix Composites)

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15 pages, 5753 KiB

Open AccessArticle

Applied Research of Applicability of High-Strength Steel for a Track of a Demining Machine in Term of Its Tribological Properties

by Miroslav Blatnický, Ján Dižo, Milan Sága and Peter Kopas

Metals 2021, 11(3), 505; https://doi.org/10.3390/met11030505 - 18 Mar 2021

Cited by 4 | Viewed by 2316

Abstract

Even today, there are countries that are affected by war and its pitfalls. The authors have decided to present a part of the accompanying research results in this article. This research precedes the design of a demining machine Božena 5. The main goal [...] Read more.

Even today, there are countries that are affected by war and its pitfalls. The authors have decided to present a part of the accompanying research results in this article. This research precedes the design of a demining machine Božena 5. The main goal of the authors’ activities was to design optimal material and geometry for a track of this machine. To achieve this goal, the authors conducted research to evaluate the microstructure of the material S960QL and its tribological lifetime. As the track of the demining machine is a welded component, the authors also investigated the influence of different welding technologies on the given parameters. The tribological research was performed on an original test device. The obtained results show that welding joints have the typical microstructure of martensitic high-strength steels and that mechanical properties can be influenced by individual welding technologies. Meanwhile, the use of the electron beam significantly extends the adhesive-abrasive lifespan compared with the MAG (metal active gas) conventional method as well as to the base material. It is interesting that the absolute value of material loss over time reached the identity for both the laser beam and the electron beam. The obtained data provide changes to apply the proposed material for the production of the solved component. Full article

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18 pages, 10725 KiB

Open AccessArticle

Precipitation Criterion for Inhibiting Austenite Grain Coarsening during Carburization of Al-Containing 20Cr Gear Steels

by Huasong Liu, Yannan Dong, Hongguang Zheng, Xiangchun Liu, Peng Lan, Haiyan Tang and Jiaquan Zhang

Metals 2021, 11(3), 504; https://doi.org/10.3390/met11030504 - 18 Mar 2021

Cited by 8 | Viewed by 2833

Abstract

AlN precipitates are frequently adopted to pin the austenite grain boundaries for the high-temperature carburization of special gear steels. For these steels, the grain coarsening criterion in the carburizing process is required when encountering the composition optimization for the crack-sensitive steels. In this [...] Read more.

AlN precipitates are frequently adopted to pin the austenite grain boundaries for the high-temperature carburization of special gear steels. For these steels, the grain coarsening criterion in the carburizing process is required when encountering the composition optimization for the crack-sensitive steels. In this work, the quantitative influence of the Al and N content on the grain size after carburization is studied through pseudocarburizing experiments based on 20Cr steel. According to the grain structure feature and the kinetic theory, the abnormal grain growth is demonstrated as the mode of austenite grain coarsening in carburization. The AlN precipitate, which provides the dominant pinning force, is ripened in this process and the particle size can be estimated by the Lifshitz−Slyosov−Wagner theory. Both the mass fraction and the pinning strength of AlN precipitate show significant influence on the grain growth behavior with the critical values indicating the grain coarsening. These criteria correspond to the conditions of abnormal grain growth when bearing the Zener pinning, which has been analyzed by the multiple phase-field simulation. Accordingly, the models to predict the austenite grain coarsening in carburization were constructed. The prediction is validated by the additional experiments, resulting in accuracies of 92% and 75% for the two models, respectively. Finally, one of the models is applied to optimize the Al and N contents of commercial steel. Full article

(This article belongs to the Special Issue Heat Treatment of Steels)

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16 pages, 7493 KiB

Open AccessArticle

Study on a New Forming Method—Thread Rolling by Crystal Plasticity Finite Element Simulation

by Yuheng Zhang, Zhiqing Hu and Liming Guo

Metals 2021, 11(3), 503; https://doi.org/10.3390/met11030503 - 18 Mar 2021

Cited by 1 | Viewed by 2607

Abstract

In order to study a new thread rolling forming process from a microscopic perspective, a polycrystalline model was established, based on the crystal plasticity finite element method (CPFEM) and Voronoi polyhedron theory. The fluidity of metals was studied to explain the reason for [...] Read more.

In order to study a new thread rolling forming process from a microscopic perspective, a polycrystalline model was established, based on the crystal plasticity finite element method (CPFEM) and Voronoi polyhedron theory. The fluidity of metals was studied to explain the reason for the concave center. The simulation results show that the strain curve of the representative element can more truly reflect the deformation behavior of the material. The grain orientations after deformation are distributed near the initial orientation. The evolution of each slip system is determined by the initial grain orientations and grain locations. The pole figures obtained from the experiment show high consistency with the pole figures obtained by simulation, which verifies the accuracy of the texture prediction by CPFEM. The experimental results show that thread rolling is more uniform in deformation than ordinary rolling. Full article

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22 pages, 1185 KiB

Open AccessFeature PaperArticle

A Holistic, Model-Predictive Process Control for Friction Stir Welding Processes Including a 1D FDM Multi-Layer Temperature Distribution Model

by Stefan P. Meyer, Sebastian Fuderer and Michael F. Zaeh

Metals 2021, 11(3), 502; https://doi.org/10.3390/met11030502 - 18 Mar 2021

Viewed by 2447

Abstract

Friction press joining is an innovative joining process for bonding plastics and metals without additives in an overlap configuration. This paper presents for the first time a model-based approach for designing a multi-variable model predictive control (MPC) for friction press joining. For system [...] Read more.

Friction press joining is an innovative joining process for bonding plastics and metals without additives in an overlap configuration. This paper presents for the first time a model-based approach for designing a multi-variable model predictive control (MPC) for friction press joining. For system modeling, a differential equation based on the heat flows was proposed and modeled as a torque-dependent function. With this model, it is possible to consider cross-effects between the axial force and the friction zone temperature. With this theoretical approach, adaptive model-predictive process control was implemented and validated for different material combinations (EN AW-6082-T6; EN AW-2024-T3; PE-HD; PA6-GF30; PPS-CF). It could be shown that the MPC has excellent control accuracy even when model uncertainties are introduced. Based on these findings, a 1D Finite Differential Method multi-layer model was developed to calculate the temperature in the plastic component, which is not measurable in situ (r = 0.93). These investigations demonstrate the high potential of the multi-variable MPC for plastic-metal direct joining. Full article

(This article belongs to the Special Issue Friction Stir Welding/Processing Technology)

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13 pages, 4382 KiB

Open AccessFeature PaperArticle

Characterization of Shock Wave Damages in Explosion Welded Mo/Cu Clads

by Pradeep Kumar Parchuri, Shota Kotegawa, Kazuhiro Ito, Hajime Yamamoto, Akihisa Mori, Shigeru Tanaka and Kazuyuki Hokamoto

Metals 2021, 11(3), 501; https://doi.org/10.3390/met11030501 - 18 Mar 2021

Cited by 4 | Viewed by 2668

Abstract

The shock wave damage during explosive welding has not been reported in a flyer Mo plate of the Mo/Cu clads. However, it would be an inevitable problem in group VI elements. This study was aimed to characterize the shock wave damage in the [...] Read more.

The shock wave damage during explosive welding has not been reported in a flyer Mo plate of the Mo/Cu clads. However, it would be an inevitable problem in group VI elements. This study was aimed to characterize the shock wave damage in the Mo plate, that is less brittle than a W plate, of explosive welded Mo/Cu clads. Cladding at low horizontal collision velocities leading to high collision angles was expected to enhance the shock wave damage, and the clads resulted in less elongation in bending tests. On the other hand, in the clads obtained at high horizontal collision velocities (HCVs) with low collision angles, their bending elongation increased significantly. The shock wave damage penetrated from the surface of a Mo plate to the Mo/Cu interface, and thus reducing thickness of a Mo plate of bending specimens increased bending plastic strain. The shock wave damage is associated with kinetic energy imparted to the flyer Mo plate, and thus loss of kinetic energy due to formation of an intermediate layer at the interface and reducing thickness of a flyer Mo plate would be very helpful for decrease of shock wave damage. Full article

(This article belongs to the Special Issue Dissimilar Material Welding and Joining)

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10 pages, 2812 KiB

Open AccessFeature PaperArticle

Austenitic Stainless-Steel Reinforcement for Seawater Sea Sand Concrete: Investigation of Stress Corrosion Cracking

by Xiang Yu, Saad Al-Saadi, Isha Kohli, Xiao-Ling Zhao and R. K. Singh Raman

Metals 2021, 11(3), 500; https://doi.org/10.3390/met11030500 - 17 Mar 2021

Cited by 8 | Viewed by 2816

Abstract

Seawater and sea sand concrete (SWSSC) is a highly attractive alternative to normal concrete (NC) that requires huge amounts of fresh water and river sand. However, reinforcements of stainless steel (instead of mild steel that is used in NC) may be required for [...] Read more.

Seawater and sea sand concrete (SWSSC) is a highly attractive alternative to normal concrete (NC) that requires huge amounts of fresh water and river sand. However, reinforcements of stainless steel (instead of mild steel that is used in NC) may be required for SWSSC. This article reports investigation of stress corrosion cracking (SCC) of AISI 316 stainless steel (SS) in simulated SWSSC and NC environments, with and without addition of silica to SWSSC and NC, employing slow strain rate testing (SSRT) at 25 and 60 °C. For the purpose of comparison, SCC of SS was also investigated in simulated seawater (SW) solution. SS showed no SCC at 25 °C in any of the test solutions. Indications of SCC were seen in SW at 60 °C, but no features of SCC in SWSSC and NC at 60 °C, as suggested by scanning electron microscopy (SEM) fractographs. While the absence of SCC in SWSSC and NC is attributed to the highly passivating alkaline condition, its absence in SWSSC also indicates the role of alkalinity to predominate the deleterious role of chloride content of SWSSC. However, the addition of silicate to SWSSC or NC triggers transgranular SCC to SS at 60 °C, as evidenced by the fractography. Full article

(This article belongs to the Special Issue Environmentally Assisted Cracking)

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16 pages, 4982 KiB

Open AccessFeature PaperArticle

Influence of Ceramic Particles Character on Resulted Properties of Zinc-Hydroxyapatite/Monetite Composites

by Klára Hosová, Jan Pinc, Andrea Školáková, Vilém Bartůněk, Petr Veřtát, Tereza Školáková, Filip Průša, Dalibor Vojtěch and Jaroslav Čapek

Metals 2021, 11(3), 499; https://doi.org/10.3390/met11030499 - 17 Mar 2021

Cited by 10 | Viewed by 2423

Abstract

Zinc and its alloys seem to be promising candidates for biodegradable applications. Those materials are often modified by other elements or compounds in order to enhance their properties. The combination of zinc and apatites is challenging for several reasons. However, the advantages connected [...] Read more.

Zinc and its alloys seem to be promising candidates for biodegradable applications. Those materials are often modified by other elements or compounds in order to enhance their properties. The combination of zinc and apatites is challenging for several reasons. However, the advantages connected with the biological aspects suggest the need for further research into such materials. In this study, three zinc-based composites with 4 and 8 wt. % of nanohydroxyapatite or nanomonetite (Zn-4MO, Zn-4HA, Zn-8HA) were prepared by sintering and subsequent extrusion. Materials prepared in this way were characterized from the microstructural, mechanical and corrosion point of view. The obtained results showed a significant influence of particle character (amount and morphology) on the strength and ductility of the prepared materials. In case of Zn-4MO, the presence of monetite significantly increased the ductility compared with the other materials. In addition, the increment of the degradation rate caused by the presence of monetite was observed as well. All obtained results pointed out to significant advantages of monetite for the preparation of Zn-apatite composites compared with hydroxyapatite. Full article

(This article belongs to the Special Issue Processing and Treatment of Hexagonal Metallic Materials)

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20 pages, 7586 KiB

Open AccessFeature PaperArticle

The Concept of a Novel Path Planning Strategy for Wire + Arc Additive Manufacturing of Bulky Parts: Pixel

by Rafael Pereira Ferreira and Américo Scotti

Metals 2021, 11(3), 498; https://doi.org/10.3390/met11030498 - 17 Mar 2021

Cited by 14 | Viewed by 4044

Abstract

An innovative trajectory strategy was proposed and accessed for wire arc additive manufacturing (WAAM), applicable to different and more complex geometries, rather than being a single solution. This strategy, named Pixel, can be defined as a complex multitask procedure to carry out optimized [...] Read more.

An innovative trajectory strategy was proposed and accessed for wire arc additive manufacturing (WAAM), applicable to different and more complex geometries, rather than being a single solution. This strategy, named Pixel, can be defined as a complex multitask procedure to carry out optimized path planning, whose operation is made through computational algorithms (heuristics), with accessible computational resources and tolerable computational time. The model layers are fractioned in squared grids, and a set of dots is systematically generated and distributed inside the sliced outlines, resembling pixels on a screen, over which the trajectory is planned. The Pixel strategy was based on creating trajectories from the technique travelling salesman problem (TSP). Unlike existing algorithms, the Pixel strategy uses an adapted greedy randomized adaptive search procedure (GRASP) metaheuristic, aided by four concurrent trajectory planning heuristics, developed by the authors. Interactions provide successive trajectories from randomized initial solutions (global search) and subsequent iterative improvements (local search). After all recurrent loops, a trajectory is defined and written in machine code. Computational evaluation was implemented to demonstrate the effect of each of the heuristics on the final trajectory. An experimental evaluation was eventually carried out using two different not easily printable shapes to demonstrate the practical feasibility of the proposed strategy. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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14 pages, 11325 KiB

Open AccessArticle

The Process Design and Rapid Superplastic Forming of Industrial AA5083 for a Fender with a Negative Angle in a Small Batch

by Zhihao Du, Guofeng Wang and Hailun Wang

Metals 2021, 11(3), 497; https://doi.org/10.3390/met11030497 - 17 Mar 2021

Cited by 6 | Viewed by 2621

Abstract

A front automobile fender with a negative angle was trial produced via rapid superplastic forming (SPF) technology. The tensile test of industrial AA5083 was carried out at elevated temperatures, and the results showed that the maximum elongation was 242% at 480 °C/0.001 s [...] Read more.

A front automobile fender with a negative angle was trial produced via rapid superplastic forming (SPF) technology. The tensile test of industrial AA5083 was carried out at elevated temperatures, and the results showed that the maximum elongation was 242% at 480 °C/0.001 s⁻¹. A rigid-plastic constitutive model of the SPF process was established. Initial dies of preforming and final forming were designed. The finite element method (FEM) was used to simulate the forming process and predict the thickness distribution of different areas. Furthermore, the dies were optimized to make the thickness distribution uniform. In the final structure, the maximum thinning ratio decreased from 83.2% to 63% due to the optimized design of the forming dies. The front automobile fender was then successfully fabricated by the preforming process and final forming process at 480 °C. A thickness measurement was carried out, and the minimum thickness of the preforming structure was 2.17 mm at the transverse tank, while that of the final structure was 2.49 mm near the edge of the lamp orifice. The average grain size grew from 20 to 35 μm. The grain growth led to the reduction of mechanical properties. Compared with the mechanical properties of the initial material, the maximum decrease in tensile strength for the material after superplastic forming was 5.78%, and that of elongation was 18.5%. Full article

(This article belongs to the Special Issue Machinability and Tribological Performance of Advanced Alloys)

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19 pages, 59517 KiB

Open AccessArticle

Feasibility Study of the Cranial Implant Fabricated without Supports in Electron Beam Melting

by Khaja Moiduddin, Syed Hammad Mian, Wadea Ameen, Hisham Alkhalefah and Abdul Sayeed

Metals 2021, 11(3), 496; https://doi.org/10.3390/met11030496 - 17 Mar 2021

Cited by 5 | Viewed by 2630

Abstract

Additive manufacturing (AM), particularly electron beam melting (EBM), is becoming increasingly common in the medical industry because of its remarkable benefits. The application of personalized titanium alloy implants produced using EBM has received considerable attention in recent times due to their simplicity and [...] Read more.

Additive manufacturing (AM), particularly electron beam melting (EBM), is becoming increasingly common in the medical industry because of its remarkable benefits. The application of personalized titanium alloy implants produced using EBM has received considerable attention in recent times due to their simplicity and efficacy. However, these tailored implants are not cost-effective, placing a tremendous strain on the patient. The use of additional materials as support during the manufacturing process is one of the key causes of its high cost. A lot of research has been done to lessen the use of supports through various types of support designs. There is indeed a noticeable paucity of studies in the literature that have examined customized implants produced without or minimal supports. This research, therefore, reports on the investigation of cranial implants fabricated with and without supports. The two personalized implants are evaluated in terms of their cost, fabrication time, and accuracy. The study showed impressive results for cranial implants manufactured without supports that cost 39% less than the implants with supports. Similarly, the implant’s (without supports) build time was 18% less than its equivalent with supports. The two implants also demonstrated similar fitting accuracy with 0.2613 mm error in the instance of implant built without supports and 0.2544 mm for the implant with supports. The results indicate that cranial implants can be produced without EBM supports, which can minimize both production time and cost substantially. However, the manufacture of other complex implants without supports needs further study. The future study also requires a detailed review of the mechanical and structural characteristics of cranial implants built without supports. Full article

(This article belongs to the Special Issue Additive Manufacturing Research and Applications)

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