Metals

19 pages, 19396 KB

Open AccessArticle

Aluminosilicochrome Produced from Technogenic Wastes as an Alternative to Conventional Ferrosilicochrome in Refined Ferrochrome Smelting

by Aristotel Issagulov, Aibar Myrzagaliyev, Saule Sagintayeva, Yerbolat Makhambetov, Diana Isagulova and Kuanysh Ilyassov

Metals 2026, 16(8), 911; https://doi.org/10.3390/met16080911 - 14 Aug 2026

Abstract

This study investigates the possibility of using aluminosilicochrome (ASC) produced from technogenic raw materials as a potential alternative to FSC-48 ferrosilicochrome in refined ferrochrome smelting. Laboratory smelting tests were carried out in an induction furnace using alumina crucibles with a charge mass of [...] Read more.

This study investigates the possibility of using aluminosilicochrome (ASC) produced from technogenic raw materials as a potential alternative to FSC-48 ferrosilicochrome in refined ferrochrome smelting. Laboratory smelting tests were carried out in an induction furnace using alumina crucibles with a charge mass of 50 g. The two variants were compared based on the material balance, SEM-EDS analysis of the metallic and slag phases, a conditional estimate of chromium transfer to the metal, and the results of thermodynamic modeling in FactSage 8.4. It was established that a Cr–Fe metallic phase is formed when both FSC-48 and ASC are used. The average metal mass was 13.8 g for FSC-48 and 13.3 g for ASC. According to SEM-EDS data, the Cr content in the metallic phase was 70.53 and 68.64 wt. %, respectively. Aluminum introduced with ASC predominantly transfers into the slag, increasing its Al content to 20.81 wt. %. The conditional estimate of total chromium transfer from the charge to the metallic phase was 91.9% for FSC-48 and 91.6% for ASC. FactSage modeling showed higher calculated ore-derived Cr recovery for ASC under equilibrium conditions; however, excessive ASC addition increased the Si content in the metal. The obtained results confirm the fundamental possibility of using ASC as a complex reductant in refined ferrochrome smelting. Full article

(This article belongs to the Section Extractive Metallurgy)

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14 pages, 29702 KB

Open AccessArticle

In Situ Investigation of Temperature and Strain-Rate-Dependent Serrated Flow and Crack Evolution in Mn13 High–Manganese Steel

by Ming Gao, Yang Liu, Yanling Zhang, Yaqiang Li, Qiang Liu and Lei Cheng

Metals 2026, 16(8), 910; https://doi.org/10.3390/met16080910 - 14 Aug 2026

Abstract

Temperature- and strain-rate-dependent serrated flow, localized plastic instability, and qualitative microcrack evolution in Mn13 Hadfield steel were investigated using stress–strain analysis and in situ tensile observation. Solution treatment at 1050 °C for 1–1.5 h followed by water quenching yielded homogeneous single-phase austenite. Type [...] Read more.

Temperature- and strain-rate-dependent serrated flow, localized plastic instability, and qualitative microcrack evolution in Mn13 Hadfield steel were investigated using stress–strain analysis and in situ tensile observation. Solution treatment at 1050 °C for 1–1.5 h followed by water quenching yielded homogeneous single-phase austenite. Type A and Type B serrations were dominant at room temperature at 1 × 10⁻³ s⁻¹ and at 100 °C at 1 × 10⁻² s⁻¹, whereas the room-temperature specimen tested at 1 × 10⁻² s⁻¹ showed delayed serration onset and pronounced Type B stress drops only at high strains. Type C serrations occurred mainly near fracture at 100 °C at 1 × 10⁻³ s⁻¹, 200 °C at 1 × 10⁻² s⁻¹ and 200 °C at 5 × 10⁻² s⁻¹. In situ observations further reveal that different serration types correspond to distinct localized deformation modes. During Type A serrations, the tracked feature exhibited unidirectional stepwise migration involving forward motion, arrest, and renewed advance. Type B serrations were associated with discontinuous pulse-like migration characterized by rapid forward motion, brief arrest, local backward motion, and renewed advance. No regular trajectory was observed during Type C stress drops; only local brightness changes and slight positional shifts occurred. These observations link macroscopic serrations to localized deformation in Mn13 steel and provide qualitative in situ evidence for grain-boundary microcrack initiation and evolution during deformation. Full article

(This article belongs to the Special Issue Metal Material Failure Analysis and Optimization)

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13 pages, 3160 KB

Open AccessArticle

HAZ Evolution in PHS1500 and Q&P1180 Steels Under Resistance Spot Welding Thermal Cycles

by Maria Emanuela Palmieri, Matteo Villa, Giuseppe Macoretta, Michele Maria Tedesco and Luigi Tricarico

Metals 2026, 16(8), 909; https://doi.org/10.3390/met16080909 - 14 Aug 2026

Abstract

Resistance spot welding (RSW) is the primary joining technology for automotive advanced high-strength steels (AHSSs), where the inherent severe thermal cycles profoundly alter the heat-affected zone (HAZ) microstructure, leading to localized variations in mechanical properties. Characterizing the spatial gradients in microstructure and the [...] Read more.

Resistance spot welding (RSW) is the primary joining technology for automotive advanced high-strength steels (AHSSs), where the inherent severe thermal cycles profoundly alter the heat-affected zone (HAZ) microstructure, leading to localized variations in mechanical properties. Characterizing the spatial gradients in microstructure and the resulting mechanical properties remains a major challenge in weld failure analysis due to the small size of the HAZ and its complex thermal history. In this study, the HAZ of two prominent AHSS grades, a first-generation press hardening steel (PHS1500) and a third-generation quenching and partitioning steel (Q&P1180), was physically simulated using a Gleeble^® 3180 thermomechanical simulator to achieve precise control over the localized thermal cycles. The investigation first evaluated the role of thermal cycle duration, governed by the welding time parameter (300 ms vs. 800 ms), on the microstructural evolution of the PHS1500 steel. Increasing the weld time from 300 ms to 800 ms reduced the cooling rate under the nominal 1400 °C condition from approximately 3000 K/s to 2500 K/s; however, no marked change was observed in the overall microstructural and hardness trends within the investigated range. Subsequently, using the 300 ms thermal profile as a reference baseline, a comparative metallurgical study was conducted between PHS1500 and Q&P1180. Under the same 300 ms thermal history, the maximum hardness reduction relative to the corresponding base material was approximately 42% for PHS1500 and 12% for Q&P1180. The hardness minima were located within FE-estimated temperature ranges close to the Ac₁ region for PHS1500 and around 600 °C for Q&P1180, respectively. This comparison highlighted the distinct microstructural responses of the two generations across the upper-critical (UCHAZ), inter-critical (ICHAZ), and sub-critical (SCHAZ) zones. Moreover, microhardness profiles were correlated with the microstructural findings, establishing a correlation among the simulated thermal history, the observed microstructural evolution, and localized mechanical performance. Full article

(This article belongs to the Special Issue Recent Advances in Microstructure, Experiment and Numerical Simulation of Steel)

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17 pages, 3792 KB

Open AccessArticle

Effects of Different Post-Processing Heat Treatment Sequences on the Mechanical Properties of AISI 316L Processed Through Laser-Directed Energy Deposition Additive Manufacturing

by Leandro João da Silva, Cauê Almeida Stein, Anselmo Thiesen, Jr., Jhonattan Gutjahr and Danielle Bond

Metals 2026, 16(8), 908; https://doi.org/10.3390/met16080908 - 14 Aug 2026

Abstract

Metal parts produced by directed energy deposition go through a complex thermal history during the deposition stage, which can result in heterogeneous microstructures and the accumulation of residual stress. While individual post-processing heat treatments are widely used to address these issues, the industrial [...] Read more.

Metal parts produced by directed energy deposition go through a complex thermal history during the deposition stage, which can result in heterogeneous microstructures and the accumulation of residual stress. While individual post-processing heat treatments are widely used to address these issues, the industrial logistics of manufacturing large components often demand specific sequences of combined treatments (e.g., applying stress relief prior to substrate detachment to prevent distortion, followed by high-temperature solubilization, or vice versa). The microstructural and mechanical consequences of altering this sequence remain underexplored. Therefore, this study aimed to investigate the effects of different post-processing heat treatment sequences on the mechanical properties of AISI 316L deposited through laser-directed energy deposition. Tensile and Charpy impact tests were carried out on the specimens under five conditions: (i) as-built; (ii) stress relief; (iii) solubilization; (iv) stress relief and solubilization; and (v) solubilization and stress relief. A statistical analysis of variance supported a comparison between each treatment’s influence on the mechanical properties under each condition. Furthermore, the typical microstructures were assessed by optical microscopy, scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The solubilization treatment reduced the ultimate tensile strength (from ~618 MPa to ~576 MPa) and the yield stress (from ~424 MPa to ~299 MPa), while no significant change was observed in elongation (ranging from 27% to 38%) due to high data dispersion. The stress relief, however, did not significantly change these mechanical properties. Considering the heat treatment combinations, the solubilization had a stronger impact on tensile stress than the stress relief, regardless of the treatment order. Impact resistance was not significantly affected by any of the heat treatments, maintaining an average of ~114 J. The solubilization treatment fully recrystallized the microstructure, while the stress relief did not promote any significant changes at an optical microscopy level. Ultimately, this study demonstrates that the microstructural transformations induced by the solubilization step dominate the final mechanical baseline, indicating that the sequence order is not a determining factor. This finding grants critical flexibility for industrial manufacturing logistics, allowing stress relief to be strategically applied when most convenient for dimensional stability without compromising final part performance. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing of Metallic Materials: Characterization, Properties and Applications)

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21 pages, 3193 KB

Open AccessArticle

Effect of Prolonged Austempering Within Transformation Stasis on the Microstructural Evolution and Mechanical Behavior of Nanostructured Bainitic Steel

by Xubiao Wang, Yanhui Wang, Dongyun Sun, Jun Cheng, Lin Wang, Wei Liu, Cheng Liu, Zhinan Yang, Fucheng Zhang and Wanshuo Sun

Metals 2026, 16(8), 907; https://doi.org/10.3390/met16080907 - 13 Aug 2026

Abstract

This study examines the evolution of microstructure, the metastability of retained austenite (RA), and the corresponding mechanical behavior exhibited by a nanostructured bainitic bearing steel subjected to prolonged austempering within a transformation stasis regime. The results indicate that following the completion of nanostructured [...] Read more.

This study examines the evolution of microstructure, the metastability of retained austenite (RA), and the corresponding mechanical behavior exhibited by a nanostructured bainitic bearing steel subjected to prolonged austempering within a transformation stasis regime. The results indicate that following the completion of nanostructured bainitic formation at 300 °C for 3 h, a prolonged austempering time does not alter the microstructure, but reduces the dislocation density in BF while increasing the carbon content in RA. For the 4 h and 6 h specimens, a reduction in the overall RA mechanical stability is observed, accompanied by different transformation rates of stress-induced martensite during tensile deformation. This behavior is largely due to the weakened constraint effect of the BF matrix and the evolution of a carbon concentration gradient within the RA. During the transformation stasis, prolonged austempering elevates the yield strength while maintaining an unchanged ultimate tensile strength, albeit with a marginal reduction in microhardness. Relative to the baseline elongation recorded for the 3 h specimen, both the 4 h and 6 h specimens exhibit enhanced ductility, with the 4 h specimen yielding a peak value of 16.8%, which is 1.66 times that of the 3 h specimen. This improvement stems largely from the greater RA volume fraction that transforms into stress-induced martensite in the 4 h specimen, as well as its continuous and stable transformation rate during tensile deformation. Therefore, it can be concluded that an appropriately prolonged austempering time within nanostructured bainitic transformation stasis is essential for optimizing mechanical performance. This study provides a low-cost, energy-saving isothermal heat treatment technical scheme for mass industrial production of high-performance bearing steel. Full article

(This article belongs to the Special Issue Advanced Steels: Microstructure, Mechanical Properties, and Surface Treatment)

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13 pages, 18318 KB

Open AccessArticle

Effect of Aging Time on Tensile Properties of 7075 Aluminum Alloy

by Yong Wang, Sawei Qiu, Tuo Ye, Qinghang Cui, Jiajun Han and Pengcheng Guo

Metals 2026, 16(8), 906; https://doi.org/10.3390/met16080906 - 13 Aug 2026

Abstract

A solid solution treatment (SST) followed by single-stage aging (0–30 h, 140 °C) was performed on 7075 aluminum alloy specimens with longitudinal axes oriented at 0°, 45° and 90° to the rolling direction. The mechanical properties and microstructure were analyzed by tensile testing, [...] Read more.

A solid solution treatment (SST) followed by single-stage aging (0–30 h, 140 °C) was performed on 7075 aluminum alloy specimens with longitudinal axes oriented at 0°, 45° and 90° to the rolling direction. The mechanical properties and microstructure were analyzed by tensile testing, optical microscope (OM), electron backscatter diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the average tensile strengths of the as-received 7075 aluminum alloy in the three directions were 304 MPa (0°), 295 MPa (45°) and 297 MPa (90°), respectively, with an anisotropy index (AI) of 0.97, indicating that the as-received samples exhibited negligible anisotropic mechanical properties. After SST, elongated grains with coarse size were formed, which is primarily attributed to the inheritance of the deformed fiber texture introduced by hot rolling. EBSD analysis of the 30 h aged specimens revealed that, within the same analyzed area, the total grain-boundary length in the 45° direction (16.4 cm) was much larger than that in the 0° (10.4 cm) and 90° (13.5 cm) directions. As the grain morphology showed no significant change between the SST and aged conditions, this grain-boundary distribution was representative of the microstructural state established during SST and persisted throughout the artificial aging process, contributing to the anisotropic mechanical properties. During artificial aging, prolonged aging time significantly facilitated the precipitation, with the 30 h aged sample exhibiting a significantly higher density of precipitates compared to the 6 h aged sample, leading to enhanced mechanical properties. The tensile strengths of the 30 h aged samples increased to 165 MPa, 236 MPa and 196 MPa in the three directions, respectively. Meanwhile, due to the fixed crystallographic orientation relationship between the precipitates and the Al matrix, the precipitates tended to form on specific planes, which enhanced the anisotropic mechanical properties. Consequently, the AI value increased from 0.97 (as-received) to 1.43 (30 h aged) with prolonged aging time. Full article

(This article belongs to the Special Issue Light Alloy and Its Application (3rd Edition))

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11 pages, 8209 KB

Open AccessArticle

Hot Deformation Behavior of a High-Strength CrNiMoV Steel Under Extremely Low Strain-Rate Conditions

by Shuai Liu, Minggui Qu and Zhenhua Wang

Metals 2026, 16(8), 905; https://doi.org/10.3390/met16080905 - 13 Aug 2026

Abstract

The ultra-large steam turbine rotor and heavy gas turbine disk are key components of power stations. They are manufactured from very large ingots, and extremely low strain rates are used during forging. In this study, a high-strength CrNiMoV steel, 25Cr1Ni4MoV, was hot-compressed at [...] Read more.

The ultra-large steam turbine rotor and heavy gas turbine disk are key components of power stations. They are manufactured from very large ingots, and extremely low strain rates are used during forging. In this study, a high-strength CrNiMoV steel, 25Cr1Ni4MoV, was hot-compressed at 1000–1200 °C and strain rates of 0.01–0.0001 s⁻¹, and the resulting deformed microstructures were observed. The peak stress ranged from 17 to 72 MPa. The hot deformation equation was obtained, and the activation energy for deformation was determined to be 329 kJ/mol, which was lower than that reported in previous studies due to the extremely low strain rate. The deformation mechanism is dynamic recrystallization even at a strain rate of 0.0001 s⁻¹. The critical strains for complete dynamic recrystallization were determined. The dynamic recrystallization grain size increased slowly with decreasing ln(Z), where Z is the Zener–Hollomon parameter, within the ln(Z) range of 22–27. However, when ln(Z) was below 21, the dynamic recrystallization grain size increased rapidly. This critical ln(Z) value is a new finding. Strategies for controlling grain size in the production of ultra-large steam turbine rotors and heavy gas turbine disk forgings were provided. Finally, future research directions were discussed. Full article

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

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19 pages, 8469 KB

Open AccessReview

Wrought Magnesium Alloy Sheets: A Comprehensive Review of Rolling Processes

by Renhong Zhu, Guangzheng Wang, Yang Li, Shaozhu Wang, Jianze Liu and Xianglong Guo

Metals 2026, 16(8), 904; https://doi.org/10.3390/met16080904 - 12 Aug 2026

Abstract

Driven by energy conservation, emission reduction and lightweight manufacturing demands, wrought magnesium alloys feature low density, high specific strength and balanced comprehensive performances, making them promising lightweight materials for aerospace, automobile, electronic and other industries. This paper systematically reviews the rolling fabrication technologies [...] Read more.

Driven by energy conservation, emission reduction and lightweight manufacturing demands, wrought magnesium alloys feature low density, high specific strength and balanced comprehensive performances, making them promising lightweight materials for aerospace, automobile, electronic and other industries. This paper systematically reviews the rolling fabrication technologies and recent research progress of wrought magnesium alloy sheets. Special attention is paid to deformation characteristics, microstructure evolution mechanisms and property regulation rules of typical rolling processes, including conventional rolling, cross rolling, accumulative roll bonding, equal-channel angular rolling, asymmetric rolling and twin-roll casting. Existing studies confirm that dynamic recrystallization, grain refinement, activation of non-basal slips and basal texture weakening act as core mechanisms to enhance the strength–ductility matching, formability and anisotropy of magnesium alloy sheets. Each rolling technology possesses unique merits in production efficiency, microstructural homogeneity, texture modification and industrial practicability. Nevertheless, several bottlenecks still restrict its large-scale promotion, such as edge cracking, strong basal texture, poor process stability and high manufacturing cost. Future research priorities lie in multi-process compound forming, intelligent parameter control and short-process eco-friendly manufacturing, so as to facilitate mass production and extensive engineering application of high-performance wrought magnesium alloy sheets. Full article

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

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21 pages, 8534 KB

Open AccessArticle

PINN-PBE Model for Describing Gibbsite Crystallization Dynamics

by Tatiana E. Litvinova, Vladimir O. Golubev and Nickolai V. Tuleshov

Metals 2026, 16(8), 903; https://doi.org/10.3390/met16080903 - 12 Aug 2026

Abstract

The industrial testing of the optimal control system for the gibbsite precipitation area revealed the cases where the optimizer finds and exploits vulnerabilities in the predictive data-driven model, recommending erroneous control actions. The present paper considers a more robust alternative, i.e., training of [...] Read more.

The industrial testing of the optimal control system for the gibbsite precipitation area revealed the cases where the optimizer finds and exploits vulnerabilities in the predictive data-driven model, recommending erroneous control actions. The present paper considers a more robust alternative, i.e., training of neural network models using a first-principle model, known as physics-informed neural network (PINN). To address the problem, the system of population balance equations (PBE) describing the bulk crystallization process was transformed into a linearized form, and a PINN-PBE model was generated, which represents a set of interconnected neural networks approximating the solution of the equation system under the batch conditions. Full article

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

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18 pages, 2187 KB

Open AccessReview

Selective Adsorption and Recovery for Low-Quality Lithium-Containing Resources: Materials, Mechanism, and Outlook

by Xiaofei Meng, Haitao Zhou, Xiaoping Zou, Yingping Jiang, Shengmei Zhang, Yanwen Sun and Chi Zhang

Metals 2026, 16(8), 902; https://doi.org/10.3390/met16080902 - 12 Aug 2026

Abstract

With the rapid expansion of the global lithium-battery industry, efficient and sustainable lithium recovery from low-grade lithium resources, such as lithium precipitation mother liquor characterized by a high sodium-to-lithium ratio, has become a critical research challenge. Among the emerging technologies, the adsorption method, [...] Read more.

With the rapid expansion of the global lithium-battery industry, efficient and sustainable lithium recovery from low-grade lithium resources, such as lithium precipitation mother liquor characterized by a high sodium-to-lithium ratio, has become a critical research challenge. Among the emerging technologies, the adsorption method, recognized for its operational simplicity, high selectivity, and process flexibility, has garnered significant attention. This review systematically summarizes recent advancements in two primary categories of adsorbents for selective lithium recovery: organic adsorbents (crown ether-based materials) and inorganic adsorbents (aluminum-based layered double hydroxides (LiAl-LDHs), titanium-based ion sieves (H₂TiO₃, H₄Ti₅O₁₂), and manganese-based ion sieves (HMn₂O₄, H₁.₆Mn₁.₆O₄, H₄Mn₅O₁₂). For each class, the synthesis methods, adsorption mechanisms, performance (capacity, selectivity, kinetics, and cycling stability), and key influencing factors are thoroughly discussed and compared. Titanium-based sieves demonstrate high capacity and stability, manganese-based materials show excellent kinetics, aluminum-based adsorbents offer industrial scalability, and crown ether-based materials exhibit superior ion size selectivity. The review also identifies limitations, such as the slow kinetics of H₂TiO₃, manganese dissolution in manganese-based ion sieves, and the cost of functionalized organics. Finally, future research directions are proposed, focusing on enhancing adsorption kinetics and stability via material design (e.g., morphology control, doping, hybridization), developing scalable and cost-effective synthesis routes, and exploring the integration of adsorption with other separation technologies to create efficient hybrid processes for the sustainable exploitation of low-grade lithium. Full article

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15 pages, 4205 KB

Open AccessArticle

Characterization of Interfacial Reaction Layers Between a Zn-5Al-3Mg Solder Alloy and Cu Substrate

by Jee-Hwan Bae, Yena Kwon, Seung-Moon Baek, Choong-Do Lee and Cheol-Woong Yang

Metals 2026, 16(8), 901; https://doi.org/10.3390/met16080901 - 12 Aug 2026

Abstract

The interfacial reaction between solder and substrate is a critical factor governing joint reliability, making it essential to understand the formation and stability of interfacial reaction layers when developing new high-temperature lead-free solders. This study investigates the interfacial reaction layers formed in Zn-5Al-3Mg [...] Read more.

The interfacial reaction between solder and substrate is a critical factor governing joint reliability, making it essential to understand the formation and stability of interfacial reaction layers when developing new high-temperature lead-free solders. This study investigates the interfacial reaction layers formed in Zn-5Al-3Mg solder/Cu substrate joints soldered at 693 K under vacuum. With a binary Zn-Al solder, the Cu substrate is progressively consumed by Zn, and the intermediate phases CuZn₄, Cu₅Zn₈, and CuZn nucleate and grow concurrently at the solder interface. The addition of a minor amount of Mg to the Zn-Al alloy, however, fundamentally alters this reaction sequence. Transmission electron microscopy analyses, including scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy (STEM-EDS), energy-filtered TEM (EF-TEM), and electron diffraction, reveal three distinct interfacial layers: an outer Mg₂Zn₁₁ layer, a middle two-phase mixture of CuZn₄/Mg₂CuZn₃, and an inner Cu₅Zn₈ layer adjacent to the Cu substrate. The biphasic CuZn₄/Mg₂CuZn₃ mixture layer is shown to form via a quasi-peritectic reaction governed by sequential four-phase equilibria in the Zn-Mg-Cu ternary system. These findings demonstrate that minor Mg additions redirect the interfacial reaction pathway between Zn-Al-based solders and Cu substrates, providing new insight for the design of high-temperature Pb-free solder systems. Full article

(This article belongs to the Special Issue Advances in Welding Processes of Metallic Materials—2nd Edition)

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27 pages, 11760 KB

Open AccessArticle

Microstructural Inheritance and Tensile Behavior of LPBF-Fabricated TA15 Titanium Alloy After Sequential Annealing

by Yunpeng Zhang, Shilong Che, Xin Lin and Xufei Lu

Metals 2026, 16(8), 900; https://doi.org/10.3390/met16080900 - 12 Aug 2026

Abstract

Laser powder bed fusion (LPBF)-fabricated TA15 titanium alloy commonly exhibits a fine acicular lath morphology, which has frequently been interpreted as martensitic in previous studies and is generally associated with high strength and limited plastic accommodation. In this study, LPBF-TA15 specimens were annealed [...] Read more.

Laser powder bed fusion (LPBF)-fabricated TA15 titanium alloy commonly exhibits a fine acicular lath morphology, which has frequently been interpreted as martensitic in previous studies and is generally associated with high strength and limited plastic accommodation. In this study, LPBF-TA15 specimens were annealed at 800, 900, and 950 °C for 2 h, followed by furnace cooling, and subsequently subjected to secondary annealing at 550 °C for 4 h. Each sequentially annealed condition was compared with its corresponding single-step condition to distinguish retained microstructural differences from the tensile-property changes associated with the subsequent treatment. Microstructural evolution and monotonic tensile properties at room temperature and 300–600 °C were investigated. Annealing at 800 °C retained a relatively fine lamellar morphology. Increasing the initial annealing temperature to 900 and 950 °C produced progressively larger apparent lath and colony scales, with the most pronounced coarsening observed at 950 °C. Tensile results are reported as mean ± standard deviation. After secondary annealing, A800-S550 exhibited the highest mean room-temperature strength among the three secondary-annealed conditions, with a yield strength of 1045.0 ± 2.6 MPa, an ultimate tensile strength of 1116.7 ± 2.3 MPa, and an elongation of 14.3 ± 0.7%. From 300 to 600 °C, its yield strength decreased from 701.0 ± 3.2 to 493.6 ± 9.8 MPa, while its ultimate tensile strength decreased from 823.5 ± 3.8 to 585.6 ± 7.1 MPa; the elongation at 600 °C was 19.0 ± 1.8%. In this study, microstructural inheritance refers to the persistence, after the common 550 °C treatment, of differences in lath and lamellar-colony scales and EBSD boundary characteristics established during initial annealing. The secondary-annealed conditions retained distinct microstructural scales and exhibited different tensile responses; however, a unique causal relationship between the retained morphology and the magnitude of the property changes was not established. Residual stress, post-heat-treatment oxygen variation, and quantitative texture evolution were not independently evaluated. The conclusions are limited to the heat-treatment schedules and monotonic tensile conditions examined in this study. Full article

(This article belongs to the Special Issue Additive Manufacturing of High-Temperature Metallic Materials and Intermetallics)

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19 pages, 23891 KB

Open AccessArticle

Comparative Study of Laser and GMAW Technologies: Effects on Mechanical Strength and Salt Spray Corrosion Performance of SGH340D + ZMA Galvanized Automotive Steel

by Stefan Dikić, Hongqiang Liu, Dragomir Glišić, Jin Pan, Yongning Zhou, Nenad Radović and Cheng Ma

Metals 2026, 16(8), 899; https://doi.org/10.3390/met16080899 - 12 Aug 2026

Abstract

The aim of this work is to investigate the influence of different welding technologies on the mechanical properties and corrosion resistance of welded joints of SGH340D + ZMA steel with a Zn–Mg–Al (ZMA) protective coating. Two different welding technologies were used: the gas [...] Read more.

The aim of this work is to investigate the influence of different welding technologies on the mechanical properties and corrosion resistance of welded joints of SGH340D + ZMA steel with a Zn–Mg–Al (ZMA) protective coating. Two different welding technologies were used: the gas metal arc welding(GMAW) process at a welding speed of 0.8 m/min and laser welding at speeds of 2 and 4 m/min. Mechanical properties were determined using tensile testing and hardness testing. Corrosion resistance was estimated using a salt spray test. Residual stresses were determined experimentally using the drill hole method. The highest residual stresses were measured in GMAW-welded joints, while the lowest were measured in laser-welded joints at a speed of 4 m/min. The sample welded by laser at a speed of 4 m/min exhibited hardness values close to the upper acceptable limit, indicating that further increases in welding speed without preheating may lead to excessive hardness. All samples exhibited good corrosion resistance in a salt chamber. According to the results, increased welding speed reduced residual stresses but increased the risk of brittle fracture. Full article

(This article belongs to the Special Issue Recent Progress in Welding Technology for Metallic Materials)

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24 pages, 5202 KB

Open AccessReview

Research Progress on Solvation Sheath Regulation Additives in ZnSO₄ Electrolytes for Aqueous Zinc-Ion Batteries

by Biao Wang and Yongsheng Ren

Metals 2026, 16(8), 898; https://doi.org/10.3390/met16080898 - 12 Aug 2026

Abstract

Aqueous zinc-ion batteries (AZIBs) are promising for scalable energy storage, yet their practical viability is constrained by zinc dendrite propagation, parasitic hydrogen evolution, and interfacial corrosion. Formulating electrolyte additives represents an economically viable strategy to address these long-standing bottlenecks by modulating the bulk [...] Read more.

Aqueous zinc-ion batteries (AZIBs) are promising for scalable energy storage, yet their practical viability is constrained by zinc dendrite propagation, parasitic hydrogen evolution, and interfacial corrosion. Formulating electrolyte additives represents an economically viable strategy to address these long-standing bottlenecks by modulating the bulk solution and double-layer environments. Diverging from traditional composition-based classifications, this review categorizes recent additive strategies according to their underlying physical chemistry mechanisms. Specifically, we evaluate how these additives regulate the primary and secondary Zn²⁺ solvation sheaths, reconstruct the electric double layer (EDL) for crystallographic facet control, induce sacrificial or mineralized solid electrolyte interphases (SEIs), and establish responsive polymer confinement networks. Furthermore, we critically discuss the operational limitations, trade-offs, and parameter dependencies of these strategies under non-ideal, realistic conditions. Finally, prospective directions are outlined—focusing on descriptor-driven design, operando non-equilibrium characterizations, and performance validation under standard industrial metrics (e.g., low E/C ratios and high depths of discharge)—to provide an objective framework for advancing electrolyte optimization in practical zinc-based energy storage. Full article

(This article belongs to the Special Issue Advanced Metallic Materials for Batteries)

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27 pages, 13063 KB

Open AccessArticle

Integrated Global–Local Finite Element Assessment of Stern Boss Structural Integrity Under Realistic Trim and Stability Conditions

by Myung-Su Yi, Da-Bin Jung, Tae-Gu Kang, Jung-Goo Park and Joo-Shin Park

Metals 2026, 16(8), 897; https://doi.org/10.3390/met16080897 - 11 Aug 2026

Abstract

This study presents a traceable global–local finite element (FE) framework for assessing stern-boss structural integrity under operationally derived loading. Two production-scale MSC Nastran models—a shell-dominant model and an otherwise equivalent global model with a locally solid stern-boss region—were compared under five vessel-specific states [...] Read more.

This study presents a traceable global–local finite element (FE) framework for assessing stern-boss structural integrity under operationally derived loading. Two production-scale MSC Nastran models—a shell-dominant model and an otherwise equivalent global model with a locally solid stern-boss region—were compared under five vessel-specific states generated from trim-and-stability weight, buoyancy, hydrostatic, ballast, and machinery-load distributions. Baseline-to-fine mesh changes were limited to 0.68% for the shell model and 1.07% for the solid model. Both models reproduced the same global deformation mode, while the solid model predicted 5.9–6.3% greater maximum vertical deflection. Within a common stern-boss assessment region, the shell and solid peak von Mises stresses were 42.1–70.9 MPa and 41.5–72.4 MPa, respectively, with differences confined to −1.4% to +2.3%. By contrast, stresses extracted at the stern-tube interface were 17.2–26.8 MPa in the shell model and 29.7–46.6 MPa in the solid model, demonstrating the importance of three-dimensional constraint, transverse shear, and through-thickness response at the local interface. The governing design-draught/APT-full condition produced a solid-model deflection of 46.8 mm and a regional stress of 72.4 MPa. Its nominal SS400 yield-utilization ratio was 0.308, whereas the LR rule-based inverse safety-factor index ranged from 1.3 to 2.1 and identified surrounding panel buckling as the more restrictive limit state. The shell model reduced wall-clock time by 38.6% and is therefore appropriate for global screening, while the solid representation is required for interface-level assessment. The framework constitutes a numerically verified, digital-twin-compatible baseline; independent validation against measured structural or shaft-line data remains necessary. Full article

(This article belongs to the Section Structural Integrity of Metals)

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17 pages, 11630 KB

Open AccessArticle

Study on the Mechanical Properties of Soluble Magnesium-Based Composites Reinforced with Graphite Particles and Carbon Fiber

by Kang Ai, Zhaoyuan Zhang, Jing Guo, Bohan Yao, Jiahui Xi and Luyan Ju

Metals 2026, 16(8), 896; https://doi.org/10.3390/met16080896 - 11 Aug 2026

Abstract

In this study, graphite particles and short-cut carbon fibers were used to prepare a hybrid-reinforced composite with AZ91 magnesium alloy as the matrix via the powder metallurgy process. The effects of different added phase ratios on microstructure, density, compressive strength, and fracture morphology [...] Read more.

In this study, graphite particles and short-cut carbon fibers were used to prepare a hybrid-reinforced composite with AZ91 magnesium alloy as the matrix via the powder metallurgy process. The effects of different added phase ratios on microstructure, density, compressive strength, and fracture morphology were investigated. The results show that the addition of 5% graphite particles alone reduced the compressive strength by 20.1% compared to pure magnesium, attributed to interfacial delamination and interlaminar peeling in the graphite’s layered structure. The introduction of carbon fibers effectively compensates for this degradation. When the carbon fiber content was increased to 10% (with graphite fixed at 5%), the compressive strength reached a peak of 375 MPa—a 63.0% increase over the graphite-only system—and the fracture strain rose to 16.98%. However, an excessive amount of carbon fibers (15%) led to agglomeration, causing the porosity to rise to 9.1% and resulting in a significant decline in mechanical properties. Microstructural analysis indicates that carbon fibers exert a reinforcing effect by sharing the load and constraining the lateral deformation of the matrix, while graphite particles induce microcracks and pores, resulting in a weakening effect; under appropriate ratios, the two can achieve synergistic reinforcement. This study provides experimental evidence for the component design and performance control of high-strength, rapidly dissolving magnesium-based composites. Full article

(This article belongs to the Special Issue Advances in Metal Matrix Composites: Preparation, Performance and Application)

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16 pages, 21873 KB

Open AccessArticle

Study on Mechanochemical Activation-Enhanced Hydrochloric Acid Leaching of Rare Earth Elements from Roasted NdFeB Waste

by Chenghong Liu, Tuo Zhao, Chunlei Guo, Erdou Li, Yufang Qin and Bo Zhang

Metals 2026, 16(8), 895; https://doi.org/10.3390/met16080895 - 11 Aug 2026

Abstract

NdFeB waste is an important rare earth secondary resource, and the current industrial practice primarily employs a hydrochloric acid preferential dissolution method to recover rare earth elements (REEs). However, approximately 1% of REEs (e.g., cerium oxide, neodymium oxide, praseodymium oxide, and dysprosium oxide) [...] Read more.

NdFeB waste is an important rare earth secondary resource, and the current industrial practice primarily employs a hydrochloric acid preferential dissolution method to recover rare earth elements (REEs). However, approximately 1% of REEs (e.g., cerium oxide, neodymium oxide, praseodymium oxide, and dysprosium oxide) remain in the leaching residue, resulting in low recovery efficiency. This work puts forward mechanochemical leaching (integrating mechanical activation and acid leaching) to replace traditional agitated leaching, which realizes synchronous mechanical activation and acid leaching within a stirred ball mill. A systematic comparison is conducted between these two leaching technologies, and the influences of operational variables on rare earth leaching efficiency are explored. The experimental results reveal that sustained mechanical grinding can pulverize particles down to the submicron level, induce substantial lattice distortion and amorphous transformation, destroy the physical coating of rare earth-bearing phases by iron oxides, and thereby drastically improve the extraction efficiency of REEs. The optimal conditions were determined as follows: stirring speed of 700 r/min, leaching temperature of 85 °C, HCl concentration of 1 mol/L, leaching time of 180 min and solid–liquid ratio of 100 g/L. Furthermore, this study reveals the synchronous evolution mechanism of particle refinement and phase transformation during mechanochemical leaching, providing an alternative and more economical recycling route for NdFeB waste. Full article

(This article belongs to the Special Issue Comprehensive Recycling of Metallurgical Solid Waste and Mineral Resources (2nd Volume))

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20 pages, 15921 KB

Open AccessArticle

Effect of Hydride Additives on the Microstructure and Hydrogen Desorption Performance of Ball-Milled Mg–Co Composites

by Alejandro Gómez, Joan Santiago Cortinez, Robinson Aguirre Ocampo, Adriana Echavarria, José A. Tamayo, Andrés F. Vargas, Carolina Ramírez, Francisco J. Bolívar, Alejandro A. Zuleta, Esteban Correa and Félix Echeverría

Metals 2026, 16(8), 894; https://doi.org/10.3390/met16080894 - 11 Aug 2026

Abstract

Magnesium-based materials are promising candidates for solid-state hydrogen storage due to their high gravimetric capacity; however, their practical application is limited by slow sorption kinetics and high thermal stability. This study investigates the influence of hydride additives on the microstructure and hydrogen desorption [...] Read more.

Magnesium-based materials are promising candidates for solid-state hydrogen storage due to their high gravimetric capacity; however, their practical application is limited by slow sorption kinetics and high thermal stability. This study investigates the influence of hydride additives on the microstructure and hydrogen desorption performance of ball-milled Mg–Co composites. Flake-like magnesium particles modified with 7 wt.% cobalt were processed by high-energy ball milling and subsequently doped with sodium hydride, potassium hydride, and calcium hydride at concentrations of 0.5 and 5 wt.%. Microstructural, phase, and surface chemical characterization revealed that additive type strongly affects dispersion, interfacial distribution, and the formation of additive-derived surface species within the Mg–Co matrix. Hydrogen sorption measurements conducted at 300–350 °C under different pressure conditions show that alkali hydrides significantly enhance low-temperature hydrogen desorption. In particular, the composite containing 5 wt.% potassium hydride exhibits a marked improvement, releasing approximately 4 wt.% hydrogen at 300 °C, while the unmodified material shows negligible desorption under the same conditions. Thermal analysis confirms that the additives modify the dehydrogenation response, although improved performance is not solely correlated with lower onset temperatures. The results demonstrate a clear asymmetry between hydrogen absorption and desorption, indicating that the primary effect of hydride additives is an enhancement in dehydrogenation kinetics. This behavior is associated with microstructural features, including additive dispersion and interfacial effects induced during processing. These findings provide insight into the design of magnesium-based hydrogen storage materials through microstructure–property relationships. Full article

(This article belongs to the Special Issue Hydrogen Storage Alloys: State of the Art)

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19 pages, 7287 KB

Open AccessArticle

Effect of ZnO on Copper Loss and Fe₃O₄ Reduction During the Copper Slag Cleaning

by Tao Wei, Haipei Zhang, Haoyuan Xu, Shuang Shao, Shichao Wu, Kai Fan and Bo Li

Metals 2026, 16(8), 893; https://doi.org/10.3390/met16080893 - 10 Aug 2026

Abstract

A mass action concentration model of FeO-Fe₂O₃-SiO₂-CaO-MgO-Al₂O₃-ZnO multi-component slag was established to address the problems of high viscosity and high copper content in oxygen-enriched top-blown copper smelting slag. Theoretical calculations, combined with experimental [...] Read more.

A mass action concentration model of FeO-Fe₂O₃-SiO₂-CaO-MgO-Al₂O₃-ZnO multi-component slag was established to address the problems of high viscosity and high copper content in oxygen-enriched top-blown copper smelting slag. Theoretical calculations, combined with experimental investigations, were performed to evaluate the effects of ZnO additions (0–25 wt.%) on phase transformation, Fe₃O₄ reduction and copper content in the slag at temperatures ranging from 1200 to 1400 °C. The results indicate that ZnO addition decreases the mass concentrations of Fe₂O₃, Fe₃O₄, Fe₂SiO₄ and SiO₂, while increasing the proportions of zinc-bearing structural units and enhancing the reducing capability of the slag. In the copper slag system, Zn²⁺ substitutes for Fe in Fe₃O₄ and Fe₂SiO₄ through isomorphous substitution, forming Fe-Zn spinel and Fe-Zn olivine. As the addition of ZnO gradually increases to 25 wt.%, the liquid slag fraction increases and the slag viscosity decreases, resulting in a reduction in copper content from 5.64 wt.% to 2.04 wt.%. Furthermore, ZnO promotes the transformation of Fe₃O₄ into zinc–iron spinel, which is more readily reducible by carbothermic reaction than Fe₃O₄ itself, thereby facilitating the overall reduction of iron oxides in the copper slag. These findings provide a theoretical basis for slag-type regulation and the efficient separation of copper from slag via high-temperature gravity settling of matte. Full article

(This article belongs to the Special Issue Efficient Utilization of Metal Mineral Resources and Low-Carbon Metallurgy)

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