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Volume 15
Issue 6
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Metals, Volume 15, Issue 6 (June 2025) – 116 articles

Cover Story (view full-size image): Oxides are produced and changed during metal additive manufacturing. We evaluated different contributions to oxide deposition in laser powder-bed fusion and found that direct oxidation of the melt pool has a minor effect. Rather, ejected hot spatter droplets oxidize as they travel through the printer atmosphere. The backscattered electron micrograph reveals oxides as dark spots on the surface of a laser-remelted Inconel 718 sample. View this paper
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22 pages, 4441 KiB  
Article
Understanding Shock Response of Body-Centered Cubic Molybdenum from a Specific Embedded Atom Potential
by Yichen Jiang, Yanchun Leng, Xiaoli Chen and Chaoping Liang
Metals 2025, 15(6), 685; https://doi.org/10.3390/met15060685 - 19 Jun 2025
Viewed by 235
Abstract
Extreme conditions induced by shock exert unprecedented force on crystal lattice and push atoms away from their equilibrium positions. Nonequilibrium molecular dynamics (MD) simulations are one of the best ways to describe material behavior under shock but are limited by the availability and [...] Read more.
Extreme conditions induced by shock exert unprecedented force on crystal lattice and push atoms away from their equilibrium positions. Nonequilibrium molecular dynamics (MD) simulations are one of the best ways to describe material behavior under shock but are limited by the availability and reliability of potential functions. In this work, a specific embedded atom (EAM) potential of molybdenum (Mo) is built for shock and tested by quasi-isentropic and piston-driven shock simulations. Comparisons of the equation of state, lattice constants, elastic constants, phase transitions under pressure, and phonon dispersion with those in the existing literature validate the reliability of our EAM potential. Quasi-isentropic shock simulations reveal that critical stresses for the beginning of plastic deformation follow a [111] > [110] > [100] loading direction for single crystals, and then polycrystal samples. Phase transitions from BCC to FCC and BCC to HCP promote plastic deformation for single crystals loading along [100] and [110], respectively. Along [111], void directly nucleates at the stress concentration area. For polycrystals, voids always nucleate on the grain boundary and lead to early crack generation and propagation. Piston-driven shock loading confirms the plastic mechanisms observed from quasi-isentropic shock simulation and provides further information on the spall strength and spallation process. Full article
(This article belongs to the Special Issue Mechanical Structure Damage of Metallic Materials)
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31 pages, 62180 KiB  
Article
Evaluation of the Suitability of High-Temperature Post-Processing Annealing for Property Enhancement in LPBF 316L Steel: A Comprehensive Mechanical and Corrosion Assessment
by Bohdan Efremenko, Yuliia Chabak, Ivan Petryshynets, Tianliang Zhao, Vasily Efremenko, Kaiming Wu, Tao Xia, Miroslav Džupon and Sundas Arshad
Metals 2025, 15(6), 684; https://doi.org/10.3390/met15060684 - 19 Jun 2025
Viewed by 414
Abstract
This study aims to comprehensively assess the suitability of post-processing annealing (at 900–1200 °C) for enhancing the key properties of 316L steel fabricated via laser powder bed fusion (LPBF). It adopts a holistic approach to investigate the annealing-driven evolution of microstructure–property relationships, focusing [...] Read more.
This study aims to comprehensively assess the suitability of post-processing annealing (at 900–1200 °C) for enhancing the key properties of 316L steel fabricated via laser powder bed fusion (LPBF). It adopts a holistic approach to investigate the annealing-driven evolution of microstructure–property relationships, focusing on tensile properties, nanoindentation hardness and modulus, impact toughness at ambient and cryogenic temperatures (−196 °C), and the corrosion resistance of LPBF 316L. Annealing at 900–1050 °C reduced tensile strength and hardness, followed by a moderate increase at 1200 °C. Conversely, ductility and impact toughness peaked at 900 °C but declined with the increasing annealing temperature. Regardless of the annealing temperature and testing conditions, LPBF 316L steel fractured through a mixed transgranular/intergranular mechanism involving dimple formation. The corrosion resistance of annealed steel was significantly lower than that in the as-built state, with the least detrimental effect being observed at 1050 °C. These changes resulted from the complex interplay of annealing-induced structural transformations, including elimination of the cellular structure and Cr/Mo segregations, reduced dislocation density, the formation of recrystallized grains, and the precipitation of nano-sized (MnCrSiAl)O3 inclusions. At 1200 °C, an abundant oxide formation strengthened the steel; however, particle coarsening, combined with the transition of (MnCrSiAl)O3 into Mo-rich oxide, further degraded the passive film, leading to a sharp decrease in corrosion resistance. Overall, post-processing annealing at 900–1200 °C did not comprehensively improve the combination of LPBF 316L steel properties, suggesting that the as-built microstructure offers a favorable balance of properties. High-temperature annealing can enhance a particular property while potentially compromising other performance characteristics. Full article
(This article belongs to the Special Issue Research on Microstructure and Performance Mechanisms of Advanced Steels and Alloys)
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16 pages, 11865 KiB  
Article
Enhancing Fracture Toughness, Strength and Ductility of Zr58.75Cu21.15Fe4.7Al9.4Nb6 Bulk Metallic Glass via Ultrasound Excitation Technique
by Xiaoming Chen, Zhe Zhang, Tuo Wang, Yuluo Li, Rui Bai, Mingming Wang and Xidong Hui
Metals 2025, 15(6), 683; https://doi.org/10.3390/met15060683 - 19 Jun 2025
Viewed by 280
Abstract
The inherent brittleness and limited toughness of bulk metallic glasses (BMGs) remain critical challenges for their application as structural engineering materials. In this study, ultrasonic excitation was applied to Zr58.75Cu21.15Fe4.7Al9.4Nb6 BMG with the aim [...] Read more.
The inherent brittleness and limited toughness of bulk metallic glasses (BMGs) remain critical challenges for their application as structural engineering materials. In this study, ultrasonic excitation was applied to Zr58.75Cu21.15Fe4.7Al9.4Nb6 BMG with the aim of enhancing its mechanical performance. The results reveal that ultrasonic treatment significantly increases the fracture toughness by approximately 28% and induces a pronounced plastic deformation plateau following yielding. This improvement in both strength and ductility is attributed to the formation of nanoscale crystalline phases and ultrasound-induced phase separation within the amorphous matrix, which collectively promote shear band multiplication and inhibit crack propagation. Full article
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20 pages, 3211 KiB  
Article
Three-Stage Optimization of Surface Finish in WEDM of D2 Tool Steel via Taguchi Design and ANOVA Analysis
by Thanh Tan Nguyen, Bui Phuoc Phi, Van Tron Tran, Van-Thuc Nguyen and Van Thanh Tien Nguyen
Metals 2025, 15(6), 682; https://doi.org/10.3390/met15060682 - 19 Jun 2025
Viewed by 292
Abstract
Wire electrical discharge machining (WEDM) is a standard micro-manufacturing technology. In WEDM, surface roughness (SR), deviation dimension (DD), and machining time (MT) are critical requirements that impact machining quality and are affected by various input parameters. The workpiece often performs multiple machining steps [...] Read more.
Wire electrical discharge machining (WEDM) is a standard micro-manufacturing technology. In WEDM, surface roughness (SR), deviation dimension (DD), and machining time (MT) are critical requirements that impact machining quality and are affected by various input parameters. The workpiece often performs multiple machining steps (roughing, semi-finishing, and finishing) to achieve high accuracy. Each machining step directly affects the accuracy and machining time, and the preceding machining step influences the subsequent machining step parameters. Many input control parameters regulate WEDM’s performance. Thus, optimizing process control parameters at each step is essential to achieve optimal results. This study investigates the influence of input parameters, including pulse on time (Ton), pulse off time (Toff), and servo voltage (SV), on SR, DD, and MT when machining AISI D2 mold steel through rough, semi-finish, and finish cutting. Taguchi and Analysis of Variance (ANOVA) are applied to analyze and optimize this WEDM process. The results display that the optimal surface roughness values for rough, semi-finish, and finish-cut stages are 2.03 µm, 1.77 µm, and 0.57 µm, corresponding to the parameter set of Ton = 6 μs, Toff = 10 μs, and SV = 30 V; Ton = 3 μs, Toff = 15 μs, and SV = 60 V; and Ton = 21 μs, Toff = 45 μs, and SV = 60 V, respectively. In addition, in the finish-cut stage, the parameters for optimal DD of 0.001 mm (0.04%) are Ton = 3 μs, Toff = 15 μs, and SV = 40 V. In contrast, those values for optimal MT of 218 s are Ton = 3 μs, Toff = 30 μs, and SV = 40 V. All optimal input values are confirmed by the manufacturing mold and die parts. Full article
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13 pages, 9140 KiB  
Article
Effect of Heat Treatment on Corrosion of an AlCoCrFeNi2.1 Eutectic High-Entropy Alloy in 3.5 wt% NaCl Solution
by Jun Jiang, Haijing Sun and Jie Sun
Metals 2025, 15(6), 681; https://doi.org/10.3390/met15060681 - 19 Jun 2025
Viewed by 403
Abstract
This paper studies how heat treatments influence the corrosion of an AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) in a 3.5 wt% NaCl solution, by comparing the corrosion behaviors of as-cast, 600 °C heat-treated, and 1000 °C heat-treated samples using microstructure characterization, electrochemical measurements, [...] Read more.
This paper studies how heat treatments influence the corrosion of an AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) in a 3.5 wt% NaCl solution, by comparing the corrosion behaviors of as-cast, 600 °C heat-treated, and 1000 °C heat-treated samples using microstructure characterization, electrochemical measurements, and surface characterization. The electrochemical results show that the pitting potential rises and the passive current density and passive film resistance are almost changeless with an increasing heat treatment temperature. The enhancement in the pitting corrosion resistance results from the increased amount of the Cr-rich FCC phase and decreased amount of the B2 phase rich in the Al element, which are induced by the heat treatment. On one hand, this microstructure evolution can make the passive film have more Cr2O3 and less Al2O3, thereby enhancing its protective properties, as confirmed by the X-ray photoelectron spectroscopy analysis. On the other hand, the decreased amount of the Al-rich B2 phase can make the pitting corrosion less prone to initiate since the B2 phase can act as the pit initiation site, which is supported by the observation of corrosion morphologies, due to its higher electrochemical activity. In a summary, the heat treatment is beneficial for improving the pitting corrosion resistance of the AlCoCrFeNi2.1 EHEA. Full article
(This article belongs to the Special Issue High-Entropy Alloy and Films: Design, Properties and Application)
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14 pages, 2510 KiB  
Article
DFT Study of Hydrostatic Pressure Effects up to 1.0 GPa on the Electronic and Magnetic Properties of Laves Phases ErAl2 and ErNi2
by Tomás López-Solenzal, José Luis Sánchez Llamazares, José Luis Enríquez-Carrejo and César Fidel Sánchez-Valdés
Metals 2025, 15(6), 680; https://doi.org/10.3390/met15060680 - 19 Jun 2025
Viewed by 279
Abstract
This study employs DFT+U calculations to investigate the ferromagnetic properties of ErAl2 and ErNi2 Laves phases under an external hydrostatic pressure P (0 GPa ≤ P ≤ 1.0 GPa). The calculated magnetic moments per formula unit for both crystalline structures align [...] Read more.
This study employs DFT+U calculations to investigate the ferromagnetic properties of ErAl2 and ErNi2 Laves phases under an external hydrostatic pressure P (0 GPa ≤ P ≤ 1.0 GPa). The calculated magnetic moments per formula unit for both crystalline structures align with experimentally reported values: 4.40 μB/f.u. in the hard magnetization <001> axis for ErAl2 and 5.56 μB/f.u. in the easy magnetization <001> axis for ErNi2. The DFT results indicate that the magnetic moment remains unchanged up to 1 GPa of hydrostatic pressure, with no structural instabilities observed, as evidenced by a nearly constant formation energy for ErAl2 and ErNi2 alloys. The simulations confirm that the magnetic behavior of ErAl2 is primarily driven by the electrons localized in the f orbitals. In contrast, for ErNi2, both d and f orbitals significantly contribute to the total magnetic moment. Finally, the electronic specific heat coefficient was calculated and reported as a function of hydrostatic pressure up to P = 1.0 GPa for each Laves phase. Full article
(This article belongs to the Special Issue Study on the Preparation and Properties of Metal Functional Materials)
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21 pages, 4948 KiB  
Article
Kinetics Study of the Hydrogen Reduction of Limonite Ore Using an Unreacted Core Model for Flat-Plate Particles
by Jindi Huang, Tao Yi, Jing Li, Mingzhou Li, Fupeng Liu and Jinliang Wang
Metals 2025, 15(6), 678; https://doi.org/10.3390/met15060678 - 19 Jun 2025
Viewed by 256
Abstract
The iron and steel industry is a major emitter of carbon. In the context of China’s dual-carbon goals, hydrogen-based reduction ironmaking technology has garnered unprecedented attention. It is considered a crucial approach to reducing carbon dioxide emissions in the steel sector and facilitating [...] Read more.
The iron and steel industry is a major emitter of carbon. In the context of China’s dual-carbon goals, hydrogen-based reduction ironmaking technology has garnered unprecedented attention. It is considered a crucial approach to reducing carbon dioxide emissions in the steel sector and facilitating the realization of carbon neutrality. This work conducted isothermal thermogravimetric analysis on limonite ore in a N2/H2 atmosphere. The influences of reduction temperature, particle size, and hydrogen partial pressure on the hydrogen reduction reaction process of limonite were investigated. Based on the principles of isothermal thermal analysis kinetics and the unreacted core model for flat-plate particles, the mechanism function and kinetic parameters for the reduction of limonite particles were determined. The research results show that the hydrogen reduction process of limonite ore is influenced by multiple factors, including temperature, hydrogen partial pressure, and particle size. Increasing the reduction temperature and hydrogen partial pressure can significantly speed up the reduction reaction rate and enhance the degree of reduction. The kinetic parameters for the hydrogen reduction of limonite particles were obtained as follows: the reaction activation energy was 44.738 kJ·mol−1, the pre-exponential factor was 31.438 m·s−1, and the rate constant for the hydrogen reduction of limonite was k=31.438×e−44.738×1000RTm⋅s−1. In addition, contour maps were plotted to predict the reaction time and reaction temperature required for a complete reduction of limonite particles of different sizes to iron (Fe) particles under varying hydrogen partial pressures. The research findings can serve as a scientific basis for optimizing hydrogen-based reduction ironmaking technology in the iron and steel industry and achieving carbon neutrality goals. Full article
(This article belongs to the Special Issue Recent Developments in Ironmaking)
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23 pages, 4322 KiB  
Article
Thermal, Metallurgical, and Mechanical Analysis of Single-Pass INC 738 Welded Parts
by Cherif Saib, Salah Amroune, Mohamed-Saïd Chebbah, Ahmed Belaadi, Said Zergane and Barhm Mohamad
Metals 2025, 15(6), 679; https://doi.org/10.3390/met15060679 - 18 Jun 2025
Viewed by 356
Abstract
This study presents numerical analyses of the thermal, metallurgical, and mechanical processes involved in welding. The temperature fields were computed by solving the transient heat transfer equation using the ABAQUS/Standard 2024 finite element solver. Two types of moving heat sources were applied: a [...] Read more.
This study presents numerical analyses of the thermal, metallurgical, and mechanical processes involved in welding. The temperature fields were computed by solving the transient heat transfer equation using the ABAQUS/Standard 2024 finite element solver. Two types of moving heat sources were applied: a surface Gaussian distribution and a volumetric model, both implemented via DFLUX subroutines to simulate welding on butt-jointed plates. The simulation accounted for key welding parameters, including current, voltage, welding speed, and plate dimensions. The thermophysical properties of the INC 738 LC nickel superalloy were used in the model. Solidification characteristics, such as dendritic arm spacing, were estimated based on cooling rates around the weld pool. The model also calculated transverse residual stresses and applied a hot cracking criterion to identify regions vulnerable to cracking. The peak transverse stress, recorded in the heat-affected zone (HAZ), reached 1.1 GPa under Goldak’s heat input model. Additionally, distortions in the welded plates were evaluated for both heat source configurations. Full article
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13 pages, 3556 KiB  
Article
High-Temperature Tensile Grain Evolution and Mechanical Properties of Additively Manufactured TA15 Aerospace Titanium Alloy
by Pengfei Li, Zhenkun Dong, Qingtao Yang, Hao Xu, Dehai Kong and Minghui Hu
Metals 2025, 15(6), 677; https://doi.org/10.3390/met15060677 - 18 Jun 2025
Viewed by 305
Abstract
This study investigates the grain characteristics and high-temperature tensile properties of an additively manufactured (AM) TA15 titanium alloy. Directed energy deposition (DED) was utilized for its high material efficiency and design flexibility to explore the alloy’s applicability in aerospace manufacturing, where TA15 is [...] Read more.
This study investigates the grain characteristics and high-temperature tensile properties of an additively manufactured (AM) TA15 titanium alloy. Directed energy deposition (DED) was utilized for its high material efficiency and design flexibility to explore the alloy’s applicability in aerospace manufacturing, where TA15 is valued for its excellent high-temperature performance. A comparative analysis between DED and hot-rolled TA15 alloys was conducted at 25 °C and 600 °C to examine the influence of grain size and crystallographic texture on mechanical behavior. The AM TA15 alloy exhibited superior tensile properties at both temperatures compared to its hot-rolled counterpart. Microstructural analysis revealed finer grain size, stronger α-phase diffraction intensity, and altered grain boundary misorientation in the AM alloy after high-temperature testing, accompanied by improved plasticity. These findings highlight the potential of thermal process optimization and microstructural tailoring to enhance the high-temperature performance of AM TA15, offering valuable insights for the fabrication of critical aerospace components. Full article
(This article belongs to the Special Issue Machining, Grinding, and Laser Processing of Metallic Materials)
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15 pages, 5025 KiB  
Article
Impact of High Contact Stress on the Wear Behavior of U75VH Heat-Treated Rail Steels Applied for Turnouts
by Ruimin Wang, Guanghui Chen, Nuoteng Xu, Linyu Sun, Junhui Wu and Guang Xu
Metals 2025, 15(6), 676; https://doi.org/10.3390/met15060676 - 18 Jun 2025
Viewed by 298
Abstract
Considering the greater contact stress of turnout rails during wear and the development of heavy-haul railways, twin-disc sliding–rolling wear tests were performed on U75VH heat-treated rail steels applied for turnouts under high contact stress ranging from 1980 MPa to 2270 MPa. The microstructure [...] Read more.
Considering the greater contact stress of turnout rails during wear and the development of heavy-haul railways, twin-disc sliding–rolling wear tests were performed on U75VH heat-treated rail steels applied for turnouts under high contact stress ranging from 1980 MPa to 2270 MPa. The microstructure of the worn surfaces was analyzed using optical microscope (OM), scanning electron microscope (SEM), 3D microscope, electron backscatter diffraction (EBSD), and hardness tests. The results indicated that after 10 h of wear, the weight loss was 63 mg at a contact stress of 1980 MPa, while it reached 95 mg at a contact stress of 2270 MPa. At a given contact stress, the wear rate increased with increasing wear time, while a nearly linear increase in wear rate was observed with increasing contact stress. As wear time and contact stress increased, the worn surface showed more pronounced wear morphology, leading to greater surface roughness. Crack length significantly increased with wear time, and higher contact stress facilitated crack propagation, resulting in longer, deeper cracks. After 10 h of wear under a contact stress of 2270 MPa, large-scale cracks with a maximum length of 128.29 μm and a maximum depth of 31.10 μm were formed, indicating severe fatigue wear. Additionally, the thickness of the plastic deformation layer increased with the wear time and contact stress. The surface hardness was dependent on the thickness of this layer. After 10 h of wear under the minimum and maximum contact stresses, hardening rates of 0.39 and 0.48 were achieved, respectively. Full article
(This article belongs to the Special Issue Metallic Materials Behaviour Under Applied Load)
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13 pages, 3067 KiB  
Article
In Situ Investigation of Deformation Mechanisms and Stress Evolution in Mg-3Al-1Zn (AZ31) Alloy Using Synchrotron X-Ray Microdiffraction
by Yuxin Cao, Li Li, Yong Wang, Tuo Ye and Changping Tang
Metals 2025, 15(6), 675; https://doi.org/10.3390/met15060675 - 17 Jun 2025
Viewed by 283
Abstract
This study employs synchrotron polychromatic X-ray microdiffraction (micro-XRD) to resolve the dynamic interplay between deformation mechanisms and stress redistribution in a commercial Mg-3Al-1Zn (AZ31) alloy under uniaxial tension. Submicron-resolution mapping across 13 incremental load steps (12–73 MPa) reveals sequential activation of deformation modes: [...] Read more.
This study employs synchrotron polychromatic X-ray microdiffraction (micro-XRD) to resolve the dynamic interplay between deformation mechanisms and stress redistribution in a commercial Mg-3Al-1Zn (AZ31) alloy under uniaxial tension. Submicron-resolution mapping across 13 incremental load steps (12–73 MPa) reveals sequential activation of deformation modes: basal slip initiates at 46 MPa, followed by tensile twinning at 64 MPa, and non-basal slip accommodation during twin propagation at 68 MPa. Key findings include accelerated parent grain rotation (up to 0.275° basal plane tilt) between 43–46 MPa, stress relaxation in parent grains coinciding with twin nucleation, and a ~35 MPa stress reversal within twins. The critical resolved shear stress (CRSS) ratio of twinning to basal slip is experimentally determined as 1.8, with orientation-dependent variations attributed to parent grain crystallography. These results provide unprecedented insights into microscale deformation pathways, critical for optimizing magnesium alloy formability and performance in lightweight applications. Full article
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12 pages, 3830 KiB  
Article
Microstructural Features and Mechanical Properties of Laser–MIG Hybrid Welded–Brazed Ti/Al Butt Joints with Different Filler Wires
by Xin Zhao, Zhibin Yang, Yonghao Huang, Hongjun Zhu and Shaozheng Dong
Metals 2025, 15(6), 674; https://doi.org/10.3390/met15060674 - 17 Jun 2025
Viewed by 345
Abstract
Laser–MIG hybrid welding–brazing was performed to join TC4 titanium alloy and 5083 aluminum alloy with ER5356, ER4043 and ER2319 filler wires. The effects of the different filler wires on the microstructural features and mechanical properties of Ti/Al welded–brazed butt joints were investigated in [...] Read more.
Laser–MIG hybrid welding–brazing was performed to join TC4 titanium alloy and 5083 aluminum alloy with ER5356, ER4043 and ER2319 filler wires. The effects of the different filler wires on the microstructural features and mechanical properties of Ti/Al welded–brazed butt joints were investigated in detail. The wetting and spreading effect of the ER4043 filler wire was the best, especially on the weld’s rear surface. Serrated-shaped and rod-like IMCs were generated at the top region of the interface of the joint with ER4043 filler wire, but rod-like IMCs did not appear at the joints with the other filler wires. Only serrated-shaped IMCs appeared in the middle and bottom regions for the three filler wires. The phase compositions of all the IMCs were inferred as being made up of TiAl3. The average thickness of the IMC layer of joints with the ER5356 and ER2319 filler wires was almost the same and thinner than that of the joint with the ER4043 filler wire. The average thickness was largest in the middle region and smallest in the bottom region for all the joints with the three filler wires. The average microhardness in the weld metal of ER5356, ER4043 and ER2319 filler wires could reach up to 77.7 HV, 91.2 HV and 85.4 HV, respectively. The average tensile strength of joints with the ER5356, ER4043 and ER2319 filler wires was 106 MPa, 238 MPa and 192 MPa, respectively. The tensile samples all fractured at the IMC interface and showed a mixed brittle–ductile fracture feature. These research results could help confirm the appropriate filler wire for the laser–MIG hybrid welding–brazing of Ti/Al dissimilar butt joints. Full article
(This article belongs to the Special Issue Laser Processing Technology for Metals)
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23 pages, 7235 KiB  
Article
Corrosion Resistance Behavior of Mg-Zn-Ce/MWCNT Magnesium Nanocomposites Synthesized by Ultrasonication-Assisted Hybrid Stir–Squeeze Casting for Sacrificial Anode Applications
by S. C. Amith, Poovazhagan Lakshmanan, Gnanavelbabu Annamalai, Manoj Gupta and Arunkumar Thirugnanasambandam
Metals 2025, 15(6), 673; https://doi.org/10.3390/met15060673 - 17 Jun 2025
Viewed by 267
Abstract
The influence of multiwall carbon nanotube (MWCNT) reinforcements on electrochemical corrosion investigations at varying NaCl concentrations (0.4 M, 0.6 M, 0.8 M, 1 M) of Mg-Zn-Ce nanocomposites is studied in this work. The Mg-Zn-Ce/MWCNT nanocomposites were developed by using an ultrasonication-assisted hybrid stir–squeeze [...] Read more.
The influence of multiwall carbon nanotube (MWCNT) reinforcements on electrochemical corrosion investigations at varying NaCl concentrations (0.4 M, 0.6 M, 0.8 M, 1 M) of Mg-Zn-Ce nanocomposites is studied in this work. The Mg-Zn-Ce/MWCNT nanocomposites were developed by using an ultrasonication-assisted hybrid stir–squeeze (UHSS) casting method with different MWCNT concentrations (0, 0.4, 0.8, 1.2 wt.%) in a Mg-Zn-Ce magnesium alloy matrix. The microstructural characterizations shown using X-ray diffraction revealed the presence of secondary phases (MgZn2, Mg12Ce), T-phase (Mg7Zn3RE), α-Mg, and MWCNT peaks. Optical microscopy results showed grain refinement in the case of nanocomposites. Transmission electron microscope studies revealed well-dispersed MWCNT, indicating the good selection of processing parameters. The uniform dispersion of MWCNTs was achieved due to a hybrid stirring mechanism along with transient cavitation, ultrasonic streaming, and squeeze effect. The higher Ecorr value of −1.39 V, lower Icorr value (5.81 µA/cm2), and lower corrosion rate of 0.1 mm/Yr (↑77%) were obtained by 0.8% nanocomposite at 0.4 M NaCl concentration, when compared to the monolithic alloy. The Mg(OH)2 passive film formation on 0.8 wt.% nanocomposite was denser, attributed to the refined grains. At higher NaCl concentration, the one-dimensional morphological advantage of MWCNT helped to act as a barrier for further Mg exposure to excessive Cl− attack, which reduced the formation of MgCl2. Therefore, the UHSS-casted Mg-Zn-Ce/MWCNT nanocomposites present a good potential as sacrificial anodes for use in a wide range of industrial applications. Full article
(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials (Third Edition))
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17 pages, 22140 KiB  
Article
Evolution of Solid Products Formed During the Cathodic Decomposition of Chalcopyrite at Different Energetic Conditions in Acetic Acid
by Laura Denisse Jasso-Recio, Juan Carlos Fuentes-Aceituno, Roberto Pérez-Garibay, Aldo Valentín Enríquez-Farías, Alfredo Flores-Valdés and Jesús Torres-Torres
Metals 2025, 15(6), 672; https://doi.org/10.3390/met15060672 - 17 Jun 2025
Viewed by 239
Abstract
This paper presents a systematic analysis of the solid products formed during the cathodic decomposition of chalcopyrite using the acetic acid system. The reduction of chalcopyrite was assessed using different electrochemical and surface characterization techniques. The effect of multiple cathodic polarizations of chalcopyrite [...] Read more.
This paper presents a systematic analysis of the solid products formed during the cathodic decomposition of chalcopyrite using the acetic acid system. The reduction of chalcopyrite was assessed using different electrochemical and surface characterization techniques. The effect of multiple cathodic polarizations of chalcopyrite immersed in acetic acid was evaluated on the formation of less refractory copper species through the interaction of chalcopyrite with monoatomic hydrogen. The reduction products obtained were characterized by the FESEM/EDS techniques. The results revealed that the iron content in the chalcopyrite lattice was continuously decreased and released into the acetic acid solution when the polarization cycles were increased from 1 to 11 starting from OCP to −2.2 V vs. SHE. The chemical analyses revealed that iron released into the solution corresponds to 0.085 and 1.95 mg/L for 1 and 11 cycles, respectively. The open circuit potential (OCP) measurements of the solid products were shifted to more cathodic potentials than that of chalcopyrite, confirming the possibility to form less refractory species in this weak organic acid. Finally, the FESEM-EDS and XRD analyses showed that chalcopyrite refractoriness decreased, producing Cu, Cu2S, CuS, CuO, and C4H6CuO4H2O species depending on the applied energetic condition. Full article
(This article belongs to the Special Issue Advances in Flotation Separation and Mineral Processing)
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25 pages, 4538 KiB  
Article
Machine Learning-Based Multi-Objective Optimization for Enhancing the Performance of Block Support Structures for Electron Beam Additive Manufacturing
by Mustafa M. Nasr, Wadea Ameen, Abdulmajeed Dabwan and Abdulrahman Al-Ahmari
Metals 2025, 15(6), 671; https://doi.org/10.3390/met15060671 - 17 Jun 2025
Viewed by 325
Abstract
Electron beam melting (EBM) technology has gained prominence owing to its ability to enhance production efficiency and meet green manufacturing standards. However, overhang structures are a significant issue for additive manufacturing due to their need for supporting structures during printing. This increases manufacturing [...] Read more.
Electron beam melting (EBM) technology has gained prominence owing to its ability to enhance production efficiency and meet green manufacturing standards. However, overhang structures are a significant issue for additive manufacturing due to their need for supporting structures during printing. This increases manufacturing time, requiring more material, extra effort, and a more complex engineering procedure. Therefore, this research aims to develop an intelligent optimization method based on AI-ANFIS/Al-ANN and improved NSGA-III, integrating the AM design, 3D printing, and post-processing phases to enhance the performance of block support structures and the quality of the EBM parts produced. To achieve this, statistical analysis was performed to detail the simultaneous influence of block support type, block support structure design, and EBM parameters on fabricating performance, warping deformation, support removal time, and support volume. After that, intelligent models based on ANFIS/ANN and the advanced NSGA-III method were developed for monitoring and optimizing the performance of specified block support structures. The results reveal that the block support type, block support structure design, and EBM parameters simultaneously significantly affect block support structures’ performance. This study illustrated that the AI models based on ANFIS might provide more accurate and reliable estimation models for monitoring and predicting support volume, support removal time, and warping deformation, exhibiting reduced errors of 0.992%, 1.2%, 1.28%, and 1.06%, respectively, in comparison to empirical measurements, ANN models, and regression models. Finally, the developed intelligent method obtains the optimal block support type, block support design, and EBM parameters to enhance the quality of produced parts, reduce material wastage, and reduce the post-processing time of fabricated EBM Ti6Al4V. Henceforth, smart systems may be employed to create innovative solutions that integrate the AM design, 3D printing, and post-processing stages. This will allow for the monitoring and improvement of AM process performance, as well as the fulfillment of Industry 4.0 requirements. Full article
(This article belongs to the Section Additive Manufacturing)
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16 pages, 4578 KiB  
Article
Corrosion Behavior Analysis of Novel Sn-2.5Ag-1.0Bi-0.8Cu-0.05Ni and Sn-1.8Bi-0.75Cu-0.065Ni Pb-Free Solder Alloys via Potentiodynamic Polarization Test
by Sang Hoon Jung and Jong-Hyun Lee
Metals 2025, 15(6), 670; https://doi.org/10.3390/met15060670 - 17 Jun 2025
Viewed by 214
Abstract
The corrosion behaviors of newly developed solder alloys with excellent mechanical properties, Sn-2.5 Ag-1.0 Bi-0.8 Cu-0.05 Ni (SABC25108N) and Sn-1.5 Bi-0.75 Cu-0.065 Ni (SBC15075N), are analyzed to supplement the corrosion behavior of the limited corrosion data in Pb- and Zn-free solder compositions. A [...] Read more.
The corrosion behaviors of newly developed solder alloys with excellent mechanical properties, Sn-2.5 Ag-1.0 Bi-0.8 Cu-0.05 Ni (SABC25108N) and Sn-1.5 Bi-0.75 Cu-0.065 Ni (SBC15075N), are analyzed to supplement the corrosion behavior of the limited corrosion data in Pb- and Zn-free solder compositions. A potentiodynamic polarization test is conducted on these compositions in a NaCl electrolyte solution, the results of which are compared with those of conventional Sn-3.0 (wt%) Ag-0.5Cu and Sn-1.2Ag-0.5Cu-0.05Ni alloys. The results indicate that SBC15075N exhibits the lowest corrosion potential and highest corrosion current density, thus signifying the lowest corrosion resistance. By contrast, SABC25108N exhibits the lowest corrosion current density and highest corrosion resistance. Notably, SABC25108N shows a slower corrosion progression in the active state and exhibits the longest passive state. The difference in corrosion resistance is affected more significantly by the formation and distribution of the Ag3Sn intermetallic compound phase owing to the high Ag content instead of by the presence of Bi or Ni. This uniform dispersion of Ag3Sn IMC phases in the SABC25108N alloy effectively suppressed corrosion propagation along the grain boundaries and reduced the formation of corrosion products, such as Sn3O(OH)2Cl2, thereby enhancing the overall corrosion resistance. These findings provide valuable insights into the optimal design of solder alloys and highlight the importance of incorporating sufficient Ag content into multicomponent compositions to improve corrosion resistance. Full article
(This article belongs to the Special Issue New Welding Materials and Green Joint Technology—2nd Edition)
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19 pages, 3263 KiB  
Article
Removal of Iron, Zinc, and Copper Impurities from Sodium Aluminate After the Bayer Process
by Vladimir Damjanović, Srećko Stopić, Duško Kostić, Mitar Perušić, Radislav Filipović, Aleksandar Mitrašinović and Dragana Kostić
Metals 2025, 15(6), 669; https://doi.org/10.3390/met15060669 - 17 Jun 2025
Viewed by 382
Abstract
This study investigates the influence of specific surface area (SSA) and aluminum hydroxide particle size on sodium aluminate’s purification efficiency in the Bayer process. This research examines how variations in SSA affect the adsorption and incorporation of contaminants such as Cu, Fe, and [...] Read more.
This study investigates the influence of specific surface area (SSA) and aluminum hydroxide particle size on sodium aluminate’s purification efficiency in the Bayer process. This research examines how variations in SSA affect the adsorption and incorporation of contaminants such as Cu, Fe, and Zn, as well as the optimal balance between effective purification and excessive Al2O3 loss. Different SSA values and purification durations are analyzed to optimize the purification process and determine conditions that maximize impurity removal while maintaining system stability. Additionally, solid residue characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) provides insights into impurity incorporation mechanisms, including isomorphic replacement, surface adsorption, and co-crystallization. This study highlights key process parameters that influence impurity behavior and crystallization dynamics, offering valuable guidance for refining industrial purification strategies and improving aluminum hydroxide quality. Full article
(This article belongs to the Special Issue Innovative Solutions for the Recovery of Metals from Primary and Secondary Raw Materials)
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16 pages, 6051 KiB  
Article
Phosphorus Removal in Metallurgical-Grade Silicon via a Combined Approach of Si-Fe Solvent Refining and SiO2-TiO2-CaO-CaF2 Slag Refining
by Yi Zhong, Qing Zhao and Juncheng Li
Metals 2025, 15(6), 668; https://doi.org/10.3390/met15060668 - 16 Jun 2025
Viewed by 211
Abstract
As a critical impurity in the production of solar-grade silicon, the concentration of phosphorus (P) significantly affects photoelectric conversion efficiency. To address the challenge of P removal in solar-grade silicon production, this study proposes a combined process of Si-Fe solvent refining and SiO [...] Read more.
As a critical impurity in the production of solar-grade silicon, the concentration of phosphorus (P) significantly affects photoelectric conversion efficiency. To address the challenge of P removal in solar-grade silicon production, this study proposes a combined process of Si-Fe solvent refining and SiO2-TiO2-CaO-CaF2 slag treatment. Under conditions utilizing collaborative refining with an alloy composition of Si-10 wt. %Fe and a slag composition of 32 wt. %SiO2-48 wt. %CaO-10 wt. %TiO2-10 wt. %CaF2, the removal rate of P in silicon can reach up to 96.8%. This paper investigates the effectiveness of combining solvent refining with slag making under fixed conditions of a Si-10 wt. %Fe alloy paired with various slag systems (no slag addition, binary slag SiO2-TiO2, ternary slag SiO2-CaO-TiO2, and quaternary slag SiO2-TiO2-CaO-CaF2). Based on the experimental results, the optimal TiO2 content in the slag system for maximizing P removal was analyzed and determined. Finally, leveraging both theoretical analysis and experimental findings, the mechanism of P removal was elucidated as a dual process: P is oxidized into Ca3(PO4)2 within the slag phase, and residual P is captured by the Fe-Si-Ti ternary phase. Full article
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15 pages, 4039 KiB  
Article
Evolution of Microstructure and Mechanical Properties of Steam Generator Material After Long-Term Operation in Nuclear Power Plant
by David Slnek, Mária Dománková, Marek Adamech, Jana Petzová, Katarína Bártová, Marek Kudláč and Matúš Gavalec
Metals 2025, 15(6), 667; https://doi.org/10.3390/met15060667 - 16 Jun 2025
Viewed by 206
Abstract
The microstructural evolution and mechanical properties of WWER 440 steam generator steel GOST 22K after long-term operation were thoroughly examined in this study. The samples were taken directly from a steam generator using the small punch test method. The uniqueness of these samples [...] Read more.
The microstructural evolution and mechanical properties of WWER 440 steam generator steel GOST 22K after long-term operation were thoroughly examined in this study. The samples were taken directly from a steam generator using the small punch test method. The uniqueness of these samples lies in the fact that they were real operating materials used in a nuclear power plant with different years of operation. The microstructure was characterized using optical microscopy and transmission electron microscopy supplemented by selective electron diffraction and semi-quantitative chemical microanalysis. It was found that with the prolongation of the operation time of the steam generator, the density of carbides increased slightly, which was reflected in a decrease in the mean distance between particles, but these differences were very small, which indicates the microstructural stability of GOST 22K steel. The stability of this steel was also confirmed by measuring its mechanical properties, which changed only minimally depending on the years of operation. The tensile strength values were in the range of 508 to 579 MPa. In the case of the ductile-to-brittle transition temperature (DBTT), a slight increase was found after 6 years of operation. The DBTT did not change significantly with subsequent operation. Full article
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23 pages, 5327 KiB  
Article
Optimized ANN Model for Predicting Buckling Strength of Metallic Aerospace Panels Under Compressive Loading
by Shahrukh Khan, Saiaf Bin Rayhan, Md Mazedur Rahman, Jakiya Sultana and Gyula Varga
Metals 2025, 15(6), 666; https://doi.org/10.3390/met15060666 - 15 Jun 2025
Viewed by 444
Abstract
The present research proposes an Artificial Neural Network (ANN) model to predict the critical buckling load of six different types of metallic aerospace grid-stiffened panels: isogrid type I, isogrid type II, bi-grid, X-grid, anisogrid, and waffle, all subjected to compressive loading. Six thousand [...] Read more.
The present research proposes an Artificial Neural Network (ANN) model to predict the critical buckling load of six different types of metallic aerospace grid-stiffened panels: isogrid type I, isogrid type II, bi-grid, X-grid, anisogrid, and waffle, all subjected to compressive loading. Six thousand samples (one thousand per panel type) were generated using the Latin Hypercube Sampling method to ensure a diverse and comprehensive dataset. The ANN model was systematically fine-tuned by testing various batch sizes, learning rates, optimizers, dense layer configurations, and activation functions. The optimized model featured an eight-layer architecture (200/100/50/25/12/6/3/1 neurons), used a selu–relu–linear activation sequence, and was trained using the Nadam optimizer (learning rate = 0.0025, batch size = 8). Using regression metrics, performance was benchmarked against classical machine learning models such as CatBoost, XGBoost, LightGBM, random forest, decision tree, and k-nearest neighbors. The ANN achieved superior results: MSE = 2.9584, MAE = 0.9875, RMSE = 1.72, and R2 = 0.9998, significantly outperforming all other models across all metrics. Finally, a Taylor Diagram was plotted to assess the model’s reliability and check for overfitting, further confirming the consistent performance of the ANN model across both training and testing datasets. These findings highlight the model’s potential as a robust and efficient tool for predicting the buckling strength of metallic aerospace grid-stiffened panels. Full article
(This article belongs to the Special Issue Mechanical Structure Damage of Metallic Materials)
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14 pages, 2626 KiB  
Article
Warpage Prediction in Wire Arc Additive Manufacturing: A Comparative Study of Isotropic and Johnson–Cook Plasticity Models
by Saeed Behseresht and Young Ho Park
Metals 2025, 15(6), 665; https://doi.org/10.3390/met15060665 - 15 Jun 2025
Viewed by 342
Abstract
Wire Arc Additive Manufacturing (WAAM), a specific type of Directed Energy Deposition (DED) additive manufacturing, has recently gained widespread attention for manufacturing industrial components. WAAM has many advantages compared to other metal AM processes such as powder bed fusion. It is not only [...] Read more.
Wire Arc Additive Manufacturing (WAAM), a specific type of Directed Energy Deposition (DED) additive manufacturing, has recently gained widespread attention for manufacturing industrial components. WAAM has many advantages compared to other metal AM processes such as powder bed fusion. It is not only cost-efficient and easily accessible, but also capable of manufacturing large-scale industrial components in a short period of time. However, due to the inherent layered nature of the process and significant heat accumulation, parts can experience severe warping, often leading to part rejection. Predicting these anomalies prior to manufacturing would allow for process parameter adjustments to reduce or eliminate residual stresses and large deformations. In this study, we develop a simulation-based model capable of accurately predicting final deformations and unintended warpages. A Johnson–Cook plasticity model with isotropic hardening is implemented through a UMAT user subroutine in Abaqus. The proposed model is then utilized to predict the residual stresses and deformations in WAAM-fabricated parts. Simple wall geometries with 4, 8, and 20 layers deposited on build plates of varying thicknesses, are tested to assess the performance of the model. Combined Johnson–Cook plasticity and isotropic hardening for the WAAM process were implemented for the first time in this study, and the model was validated against experimental data, showing a maximum deviation of 4%. Thermal analysis of a four-layer-high wall took 12 min, while structural analysis using the proposed model took 1 h and 40 min. In comparison, thermo-mechanical analysis of the same geometry reported in the literature takes 14 h. The results demonstrate that the proposed model is not only highly accurate in predicting warpage but also significantly faster than other methodologies reported in the literature. Full article
(This article belongs to the Special Issue Additive Manufacturing and Processing of Metallic Alloys and Composites)
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17 pages, 39047 KiB  
Article
Process Studies on the W-C-Ti System Using a High-Throughput Laser-Based Additive Manufacturing Approach
by Tim Schubert, Christiana Malchus, Julian Schurr, Emanuel Wengenmayr, Timo Bernthaler and Gerhard Schneider
Metals 2025, 15(6), 664; https://doi.org/10.3390/met15060664 - 14 Jun 2025
Viewed by 293
Abstract
Conventional WC-Co hard metals have proven to be difficult to manufacture by means of laser powder bed fusion (PBF-LB), resulting in residual pores, crack formation, foreign phase formation, and the inhomogeneous growth of the carbide phase. Alternative compositions such as the W-C-Ti system [...] Read more.
Conventional WC-Co hard metals have proven to be difficult to manufacture by means of laser powder bed fusion (PBF-LB), resulting in residual pores, crack formation, foreign phase formation, and the inhomogeneous growth of the carbide phase. Alternative compositions such as the W-C-Ti system presented in this study need to be investigated. Through the employment of a high-throughput screening approach, 11 alloy compositions were investigated to determine the influence of the carbon content and tungsten–titanium ratios on microstructure formation and basic mechanical properties. Two screenings were conducted, with one varying the carbon content (10–35 at.%) and the other adjusting the W/Ti ratios (10:90 to 60:40 at.%). Microstructural analyses using scanning electron microscopy (SEM), X-ray diffraction (XRD), and hardness measurements provided insights into phase formation, grain distribution, and mechanical properties. The results showed that increasing the carbon content significantly enhanced the hardness (from 681 HV (10 at.% C) to 1898 HV (35 at.% C)) due to higher δ-(Ti,W)C1−x carbide phase fractions. Alloys with a higher tungsten content exhibited finer microstructures and an improved crack resistance while maintaining a high hardness (1900–2100 HV). This study identified an alloy with 32.5 at.% W, 32.5 at.% Ti, and 35 at.% C as a promising candidate for further investigation, with properties similar to those of a conventional WC-Co hard metal. Full article
(This article belongs to the Section Additive Manufacturing)
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27 pages, 6313 KiB  
Review
Experimental and Simulation Research Progress on the Solidification Structure Evolution of High Chromium Cast Iron
by Longxiao Huang, Yang Liu and Hanguang Fu
Metals 2025, 15(6), 663; https://doi.org/10.3390/met15060663 - 13 Jun 2025
Viewed by 330
Abstract
High-chromium cast irons (HCCIs) have emerged as preferred materials for critical wear-resistant components operating under extreme conditions, owing to their excellent wear resistance, low cost, and good castability. They are widely used in metallurgy, energy, and mechanical engineering industries. The evolution of solidification [...] Read more.
High-chromium cast irons (HCCIs) have emerged as preferred materials for critical wear-resistant components operating under extreme conditions, owing to their excellent wear resistance, low cost, and good castability. They are widely used in metallurgy, energy, and mechanical engineering industries. The evolution of solidification microstructure directly governs the final properties of HCCIs, making the in-depth investigation of their solidification behavior of great significance. This paper provides a comprehensive review of recent experimental and simulation-based advances in understanding the solidification microstructure evolution of HCCIs. The effects of alloy composition, cooling rate, and inoculation treatments on microstructure development and phase distribution during solidification are critically analyzed. Furthermore, the application of simulation techniques—including thermodynamic modeling, phase-field method, cellular automata, and finite element analysis—is discussed in detail, highlighting their roles in revealing the mechanisms of microstructural evolution. Finally, the current challenges and potential future research directions in the study of the solidification behavior of high-chromium cast irons are outlined. Full article
(This article belongs to the Special Issue Calphad Tools for the Metallurgy of Solidification)
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10 pages, 868 KiB  
Article
Thermal Demercurization of Coal Sorbents
by Bagdaulet Kenzhaliyev, Valeriy Volodin, Sergey Trebukhov, Alina Nitsenko, Xeniya Linnik, David Magomedov and Yerkebulan Kilibayev
Metals 2025, 15(6), 662; https://doi.org/10.3390/met15060662 - 13 Jun 2025
Viewed by 226
Abstract
The extraction of mercury in the vapor–gas phase from coal sorbents, used to capture mercury from industrial waste gases, was studied herein to develop a unified technology. The behavior of mercury compounds (Hg2Cl2 and HgCl2) under conditions of [...] Read more.
The extraction of mercury in the vapor–gas phase from coal sorbents, used to capture mercury from industrial waste gases, was studied herein to develop a unified technology. The behavior of mercury compounds (Hg2Cl2 and HgCl2) under conditions of thermal demercurization in a fore vacuum and at atmospheric pressure was examined using partial pressure diagrams. It was established that the stable phases during the technological process are vaporous mercury and Cl2. As a result of technological research and extensive testing with developed equipment at 400–800 °C and pressure in the range of 0.13–91.99 kPa, it was established that mercury in a vacuum under these conditions almost completely enters the vapor–gas phase (99.4–99.97%). A similar degree of mercury extraction from a coal sorbent was achieved at 600–800 °C at atmospheric pressure. A study was conducted, and it was established that the sorbent after thermal demercurization—in terms of its sorption capacity for gold—was practically comparable to fresh, unused Norit sorbent. Full article
(This article belongs to the Section Extractive Metallurgy)
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17 pages, 2280 KiB  
Article
Effect of PBF-LB/M Processing on the Microstructural Evolution and Local Mechanical Properties of Novel Al-Fe-Si-Cr-Ni Alloy
by Alessandra Martucci, Paolo Fino and Mariangela Lombardi
Metals 2025, 15(6), 661; https://doi.org/10.3390/met15060661 - 13 Jun 2025
Viewed by 271
Abstract
The present study aims to investigate the microstructural evolution and local mechanical properties of an AlFe18Si8Cr5Ni2 alloy processed via Powder Bed Fusion–Laser-Based Manufacturing (PBF-LB/M). Designed with a focus on sustainability, this alloy was produced by deriving the necessary elements from AlSi10Mg and 304L [...] Read more.
The present study aims to investigate the microstructural evolution and local mechanical properties of an AlFe18Si8Cr5Ni2 alloy processed via Powder Bed Fusion–Laser-Based Manufacturing (PBF-LB/M). Designed with a focus on sustainability, this alloy was produced by deriving the necessary elements from AlSi10Mg and 304L steel, two of the most widely used alloys and, consequently, among the easiest materials to source from machining scrap. By leveraging iron, chromium, and nickel from these widespread standard compositions, the alloy mitigates the detrimental effects of Fe contamination in Al-based alloys while simultaneously enhancing mechanical performance. A comprehensive investigation of the impact of rapid solidification and thermal cycling offered novel insights into phase stability, elemental distribution, and local mechanical behavior. In particular, microstructural analyses using scanning electron microscopy (SEM), field emission SEM, energy-dispersive X-ray spectroscopy, X-ray diffraction, and differential scanning calorimetry revealed significant phase modifications post PBF-LB/M processing, including Fe-rich acicular phase segregation at melt pool boundaries and enhanced strengthening phase formation. In addition, nanoindentation mapping was used to demonstrate the correlation between microstructural heterogeneity and local mechanical properties. The findings contribute to a deeper understanding of Al-Fe-Si-Cr-Ni alloy changes after the interaction with the laser, supporting the development of high-performance, sustainable Al-based materials for PBF-LB/M applications. Full article
(This article belongs to the Special Issue Microstructure, Crystallography, and Mechanical Properties of Metallic Materials)
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15 pages, 1470 KiB  
Article
Multiscale Modeling and Analysis of Hydrogen-Enhanced Decohesion Across Block Boundaries in Low-Carbon Lath Martensite
by Ivaylo H. Katzarov
Metals 2025, 15(6), 660; https://doi.org/10.3390/met15060660 - 13 Jun 2025
Viewed by 330
Abstract
Low-carbon lath martensite is highly susceptible to hydrogen embrittlement due to the presence of a high density of lath/block boundaries. In this study, I employ a continuum decohesion model to investigate the effects of varying hydrogen concentrations and tensile loads on the cohesive [...] Read more.
Low-carbon lath martensite is highly susceptible to hydrogen embrittlement due to the presence of a high density of lath/block boundaries. In this study, I employ a continuum decohesion model to investigate the effects of varying hydrogen concentrations and tensile loads on the cohesive strength of low- and high-angle block boundaries. The thermodynamic properties of the cohesive zone are described using excess variables, which establish a link between atomistic energy calculations and the continuum model for gradual decohesion at a grain boundary. The aim of this study is to develop an in-depth understanding of how hydrogen affects the cohesive strength of block boundaries in a lath martensitic structure by integrating continuum and atomistic computational modeling and to apply the resulting insights to investigate the effects of varying hydrogen concentrations and tensile loads on interface decohesion. I incorporate hydrogen mobility and segregation at low- and high-angle twist boundaries in body-centered cubic (bcc) Fe to quantify the hydrogen-induced effects on progressive decohesion under tensile stress. A constant hydrogen flux through the free surfaces of a bicrystal containing a block boundary is imposed to simulate realistic boundary conditions. The results of the simulations show that, in the presence of hydrogen flux, separation across the block boundaries occurs at a tensile load significantly lower than the critical stress required for rupture in a hydrogen-free lath martensitic structure. Full article
(This article belongs to the Special Issue Hydrogen Embrittlement of Metals: Behaviors and Mechanisms)
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14 pages, 3101 KiB  
Article
Construction of CuCo2O4@NiFe-LDH Core–Shell Heterostructure for High-Performance Hybrid Supercapacitors
by Yang Chen, Man Li, Chengyu Xue and Fuxiang Wei
Metals 2025, 15(6), 659; https://doi.org/10.3390/met15060659 - 13 Jun 2025
Viewed by 368
Abstract
Transition metal oxides (TMOs) are considered to be highly promising materials for supercapacitor electrodes due to their low cost, multiple convertible valence states, and excellent electrochemical properties. However, inherent limitations, including restricted specific surface area and low electrical conductivity, have largely restricted their [...] Read more.
Transition metal oxides (TMOs) are considered to be highly promising materials for supercapacitor electrodes due to their low cost, multiple convertible valence states, and excellent electrochemical properties. However, inherent limitations, including restricted specific surface area and low electrical conductivity, have largely restricted their application in supercapacitors. In this paper, core–shell heterostructures of nickel–iron layered double hydroxide (NiFe-LDH) nanosheets uniformly grown on CuCo2O4 nanoneedles were synthesized by hydrothermal and calcination methods. It is found that the novel core–shell structure of CuCo2O4@NiFe-LDH improves the electrical conductivity of the electrode materials and optimizes the charge transport path. Under the synergistic effect of the two components and the core–shell heterostructure, the CuCo2O4@NiFe-LDH electrode achieves an ultra-high specific capacity of 323.4 mAh g−1 at 1 A g−1. And the capacity retention after 10,000 cycles at 10 A g−1 is 90.66%. In addition, the assembled CuCo2O4@NiFe-LDH//RGO asymmetric supercapacitor device achieved a considerable energy density (68.7 Wh kg−1 at 856.3 W kg−1). It also has 89.36% capacity retention after 10,000 cycles at 10 A g−1. These properties indicate the great potential application of CuCo2O4@NiFe-LDH in the field of high-performance supercapacitors. Full article
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20 pages, 12096 KiB  
Article
Effect on the Electrochemical Properties of PEO Films Produced on Commercially Pure Titanium Using Multicomponent Oxide Coatings
by Lauri Ruberti, Heloisa Andréa Acciari, Diego Rafael Nespeque Correa, Yasmin Bastos Pissolitto, Elidiane Cipriano Rangel, Francisco Trivinho-Strixino and Nilson Cristino da Cruz
Metals 2025, 15(6), 658; https://doi.org/10.3390/met15060658 - 13 Jun 2025
Viewed by 451
Abstract
Titanium has specific uses due to its cost, which is counterbalanced by its extraordinary chemical and physical properties. Submarine hulls and nuclear power plant pipes have been made of titanium since the last century due to its high corrosion resistance, and the aircraft [...] Read more.
Titanium has specific uses due to its cost, which is counterbalanced by its extraordinary chemical and physical properties. Submarine hulls and nuclear power plant pipes have been made of titanium since the last century due to its high corrosion resistance, and the aircraft industry has also exploited its remarkable properties, such as lightness and high melting point. Surface modifications by plasma electrolytic oxidation (PEO) may increase its corrosion resistance, roughness and wettability. Furthermore, greater corrosion resistance is a rather attractive property in nuclear power plant pipes, although the increased roughness and wettability are disadvantageous downsides as they favor the attachment of marine organisms. Nonetheless these new features are particularly interesting for biomedical applications. In this study, PEO films were produced on commercially pure titanium substrates using different electrolytes, one of which contains zirconium dioxide and the other consisting of tantalum pentoxide, in addition to a third one composed of a combination of the former two. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses were performed in addition to contact angle and roughness measurements, and electrochemical tests were carried out to comparatively characterize the different film compositions. The results revealed that excellent corrosion resistance was achieved by mixing oxides in the electrolyte. Full article
(This article belongs to the Special Issue Surface Engineering and Properties of Metallic Biomaterials)
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26 pages, 1058 KiB  
Article
Complex Model for Hot Metal Temperature Prediction: Torpedo Car and Ladle Processes
by Milan Durdán, Ján Terpák, Marek Laciak, Ján Kačur, Patrik Flegner and Gabriel Tréfa
Metals 2025, 15(6), 657; https://doi.org/10.3390/met15060657 - 12 Jun 2025
Viewed by 376
Abstract
Hot metal is produced in a blast furnace. Subsequently, the hot metal is loaded from the blast furnace into a torpedo car and transported to the ladle, where the desulfurization process of the hot metal is realized. After desulfurization, the hot metal is [...] Read more.
Hot metal is produced in a blast furnace. Subsequently, the hot metal is loaded from the blast furnace into a torpedo car and transported to the ladle, where the desulfurization process of the hot metal is realized. After desulfurization, the hot metal is poured from the ladle into the oxygen converter. The temperature of the hot metal has an impact on the steelmaking process realized in the oxygen converter. The complex model presented in the article calculates the temperature drop of the hot metal in the torpedo car and the ladle. Predicting the hot metal temperature behavior allows for determining the length of time the hot metal transport requires and thus initiating steelmaking at its required hot metal temperature. This model, based on heat transfer by conduction, convection, radiation, heat accumulation, and chemical reactions, also allows for the monitoring of the hot metal temperature drop in the torpedo car and the ladle, the analysis of the influence of the linings in terms of heat accumulation, the investigation of the desulfurization process in the ladle, and the optimization torpedo and ladle selection in terms of the accumulated heat in the lining for their entry into the hot metal transport process. An absolute and relative error calculation was used to verify the proposed model. Full article
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11 pages, 3992 KiB  
Article
Atomistic-Level Insights into MgO and Na2O Modifications of Molten Aluminosilicate Slag: A Molecular Dynamics Research on Structural Evolution and Properties
by Chunhe Jiang, Bo Liu, Jianliang Zhang and Kejiang Li
Metals 2025, 15(6), 656; https://doi.org/10.3390/met15060656 - 12 Jun 2025
Viewed by 535
Abstract
Molecular dynamics simulations were employed to systematically investigate the synergistic effects of Na2O and MgO on the atomistic-scale structural evolution and properties of CaO–SiO2–Al2O3-based slags. By constructing slag models with varying Na2O/MgO ratios, [...] Read more.
Molecular dynamics simulations were employed to systematically investigate the synergistic effects of Na2O and MgO on the atomistic-scale structural evolution and properties of CaO–SiO2–Al2O3-based slags. By constructing slag models with varying Na2O/MgO ratios, the variations in pair distribution functions, oxygen structural units, coordination environments, diffusion coefficients, and viscosity were analyzed in detail. Compared with Na2O, MgO exhibits a stronger ability to disrupt oxygen structural units. The relative content of Na2O and MgO does not significantly affect the bond lengths within the basic network structure. As the MgO content increases, a greater proportion of bridging oxygens and tricluster oxygens are converted into non-bridging oxygens and free oxygens, markedly reducing the degree of polymerization in the slag network. Although MgO also promotes the formation of tetrahedrally coordinated Al (Al4) more effectively than Na2O, its dominant role in enhancing slag fluidity is primarily attributed to its impact on the oxygen structural units. Despite the much higher self-diffusion coefficient of Na+ compared to Mg2+, MgO more significantly reduces the overall viscosity and enhances the fluidity of the melt than Na2O. Therefore, although the number of Na atoms is greater under equal mass conditions, Mg demonstrates a considerably stronger capacity to depolymerize the slag structure. Full article
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