Metals

18 pages, 5584 KiB

Open AccessArticle

Physical and Mechanical Properties of Ti-Zr-Nb Alloys for Medical Use

by Konstantin V. Sergienko, Sergei V. Konushkin, Mikhail A. Kaplan, Artem D. Gorbenko, Yucheng Guo, Elena O. Nasakina, Maria A. Sudarchikova, Tatiana M. Sevostyanova, Yaroslava A. Morozova, Lyudmila A. Shatova, Sofia A. Mikhlik, Mikhail A. Sevostyanov and Alexey G. Kolmakov

Metals 2024, 14(11), 1311; https://doi.org/10.3390/met14111311 - 20 Nov 2024

Abstract

The work described in this article is aimed at investigating the properties of a group of Ti-Zr-Nb alloys. In modern orthopedics and traumatology, the use of materials for bone implants with a minimum modulus of elasticity is becoming increasingly important. This is due [...] Read more.

The work described in this article is aimed at investigating the properties of a group of Ti-Zr-Nb alloys. In modern orthopedics and traumatology, the use of materials for bone implants with a minimum modulus of elasticity is becoming increasingly important. This is due to a number of advantages that allow for better integration of the implants with the bone tissue, including the reduction in the detrimental effect of the load-shielding effect, a better load distribution, and stress distribution, which allows for increasing the life of the implant. It is known that the lowest modulus of elasticity in titanium alloys at normal temperature is achieved by the phase composition consisting of metastable β-phase. It is possible to achieve the desired structure by a combination of alloy composition selection and heat treatment. Quenching of titanium alloys allows for the high-temperature β-phase to be fixed. This paper provides justification of the choice of compositions of the studied alloys by calculation methods. The structure of alloys after melting in a vacuum electric arc furnace in an argon environment was studied. The ingots obtained had a dendritic structure. Homogenizing annealing in a vacuum furnace at 1000 °C for 4 h was used to equalize the composition. The structure of the alloyed sheets after hot rolling and hot rolling and quenching was investigated. The microstructure of the plates in both variants had uniform grains of polyhedral shape. X-ray phase analysis of the plates showed that the content of metastable β-phase was 100% before and after quenching. Microhardness testing of the plates showed no significant effect of quenching. The result of the mechanical properties study showed an increase in the plasticity of the material after quenching, with the tensile plots of the samples after quenching reflecting the area where the reverse phase transition of β’<-> α’’ occurs. Mechanical studies by cyclic loading showed the presence of a superelasticity effect. The Young’s modulus study gave a result of 51 GPa for one of the compositions studied. The combination of properties of the materials under investigation has the potential for promising use as a basis for bone implants. Full article

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10 pages, 8729 KiB

Open AccessArticle

Effect of Extrusion Ratio on Microstructure and Properties of Al-1.5Fe-0.4Cr Alloy Obtained by Continuous Rheo-Extrusion

by Yunhe Ning, Li Yang, Minqiang Gao and Renguo Guan

Metals 2024, 14(11), 1310; https://doi.org/10.3390/met14111310 - 20 Nov 2024

Abstract

Due to the shortage of primary Al resources and significant consumption of Al resources, recycled Al has become a focus of attention. In the process of recycling Al, the Fe element is the most hazardous impurity element, and the coarse Fe-containing phases lead [...] Read more.

Due to the shortage of primary Al resources and significant consumption of Al resources, recycled Al has become a focus of attention. In the process of recycling Al, the Fe element is the most hazardous impurity element, and the coarse Fe-containing phases lead to a reduction in the mechanical properties of recycled Al. In this work, an Al alloy with 1.5 wt% Fe and 0.4 wt% Cr was viewed as a recycled Al, approximately. The continuous rheo-extrusion technique was used to refine the Fe-containing phases in the Al-1.5Fe-0.4Cr alloy, improving the mechanical properties of the alloy. The effect of the extrusion ratio on the microstructure and properties of the continuous rheo-extrusion was investigated. The results showed that, when the extrusion ratio was changed from 4 to 5, the percentage of low-angle grain boundaries in the alloy increased from 45.5% to 53.1%, the average orientation angle reduced from 23.9° to 23.3°, and the grain size decreased from 4.3 ± 0.2 μm to 2.6 ± 0.1 μm. As a result, the ultimate tensile strength, yield strength and elongation of the alloy, with an extrusion ratio of 5, were 161.5 ± 2.8 MPa, 112.3 MPa ± 2.6, and 36.9% ± 1.6%, respectively. Grain refinement and Fe-containing phase refinement were responsible for the improvement in the mechanical properties of the alloy. Full article

(This article belongs to the Special Issue Advances in Lightweight Material Forming Technology)

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21 pages, 13020 KiB

Open AccessArticle

Comparison of Strengthening Mechanism of the Nb, V, and Nb-V Micro-Alloyed High-Strength Bolt Steels Investigated by Microstructural Evolution and Strength Modeling

by Hui Wen, Qian Wang, Yueyuan Dou, Qiang Wang, Xiaochun Xu and Qingfeng Wang

Metals 2024, 14(11), 1309; https://doi.org/10.3390/met14111309 - 20 Nov 2024

Abstract

The strengthening mechanism of Nb, V, and Nb-V micro-alloyed high-strength bolt steels was investigated and compared using microstructural evolution and strength modeling. Optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the microstructure [...] Read more.

The strengthening mechanism of Nb, V, and Nb-V micro-alloyed high-strength bolt steels was investigated and compared using microstructural evolution and strength modeling. Optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the microstructure and precipitations. The results show that Nb-V composite micro-alloyed steel possessed a higher yield strength compared with Nb or V micro-alloyed steel when quenched at 870 °C and tempered at 450–650 °C. Furthermore, the strength increment of Nb-V micro-alloyed steel with respect to Nb or V micro-alloyed steel reached the maximum at a tempering temperature of 600 °C, and precipitation strengthening and dislocation strengthening presented higher strength contributions in Nb-V micro-alloyed steel than in Nb micro-alloyed steel and V micro-alloyed steel owing to the higher volume fraction and finer precipitate size. When V was added in combination with Nb in steel, the number of Nb-rich carbonitrides increased, which resulted in a higher volume fraction of the effective pinning particles-Nb-rich (Ti,Nb,V)(C,N) with diameters smaller than 50 nm and led to an enhanced refinement of the prior austenite grain. In addition, Nb could reduce the consumption of V during quenching, allowing more V to be solid-solved in the matrix after quenching, thereby further enhancing the precipitation strengthening effect of V during tempering. Full article

(This article belongs to the Special Issue Microalloying in Ferrous and Non-ferrous Alloys)

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20 pages, 4740 KiB

Open AccessArticle

Extrusion-Based Additive Manufacturing of WC-10Co Cemented Carbide Produced with Bimodal Ultrafine/Micron WC Particles

by Mikhail Sergeevich Lebedev, Vladimir Vasilevich Promakhov, Lyudmila Yurievna Ivanova, Natalya Valentinovna Svarovskaya, Marina Ivanovna Kozhukhova and Marat Izralievich Lerner

Metals 2024, 14(11), 1308; https://doi.org/10.3390/met14111308 - 20 Nov 2024

Abstract

This article researches the effect of ultrafine (submicron) tungsten carbide powder addition on the microstructure and mechanical properties of WC-10Co cemented carbide produced by the extrusion of a highly filled polymer. This addition aims to develop a material with a good combination of [...] Read more.

This article researches the effect of ultrafine (submicron) tungsten carbide powder addition on the microstructure and mechanical properties of WC-10Co cemented carbide produced by the extrusion of a highly filled polymer. This addition aims to develop a material with a good combination of toughness, hardness, and yield strength. The results demonstrate that increasing the ratio between ultrafine and micron WC particles from 0/100 to 45/55 in the initial powder results in successive decreases in average grain size from 2.61 µm to 1.75 µm. When 45% of ultrafine powder is introduced into the mixture, a high number of fine tungsten carbide grains is produced. This promotes inter-grain contact and reduces the free path of the binder phase, which results in a more rigid structure and in the material becoming more brittle. The best mechanical characteristics are achieved in WC-10Co cemented carbide with 15% content of ultrafine powder in the total weight of WC. Here, a microstructure with a bimodal distribution of tungsten carbide grains in a virtually non-intermittent cobalt phase was formed. This allowed us to achieve a compressive strength of 2449 MPa at the deformation of 6.69%, while the modulus of elasticity was 38.8 GPa. The results indicate a good combination of strength and ductility properties in the developed cemented carbide. Full article

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14 pages, 4618 KiB

Open AccessArticle

Microstructural and Morphological Properties of AlNiCo and CoNi Alloys: An In-Depth Study Based on Low-Energy Mechanical Alloying

by Gilberto Cruz Nieto, Jesús Noé Rivera Olvera, Sebastián Díaz de la Torre, Vicente Garibay Febles, Jesús Palacios Gómez, Leonardo Gonzalez Reyes and Lucía Graciela Diaz Barriga Arceo

Metals 2024, 14(11), 1307; https://doi.org/10.3390/met14111307 (registering DOI) - 20 Nov 2024

Abstract

This study focused on synthesizing AlNiCo and CoNi materials using a low-energy milling process. The aim was to explore the formation of low-energy phases in both systems, contrasting with the typical research on phases formed under high-energy conditions. In the Co-20 wt% Ni [...] Read more.

This study focused on synthesizing AlNiCo and CoNi materials using a low-energy milling process. The aim was to explore the formation of low-energy phases in both systems, contrasting with the typical research on phases formed under high-energy conditions. In the Co-20 wt% Ni system, the phases

{Co}_{0.75} {Ni}_{0.25}

and Ni were identified, as well as the FCC cubic phase of CoNi, using X-ray diffraction (XRD) with a molybdenum radiation source. The observed behavior aligned closely with the miscibility curve in the equilibrium phase diagram, which included a region of alloys with varying structures and similar compositions. A notable feature was the presence of a predominantly dispersed hexagonal Ni zone, consisting of nanoparticles. Transmission electron microscopy (TEM) was employed to observe the FCC CoNi phase, which displayed a specific arrangement. AlNiCo and CoNi alloys were successfully synthesized through mechanical alloying, incorporating equilibrium and non-equilibrium phases. Full article

(This article belongs to the Special Issue Powder Metallurgy of Metallic Materials)

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15 pages, 26265 KiB

Open AccessArticle

Reduction Behaviors of Silicon–Ferrite from Calcium and Aluminum in a Hydrogen-Rich Blast Furnace

by Keshuai Du, Changqing Hu, Xuefeng Shi and Guangqing Yang

Metals 2024, 14(11), 1306; https://doi.org/10.3390/met14111306 - 19 Nov 2024

Abstract

Silicon–ferrite from calcium and aluminum (SFCA) is one of the primary binding phases in sinter. To better investigate the reduction process of SFCA under hydrogen-rich conditions in a blast furnace, isothermal reduction experiments were designed using three different hydrogen volume fractions (6%, 10%, [...] Read more.

Silicon–ferrite from calcium and aluminum (SFCA) is one of the primary binding phases in sinter. To better investigate the reduction process of SFCA under hydrogen-rich conditions in a blast furnace, isothermal reduction experiments were designed using three different hydrogen volume fractions (6%, 10%, and 14%) at temperatures within the blast furnace’s lump zone range (1073 K, 1173 K, and 1273 K). The experimental results revealed that the reduction of SFCA proceeds in two stages: in the first stage, SFCA is initially reduced to Fe3O4; in the second stage, Fe3O4 is further reduced to FeO, with the equilibrium phases being FeO, Ca2Al2SiO7, and Ca2SiO4. The fastest reduction rate was observed at 1273 K. When the hydrogen volume fraction was 6% and the temperatures were 1073 K, 1173 K, and 1273 K, the reaction mechanism followed the 3D diffusion model (G-B), with an apparent activation energy of 32.087 kJ·

{mol}^{- 1}

and a pre-exponential factor of 0.1419. In comparison, at hydrogen volume fractions of 10% and 14%, the reaction mechanism shifted to the Shrinking core model (n = 3). The findings of this study can provide guidance for actual production and optimization of blast furnace parameters aimed at achieving low-carbon emissions in the steel-making process. Full article

15 pages, 38734 KiB

Open AccessArticle

Material Flow and Microstructural Evolution in Friction Stir Welding of LAZ931 Duplex Mg-Li Alloys

by Shiquan Cui, Wenguan Cao, Qi Zhang, Liguo Wang, Yufeng Sun and Shaokang Guan

Metals 2024, 14(11), 1305; https://doi.org/10.3390/met14111305 - 19 Nov 2024

Abstract

The material flow behavior during friction stir welding (FSW) plays a critical role in the quality of final joints. In this study, the FSW of LAZ931 duplex Mg alloy was carried out at a rotation speed of 800 rpm and welding speeds of [...] Read more.

The material flow behavior during friction stir welding (FSW) plays a critical role in the quality of final joints. In this study, the FSW of LAZ931 duplex Mg alloy was carried out at a rotation speed of 800 rpm and welding speeds of 50, 100, and 200 mm/min, respectively. A thin pure Mg strip inserted at the interface between the two Mg-Li alloy plates was used as a marker to study the flow behavior of the materials in the FSW process. Sound welds with no defects were obtained for all three welding speeds. The microstructural evaluations along the marker on the horizontal cross-section around the keyhole of the welds were characterized. As the welding speed increased, the marker came closer to the keyhole, indicating the decreased extent of the plastic deformation of the material. In the shoulder-affected zone (SAZ), the thickness of the marker reduced gradually in the accelerating stage and finally accumulated together in the decelerating stage. However, in the pin-affected zone (PAZ), the thickness of the marker reduced sharply in the accelerating stage and then became dispersed in the decelerating stage, and the degree of dispersion decreased as the weld speed increased. As a result, an elongated grain structure was formed in the SAZ, while two equiaxial grain structures were formed in the PAZ. The material on the advancing side was refined by the pin and deposited in the weld to form a fine equiaxial grain structure due to the high strain rate. In contrast, the material on the retreating side was pushed by the pin and thus directly deposited in the weld to form a coarse equiaxial grain structure. In addition, the area of the fine equiaxial grain structure was reduced obviously with the increase in welding speed. Full article

(This article belongs to the Special Issue Characterization, Analysis, and Defects in Metallic Materials and Their Welds)

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20 pages, 31298 KiB

Open AccessArticle

Additive Manufacturing and Precipitation Hardening of Low-Alloyed Copper Alloys Containing Chromium and Hafnium

by Julia Dölling, Samira Gruber, Felix Kovermann, Lukas Stepien, Elmar Beeh, Elena Lopez, Christoph Leyens, Hans-Günther Wobker and Andreas Zilly

Metals 2024, 14(11), 1304; https://doi.org/10.3390/met14111304 - 19 Nov 2024

Abstract

Copper alloys with chromium and hafnium offer the possibility of precipitation hardening and combine enhanced strength with high electrical and thermal conductivities. The production process, which starts with raw materials, involves powder production by gas atomization and leads to additive manufacturing by laser [...] Read more.

Copper alloys with chromium and hafnium offer the possibility of precipitation hardening and combine enhanced strength with high electrical and thermal conductivities. The production process, which starts with raw materials, involves powder production by gas atomization and leads to additive manufacturing by laser powder bed fusion with different parameter sets. The aim is to utilize precipitation reactions afterwards in CuHf0.7Cr0.35 during temperature exposure for further property optimization. This research focuses on the low-alloyed copper alloy with hafnium and chromium, compares this with conventionally manufactured specimens, and relates the alloy to additively manufactured specimens of other benchmark alloys such as CuCr1Zr. Measurements of hardness and electrical conductivity are accompanied by metallographic investigations to understand the behavior of CuHf0.7Cr0.35 manufactured by generative methods. In the as-built condition, melting traces remain visible in the microstructure, and hardness values of 101 HV and an electrical conductivity of 17.5 MS/m are reached. Solution annealing completely recrystallizes the microstructure, and the following quenching holds further alloying elements in supersaturated solid solution, resulting in 73 HV and 16.5 MS/m. Subsequent target-oriented precipitation reactions enable peak values of about 190 HV and 42 MS/m. Future research will assess mechanical and physical properties at elevated temperatures and evaluate possible applications. Full article

(This article belongs to the Special Issue Recent Developments in Laser Additive Manufacturing of Metallic Materials)

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12 pages, 5433 KiB

Open AccessArticle

Low-Acid Leaching for Preferential Lithium Extraction and Preparation of Lithium Carbonate from Rare Earth Molten Salt Electrolytic Slag

by Zaoming Chen, Ruzhen Peng, Zhen Xiang, Fupeng Liu, Jinliang Wang and Xirong Chen

Metals 2024, 14(11), 1303; https://doi.org/10.3390/met14111303 - 19 Nov 2024

Abstract

In this work, lithium was preferentially recovered through the low-acid leaching from rare earth molten salt electrolytic slag (REMSES) with a leaching temperature of 60 °C. The influence on lithium extraction was investigated in detail in different leaching conditions. The optimal conditions were [...] Read more.

In this work, lithium was preferentially recovered through the low-acid leaching from rare earth molten salt electrolytic slag (REMSES) with a leaching temperature of 60 °C. The influence on lithium extraction was investigated in detail in different leaching conditions. The optimal conditions were as follows: liquid-to-solid ratio (10 mL/g), sulfuric acid concentration (0.8 mol/L), leaching time (60 min) and leaching temperature (60 °C). This yielded a lithium extraction rate of 98.52% and a lithium carbonate purity of 99.5%. It was fitted using an empirical model; the kinetics showed that internal diffusion control conformed to the low-acid leaching reaction, which had an apparent activation energy of 10.81 kJ/mol for lithium. The total profit from the whole process was USD 0.2576 when dealing with 1.0 kg of REMSES. Moreover, in the sulfuric acid system, the leaching reaction mechanism was carefully investigated between 30 and 90 °C. An innovative process of recovering lithium from REMSES was achieved with environmental friendliness and good economic returns. Compared to traditional leaching using concentrated sulfuric acid, this cleaner recycling method conforms to the concept of green, low-carbon sustainable development, with high lithium selectivity, low impurity content in the filtrate and low acid consumption. Full article

(This article belongs to the Special Issue Deposition of Metals and Their Application in Catalytic Processes of Energy Interest (2nd Edition))

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17 pages, 1824 KiB

Open AccessArticle

Microstructural and Magnetic Characteristics of High-Entropy FeCoNiMnTi Alloy Produced via Mechanical Alloying

by Chérif Ben Ammar, Nawel Khitouni, Marzook Alshammari, Abdulrahman Alsawi, Mohamed Khitouni, Joan-Josep Suñol and Mahmoud Chemingui

Metals 2024, 14(11), 1302; https://doi.org/10.3390/met14111302 - 18 Nov 2024

Abstract

In the current study, X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer techniques were used to examine the impact of milling time on the microstructural and magnetic characteristics of Fe₃₀Co₂₀Ni₂₀Mn₂₀Ti₁₀ (at%) produced via [...] Read more.

In the current study, X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer techniques were used to examine the impact of milling time on the microstructural and magnetic characteristics of Fe₃₀Co₂₀Ni₂₀Mn₂₀Ti₁₀ (at%) produced via mechanical alloying. Results demonstrate that phase change is dependent on up to 30 h of milling. In terms of the hcp-Fe₂Ti intermetallic and the BCC-FeCoNiMnTi supersaturated solid solution, the system maintains its two-phase structure at higher times. Additionally, the final average crystallite size was estimated to be approximately 10 nm, and the lattice strain was found to be between 0.95 and 1.15 %. As a function of milling time, the magnetic properties are discussed with the microstructural and crystallographic alterations. The collected powder after 100 h of milling has an Ms value of 28 emu/g and a Hc value of 25 Am⁻¹, which is consistent with exceptional soft magnetics. This is essentially due to the Fe₂Ti intermetallic and the BCC-Fe-based solid solution production, together with the refinement of the crystallite size. Furthermore, the presence of paramagnetic Ti atoms in solid solution and the development of high densities of defects and interfaces have been connected to the low value of Ms. Full article

(This article belongs to the Special Issue Feature Papers in Crystallography and Applications of Metallic Materials (2nd Edition))

35 pages, 6044 KiB

Open AccessArticle

The Study and Application on Ductile Fracture Criterion of Dual Phase Steels During Forming

by Lianxing Zhao, Xiaotao Fei, Chaifeng Sun, Peng Liu and Di Li

Metals 2024, 14(11), 1301; https://doi.org/10.3390/met14111301 - 18 Nov 2024

Abstract

High-strength steel exhibits complex fracture behavior due to the interplay between shear and necking mechanisms during stamping and forming processes, posing challenges to achieving the dimensional accuracy and reliability demanded for automotive body panels. Existing prediction methods often fail to simultaneously account for [...] Read more.

High-strength steel exhibits complex fracture behavior due to the interplay between shear and necking mechanisms during stamping and forming processes, posing challenges to achieving the dimensional accuracy and reliability demanded for automotive body panels. Existing prediction methods often fail to simultaneously account for both tensile and shear fracture characteristics, thereby limiting their predictive accuracy under diverse stress conditions. To address this limitation, we propose a ductile fracture criterion that integrates both tensile and shear mechanisms, calibrated using a single tensile–shear test to facilitate practical engineering applications. This study investigates the fracture characteristics of DP780 dual-phase steel through numerical analysis and tensile–shear experiments. The findings establish a relationship between stress triaxiality and ultimate fracture strain across varying stress states, represented by the B–W curve. Simulations reveal distinct stress triaxiality behaviors under different loading conditions: under uniaxial tensile loading, triaxiality ranges from 0.33 to 0.6, with fracture strain decreasing monotonically as triaxiality increases. Under shear loading, triaxiality ranges from 0 to 0.33, with fracture strain increasing monotonically as triaxiality rises. Additional bending simulations validate that this criterion, along with the B–W curve, reliably predicts the fracture behavior of DP780, offering an effective tool for predicting fracture in dual-phase steels during stamping and forming processes. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

15 pages, 18440 KiB

Open AccessArticle

Evaluation of Continuous GMA Welding Characteristics Based on the Copper-Plating Method of Solid Wire Surfaces

by Dong-Yoon Kim and Jiyoung Yu

Metals 2024, 14(11), 1300; https://doi.org/10.3390/met14111300 - 18 Nov 2024

Abstract

Gas metal arc welding (GMAW) is widely used in various industries, such as automotive and heavy equipment manufacturing, because of its high productivity and speed, with solid wires being selected based on the mechanical properties required for welded joints. GMAW consists of various [...] Read more.

Gas metal arc welding (GMAW) is widely used in various industries, such as automotive and heavy equipment manufacturing, because of its high productivity and speed, with solid wires being selected based on the mechanical properties required for welded joints. GMAW consists of various components, among which consumables such as the contact tip and continuously fed solid wire have a significant impact on the weld quality. In particular, the copper-plating method can affect the conductivity and arc stability of the solid wire, causing differences in the continuous welding performance. This study evaluated the welding performance during 60 min continuous GMAW using an AWS A5.18 ER70S-3 solid wire, which was copper-plated using chemical plating (C-wire) and electroplating (E-wire). The homogeneity and adhesion of the copper-plated surface of the E-wire were superior to those of the C-wire. The E-wire exhibited better performance in terms of arc stability. The wear rate of the contact tip was approximately 45% higher when using the E-wire for 60 min of welding compared with the C-wire, which was attributed to the larger variation rate in the cast and helix in the E-wire. Additionally, the amount of spatter adhered to the nozzle during 60 min, with the E-wire averaging 5.9 g, approximately half that of the C-wire at 12.9 g. The E-wire exhibits superior arc stability compared with the C-wire based on the spatter amount adhered to the nozzle. This study provides an important reference for understanding the impact of copper plating methods and wire morphology on the replacement cycles of consumable welding parts in automated welding processes such as continuous welding and wire-arc additive manufacturing. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels (2nd Edition))

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12 pages, 4713 KiB

Open AccessFeature PaperArticle

Liquid Metal Leaching for Rare Earth Magnet Recycling

by Emmanuel Opoku, Chinenye Chinwego, Adam Powell and Brajendra Mishra

Metals 2024, 14(11), 1299; https://doi.org/10.3390/met14111299 - 18 Nov 2024

Abstract

This study investigates the optimization of liquid metal leaching for recycling rare earth elements (REEs) from NdFeB magnets, a critical step in addressing the increasing demand for these materials in various high-tech applications. We explored the effects of leaching time, stirring, and magnet [...] Read more.

This study investigates the optimization of liquid metal leaching for recycling rare earth elements (REEs) from NdFeB magnets, a critical step in addressing the increasing demand for these materials in various high-tech applications. We explored the effects of leaching time, stirring, and magnet demagnetization on the yield of the leaching process using molten magnesium. Conducted at 900 °C, our experiments assessed the leaching process over periods of 2, 3.5, and 5 h, with and without the application of stirring. Our findings show that longer leaching times considerably increase neodymium (Nd) and praseodymium (Pr) leaching yield, with a notable peak in efficiency found at 5 h. Stirring improved the uniformity of REEs significantly and resulted in up to 80% yield. Furthermore, our data show that pre-leaching magnet demagnetization improves leaching specificity, significantly reducing the presence of non-target metals like nickel and copper. These insights offer a pathway to more cost-effective recycling of REEs from magnet scrap, which is essential for environmentally conscious management of resources amid the escalating global demand for REEs. Full article

(This article belongs to the Special Issue Metal Processing for Sustainability)

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10 pages, 12436 KiB

Open AccessArticle

Analysis of Stored Energy Distribution in Three Directions of Tantalum in Deformed and Annealed States

by Yanjun Zhou, Yahui Liu, Qianqian Zhu and Shaodan Yang

Metals 2024, 14(11), 1298; https://doi.org/10.3390/met14111298 - 17 Nov 2024

Abstract

Microstructures in high-purity tantalum (Ta) were analyzed in three directions, focusing on the evolution of stored energy during rolling and heating processes. Results indicated significant fluctuation in the transaction direction (TD) surface, which was observed in both deformed and annealed states. This phenomenon [...] Read more.

Microstructures in high-purity tantalum (Ta) were analyzed in three directions, focusing on the evolution of stored energy during rolling and heating processes. Results indicated significant fluctuation in the transaction direction (TD) surface, which was observed in both deformed and annealed states. This phenomenon is attributed to the alternately arranged {111}<uvw>(<111>//normal direction (ND)) and {100}<uvw>(<100>//ND) oriented grains, coupled with the substantial energy difference between them, even after 12 passes. Additionally, through the estimation and calculation of stored energy based on band contrast from electron backscatter diffraction and X-ray line profile analyses, the recovery kinetics for different directions and grain types were quantitatively assessed. Findings revealed that the dislocation density of {111} grains decreased significantly more than that of {100} grains when annealed at 1073 K. The degree of recovery was closely related to temperature, dislocation density, and dislocation type. Full article

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14 pages, 5811 KiB

Open AccessArticle

Influence of Cold-Rolling Processes on the Dimensional Accuracy and Roughness of Small-Diameter Thick-Walled Seamless Tubes

by Xiuping Ding, Ran Li, Pengfei Jin, Weijie Wang, Cheng Zhang, Minyu Ma and Jinfeng Huang

Metals 2024, 14(11), 1297; https://doi.org/10.3390/met14111297 - 16 Nov 2024

Abstract

Cold pilgering is widely utilized in high-end applications for the precise shaping of seamless tubes due to its capacity for large deformation, which reduces the number of deformation processes and shortens production cycles. However, there is a gap in the research on the [...] Read more.

Cold pilgering is widely utilized in high-end applications for the precise shaping of seamless tubes due to its capacity for large deformation, which reduces the number of deformation processes and shortens production cycles. However, there is a gap in the research on the cold pilgering of small-diameter, thick-walled seamless tubes, specifically those with an outer diameter–wall thickness ratio of ≤3. In this study, cold pilgering tests were performed on Cr-Mo-V hot-working die steel small-diameter thick-walled tubes. It was discovered that increasing the feed rate results in greater deviations in both inner diameter and wall thickness, although it has little effect on inner wall roughness. In contrast, increasing wall thickness reduction leads to higher wall thickness deviation but reduces inner surface roughness without significantly affecting inner diameter deviation. The study also found that a decrease in the initial inner wall roughness before pilgering results in improved final roughness. Under optimal conditions, the average inner surface roughness S_a can reach 0.177 μm, and small-diameter thick-walled seamless tubes with deviations in the inner diameter and wall thickness of 0.05 mm and 0.03 mm, respectively, are obtained. After tempering at 600 °C, the tensile strength (R_m) and yield strength (R_p0.₂) of the cold-pilgered tube reach 1092 MPa and 947 MPa, respectively, and the elongation (δ₅%) and impact energy (A_kU) increase to 20.4% and 61.5 J, respectively. Full article

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53 pages, 24284 KiB

Open AccessReview

Multi-Metal Additive Manufacturing by Extrusion-Based 3D Printing for Structural Applications: A Review

by Alina Mazeeva, Dmitriy Masaylo, Gleb Konov and Anatoliy Popovich

Metals 2024, 14(11), 1296; https://doi.org/10.3390/met14111296 - 16 Nov 2024

Abstract

Additive manufacturing (AM) is a rapidly developing technical field that is becoming an irreplaceable tool to fabricate unique complex-shaped parts in aerospace, the automotive industry, medicine, and so on. One of the most promising directions for AM application is the design and production [...] Read more.

Additive manufacturing (AM) is a rapidly developing technical field that is becoming an irreplaceable tool to fabricate unique complex-shaped parts in aerospace, the automotive industry, medicine, and so on. One of the most promising directions for AM application is the design and production of multi-material components with different types of chemical, structural, and architectural gradients that also promote a breakthrough in bio-inspired approaches. At the moment there are a lot of different AM techniques involving various types of materials. This paper represents a review of extrusion-based AM techniques using metal-polymer composites for structural metal parts fabrication. These methods are significantly cheaper than powder bed fusion (PBF) and directed energy deposition (DED) techniques, though have a lower degree of part detail. Thus, they can be used for low-scale production of the parts that are not rentable to produce with PBF and DED. Multi-material structures application in machinery, main aspects of feedstock preparation, the subsequent steps of extrusion-based 3D printing, and the following treatment for manufacturing single-metallic and multi-metallic parts are considered. Main challenges and recommendations are also discussed. Multi-metallic extrusion-based 3D printing is just a nascent trend requiring further wide investigation, though even now it shows pretty interesting results. Full article

(This article belongs to the Section Additive Manufacturing)

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11 pages, 2093 KiB

Open AccessArticle

An Improved Process for Solving the Sintering Problem of Al-Si Alloy Powder Metallurgy

by Hexin Tian, Fachang Zhao, Dongmei Ma, Xingming Zhao, Jingran Meng, Guangan Zhang and Fufa Wu

Metals 2024, 14(11), 1295; https://doi.org/10.3390/met14111295 - 16 Nov 2024

Abstract

The Al-Si alloy prepared by the traditional powder metallurgy method has the problems of difficult sintering and low mechanical properties. In this paper, rotary extrusion combined with rapid solidification/powder metallurgy technology (RS/PM) is proposed and designed to produce an Al-10Si alloy. In subsequent [...] Read more.

The Al-Si alloy prepared by the traditional powder metallurgy method has the problems of difficult sintering and low mechanical properties. In this paper, rotary extrusion combined with rapid solidification/powder metallurgy technology (RS/PM) is proposed and designed to produce an Al-10Si alloy. In subsequent sintering at different temperatures, better metallurgical bonding between particles can be achieved to fulfil the aim of improving the mechanical properties of the material. Additionally, the continuous preparation of materials can be achieved. Finally, it is verified that the density of the Al-10Si alloy sintered at 525 °C is 2.61 g/cm³, reaching 97.0% of the theoretical density, and the tensile strength reaches 336 MPa, which is much higher than that of the alloy prepared by the traditional casting method and powder metallurgy method. Full article

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16 pages, 5358 KiB

Open AccessArticle

High-Entropy Alloy Laser Cladding with Cable-Type Welding Wire: Experimental Study and First-Principles Calculations

by Wenjun Wang, Yifei Zheng, Zhihui Cai, Wenjian Zheng, Cai Zhang, Yu Wang, Zhiyong Zhao, Daochen Feng, Yinghe Ma and Jianguo Yang

Metals 2024, 14(11), 1294; https://doi.org/10.3390/met14111294 - 16 Nov 2024

Abstract

The Co-Cr-Fe-Ni high-entropy alloy (HEA) is particularly suitable for preparing coatings due to its excellent comprehensive properties. In this study, we use the laser cladding method to prepare Co-Cr-Fe-Ni HEA coatings with Co-Cr-Fe-Ni cable-type welding wire (CTWW) as the filling material and investigated [...] Read more.

The Co-Cr-Fe-Ni high-entropy alloy (HEA) is particularly suitable for preparing coatings due to its excellent comprehensive properties. In this study, we use the laser cladding method to prepare Co-Cr-Fe-Ni HEA coatings with Co-Cr-Fe-Ni cable-type welding wire (CTWW) as the filling material and investigated the dilution rates of the coatings by experimental studies and first-principles calculations. The dilution rate is reduced to about 50% by changing the wire feeding speed, and a Co-Cr-Fe-Ni HEA coating with near nominal composition was prepared by multi-layer cladding. The HEA coating with near nominal composition is successfully prepared in the fourth layer of cladding. The coating is dense and uniform, with good metallurgical bonding. The mechanical properties of the coating were explored using first-principles calculations. All four coatings exhibit a single face-centered cubic (FCC) phase with good mechanical stability in the ground state. The bulk modulus B, shear modulus G, and Young’s modulus E of the four layers of coatings are gradually decreasing from B = 202 GPa, G = 136 GPa, and E = 334 GPa to B = 239 GPa, G = 154 GPa, and E = 380 GPa. The brittleness of the coating shows a trend of first decreasing and then increasing, and the coating closest to the nominal composition has the highest brittleness. Full article

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18 pages, 14402 KiB

Open AccessArticle

Steel Chips as a Raw Material for MEX

by Catarina Duarte Batista and Maria Teresa Freire Vieira

Metals 2024, 14(11), 1293; https://doi.org/10.3390/met14111293 - 15 Nov 2024

Abstract

In recent years, metal chip powders obtained from solid-state processes have shown great potential as a sustainable raw material for powder technologies. The material and fragmentation process of the chips has a significant role in the final characteristics of the powder particles, such [...] Read more.

In recent years, metal chip powders obtained from solid-state processes have shown great potential as a sustainable raw material for powder technologies. The material and fragmentation process of the chips has a significant role in the final characteristics of the powder particles, such as size and particle size distribution, shape, surface, and structure, which are essential parameters to consider when converting chips to powder for applications. However, tool steel chips as a powder raw material have not yet been significantly studied. In this study, the steel chips were from machining AISI H13 steel and the milling process used a ball mill, and the challenge was to obtain powder particle sizes of around 20 µm with suitable properties from the application of envisaged material extrusion (MEX). A comparison study with the commercial raw material for MEX, such as powder metal filament extrusion, was performed. This study highlights the behaviors of chip powders during all steps of MEX, namely, feedstock and filament production, 3D object shaping, thermal de-binding, and sintering. A comparison of the mixture based on powder from chips and commercial powders for MEX was performed after evaluating the mixing torque of the powder and the system of binders and additives suitable for the rheological characteristics required for an extrusion mixture, and optimizing the binder removal and the sintering conditions. The 3D objects resulting from chip powders had a refined microstructure, showing an increase of 15% in the microhardness when compared with the those resulting from commercial powders. Full article

(This article belongs to the Special Issue Advances in Recycling and Reuse of Metals)

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