Metals

12 pages, 3167 KiB

Open AccessArticle

Atomistic Simulation of the Interaction between the Σ9[110](221) Shear-Coupled Grain Boundary Motion and the Cu-rich Precipitates in α-Iron

by Jian Yin, Huaiyu Hou, Jing-Tao Wang, Xiangbing Liu, Chaoliang Xu, Yuanfei Li, Wangjie Qian, Xiao Jin, Huanchun Wu, Wenqing Jia and Qiwei Quan

Metals 2024, 14(2), 252; https://doi.org/10.3390/met14020252 - 19 Feb 2024

Cited by 1 | Viewed by 1237

Abstract

Shear-coupled grain boundary motion (SCGBM) is an important and efficacious plasticity mechanism in the deformation of metals. In this work, a molecular dynamic (MD) simulation of the interaction between the SCGBM of Σ9[110](221) GB and Cu-rich precipitates in α-iron was carried out. The [...] Read more.

Shear-coupled grain boundary motion (SCGBM) is an important and efficacious plasticity mechanism in the deformation of metals. In this work, a molecular dynamic (MD) simulation of the interaction between the SCGBM of Σ9[110](221) GB and Cu-rich precipitates in α-iron was carried out. The effects of the size, the temperature, and the composition of the Cu precipitates were also studied. It was found that the precipitates inhibited the GB motion significantly, and the configuration transformation from spheroid to ellipsoid was also investigated in the simulation results. The critical stress of the interaction increased with the size of the precipitates. At higher temperatures, the GB sliding event increased the critical stress of the GB motion, which was higher than that of the interaction, inducing no stress-rise stage in the stress–time curve. The critical stress of the CuNi precipitates on the SCGBM was higher than that of the pure Cu precipitates with the same size, which was one of the reasons for the outstanding strength of the high-strength low-alloy (HSLA) steels compared with the traditional Cu-containing steels. Full article

(This article belongs to the Section Computation and Simulation on Metals)

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18 pages, 21025 KiB

Open AccessArticle

Hydrogen Embrittlement of Ti-Al6-V4 Alloy Manufactured by Laser Powder Bed Fusion Induced by Electrochemical Charging

by Michaela Roudnicka, Zdenek Kacenka, Drahomir Dvorsky, Jan Drahokoupil and Dalibor Vojtech

Metals 2024, 14(2), 251; https://doi.org/10.3390/met14020251 - 19 Feb 2024

Viewed by 1536

Abstract

The 3D printing of Ti-Al6-V4 alloy is subject to much current investigation, with Laser Beam Powder Bed Fusion (PBF-LB/M) being one of the most applied technologies. Ti-Al6-V4 alloy, despite its great material properties, is susceptible to hydrogen penetration and consequent embrittlement. The level [...] Read more.

The 3D printing of Ti-Al6-V4 alloy is subject to much current investigation, with Laser Beam Powder Bed Fusion (PBF-LB/M) being one of the most applied technologies. Ti-Al6-V4 alloy, despite its great material properties, is susceptible to hydrogen penetration and consequent embrittlement. The level of susceptibility to hydrogen penetration depends on the microstructural state of the alloy. In this work, we compare the effect of electrochemical charging by hydrogen on Ti-Al6-V4 alloy prepared by PBF-LB/M, either in the as-built state or annealed, and conventionally prepared alloy. At the same charging conditions, considerably different hydrogen concentrations were achieved, with the as-built 3D-printed material being the most susceptible. The changes in mechanical properties are discussed in relation to changes in microstructure, studied using microscopy, X-ray, and electron diffraction techniques. Full article

(This article belongs to the Special Issue Study of Hydrogen Embrittlement of Metallic Materials)

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18 pages, 12412 KiB

Open AccessArticle

Effect of Laser Scanning Speed and Fine Shot Peening on Pore Characteristics, Hardness, and Residual Stress of Ti-6Al-4V Fabricated by Laser Powder Bed Fusion

by Kanawat Ratanapongpien, Anak Khantachawana and Katsuyoshi Kondoh

Metals 2024, 14(2), 250; https://doi.org/10.3390/met14020250 - 19 Feb 2024

Cited by 3 | Viewed by 1610

Abstract

There is a concern regarding sub-surface pores within laser powder bed fusion of Ti-6Al-4V, which can initiate cracks and reduce mechanical properties, especially after machining for surface finishing. This study investigated the effect of laser scanning speed and fine shot peening on the [...] Read more.

There is a concern regarding sub-surface pores within laser powder bed fusion of Ti-6Al-4V, which can initiate cracks and reduce mechanical properties, especially after machining for surface finishing. This study investigated the effect of laser scanning speed and fine shot peening on the pore characteristics, hardness, and residual stress of Ti-6Al-4V fabricated by laser powder bed fusion using scanning electron microscopy, X-ray micro-computed tomography, Vickers hardness, and X-ray diffraction. As the laser scanning speed increased, the number of pores and pore size increased, which reduced the hardness of Ti-6Al-4V. Most pores were less than 20 µm in size and randomly distributed. The fine shot peening generated plastic deformation and compressive residual stress on the surface, leading to higher hardness, with similar surface properties at all scanning speeds. The depth of compressive residual stress by fine shot peening varied corresponding to the scanning speeds. Increasing the scanning speed accelerated the rate of conversion between the compressive and tensile residual stresses, and decreased the depth of the maximum hardness by the fine shot peening from initial tensile residual stress within Ti-6Al-4V fabricated by laser powder bed fusion, thus reducing the enhancement achieved by the fine shot peening. Full article

(This article belongs to the Special Issue Additive Manufacturing Process and Laser Welding of Metals)

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20 pages, 23576 KiB

Open AccessArticle

Effect of Coiling Temperature on Microstructures and Precipitates in High-Strength Low-Alloy Pipeline Steel after Heavy Reduction during a Six-Pass Rolling Thermo-Mechanical Controlled Process

by Yicong Lei, Wen Yang, Charles W. Siyasiya and Zhenghua Tang

Metals 2024, 14(2), 249; https://doi.org/10.3390/met14020249 - 18 Feb 2024

Cited by 1 | Viewed by 1279

Abstract

Nb-Ti high-strength low-alloy pipeline steel was subjected to a six-pass rolling process followed by the coiling process at different temperatures between 600 and 650 °C using the thermo-mechanical testing system Gleeble 3500 (Gleeble, New York, NY, USA). This experimental steel was subjected to [...] Read more.

Nb-Ti high-strength low-alloy pipeline steel was subjected to a six-pass rolling process followed by the coiling process at different temperatures between 600 and 650 °C using the thermo-mechanical testing system Gleeble 3500 (Gleeble, New York, NY, USA). This experimental steel was subjected to 72% heavy reduction through a thermos-mechanical controlled process. Thereafter, the microstructures were observed using optical microscopy, scanning electron microscopy, electron backscatter scanning diffraction, and transmission electron microscopy coupled with energy dispersive spectrometry and selected area electron diffraction. For the selected three coiling temperatures of 600, 625, and 650 °C, acicular ferrite, polygonal ferrite, and pearlite were observed, and morphology and statistical analysis were adopted for the study of precipitates. Based on the estimation by the Ashby–Orowan formula, the incremental strength through precipitation strengthening decreases with coiling temperatures and reaches 26.67 Mpa at a coiling temperature of 600 °C. Precipitation-time-temperature curves were obtained to explain the transformation of precipitates. The (Nb, Ti)(C, N) particles tended to precipitate in the acicular ferrite with [011]_{(Nb, Ti)(C, N)}//[011]_α-Fe orientation. The lower coiling temperature provided enough driving force for the nucleation of precipitates while inhibiting their growth. Full article

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

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19 pages, 6943 KiB

Open AccessArticle

Surface Modification of Diatomite-Based Micro-Arc Coatings for Magnesium Implants Using a Low-Energy High-Current Electron Beam Processing Technique

by Mariya B. Sedelnikova, Alexander D. Kashin, Olga V. Bakina, Pavel V. Uvarkin, Nikita A. Luginin, Yurii P. Sharkeev, Margarita A. Khimich, Olga V. Kazmina, Edgar S. Dvilis and Konstantin V. Ivanov

Metals 2024, 14(2), 248; https://doi.org/10.3390/met14020248 - 18 Feb 2024

Viewed by 1274

Abstract

The present study showcases a novel effective technique for the surface modification of micro-arc diatomite coatings using low-energy, high-current electron beams (LEHCEBs). A variety of methods such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, the X-ray diffraction method, scratch testing, the potentiodynamic polarization [...] Read more.

The present study showcases a novel effective technique for the surface modification of micro-arc diatomite coatings using low-energy, high-current electron beams (LEHCEBs). A variety of methods such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, the X-ray diffraction method, scratch testing, the potentiodynamic polarization method, immersion testing in SBF, and flow cytometry have been used to study the coatings. During processing, the electron beams’ energy density ranged between 2.5–7.5 J/cm². After the LEHCEB treatment, the surface morphology of the coatings changed completely. The corrosion resistance of the LEHCEB-treated coated samples increased significantly, as evidenced by the decrease in corrosion current to 4.6 × 10⁻¹⁰ A·cm⁻² and the increase in polarization resistance to 1.4 × 10⁸ Ω·cm². The electron beam treatment also increased the adhesion strength of the coatings to the magnesium substrate by 1.8–2.5 times compared to untreated coatings. Additionally, biological studies have shown the high viability of the NIH/3T3 cell line after contact with the samples of the coating extracts. Full article

(This article belongs to the Special Issue Surface Treatment of Alloys for Biomedical Application)

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10 pages, 6224 KiB

Open AccessArticle

Phytic-Acid-Modified Copper Foil as a Current Collector for Lithium-Ion Batteries

by Mingtao Gan, Mengjun Zhu, Jiangping Tu, Xiuli Wang and Changdong Gu

Metals 2024, 14(2), 247; https://doi.org/10.3390/met14020247 - 18 Feb 2024

Cited by 1 | Viewed by 2418

Abstract

Electrolytic copper foil is ideal for use in the anode current collectors of lithium-ion batteries (LIBs) because of its abundant reserves, good electrical conductivity, and soft texture. However, electrolytic copper foil is prone to corrosion in electrolytes and weak bonding to the anode [...] Read more.

Electrolytic copper foil is ideal for use in the anode current collectors of lithium-ion batteries (LIBs) because of its abundant reserves, good electrical conductivity, and soft texture. However, electrolytic copper foil is prone to corrosion in electrolytes and weak bonding to the anode substance. Surface modification of copper foil is considered an effective method of improving the overall electrochemical performance of LIBs. In this study, a 5 nm thickness phytic acid (PA)-based film is constructed on electrolytic copper foil using a fast electrodeposition process (about 10 s). PA-treated copper foil (PA-Cu) displays an improved corrosion resistance in electrolytes because of a strong complexation between the PA and copper. It is found that PA-treated copper foil also bonds better with graphite particles compared with pristine copper foil. LIBs with PA-Cu foils as their current collectors exhibit enhanced cycling stability, improved capacity retention, and superior rate performance at both low and high current densities. Our study offers a novel avenue for the development of high-performance electrode current collector materials for LIBs. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion and Protection of Metallic Materials)

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14 pages, 4227 KiB

Open AccessArticle

Multi-Objective Optimization of Low-Alloy Hot-Rolled Strip Cooling Process Based on Gray Correlation Analysis

by Rundong Xue and Aigeng Fei

Metals 2024, 14(2), 246; https://doi.org/10.3390/met14020246 - 18 Feb 2024

Viewed by 1011

Abstract

The residual stress in low-alloy hot-rolled strips seriously affects the use and processing of products. Reducing residual stress is important for improving the product quality of hot-rolled strips. In this paper, the changes in grain size and residual stress of hot-rolled strips under [...] Read more.

The residual stress in low-alloy hot-rolled strips seriously affects the use and processing of products. Reducing residual stress is important for improving the product quality of hot-rolled strips. In this paper, the changes in grain size and residual stress of hot-rolled strips under different cooling processes were investigated via thermal simulation experiments and electron backscatter diffraction. It was found that the optimum cooling process solution for single-objective optimization of grain size was a final rolling temperature of 875 °C, a laminar cooling speed of 50 °C/s, and a coiling temperature of 550 °C. When single-objective optimization of residual stress was carried out, the optimal cooling process scheme was 900 °C for final rolling temperature, 20 °C/s for laminar cooling speed, and 625 °C for coiling temperature. The significance of the effect of cooling processes on grain size and residual stress was analyzed based on the extreme deviation of the effect of each cooling process on grain size and residual stress in orthogonal experiments. The results show that the coiling temperature was the most influential factor on grain size and residual stress among the cooling process parameters. The difference was that grain size increased with increasing coiling temperature, and residual stress decreased with increasing coiling temperature. Using both grain size and residual stress as evaluation indicators, a multi-objective optimization of the cooling process for hot-rolled strips was carried out via the gray correlation analysis method. The optimized solution was 875 °C final rolling temperature, 30 °C/s laminar cooling speed, and 625 °C coiling temperature. At this time, the grain size was 4.8 μm, and the KAM (Kernel Average Misorientation) was 0.40°. The grain size under the actual production process scheme was 4.4 μm with a KAM of 0.78°. Compared to the actual production process solution, the multi-objective optimization solution showed little change in grain size, with only a 9% increase and a 49% reduction in KAM. The optimization scheme in this paper could significantly reduce the level of residual stresses while ensuring the fine grain size of hot-rolled strips, thus improving the overall quality of hot-rolled strips. Full article

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25 pages, 1369 KiB

Open AccessArticle

Prediction of Activity Coefficients and Osmotic Coefficient of Electrolyte Solutions Containing Rb⁺ by the Electrolyte Molecular Interaction Volume Model and the Electrolyte Molecular Interaction Volume Model-Energy Term

by Yanshan Wu and Dongping Tao

Metals 2024, 14(2), 245; https://doi.org/10.3390/met14020245 - 17 Feb 2024

Viewed by 1174

Abstract

The purpose of this study is to predict two-electrolyte solutions containing Rb⁺, explore its characteristics to better solve the problems existing in the natural environment, and promote the development of high technology. We fit and predict the activity and osmotic coefficients [...] Read more.

The purpose of this study is to predict two-electrolyte solutions containing Rb⁺, explore its characteristics to better solve the problems existing in the natural environment, and promote the development of high technology. We fit and predict the activity and osmotic coefficients of nineteen single-electrolyte solutions and seven two-electrolyte solutions containing Rb⁺ using the electrolytr Molecular Interaction Volume Model and the electrolyte Molecular Interaction Volume Model-Energy Termmodels. The average relative errors of the activity coefficient and osmotic coefficient calculated by eMIVM in aqueous monoelectrolyte solution were 0.59% and 0.38%, respectively, and for eMIVM-ET they were 1.06% and 0.38%, respectively. The average relative errors of activity coefficient and osmotic coefficient calculated by eMIVM-ET in organic single-electrolyte solution were 1.33% and 0.48%, respectively, while for eMIVM they were 1.49% and 0.48%, respectively. When predicting the activity coefficient and osmotic coefficient of two-electrolyte solutions containing Rb⁺, the average relative errors calculated by the eMIVM-ET model were 23% and 13%, respectively, while the values calculated by the eMIVM model were 34% and 17%, respectively. The results show that eMIVM-ET has a good fitting effect in organic monoelectrolyte solutions, and eMIVM has a good fitting effect in aqueous monoelectrolyte solutions. In the prediction of two-electrolyte solutions, the eMIVM-ET model performs better than the eMIVM model. Full article

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11 pages, 4378 KiB

Open AccessArticle

The Effect of Fe on the Mechanical Properties of Stellite 6

by Min Ah Baek, Gyu Byeong Kang, Gyeong Chan Suk, Seong Chan Hong, Young Do Kim and Tae-Wook Na

Metals 2024, 14(2), 244; https://doi.org/10.3390/met14020244 - 17 Feb 2024

Viewed by 1518

Abstract

Stellite 6 is a Co-based alloy with excellent wear and corrosion resistance, resulting in it frequently being used as a hard-facing material. The main defect that occurs in the hard-facing process is the peeling of the hard-facing layer, which is caused by thermal [...] Read more.

Stellite 6 is a Co-based alloy with excellent wear and corrosion resistance, resulting in it frequently being used as a hard-facing material. The main defect that occurs in the hard-facing process is the peeling of the hard-facing layer, which is caused by thermal stress due to differences in thermal expansion coefficients. This peeling phenomenon can be prevented by using a material with an intermediate coefficient of thermal expansion as a buffer layer. Component surfaces are strengthened through a technique called hard-facing, which increases the components’ resistance to wear. In order to increase the wear and corrosion resistance of metal components, a high-hardness substance is usually coated onto their surface. Grinding is carried out to smooth the surface after the material is welded onto the base component. Small pieces, also referred to as “scrap”, are frequently produced during this surface machining procedure. In the hard-facing process, scrap containing a mixture of base material and Stellite 6 is generated during material processing. If this scrap can be used as a buffer layer, the cost of raw materials can be reduced through the recycling of resources, and the overall energy consumption for recycling can be reduced because the process of separating Stellite 6 from the scrap is eliminated. In this study, the physical properties of Stellite 6 with Fe added were explored to determine whether the scrap produced could be used as a buffer layer. When iron was added to the mixture, the amount of carbide decreased, in addition to the wear resistance and hardness decreasing. Regarding the thermal expansion coefficient, the thermal expansion coefficient of Stellite 6 was found to be 15.879 μm/m·°C at 300 °C, and that of Stellite 6 with 40% Fe added was found to be 14.313 μm /m·°C at 300 °C. The thermal expansion coefficient of carbon steel is reported to be 12.8 μm /m·°C at 300 °C; thus, Stellite 6 with 40% Fe can be used as a buffer layer for Stellite 6 and carbon steel because of its suitable thermal expansion coefficient. Full article

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14 pages, 8415 KiB

Open AccessArticle

Dissolution of CaO in SiO₂-CaO-Al₂O₃ Slag in Si Production

by Marit Buhaug Folstad, Kristian Etienne Einarsrud and Merete Tangstad

Metals 2024, 14(2), 243; https://doi.org/10.3390/met14020243 - 16 Feb 2024

Viewed by 1398

Abstract

This work investigates the dissolution of CaO into three different compositions of SiO₂-CaO-Al₂O₃ slag similar to those found in industrial Si furnaces. It was found that CaO dissolution into the slag is fast. During the dissolution process, a [...] Read more.

This work investigates the dissolution of CaO into three different compositions of SiO₂-CaO-Al₂O₃ slag similar to those found in industrial Si furnaces. It was found that CaO dissolution into the slag is fast. During the dissolution process, a layer containing 35–42% CaO was formed between the CaO particle and the slag, which corresponded to the phases CaO·Al₂O₃·2SiO₂ or 2CaO·Al₂O₃·SiO₂ in this study. Two models were investigated to determine the dissolution rate of the three slags. In the first model, the CaO particle is assumed to be a smooth shrinking sphere, and the rate controlled by the chemical reaction rate. The second model assumes that the rate is controlled by mass transport and depends on the diffusion rate of CaO through a boundary layer on the surface of the CaO. Both models gave similar accuracy to the experimental values, and a proportional relationship between the rate constants and the viscosities was obtained. At 1500 °C, the diffusion coefficients were found to be in the order of 10⁻⁶ cm²/s. Full article

(This article belongs to the Topic Advanced Processes in Metallurgical Technologies)

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16 pages, 12845 KiB

Open AccessArticle

Surface Polishing of an Inconel 625 Bar by a Super-Fast MAF Process for a Solenoid Valve Stem Used in a Hydrogen Tank

by Hwi-Joong Kim, Lida Heng and Sang-Don Mun

Metals 2024, 14(2), 242; https://doi.org/10.3390/met14020242 - 16 Feb 2024

Cited by 1 | Viewed by 1302

Abstract

This study explores a super-fast magnetic abrasive finishing (MAF) process for polishing the surface of an Inconel 625 bar workpiece for a hydrogen solenoid valve stem. The Inconel 625 bar was chosen to replace the existing STS 316 bar material, previously used for [...] Read more.

This study explores a super-fast magnetic abrasive finishing (MAF) process for polishing the surface of an Inconel 625 bar workpiece for a hydrogen solenoid valve stem. The Inconel 625 bar was chosen to replace the existing STS 316 bar material, previously used for a hydrogen solenoid valve stem. The cylindrical surface of Inconel 625 bars was polished by a super-fast MAF process with high rotational speeds of 1000, 5000, 15,000, and 25,000 RPM and a super-strong magnetic field of 550 mT. The polishing characteristics of this process were evaluated according to the type of abrasives, rotational speeds of the workpiece and processing time. As a result, a super-smooth Inconel 625 bar was successfully achieved, with a surface roughness (Ra) reduced from 0.31 μm to 0.02 μm under the optimal conditions (15,000 RPM, CNT particles (0.04 μm), PCD diamond abrasive (1 μm), Fe (#200), 0.5 g of light oil, and 16 min of processing time). Also, the Ansys analysis results showed suitable strain, equivalent stress, and safety factor of the Inconel 625 bar. This confirmed that, after a super-fast MAF process, an Inconel 625 bar is feasible for application in Hydrogen (H₂) tanks instead of a conventional STS 316 bar. Full article

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17 pages, 3458 KiB

Open AccessArticle

Acid Treatments of Ti-Based Metallic Glasses for Improving Corrosion Resistance in Implant Applications

by Nora Fernández-Navas, Viktoriia Shtefan, Martin Hantusch and Annett Gebert

Metals 2024, 14(2), 241; https://doi.org/10.3390/met14020241 - 16 Feb 2024

Viewed by 1174

Abstract

Ti-based bulk metallic glasses are promising materials for metallic bone implants, mainly due to their mechanical biofunctionality. A major drawback is their limited corrosion resistance, with high sensitivity to pitting. Thus, effective surface treatments for these alloys must be developed. This work investigates [...] Read more.

Ti-based bulk metallic glasses are promising materials for metallic bone implants, mainly due to their mechanical biofunctionality. A major drawback is their limited corrosion resistance, with high sensitivity to pitting. Thus, effective surface treatments for these alloys must be developed. This work investigates the electrochemical treatment feasibility of nitric acid (HNO₃) solution for two bulk glass-forming alloys. The surface states obtained at different anodic potentials are characterized with electron microscopy and Auger electron spectroscopy. The corrosion behavior of the treated glassy alloys is analyzed via comparison to non-treated states in phosphate-buffered saline solution (PBS) at 37 °C. For the glassy Ti₄₇Zr_7.5Cu₃₈Fe_2.5Sn₂Si₁Ag₂ alloy, the pre-treatment causes pseudo-dealloying, with a transformation from naturally passivated surfaces to Ti- and Zr-oxide nanoporous layers and Cu-species removal from the near-surface regions. This results in effective suppression of chloride-induced pitting in PBS. The glassy Ti₄₀Zr₁₀Cu₃₄Pd₁₄Sn₂ alloy shows lower free corrosion activity in HNO₃ and PBS due to Pd stabilizing its strong passivity. However, this alloy undergoes pitting under anodic conditions. Surface pre-treatment results in Cu depletion but causes enrichment of Pd species and non-homogeneous surface oxidation. Therefore, for this glassy alloy, pitting cannot be completely inhibited in PBS. Concluding, anodic treatments in HNO₃ are more suitable for Pd-free glassy Ti-based alloys. Full article

(This article belongs to the Special Issue Recent Surface Treatments of Metals and Their Alloys)

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1 pages, 1346 KiB

Open AccessCorrection

Correction: Tamadon et al. Development of Metallographic Etchants for the Microstructure Evolution of A6082-T6 BFSW Welds. Metals 2017, 7, 423

by Abbas Tamadon, Dirk J. Pons, Kamil Sued and Don Clucas

Metals 2024, 14(2), 240; https://doi.org/10.3390/met14020240 - 16 Feb 2024

Viewed by 779

Abstract

In the original publication [...] Full article

18 pages, 4895 KiB

Open AccessArticle

Inverse Design of Aluminium Alloys Using Genetic Algorithm: A Class-Based Workflow

by Ninad Bhat, Amanda S. Barnard and Nick Birbilis

Metals 2024, 14(2), 239; https://doi.org/10.3390/met14020239 - 16 Feb 2024

Cited by 4 | Viewed by 1724

Abstract

The design of aluminium alloys often encounters a trade-off between strength and ductility, making it challenging to achieve desired properties. Adding to this challenge is the broad range of alloying elements, their varying concentrations, and the different processing conditions (features) available for alloy [...] Read more.

The design of aluminium alloys often encounters a trade-off between strength and ductility, making it challenging to achieve desired properties. Adding to this challenge is the broad range of alloying elements, their varying concentrations, and the different processing conditions (features) available for alloy production. Traditionally, the inverse design of alloys using machine learning involves combining a trained regression model for the prediction of properties with a multi-objective genetic algorithm to search for optimal features. This paper presents an enhancement in this approach by integrating data-driven classes to train class-specific regressors. These models are then used individually with genetic algorithms to search for alloys with high strength and elongation. The results demonstrate that this improved workflow can surpass traditional class-agnostic optimisation in predicting alloys with higher tensile strength and elongation. Full article

(This article belongs to the Special Issue Advanced Applications of Artificial Intelligence in Metallic Materials Processing)

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15 pages, 25356 KiB

Open AccessArticle

Effects of Aging Treatments on the Age Hardening Behavior and Microstructures in an Al-Mg-Si-Cu Alloy

by Limei Liu, Yingpeng Hou, Tuo Ye, Like Zhang, Xuan Huang, Yuqing Gong, Chao Liu, Yuanzhi Wu and Shiyun Duan

Metals 2024, 14(2), 238; https://doi.org/10.3390/met14020238 - 15 Feb 2024

Cited by 3 | Viewed by 1915

Abstract

In this study, we investigated the effects of modified aging treatments on the microstructures and hardness in a commercial 6016 Al alloy through hardness tests and transmission electron microscopy (TEM) observations. The results demonstrate that many fine needle-like β″ phases contribute to the [...] Read more.

In this study, we investigated the effects of modified aging treatments on the microstructures and hardness in a commercial 6016 Al alloy through hardness tests and transmission electron microscopy (TEM) observations. The results demonstrate that many fine needle-like β″ phases contribute to the high hardness of peak-aged (T6) alloys. Over-aging treatments lead to the precipitation of lath-like β′, β″/disordered, or B′/disordered composite phases. Moderate over-aging treatment results in the coarsening of grain boundary precipitates (GBPs) and widening of the precipitate-free zone (PFZ), while heavy over-aging treatment triggers the re-precipitation of Cu-containing GBPs and increases the number density of GBPs. A retrogression and re-aging (RRA) treatment precipitates β″, lath-like β′, and disordered phases, while a two-step aging (T78) treatment precipitates β″, B′, and disordered phases. Both the T78 and the RRA treatments lead to the coarsening of GBPs and the widening of PFZs. The decreased hardness during over-aging treatments is attributed to a combination of coarsening intragranular precipitates and/or wider PFZs. The T78 and RRA tempers achieve 95.5% and 94% of the hardness values of the T6 treatment, respectively. The hardness values of the RRA and T78 treated alloys are related to the finer nano-sized precipitates formed during the high temperature process. These precipitates can compensate for the loss of hardness caused by the increase in the widths of the PFZs and the coarsening of the matrix precipitates. The relationship between the hardness and microstructures such as PFZs and precipitates in the matrix during various heat treatments is elucidated. Full article

(This article belongs to the Special Issue Aluminum Alloys: Structures, Properties and Applications)

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15 pages, 5222 KiB

Open AccessArticle

Atomic-Scale Dislocation Structure Evolution and Crystal Ordering Analysis of Melting and Crystallization Microprocesses in Laser Powder Bed Melting of γ-TiAl Alloys

by Bangjie Gu, Quanlong Wang, Chenglong Ma, Lei Han, Wentao Wei and Xiao Li

Metals 2024, 14(2), 237; https://doi.org/10.3390/met14020237 - 15 Feb 2024

Viewed by 1514

Abstract

Laser Powder Bed Fusion (LPBF) technology exhibits significant advantages in the manufacturing of components with high dimensional accuracy and intricate internal cavities. However, due to the inherent room-temperature brittleness and high-temperature gradient induced by the laser forming process, the LPBF fabrication of γ-TiAl [...] Read more.

Laser Powder Bed Fusion (LPBF) technology exhibits significant advantages in the manufacturing of components with high dimensional accuracy and intricate internal cavities. However, due to the inherent room-temperature brittleness and high-temperature gradient induced by the laser forming process, the LPBF fabrication of γ-TiAl alloy is often accompanied by the initiation and propagation of defects. The aim of this study is to investigate the forming process of γ-TiAl alloy by the LPBF method through molecular dynamics simulation, and to explain the microparticle arrangement and displacement evolution of the melting and crystallization processes, thus elucidating the link between the variations in the laser process parameters and defect generation during microscopic laser heating. The results show that during the melting process, the peaks of the radial distribution function (RDF) decrease rapidly or even disappear due to laser heating, and the atomic disorder is increased. Although subsequent cooling crystallization reorders the atomic arrangement, the peak value of the RDF after crystallization is still 19.3% lower than that of the original structure. By setting different laser powers (200–800 eV/ps) and scanning speeds (0.2–0.8 Å/ps), the effects of various process parameters on microforming and defect evolution are clarified. When the laser power increases from 200 to 400 eV/ps, the stable value of atomic displacement rises from 6.66 to 320.87, while it rises from 300.54 to 550.14 when the scanning speed is attenuated from 0.8 to 0.4 Å/ps, which indicates that, compared with the scanning speed, the atomic mean-square displacements are relatively more sensitive to the fluctuation of laser power. Dislocation analysis reveals that a higher laser power significantly increases the cooling rate during the forming process, which further aggravates the generation and expansion of dislocation defects. Full article

(This article belongs to the Section Additive Manufacturing)

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14 pages, 3567 KiB

Open AccessArticle

Improved Corrosion Properties of Mg-Gd-Zn-Zr Alloy by Micro-Arc Oxidation

by Xue Geng, Qiangsheng Dong and Xiaobo Zhang

Metals 2024, 14(2), 236; https://doi.org/10.3390/met14020236 - 15 Feb 2024

Cited by 1 | Viewed by 1258

Abstract

In order to improve the corrosion resistance of Mg-3Gd-1Zn-0.4Zr (GZ31K) alloys for biomedical application, the alloy was micro-arc oxidation (MAO)-treated using silicate electrolyte system under various voltages (400 V, 425 V, 450 V, 475 V). The effects of voltage on the microstructure and [...] Read more.

In order to improve the corrosion resistance of Mg-3Gd-1Zn-0.4Zr (GZ31K) alloys for biomedical application, the alloy was micro-arc oxidation (MAO)-treated using silicate electrolyte system under various voltages (400 V, 425 V, 450 V, 475 V). The effects of voltage on the microstructure and corrosion properties of MAO coating were investigated via X-ray diffraction (XRD) and a scanning electron microscope (SEM) combined with an energy-dispersive spectrometer (EDS), X-ray photoelectron spectroscope (XPS), and electrochemical experiments. The results showed that, with the increase in voltage, the MAO coatings became thicker and the micropores on the MAO coating increased in diameter. The main phase compositions of the MAO coatings were MgO and Mg₂SiO₄. Potentiodynamic polarization curve results showed that MAO coatings could enhance corrosion resistances, where the corrosion current density decreased by six orders of magnitude and the corrosion potential of the specimens increased by 300 mV for the voltage of 450 V in the MAO treatment; nevertheless, the corrosion resistance rapidly deteriorated due to the creation of large micropores in the MAO coating, which provide a pathway for corrosive media when the voltage is 475 V. The electrochemical impedance spectroscopy results showed that MAO treatments could increase low-frequency modulus resistance and increase the corrosion resistance of Mg alloys. In addition, MAO-treated GZ31K alloys still exhibited uniform corrosion, which is desirable for biomedical applications. Full article

(This article belongs to the Special Issue Study on Surface Modification and Corrosion Prevention of Materials)

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26 pages, 7000 KiB

Open AccessReview

Machine Learning Design for High-Entropy Alloys: Models and Algorithms

by Sijia Liu and Chao Yang

Metals 2024, 14(2), 235; https://doi.org/10.3390/met14020235 - 15 Feb 2024

Cited by 6 | Viewed by 4188

Abstract

High-entropy alloys (HEAs) have attracted worldwide interest due to their excellent properties and vast compositional space for design. However, obtaining HEAs with low density and high properties through experimental trial-and-error methods results in low efficiency and high costs. Although high-throughput calculation (HTC) improves [...] Read more.

High-entropy alloys (HEAs) have attracted worldwide interest due to their excellent properties and vast compositional space for design. However, obtaining HEAs with low density and high properties through experimental trial-and-error methods results in low efficiency and high costs. Although high-throughput calculation (HTC) improves the design efficiency of HEAs, the accuracy of prediction is limited owing to the indirect correlation between the theoretical calculation values and performances. Recently, machine learning (ML) from real data has attracted increasing attention to assist in material design, which is closely related to performance. This review introduces common and advanced ML models and algorithms which are used in current HEA design. The advantages and limitations of these ML models and algorithms are analyzed and their potential weaknesses and corresponding optimization strategies are discussed as well. This review suggests that the acquisition, utilization, and generation of effective data are the key issues for the development of ML models and algorithms for future HEA design. Full article

(This article belongs to the Special Issue Light Alloys and Composites)

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16 pages, 4056 KiB

Open AccessArticle

Selective Recovery of Scandium (Sc) from Sulfate Solution of Bauxite Residue Leaching Using Puromet MTS9580 Ion-Exchange Sorption

by Julia Napol’skikh, Andrei Shoppert, Irina Loginova, Sergey Kirillov and Dmitry Valeev

Metals 2024, 14(2), 234; https://doi.org/10.3390/met14020234 - 15 Feb 2024

Viewed by 1476

Abstract

Rare earth elements (REEs) and Sc are concentrated in aluminum production byproducts. The novel REEs recovery approach, which involves leaching with acid at a pH > 3 in the presence of MgSO₄, results in the formation of a pregnant leach solution [...] Read more.

Rare earth elements (REEs) and Sc are concentrated in aluminum production byproducts. The novel REEs recovery approach, which involves leaching with acid at a pH > 3 in the presence of MgSO₄, results in the formation of a pregnant leach solution (PLS) with a low concentration of iron (Fe) and titanium (Ti) and a large number of valuable elements. This work studies the application of chelating resin Puromet MTS9580 in the sorption recovery of Sc from sulfate solutions. To analyze the static Sc sorption data, Langmuir, Freundlich, and Temkin isotherm models were used. The Langmuir isotherm model was the best fitted to the experimental data, with a coefficient of determination (R²) of 0.983. The dynamic adsorption experiment was conducted using a PLS and a simulated solution without contaminants. Adsorption of Sc from the simulated solution was better fitted to the Thomas model with a Sc capacity greater than 6.4 mg mL⁻¹. Because Ti had a gradual decrease in C/C₀, which the Thomas model was unable to simulate, the modified dose-response (MDR) model fitted better with PLS with a Sc capacity greater than 3.8 mg mL⁻¹. The NaHCO₃ solution (200 g L⁻¹) effectively desorbed Sc (>98%) from simulated and PLS solutions after 1.5 h of stirring in a batch mode. After 1.5 h of desorption, the concentration of Sc in the desorption solution was 461.5 mg L⁻¹, while the concentration of Mg and Ti was lower than 200 mg L⁻¹ and 50 mg L⁻¹, respectively. Full article

(This article belongs to the Special Issue Selective Separation and Comprehensive Recovery of Valuable Metals)

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17 pages, 3592 KiB

Open AccessReview

Towards the Circularity of the EU Steel Industry: Modern Technologies for the Recycling of the Dusts and Recovery of Resources

by Marco Simoni, Wolfgang Reiter, Julian Suer, Loredana Di Sante, Filippo Cirilli, Fabio Praolini, Manuel Mosconi, Marta Guzzon, Enrico Malfa, David Algermissen and Johannes Rieger

Metals 2024, 14(2), 233; https://doi.org/10.3390/met14020233 - 14 Feb 2024

Cited by 1 | Viewed by 2178

Abstract

The EU steel industry accounts for a crude steel production of 140 Mt/y, provided by the integrated (57%) and electric (43%) routes, which respectively require up to 6.0 and 0.6 MWh/t_CrudeSteel of energy input, and emits on average 1.85 and 0.4 t [...] Read more.

The EU steel industry accounts for a crude steel production of 140 Mt/y, provided by the integrated (57%) and electric (43%) routes, which respectively require up to 6.0 and 0.6 MWh/t_CrudeSteel of energy input, and emits on average 1.85 and 0.4 t_CO2/t_CrudeSteel. The mitigation of such CO₂ emissions is crucial, and would involve the direct avoidance of carbon, improvement of energy efficiency, and carbon capture. However, the environmental burden of the steel industry cannot be limited to this, given the very large amount (approximately 5 Mt) of residues landfilled every year in the EU. This practice cannot be sustained anymore, since it represents a detrimental waste of resources and burden to the environment. These aspects require prompt action to meet the Green Deal goals envisioned for 2030. This review paper aims to provide an overview of the main state-of-the-art technologies commercially (and not) available for the effective treatment of a wide variety of residues. To enrich this overview with further potential candidates towards a more sustainable steel manufacturing process, the combined application of two technologies (a plasma reactor and a RecoDust unit for the recovery of metals and minerals, respectively) at TRL 5-6 is also investigated here. Full article

(This article belongs to the Topic Energy-Saving and Emission Reduction in Metallurgy)

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19 pages, 5188 KiB

Open AccessArticle

Compression and Tensile Testing of L-PBF Ti-6Al-4V Lattice Structures with Biomimetic Porosities and Strut Geometries for Orthopedic Implants

by Dimitri P. Papazoglou, Amy T. Neidhard-Doll, Margaret F. Pinnell, Dathan S. Erdahl and Timothy H. Osborn

Metals 2024, 14(2), 232; https://doi.org/10.3390/met14020232 - 14 Feb 2024

Cited by 6 | Viewed by 1950

Abstract

In an effort to contribute to the ongoing development of ASTM standards for additively manufactured metal lattice specimens, particularly within the field of medicine, the compressive and tensile mechanical properties of biomimetic lattice structures produced by laser powder bed fusion (L-PBF) using Ti-6Al-4V [...] Read more.

In an effort to contribute to the ongoing development of ASTM standards for additively manufactured metal lattice specimens, particularly within the field of medicine, the compressive and tensile mechanical properties of biomimetic lattice structures produced by laser powder bed fusion (L-PBF) using Ti-6Al-4V feedstock powder were investigated in this research. The geometries and porosities of the lattice structures were designed to facilitate internal bone growth and prevent stress shielding. A thin strut thickness of 200 µm is utilized for these lattices to mimic human cancellous bone. In addition to a thin strut size, two different strut geometries were utilized (cubic and body-centered cubic), along with four different pore sizes (400, 500, 600, and 900 µm, representing 40–90% porosity in a 10 mm cube). A 10 mm³ cube was used for compression testing and an experimental pin-loaded design was implemented for tensile testing. The failure mode for each specimen was examined using scanning electron microscopy (SEM). Lattice structures were compared to the mechanical properties of human cancellous bone. It was found that the elastic modulus of human cancellous bone (10–900 MPa) could be matched for both the tensile (92.7–129.6 MPa) and compressive (185.2–996.1 MPa) elastic modulus of cubic and body-centered cubic lattices. Body-centered cubic lattices exhibited higher compressive properties over cubic, whereas cubic lattices exhibited superior tensile properties. The experimental tensile specimen showed reacquiring failures close to the grips, indicating that a different tensile design may be required for consistent data acquisition in the future. Full article

(This article belongs to the Section Additive Manufacturing)

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15 pages, 8950 KiB

Open AccessArticle

Research of a Novel Non-Axisymmetric Side-Compressed Variable Polarity Plasma Arc and Its Pressure Distribution Characteristics

by Hongxing Zhao, Chunli Yang and Chenglei Fan

Metals 2024, 14(2), 231; https://doi.org/10.3390/met14020231 - 14 Feb 2024

Cited by 1 | Viewed by 1077

Abstract

In the keyhole variable polarity plasma arc weldng (VPPAW) process at horizontal position, the metal driven by gravity gathered on one side of the molten pool, and the weld formation is difficult, especially for thick workpiece welding. A specially designed experiment to analyze [...] Read more.

In the keyhole variable polarity plasma arc weldng (VPPAW) process at horizontal position, the metal driven by gravity gathered on one side of the molten pool, and the weld formation is difficult, especially for thick workpiece welding. A specially designed experiment to analyze the influence of gravity on weld formation and a novel nozzle structure with side holes was proposed to generate a novel non-axisymmetric side-compressed plasma arc and redistribute arc pressure. The arc shape and pressure distribution were studied, and the ratio of difference for arc pressure in different directions Rp was introduced to evaluate the effects of non-axisymmetric side compression for the plasma arc. The results indicate that the non-axisymmetric distributed side holes reshape the plasma arc both in the EN and EP phases. The pressure of the non-axisymmetric side-compressed plasma arc decreases relatively strongly in one direction (direction b) and relatively weakly in the other direction (direction a). Rp is significant at 1 mm to 5 mm from the arc center, with a relatively large Rp within this range. The compression effect is enhanced with an increase in welding current or plasma gas flow rate, and Rp increases from 24% to 49% as the plasma gas flow rate increases from 2 L/min to 4.5 L/min. Specially designed validation experiments confirm that the new plasma arc significantly affects the weld formation in keyhole VPPAW process. An aluminum alloy workpiece with 8 mm thickness and no groove preparation was welded by the novel plasma arc in a horizontal welding position, and the weld is well formed. Full article

(This article belongs to the Special Issue Advanced Welding Technology in Metals III)

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11 pages, 2990 KiB

Open AccessArticle

Cold Rolling Technology Optimization for EN AW 4343/3003/4343 Cladded Aluminum Alloys and Influence of Parameters on Microstructure, Mechanical Properties and Sustainable Recyclability

by Bojan Kropf, Peter Cvahte, Matija Arzenšek and Jakob Kraner

Metals 2024, 14(2), 230; https://doi.org/10.3390/met14020230 - 14 Feb 2024

Viewed by 1607

Abstract

The present study investigates the accumulative roll bonding process applied to the EN AW 3003 aluminum alloy, serving as a composite material on both sides and consisting of the EN AW 4343 aluminum alloy. For the characterization of the optical microscopy, corrosion tests [...] Read more.

The present study investigates the accumulative roll bonding process applied to the EN AW 3003 aluminum alloy, serving as a composite material on both sides and consisting of the EN AW 4343 aluminum alloy. For the characterization of the optical microscopy, corrosion tests with saltwater acetic acid and mechanical properties before and after the braze test were employed. The numerical simulations accurately predicted the industrial cold rolling values for the rolling force and surface temperature. The most comprehensive understanding of the cold rolling parameters for both side-cladded materials was achieved by combining predictions for cladded and uncladded materials. The thickness of the cladded layer presented as a percentage after roll bonding was 18.7%. During the cold rolling and annealing, the cladded thickness was increased to 24.7% of the final 0.3 mm of the total cold-rolled product thickness. According to the performed braze test for final thickness, the ultimate tensile strength and yield strength were decreased, and the elongation increased to 18.1%. In addition to the described changes in mechanical properties, the material’s anisotropy improved from 5.4% in the cold-rolled condition to 2.0% after the braze test. After multiple re-meltings of the cladded material, the analyzed chemical compositions allow for recycling and reuse as different 4xxx, 5xxx, and 6xxx alloys. Full article

(This article belongs to the Special Issue Numerical and Experimental Advances in Metal Processing)

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12 pages, 4419 KiB

Open AccessArticle

pH Sensing for Early Detection of Septic Inflammation Based on Intrinsic Titanium β-Alloy Nanotubular Oxides

by Jaroslav Fojt, Jan Šťovíček, Jitřenka Jírů and Vojtěch Hybášek

Metals 2024, 14(2), 229; https://doi.org/10.3390/met14020229 - 14 Feb 2024

Viewed by 1203

Abstract

Orthopaedic surgeries like total hip and knee arthroplasty play a crucial role in restoring joint function for individuals with osteoarthritis. Deep bacterial infections are one of the most serious complications for orthopaedic implants. An infectious complication of an orthopaedic implant requires long-term and [...] Read more.

Orthopaedic surgeries like total hip and knee arthroplasty play a crucial role in restoring joint function for individuals with osteoarthritis. Deep bacterial infections are one of the most serious complications for orthopaedic implants. An infectious complication of an orthopaedic implant requires long-term and demanding treatment, often with repeated surgical procedures, and can lead to serious consequences such as implant failure, sepsis, and even death. Early detection of complications is of key importance for efficient therapy. The objective of this work is to investigate the possibilities of the nanotubular TiNbTa oxide for pH change sensing. Different surface treatments which lead to different surface natures were tested. For experiments, the inflammation was simulated by pH changes in the physiological solution. The response of the surface was monitored via the electrode potential changes. The results show that the nanotubular surface prepared on the TiNbTa alloy is a good possible candidate for pH sensing devices. Full article

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16 pages, 4963 KiB

Open AccessArticle

Molecular Dynamics Research on Fe Precipitation Behavior of Cu95Fe5 Alloys during Rapid Cooling

by Xufeng Wang, Xufeng Gao, Zhibo Lai, Zongen Han and Yungang Li

Metals 2024, 14(2), 228; https://doi.org/10.3390/met14020228 - 13 Feb 2024

Viewed by 1158

Abstract

To investigate structural changes, the Cu95Fe5 alloy system was subjected to cooling rates of 1 × 10¹³ K/s, 2 × 10¹² K/s, 2 × 10¹¹ K/s, and 2 × 10¹⁰ K/s using the molecular dynamics simulation method. The results [...] Read more.

To investigate structural changes, the Cu95Fe5 alloy system was subjected to cooling rates of 1 × 10¹³ K/s, 2 × 10¹² K/s, 2 × 10¹¹ K/s, and 2 × 10¹⁰ K/s using the molecular dynamics simulation method. The results revealed that decreasing the cooling rate caused an increase in the phase transition temperature. Further, the structure of the alloy system exhibited a tendency towards increased stability following cooling at lower cooling rates. The Fe precipitation behavior of the Cu95Fe5 alloys during cooling at the rate of 2 × 10¹⁰ K/s was further explored, with the results suggesting that the formation and growth of the Fe cluster is a continuous process governed by the nucleation and growth mechanism. The size and number of Fe clusters formed at different stages were found to be affected by three factors, namely, the interaction force between the Fe atoms, the diffusion ability of the Fe atoms, and the interfacial energy between the Fe cluster and Cu matrix. When the alloy temperature exceeded 1400 K, the accumulation of the Fe atoms was facilitated by their strong interaction. However, the high temperatures and the large diffusion coefficient of the Fe atoms acted as inhibitors to the growth of Fe clusters, despite the intense thermal activities. As the temperature was reduced from 1400 K to 1050 K, the Fe atoms moved with a reduced intensity in a narrower area, and both the number of Fe atoms in the largest cluster and the number of clusters increased due to the action of the interaction force between the Fe atoms. Upon lowering the temperature from 1050 K to 887 K, the size of the largest Fe cluster increased rapidly, while the number of clusters decreased gradually. The growth of the largest Fe cluster could be partly attributed to the diffusion of single Fe atoms into the cluster under the action of the interaction force between the Fe atoms, in addition to the gathering and combination of multiple clusters. When the temperature was lowered from 967 K to 887 K, the diffusion coefficient of the Fe atoms approached 0, indicating that the non-diffusive local structure rearrangements of atoms dominated in the system structure change process. The interface energy governed the combination of the Fe clusters in this stage. At a temperature below 887 K, the alloy crystallized, the activities of the Fe atoms were reduced due to a low temperature, and the movement range of the Fe atoms was small at a fast cooling rate. As such, both the size and number of Fe clusters showed no obvious changes. Full article

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15 pages, 2833 KiB

Open AccessArticle

Improvement in the Hydrogen Storage Properties of MgH₂ by Adding NaAlH₄

by Young-Jun Kwak, Myoung-Youp Song and Ki-Tae Lee

Metals 2024, 14(2), 227; https://doi.org/10.3390/met14020227 - 13 Feb 2024

Cited by 2 | Viewed by 1379

Abstract

Milled MgH₂, MgH₂-10NaAlH₄, MgH₂-30NaAlH₄, MgH₂-50NaAlH₄, and MgH₂-2Ni-10NaAlH₄ samples were prepared by milling in a planetary ball mill in hydrogen atmosphere (reactive mechanical milling, RMM). Decomposition temperatures [...] Read more.

Milled MgH₂, MgH₂-10NaAlH₄, MgH₂-30NaAlH₄, MgH₂-50NaAlH₄, and MgH₂-2Ni-10NaAlH₄ samples were prepared by milling in a planetary ball mill in hydrogen atmosphere (reactive mechanical milling, RMM). Decomposition temperatures of milled MgH₂, NaAlH₄, MgH₂-10NaAlH₄, and MgH₂-30NaAlH₄ were examined in a Sieverts-type hydrogen absorption and release apparatus, in which the hydrogen pressures were kept nearly constant during hydrogen absorption or release. As the content of NaAlH₄ in the sample increased, the temperature at the highest peak in the ratio of increase in released hydrogen quantity to increase in temperature versus temperature curve decreased. Hydriding in 12 bar hydrogen and dehydriding in 1.0 bar hydrogen at 593 K of MgH₂-30NaAlH₄ are performed by the reversible reactions MgH₂ ⇔ Mg + H₂ and 17MgH₂ + 12Al ⇔ Mg₁₇Al₁₂ + 17H₂. MgH₂-30NaAlH₄ was the best Mg-based composite among Mg-based alloys in which an oxide, a halide, a fluoride, or a complex hydride was added, with a high hydrogen absorption rate for 2.5 min (2.20 wt% H/min) and a large effective hydrogen storage capacity (7.42 wt% H). Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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14 pages, 2198 KiB

Open AccessArticle

Effects of Chemical Short-Range Order and Lattice Distortion on Crack-Tip Behavior of Medium-Entropy Alloy by Atomistic Simulations

by Xiuju Zhu, Fuhua Cao, Lanhong Dai and Yan Chen

Metals 2024, 14(2), 226; https://doi.org/10.3390/met14020226 - 13 Feb 2024

Cited by 1 | Viewed by 1268

Abstract

It is well demonstrated that the complex chemical fluctuations on high/medium-entropy alloys (H/MEAs) play critical roles in their deformation process, but there are few reports related to the effect of such complex chemical fluctuations on the crack behavior. In this paper, the effects [...] Read more.

It is well demonstrated that the complex chemical fluctuations on high/medium-entropy alloys (H/MEAs) play critical roles in their deformation process, but there are few reports related to the effect of such complex chemical fluctuations on the crack behavior. In this paper, the effects of chemical short-range order (CSRO) and lattice distortion (LD) on the crack-tip behavior of CrCoNi MEAs under mode I loading at room temperature are investigated by carrying out molecular dynamics (MD) simulation, hybrid MD/Monte-Carlo (MC) simulation and the J-integral method. The results reveal that CSRO can improve the J-integral value without significant changes in the localized deformation zone size. On the contrary, LD can lower the J-integral value with an increase in the localized deformation zone size. The energetic analysis shows that CSRO improves the activation energy barrier of Shockley partial dislocation from the crack-tip while LD reduces the activation energy barrier. Our work is a step forward in understanding the effects of CSRO and LD on the crack-tip behavior and deformation mechanisms of CrCoNi MEAs. Full article

(This article belongs to the Special Issue Deformation Behavior and Mechanical Properties of High Entropy Alloys (2nd Edition))

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17 pages, 14490 KiB

Open AccessArticle

The Effect of Deformation and Isothermal Heat Treatment of a 5005 Aluminum Alloy

by Jon Holmestad, Calin Daniel Marioara, Benedikte Jørgensen Myrold and Ola Jensrud

Metals 2024, 14(2), 225; https://doi.org/10.3390/met14020225 - 12 Feb 2024

Cited by 1 | Viewed by 1354

Abstract

In the aluminum industry, forming is an important process step that introduces dislocations in the material. To investigate the effect of dislocation retention after ageing on 6xxx-series alloys, a non-heat-treatable 5005 alloy was selected to measure the change in mechanical properties due to [...] Read more.

In the aluminum industry, forming is an important process step that introduces dislocations in the material. To investigate the effect of dislocation retention after ageing on 6xxx-series alloys, a non-heat-treatable 5005 alloy was selected to measure the change in mechanical properties due to dislocation annihilation during dynamic recovery. However, the isothermal ageing treatment led to an unexpected and significant increase in mechanical properties after deformation. Increases in yield strength of 120% and tensile strength of 50% compared with the as-received material were achieved. However, this caused a significant decrease in elongation properties. The deformation start temperature did not have any impact on the final mechanical properties. TEM analysis attributed the increase in mechanical properties to an increased precipitation and dislocation density compared with the undeformed reference material. The precipitates are located along dislocation lines, showing that the solute elements are preferentially segregating to dislocations and precipitating. The precipitates were typical for the Al–Mg–Si(–Cu) system; therefore, the low amounts of Si and, to a lesser extent, Cu were responsible for the precipitation hardening in the 5005 alloy. Full article

(This article belongs to the Special Issue Selected Papers from the 5th International Conference on Light Materials LightMAT 2023)

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11 pages, 5490 KiB

Open AccessArticle

Synthesis of Nickel-Based Nanoparticles by Pulsed Laser Ablation in Liquids: Correlations between Laser Beam Power, Size Distribution and Cavitation Bubble Lifetime

by Atikur Rahman and Grégory Guisbiers

Metals 2024, 14(2), 224; https://doi.org/10.3390/met14020224 - 12 Feb 2024

Cited by 1 | Viewed by 2531

Abstract

Pulsed laser ablation in liquids (PLAL) is a colloidal synthesis technique attracting significant interest from the scientific community due to the quality of the nanoparticles being produced. In this type of synthesis protocol, the cavitation bubble plays a vital role during the synthesis [...] Read more.

Pulsed laser ablation in liquids (PLAL) is a colloidal synthesis technique attracting significant interest from the scientific community due to the quality of the nanoparticles being produced. In this type of synthesis protocol, the cavitation bubble plays a vital role during the synthesis of nanoparticles. This work studied the effect of the laser beam power on cavitation bubble lifetime. Three different laser beam power values (5.8 W, 7.5 W and 10.5 W) were used to irradiate a pure nickel target in de-ionized (DI) water to synthesize nickel-based nanoparticles. The optimal repetition rate maximizing the production of nanoparticles was determined by atomic emission spectroscopy for each laser beam power. It was determined that the optimal repetition rate increased exponentially with laser beam power, while the cavitation bubble lifetime decreased logarithmically with the laser beam power. Moreover, the effect of the laser beam power on the cavitation bubble lifetime also had an effect on the size distribution of the nanoparticles being produced; the smallest size distribution was obtained at the highest laser beam power. Full article

(This article belongs to the Topic Laser Processing of Metallic Materials)

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13 pages, 7912 KiB

Open AccessArticle

Effects of Low Nickel Content on Microstructure and High-Temperature Mechanical Properties of Al-7Si-1.5Cu-0.4Mg Aluminum Alloy

by Hongping Chen, Shusen Wu, Jianyu Li, Dijia Zhao and Shulin Lü

Metals 2024, 14(2), 223; https://doi.org/10.3390/met14020223 - 12 Feb 2024

Cited by 1 | Viewed by 1309

Abstract

In this paper, the effects of Ni content on the room and elevated temperature (250 °C) tensile strength of Al-7Si-1.5Cu-0.4Mg-0.3Mn-0.1RE-xNi (x = 0, 0.3, 0.6, 0.9 wt.%) alloys were investigated, along with microstructure characterization and tensile testing. In the as-cast state, the dominant [...] Read more.

In this paper, the effects of Ni content on the room and elevated temperature (250 °C) tensile strength of Al-7Si-1.5Cu-0.4Mg-0.3Mn-0.1RE-xNi (x = 0, 0.3, 0.6, 0.9 wt.%) alloys were investigated, along with microstructure characterization and tensile testing. In the as-cast state, the dominant Ni-rich phases were primarily the γ-Al7Cu4Ni and δ-Al3CuNi phases. Following the solution heat treatment, a significant reduction in the γ-Al7Cu4Ni phase was noted, accompanied by the emergence of numerous small ε-Al3Ni phases. Both room temperature strength and high temperature strength at 250 °C exhibited a consistent increase with rising Ni content, reaching 405 MPa and 261 MPa, respectively, at 0.9 Ni content, which were increased by 6.4% and 16.8%, respectively, compared with 0 Ni content. The elongation exhibited an oscillating increase within the Ni content range of 0 to 0.6, reaching peak values of 2.6% in room temperature and 4.3% in high temperature at 0.6 Ni, followed by a rapid decline. At 0.6 Ni content, the alloy demonstrated a well-balanced combination of mechanical properties, featuring commendable strength and plasticity. Full article

(This article belongs to the Special Issue Aluminum Alloys: Structures, Properties and Applications)

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