Metals

16 pages, 8339 KB

Open AccessArticle

Effect of Ultrasonic Power on the Performance of Dissimilar Al Alloy Friction Stir Lap Welds

by Yu Chen, Rongcheng Liu, Jie Tan and Jizhong Li

Metals 2025, 15(9), 1017; https://doi.org/10.3390/met15091017 (registering DOI) - 12 Sep 2025

Ultrasonic-assisted friction stir lap welding (FSLW) was employed to join dissimilar aluminum alloys, namely Al-7075 and Al-5052. The effect of ultrasonic power on the weld performance was systematically investigated. Increasing the ultrasonic power enhanced the material flow, resulting in a significant reduction in [...] Read more.

Ultrasonic-assisted friction stir lap welding (FSLW) was employed to join dissimilar aluminum alloys, namely Al-7075 and Al-5052. The effect of ultrasonic power on the weld performance was systematically investigated. Increasing the ultrasonic power enhanced the material flow, resulting in a significant reduction in the cavity area in the nugget zone, from 0.37 mm² to 0.01 mm², as the ultrasonic power was increased from 0 W to 600 W. Simultaneously, increasing the ultrasonic power accelerated the dynamic recrystallization in the nugget zone, refining the grain size by 46%. This grain refinement consequently enhanced the hardness of the nugget zone, yielding an increase of approximately 10 HV. However, the excessive ultrasonic power level of 600 W also amplified the ultrasonic punch effect, inducing interfacial crack formation between Al-7075 and Al-5052 on the advancing side. These defects (cavity and interfacial crack) significantly influenced the joint failure behavior: the non-ultrasonic-assisted FSLW joints failed at the cavity, while the 600 W-ultrasonic-assisted FSLW joints failed along the interfacial crack. Comparatively, an ultrasonic power of 300 W suppressed both the cavity and interfacial crack, producing FSLW joints with the highest shear strength among all tested ultrasonic power levels (0 W, 300 W, and 600 W). Full article

(This article belongs to the Section Welding and Joining)

22 pages, 2689 KB

Open AccessArticle

Ultrasonic Enhancement of Tin Dissolution in NaOH/H₂O₂ System: Electrochemical and Passivation Modulation

by Dongbin Wang, Mingge Fu, Tian Wang, Wenlong Miao, Liuxin Xiang, Thiquynhxuan Le and Libo Zhang

Metals 2025, 15(9), 1016; https://doi.org/10.3390/met15091016 - 12 Sep 2025

Abstract

In the alkaline process for sodium stannate preparation, the oxidative dissolution of tin in the NaOH-H₂O₂ system originates from a spontaneous electrochemical reaction. This study elucidates the mechanism of ultrasound-enhanced tin dissolution in NaOH/H₂O₂ solutions from an [...] Read more.

In the alkaline process for sodium stannate preparation, the oxidative dissolution of tin in the NaOH-H₂O₂ system originates from a spontaneous electrochemical reaction. This study elucidates the mechanism of ultrasound-enhanced tin dissolution in NaOH/H₂O₂ solutions from an electrochemical perspective, with particular emphasis on the tripartite regulatory effects of ultrasound on mass transfer, passivation suppression, and reaction pathway modulation. Electrochemical analysis indicates that ultrasound enhances mass transfer by disrupting the diffusion boundary layer, delays passivation, accelerates the exfoliation of the passive layer, and generates hydroxyl radicals that lower cathodic activation barriers. Under the action of 30 W ultrasound, the apparent diffusion coefficient of the solution increases and the passivation process of the tin sheet is delayed (the oxidation peak potential shift changes from −0.76 V to −0.70 V). After the passive layer is exfoliated by ultrasound, the charge transfer resistance decreases by 85.8% (from 8.09 ± 0.01 Ω to 1.15 ± 0.01 Ω). Ultrasound effectively overcomes the kinetic limitations imposed by the passivation layer through a triple synergistic mechanism involving mass transfer enhancement, passivation inhibition, and -OH path regulation. Full article

(This article belongs to the Special Issue Preparation of Metal Compounds—from Fundamental Mechanisms to Circular Economy Applications)

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19 pages, 5293 KB

Open AccessArticle

Investigation of Hot Deformation Behavior for 45CrNi Steel by Utilizing an Improved Cellular Automata Method

by Jinhua Zhao, Shitong Dong, Hongru Lv and Wenwu He

Metals 2025, 15(9), 1015; https://doi.org/10.3390/met15091015 - 12 Sep 2025

Abstract

The hot deformation discipline of typical 45CrNi steel under a strain rate ranging from 0.01 s⁻¹ to 1 s⁻¹ and deformation temperature between 850 °C and 1200 °C was investigated through isothermal hot compression tests. The activation energy involved in the [...] Read more.

The hot deformation discipline of typical 45CrNi steel under a strain rate ranging from 0.01 s⁻¹ to 1 s⁻¹ and deformation temperature between 850 °C and 1200 °C was investigated through isothermal hot compression tests. The activation energy involved in the high-temperature deformation process was determined to be 361.20 kJ·mol⁻¹, and a strain-compensated constitutive model, together with dynamic recrystallization (DRX) kinetic models, was successfully established based on the Arrhenius theory. An improved second-phase (SP) cellular automaton (CA) model considering the influence of the pinning effect induced by SP particles on the DRX process was developed, and the established SP-CA model was further utilized to predict the evolution behavior of parent austenite grain in regard to the studied 45CrNi steel. Results show that the average absolute relative error (AARE) associated with the austenite grain size and the DRX volume fraction achieved through the simulation and experiment was overall below 5%, indicating good agreement between the simulation and experiment. The pinning force intensity could be controlled by regulating the size and volume fraction of SP particles involved in the established SP-CA model, and the DRX behavior and the average grain size of the studied 45CrNi steel treated by high-temperature compression could also be predicted. The established SP-CA model exhibits significant potential for universality and is expected to provide a powerful simulation tool and theoretical foundation for gaining deeper insights into the microstructural evolution of metals or alloys during high-temperature deformation. Full article

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29 pages, 5135 KB

Open AccessArticle

Constitutive Modeling of Creep–Fatigue Interaction in 1Cr-1Mo-0.25V Steel for Hold-Time Testing

by Federico Bucciarelli, Alessandro Guazzini, Tommaso Grossi, Giuseppe Macoretta and Bernardo Disma Monelli

Metals 2025, 15(9), 1014; https://doi.org/10.3390/met15091014 - 12 Sep 2025

Abstract

In the field of energy production, creep–fatigue interaction is a typical failure mode that might compromise the structural integrity of both rotating equipment and pressure vessels. Common design practices approach the problem in a conservative way by using high safety factors, which typically [...] Read more.

In the field of energy production, creep–fatigue interaction is a typical failure mode that might compromise the structural integrity of both rotating equipment and pressure vessels. Common design practices approach the problem in a conservative way by using high safety factors, which typically results in additional costs for manufacturing companies. The aim of this article, in the framework of continuum damage mechanics approaches, is to present a novel fatigue damage-based constitutive law. The presented law is directly inspired by well-assessed creep-based rules, suggesting a similarity in the behavior. On the other hand, creep deformation and damage are calculated with a more recent approach. The identification of the model parameters was carried out by interpreting experimental results obtained from low-cycle fatigue and creep relaxation tests performed on a commonly used ferritic–martensitic steel for power generation rotor forgings. To validate the proposed models, they were used to estimate material life consumption when the material was subjected to fully reversed axial loading conditions with hold time under tensile load. Different loading conditions at different total strain ranges and hold times were simulated, and good agreement was found between the predicted and experimental life, thus confirming the validity of the proposed models. Full article

(This article belongs to the Special Issue Numerical Modelling of Mechanical Properties for Metallic Materials)

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13 pages, 41617 KB

Open AccessArticle

Characterization of the Carbides in Carburized CSS-42L Steel and Their Effect on the Fatigue Failure Mechanism

by Ming Liu, Xingyu Lu, Chengshuai Lei, Xinxin Ma and Hongwei Liu

Metals 2025, 15(9), 1013; https://doi.org/10.3390/met15091013 - 11 Sep 2025

Abstract

The types of carbides and their effects on the fatigue failure mechanism in carburized CSS-42L steel were systematically studied in the present investigation. The results indicate that the main carbides in carburized CSS-42L steel are Cr-rich M₂₃C₆ carbides and Mo-rich [...] Read more.

The types of carbides and their effects on the fatigue failure mechanism in carburized CSS-42L steel were systematically studied in the present investigation. The results indicate that the main carbides in carburized CSS-42L steel are Cr-rich M₂₃C₆ carbides and Mo-rich M₆C carbides. M₂₃C₆ carbides precipitate along grain boundaries and interconnect, forming network carbides. Rolling contact fatigue (RCF) tests reveal that fatigue cracks in CSS-42L steel can initiate both at the contact surface and within the subsurface. During RCF, the spalling of large-sized, networked M₂₃C₆ carbides creates micro-spalling pits on the contact surface, inducing local stress concentration that triggers the initiation of surface cracks. The surface cracks initially propagate perpendicularly to the contact surface and then shift to propagate parallelly to the contact surface, ultimately causing large-scale spalling of the surface layer. Subsurface cracks initiate at a position approximately 100 μm below the contact surface, with their propagation direction roughly parallel to the contact surface. Meanwhile, the development of subsurface cracks can connect with surface cracks, leading to the expansion of surface micro-pitting. Network carbides facilitate the propagation of secondary cracks, leading to the formation of grid-distributed crack networks. Full article

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29 pages, 4438 KB

Open AccessReview

AI Design for High Entropy Alloys: Progress, Challenges and Future Prospects

by Enzhi Xie and Chao Yang

Metals 2025, 15(9), 1012; https://doi.org/10.3390/met15091012 - 11 Sep 2025

Abstract

High-entropy alloys have demonstrated significant application potential in many industrial fields due to their outstanding comprehensive properties. However, the complex multi-component compositions pose challenges for traditional design approaches. In recent years, artificial intelligence (AI) technology, with its powerful capabilities in data analysis, prediction, [...] Read more.

High-entropy alloys have demonstrated significant application potential in many industrial fields due to their outstanding comprehensive properties. However, the complex multi-component compositions pose challenges for traditional design approaches. In recent years, artificial intelligence (AI) technology, with its powerful capabilities in data analysis, prediction, and optimization, has provided new pathways for rapid discovery and performance modulation of high-entropy alloys. This paper systematically reviews the latest advancements in AI applications for high-entropy alloy design, covering key technologies such as machine learning models (e.g., active learning, generative models, transfer learning), high-throughput computing and experimental data processing, phase structure and property prediction. It also presents typical application cases, including compositional optimization, phase structure prediction, performance synergistic regulation, and novel material discovery. Although AI has significantly improved design efficiency and accuracy, challenges remain, such as the scarcity of high-quality data, insufficient model interpretability, and interdisciplinary integration. Future efforts should focus on building a more robust data ecosystem, enhancing model transparency, and strengthening closed-loop validation between AI and experimental science to advance intelligent design and engineering applications of high-entropy alloys. Full article

(This article belongs to the Special Issue Advances in High-Entropy Alloys’ Microstructure, Properties and Preparation)

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31 pages, 5517 KB

Open AccessArticle

Optimization of Cold Gas Dynamic Spray Coatings Using Agglomerated Al–Zn–TiO₂ Powders on Steel

by Bauyrzhan Rakhadilov, Kaiyrzhan Berikkhan, Zarina Satbayeva, Ainur Zhassulan, Aibek Shynarbek and Kuanysh Ormanbekov

Metals 2025, 15(9), 1011; https://doi.org/10.3390/met15091011 - 11 Sep 2025

Abstract

Cold gas dynamic spraying (CGDS) enables the production of protective coatings without melting or oxidation. In this study, Al–Zn–TiO₂ composite powders were prepared by wet agglomeration with binders and by dry mechanical mixing, and deposited onto mild steel substrates. COMSOL simulations of [...] Read more.

Cold gas dynamic spraying (CGDS) enables the production of protective coatings without melting or oxidation. In this study, Al–Zn–TiO₂ composite powders were prepared by wet agglomeration with binders and by dry mechanical mixing, and deposited onto mild steel substrates. COMSOL simulations of gas dynamics and particle acceleration identified optimal parameters (0.6 MPa, 600 °C, 15 mm, 90°), which were then validated experimentally. Coatings formed under these conditions exhibited dense microstructures, minimal porosity (~0.5%), and continuous, defect-free interfaces with the substrate. SEM and XRD confirmed solid-state bonding without new phase formation. Corrosion tests in 3.5% NaCl revealed a tenfold reduction in corrosion current density compared to bare steel, resulting from synergistic sacrificial (Zn), barrier (Al), and reinforcing/passivating (TiO₂) effects. Tribological tests demonstrated reduced friction (CoF ≈ 0.4–0.5) and wear volume. Compared with reported Al- or Zn-based cold- and thermal-sprayed coatings, the optimized Al–Zn–TiO₂ system shows superior performance, highlighting its potential for industrial anti-corrosion and wear-resistant applications. Full article

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14 pages, 1972 KB

Open AccessArticle

Influence of Adjusted Melt Pool Geometries on Residual Stress in 316L LPBF Processes

by Fabian Eichler, Nicolae Balc, Sebastian Bremen and Julius Sauren

Metals 2025, 15(9), 1010; https://doi.org/10.3390/met15091010 - 11 Sep 2025

Abstract

Residual stress remains a significant challenge in the widespread adoption of the Laser Powder Bed Fusion (LPBF) process, due to its detrimental impact on dimensional accuracy and post-processing requirements and hinders further processing with methods such as welding. Different strategies have already been [...] Read more.

Residual stress remains a significant challenge in the widespread adoption of the Laser Powder Bed Fusion (LPBF) process, due to its detrimental impact on dimensional accuracy and post-processing requirements and hinders further processing with methods such as welding. Different strategies have already been explored to reduce or mitigate these stresses, including preheating, alternating scan strategies, and heat treatments. In this study, a less commonly investigated approach is examined: the influence of melt pool geometry—specifically layer height and track width—on the residual stresses in LPBF-manufactured 316L stainless steel. By systematically varying these parameters, the resulting internal stress states are compared by distortion measurements of cantilever parts to determine potential correlations and mechanisms of influence. The findings aim to contribute to a deeper understanding of process–structure–property relationships in LPBF and to offer a new avenue for stress control through geometrical process parameter optimization. It can be concluded that among all the strategies for preventing and mitigating residual stress in LPBF, the examined approach has a relatively small influence. The results show that increasing layer thickness and decreasing spot diameter have beneficial effects on the resulting deformations. Full article

(This article belongs to the Special Issue Research on Fabrication Technologies and Service Performance of Metal Materials in Additive Manufacturing)

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22 pages, 5391 KB

Open AccessArticle

An Experimental Study on Tensile Characteristics of Ti-6Al-4V Thin Struts Made by Laser Powder-Bed Fusion: Effects of Strut Geometry and Linear Energy Density

by Rabiul Islam, Beytullah Aydogan and Kevin Chou

Metals 2025, 15(9), 1009; https://doi.org/10.3390/met15091009 - 11 Sep 2025

Abstract

Laser powder bed fusion (L-PBF) enables the fabrication of complex lattice-type structures composed of thin struts, offering lightweight, high-strength advantages in aerospace and biomedical applications, among others. While extensive research has examined full lattices and process parameter effects individually, the combined influence of [...] Read more.

Laser powder bed fusion (L-PBF) enables the fabrication of complex lattice-type structures composed of thin struts, offering lightweight, high-strength advantages in aerospace and biomedical applications, among others. While extensive research has examined full lattices and process parameter effects individually, the combined influence of strut geometry, configuration, and processing conditions on mechanical properties remains less understood. This study investigates how the strut number, strut size, cross-sectional shape, and laser energy input affect the mechanical properties of thin-strut L-PBF tensile specimens. Ti-6Al-4V struts were designed and fabricated using an EOS M270 system using five linear energy density (LED) levels. The fabricated specimens were measured in porosity using micro-scaled computed tomography and further evaluated using a tensile tester. The results showed that increasing the strut number leads to significant reductions in tensile strength, even with the same overall cross-sectional area, especially at low LED levels. Size effects on mechanical strengths were observed, though mostly minimal, except at the smallest strut size, where defects tend to be more critical. Circular and square shapes performed similarly under general LED conditions; however, square struts exhibited inferior behavior at the lowest LED level. Overall, LED is the most influential factor, with the greatest tensile strength occurring near 0.2 J/mm; further decreasing or increasing the LED both increase the porosity, degrading mechanical strengths. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Experiments and Modelling)

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23 pages, 7971 KB

Open AccessArticle

Investigation on Strain-Forming Limits and Manufacturing Optimization of a Single Deep-Drawing Process Concerning 304 Stainless Steel’s Thin Sheet

by Yajie Li, Jianguang Xu and Baifeng Luan

Metals 2025, 15(9), 1008; https://doi.org/10.3390/met15091008 - 10 Sep 2025

Abstract

In order to solve the problems of wrinkling, cracking, and springback that occur during the single deep drawing forming process of household stainless steel sinks without annealing, the deep drawing process of thin SUS304 stainless steel was studied using a DYNAFORM numerical simulation [...] Read more.

In order to solve the problems of wrinkling, cracking, and springback that occur during the single deep drawing forming process of household stainless steel sinks without annealing, the deep drawing process of thin SUS304 stainless steel was studied using a DYNAFORM numerical simulation and experimental analysis. The uniaxial tensile test results indicate that 304 stainless steel exhibits different levels of plasticity in different directions. The TD direction, which is perpendicular to the rolling direction, has the lowest elongation, which is 11.8% lower than that in the rolling direction. The maximum bulging depth of the thin specimens in the finite element simulation reached 17.142 mm, and the maximum bulging depth of the specimens with cracks in the experiment was 16.572 mm, indicating that the results of the finite element simulation were in good agreement with those of the experiment. Finally, through simulation and experimentation, the optimal process for forming stainless thin steel sinks was obtained when the fillet radius R was 5 mm, the stamping speed was 20 mm/s, the blank holder force was 3 MPa, and the friction coefficient was 0.120. Full article

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17 pages, 1765 KB

Open AccessArticle

A Meshless Multiscale and Multiphysics Slice Model for Continuous Casting of Steel

by Božidar Šarler, Boštjan Mavrič, Tadej Dobravec and Robert Vertnik

Metals 2025, 15(9), 1007; https://doi.org/10.3390/met15091007 - 10 Sep 2025

Abstract

A simple Lagrangian travelling slice model has been successfully used to predict the relations between the process parameters and the strand temperatures in the continuous casting of steel. The present paper aims to include a simple macrosegregation, grain structure and mechanical stress and [...] Read more.

A simple Lagrangian travelling slice model has been successfully used to predict the relations between the process parameters and the strand temperatures in the continuous casting of steel. The present paper aims to include a simple macrosegregation, grain structure and mechanical stress and deformation model on top of the thermal slice framework. The basis of all the mentioned models is the slice heat-conduction model that considers the complex heat extraction mechanisms in the mould, with the sprays, rolls, and through radiation. Its main advantage is the fast calculation time, which is suitable for the online control of the caster. The macroscopic thermal and species transfer models are based on the continuum mixture theory. The macrosegregation model is based on the lever rule microsegregation model. The thermal conductivity and species diffusivity of the liquid phase are artificially enhanced to consider the convection of the melt. The grain structure model is based on cellular automata and phase-field concepts. The calculated thermal field is used to estimate the thermal contraction of the solid shell, which, in combination with the metallostatic pressure, drives the elastic-viscoplastic solid-mechanics models. The solution procedure of all the models is based on the meshless radial basis function generated finite difference method on the macroscopic scale and the meshless point automata concept on the grain structure scale. Simulation results point out the areas susceptible to hot tearing. Full article

(This article belongs to the Special Issue Advanced Simulation and Modeling Technologies of Metallurgical Processes—2nd Edition)

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24 pages, 5495 KB

Open AccessArticle

Self-Organization in Metal Plasticity: An ILG Update

by Avraam Konstantinidis, Konstantinos Spiliotis, Amit Chattopadhyay and Elias C. Aifantis

Metals 2025, 15(9), 1006; https://doi.org/10.3390/met15091006 - 10 Sep 2025

Abstract

In a 1987 article of the last author dedicated to the memory of a pioneer of classical plasticity Aris Philips of Yale, the last author outlined three examples of self-organization during plastic deformation in metals: persistent slip bands (PSBs), shear bands (SBs) and [...] Read more.

In a 1987 article of the last author dedicated to the memory of a pioneer of classical plasticity Aris Philips of Yale, the last author outlined three examples of self-organization during plastic deformation in metals: persistent slip bands (PSBs), shear bands (SBs) and Portevin Le Chatelier (PLC) bands. All three have been observed and analyzed experimentally for a long time, but there was no theory to capture their spatial characteristics and evolution in the process of deformation. By introducing the Laplacian of dislocation density and strain in the standard constitutive equations used for these phenomena, corresponding mathematical models and nonlinear partial differential equations (PDEs) for the governing variable were generated, the solution of which provided for the first time estimates for the wavelengths of the ladder structure of PSBs in Cu single crystals, the thickness of stationary SBs in metals and the spacing of traveling PLC bands in Al-Mg alloys. The present article builds upon the 1987 results of the aforementioned three examples of self-organization in plasticity within a unifying internal length gradient (ILG) framework and expands them in 2 major ways by: (i) introducing the effect of stochasticity and (ii) capturing statistical characteristics when PDEs are absent for the description of experimental observations. The discussion focuses on metallic systems, but the modeling approaches can be used for interpreting experimental observations in a variety of materials. Full article

(This article belongs to the Special Issue Self-Organization in Plasticity of Metals and Alloys)

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17 pages, 7205 KB

Open AccessArticle

Evolution of Microstructure and the Influence of Carbides on Hardness Properties in Martensitic Stainless Steel 90Cr18MoV During Heat Treatment

by Shengfu Yuan, Ruizhi Wang, Xuelin Wang, Fajian Jiang, Chengjia Shang and Xinghua Wu

Metals 2025, 15(9), 999; https://doi.org/10.3390/met15090999 - 9 Sep 2025

Viewed by 345

Abstract

In this study, we utilized Thermo-Calc software (2023a) to optimize the heat treatment process of martensitic stainless steel 90Cr18MoV through phase diagram calculations. The microhardness of 90Cr18MoV was characterized using a nanoindentation instrument. The microstructural morphology of the samples was analyzed using scanning [...] Read more.

In this study, we utilized Thermo-Calc software (2023a) to optimize the heat treatment process of martensitic stainless steel 90Cr18MoV through phase diagram calculations. The microhardness of 90Cr18MoV was characterized using a nanoindentation instrument. The microstructural morphology of the samples was analyzed using scanning electron microscopy (SEM). The composition of the samples was characterized through scanning electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Additionally, laser confocal microscopy (FIB) and transmission electron microscopy (TEM) were employed to characterize the precipitate phase composition and size before and after heat treatment, while also observing the dislocation structure within the samples. The relationship between the quenching temperature and the percentage of residual austenite content in the material was established. The influence of the dislocation structure and precipitate size on the hardness of the samples was investigated. The research findings confirm that the observed secondary hardening phenomenon in tempered samples is attributed to the co-precipitation of two types of carbides, M₂₃C₆ and MC, within the matrix. The study investigated the effects of the tempering temperature and duration on the size of secondary precipitates, indicating that M₂₃C₆ and MC particles with sizes less than or equal to 20 nm contribute to enhancing the matrix, while particles larger than 30 nm lead to a reduction in hardness after tempering. Notably, during the tempering process, M₂₃C₆ precipitated from the matrix nucleates on MC. Full article

(This article belongs to the Special Issue Design, Preparation and Properties of High Performance Steels)

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17 pages, 3186 KB

Open AccessArticle

Investigation of the Effects of Gas Metal Arc Welding and Friction Stir Welding Hybrid Process on AA6082-T6 and AA5083-H111 Aluminum Alloys

by Mariane Chludzinski, Leire Garcia-Sesma, Oier Zubiri, Nieves Rodriguez and Egoitz Aldanondo

Metals 2025, 15(9), 1005; https://doi.org/10.3390/met15091005 - 9 Sep 2025

Viewed by 419

Abstract

Friction stir welding (FSW) has emerged as a solid-state joining technique offering notable advantages over traditional welding methods. Gas metal arc welding (GMAW), a fusion-based process, remains widely used due to its high efficiency, productivity, weld quality, and ease of automation. To combine [...] Read more.

Friction stir welding (FSW) has emerged as a solid-state joining technique offering notable advantages over traditional welding methods. Gas metal arc welding (GMAW), a fusion-based process, remains widely used due to its high efficiency, productivity, weld quality, and ease of automation. To combine the benefits of both techniques, a hybrid welding approach integrating GMAW and FSW has been developed. This study investigates the impact of this hybrid technique on the joint quality and properties of AA5083-H111 and AA6082-T6 aluminum alloys. Butt joints were produced on 6 mm thick plates, with variations in friction process parameters. Characterization included macro- and microstructural analyses, mechanical testing (hardness and tensile strength), and corrosion resistance evaluation through stress corrosion cracking tests. Results showed that FSW significantly refined and homogenized the microstructure in both alloys. AA5083-H111 welds achieved a joint efficiency of 99%, while AA6082-T6 reached 66.7%, differences attributed to their distinct strengthening mechanisms and the thermal–mechanical effects of FSW. To assess hydrogen-related behavior, slow strain rate tensile (SSRT) tests were conducted in both inert and hydrogen-rich environments. Hydrogen content was measured in arc, friction, and overlap zones, revealing variations depending on the alloy and microstructure. Despite these differences, both alloys exhibited negligible hydrogen embrittlement. In conclusion, the GMAW–FSW hybrid process successfully produced sound joints with good mechanical and corrosion resistance performance in both aluminum alloys. The findings demonstrate the potential of hybrid welding as a viable method for enhancing weld quality and performance in applications involving dissimilar aluminum alloys. Full article

(This article belongs to the Section Welding and Joining)

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22 pages, 3506 KB

Open AccessArticle

Influence of Inhomogeneous Plastic Strain and Crystallographic Orientations on Fatigue-Induced Dislocation Structures in FCC Metals

by Tianchang Ma, Yuyang Bai, Haomeng Shi, Yanlong Wei and Chunwei Zhang

Metals 2025, 15(9), 1004; https://doi.org/10.3390/met15091004 - 9 Sep 2025

Viewed by 124

Abstract

Owing to the differences in crystallographic orientations among individual grains, dislocation structures in polycrystals are inherently inhomogeneous from grain to grain. Since intergranular incompatibility is inevitable during plastic deformation, it may consequently lead to unpredictable plastic strain localization, which in turn facilitates the [...] Read more.

Owing to the differences in crystallographic orientations among individual grains, dislocation structures in polycrystals are inherently inhomogeneous from grain to grain. Since intergranular incompatibility is inevitable during plastic deformation, it may consequently lead to unpredictable plastic strain localization, which in turn facilitates the initiation of fatigue crack. Therefore, to elucidate the mechanisms underlying inhomogeneous deformation in polycrystals, this study systematically examines the fatigue-induced dislocation structures in polycrystalline SUS316L stainless steel. We then directly compare them with those in copper single crystals to clarify the dependence of the dislocation structures on crystallographic orientation. SEM characterization demonstrates that high plastic strain near grain boundaries promotes the formation of secondary cell bands (CBs) overlapping the primary CBs, which is attributable to the simultaneous activation of multiple-slip systems under high plastic strain amplitudes. In addition to strain localization, competition among candidate secondary slip systems strongly governs the dislocation structures. Notably, a new type of deformation band (DB) on the (010) plane is identified in a non-coplanar double-slip-oriented grain, a feature not observed in single crystals, indicating that polycrystals accommodate plastic strain through distinct mechanisms. Detailed dislocation structure analysis provides theoretical guidance for mitigating fatigue crack initiation through the manipulation of dislocations. Full article

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18 pages, 3503 KB

Open AccessArticle

Influence of Different Heat Treatments on Microstructure Evolution and High-Temperature Tensile Properties of LPBF-Fabricated H13 Hot Work Steel

by Mohamed Meher Monjez, Narges Omidi, Pedram Farhadipour, Abderrazak El Ouafi and Noureddine Barka

Metals 2025, 15(9), 1003; https://doi.org/10.3390/met15091003 - 9 Sep 2025

Viewed by 167

Abstract

This study investigates the effect of tensile test temperatures, ranging from 300 °C to 600 °C, on the microstructure, mechanical properties, and fracture behavior of AISI H13 11 tool steel manufactured by laser powder bed fusion (LPBF) under three material conditions: As-Built (AB), [...] Read more.

This study investigates the effect of tensile test temperatures, ranging from 300 °C to 600 °C, on the microstructure, mechanical properties, and fracture behavior of AISI H13 11 tool steel manufactured by laser powder bed fusion (LPBF) under three material conditions: As-Built (AB), Direct Double-Tempered (DTT), and 13 Quenched and Double-Tempered (QTT). Optical and SEM observations show that quenching before tempering leads to a more homogeneous microstructure. Full austenitization during quenching eliminates the laser track patterns and cellular structures characteristic of the AB and DTT conditions, resulting in a microstructure like that of conventionally processed material. Tensile test results reveal that, while all material conditions (AB, DTT, and QTT) perform similarly at lower temperatures (up to 300 °C), significant differences emerge at elevated temperatures. At 300 °C, AB, DTT, and QTT maintain 87.5%, 85.8%, and 83.1% of their room-temperature yield strength, respectively. However, beyond this point, the DTT condition clearly outperforms the others. QTT shows a sharp decline above 300 °C, retaining only ~24% of its yield strength, whereas AB and DTT maintain approximately 80%. The superior performance of DTT becomes more evident at higher temperatures: it retains 25% and 20% of its yield strength at 500 °C and 600 °C, respectively, higher than both AB and QTT. Full article

(This article belongs to the Special Issue Laser Additive Manufacturing of Metallic Alloys)

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13 pages, 5841 KB

Open AccessArticle

Influence of Heat Treatment on the Microstructure and Properties of 2319 Aluminum Alloy Produced by Wire Arc Additive Manufacturing

by Yuxin Pan, Zhensen Guo, Xiaoqiang Li and Lei Wen

Metals 2025, 15(9), 1002; https://doi.org/10.3390/met15091002 - 9 Sep 2025

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Abstract

A single-layer wall specimen of 2319 aluminum alloy was fabricated by the wire arc additive manufacturing (WAAM) technique through layer-by-layer welding, and it was then subjected to solution treatment and aging treatment. This study investigated the changes in the microstructure, mechanical properties, and [...] Read more.

A single-layer wall specimen of 2319 aluminum alloy was fabricated by the wire arc additive manufacturing (WAAM) technique through layer-by-layer welding, and it was then subjected to solution treatment and aging treatment. This study investigated the changes in the microstructure, mechanical properties, and corrosion resistance of the materials after deposition and heat treatment. The results show that in the as-deposited microstructure, there is a second phase in the form of a network structure. In addition, the number of impurity phases is large, and their sizes are relatively big. After solution treatment, most of the second phase is dissolved, and the remaining impurity phases are mainly the θ phase, with relatively small sizes. After subsequent aging treatment, a fine and dispersedly distributed second phase is formed in the dendrites. Compared with the as-deposited state, the number of secondary phases in the matrix after heat treatment is significantly reduced, and the distribution is more dispersed, which improves the mechanical properties and corrosion resistance of the material. After heat treatment, the tensile strengths in the horizontal and vertical directions of the alloy reach 362 MPa and 339 MPa, respectively, which are increased by 60.7% and 63.8% compared with the as-deposited state. However, the plastic deformation ability of the material after aging treatment decreases to a certain extent. Full article

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11 pages, 2870 KB

Open AccessArticle

Effect of Adding TiZr-Based Amorphous Interlayer Through Electron Beam Welding on the Microstructure and Properties of Ti/Al Joints

by Lei Chen, Bo Zhang, Rongzheng Xu and Li Zhang

Metals 2025, 15(9), 1001; https://doi.org/10.3390/met15091001 - 9 Sep 2025

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Abstract

In this study, electron beam welding (EBW) experiments for TA1 and industrial high-purity Al were carried out, and the effects of a Ti_32.8Zr_30.2Cu₉Ni_5.3Be_22.7 amorphous interlayer on the microstructure and properties of the welded joints [...] Read more.

In this study, electron beam welding (EBW) experiments for TA1 and industrial high-purity Al were carried out, and the effects of a Ti_32.8Zr_30.2Cu₉Ni_5.3Be_22.7 amorphous interlayer on the microstructure and properties of the welded joints were investigated. This is the first application of this interlayer material in the field of Ti/Al dissimilar-metal welding. In order to better improve the interfacial reaction of the welded joints and effectively control the thickness of intermetallic compounds (IMCs), the electron beam was offset by 1 mm towards the Al side. The results indicate that the amorphous interlayer was beneficial for improving the performance of the welded joints, with the maximum tensile strength reaching 94.8 MPa, which was 97% of the strength of the Al base material (97.7 MPa). The thickness of the Ti-Al intermetallic compound (IMC) layer formed in the upper part of the welded joints was lower compared with the joints without an interlayer, and the IMC layer formed in the lower part of the welded joints was only 1–2 μm. Additionally, a large number of small-sized and dispersed Ti-Al and Al-Zr IMCs were generated on the Al side, which positively impacted the performance of the welded joints. Full article

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35 pages, 3189 KB

Open AccessArticle

In Situ and Laboratory Investigation of the Anti-Corrosion and Anti-Fouling Efficacy of an Innovative Biocide-Free Coating for Naval Steels

by Polyxeni Vourna, Pinelopi P. Falara and Nikolaos D. Papadopoulos

Metals 2025, 15(9), 1000; https://doi.org/10.3390/met15091000 - 9 Sep 2025

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Abstract

This study presents an in situ and laboratory evaluation of an innovative biocide-free nanocomposite coating designed to provide dual anti-corrosion and anti-fouling protection for EH36 naval steel in marine environments. The coating, comprising polyaniline nanorods, titanium dioxide nanoparticles, and Fe₃O₄ [...] Read more.

This study presents an in situ and laboratory evaluation of an innovative biocide-free nanocomposite coating designed to provide dual anti-corrosion and anti-fouling protection for EH36 naval steel in marine environments. The coating, comprising polyaniline nanorods, titanium dioxide nanoparticles, and Fe₃O₄-functionalized multiwalled carbon nanotubes embedded in a robust resin matrix, was systematically assessed through electrochemical, microscopic, and field-based methods. Laboratory immersion tests and extended exposures at two Mediterranean sea sites (Thessaloniki and Heraklion) revealed substantial improvements in corrosion resistance and significant suppression of marine biofouling over periods of up to 24 months. Electrochemical measurements demonstrated that coated specimens maintained a corrosion inhibition efficiency exceeding 93% throughout the study, exhibiting markedly lower corrosion current densities and higher charge transfer resistances than uncoated controls. Impedance spectroscopy and equivalent circuit modeling confirmed sustained barrier properties, while digital imaging and qualitative biological assessments showed reduced colonization by both micro- and macrofouling organisms. Comparative analysis with conventional biocidal and alternative eco-friendly coatings underscored the superior durability, environmental compatibility, and anti-fouling efficacy of the developed system. The results highlight the coating’s promise as a sustainable, high-performance solution for long-term protection of naval steels against the combined challenges of corrosion and biofouling in harsh marine settings. Full article

(This article belongs to the Special Issue Surface Treatments and Coating of Metallic Materials)

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15 pages, 6153 KB

Open AccessArticle

Hot Deformation Behavior and Processing Maps of Nitrogen-Containing 2Cr13 Corrosion-Resistant Plastic Die Steel

by Baoshuai Chu, Shengwei Cheng and Wen Yang

Metals 2025, 15(9), 998; https://doi.org/10.3390/met15090998 - 8 Sep 2025

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Abstract

To investigate the hot deformation behavior of nitrogen-containing 2Cr13 (2Cr13N) corrosion-resistant plastic mold steel, uniaxial compression tests were conducted at temperatures ranging from 850 to 1200 °C and strain rates between 0.01 and 10 s⁻¹. The results indicate that the flow [...] Read more.

To investigate the hot deformation behavior of nitrogen-containing 2Cr13 (2Cr13N) corrosion-resistant plastic mold steel, uniaxial compression tests were conducted at temperatures ranging from 850 to 1200 °C and strain rates between 0.01 and 10 s⁻¹. The results indicate that the flow stress exhibits pronounced peak characteristics under conditions of low strain rate and high temperature, with peak stress decreasing as deformation temperature increases and strain rate decreases. Using the Arrhenius model, a hot deformation equation was established, and activation energy for deformation was 454.85 kJ/mol. The processing diagram was constructed based on the dynamic material model (DMM) theory. The optimal hot working window was at 1050–1150 °C with a strain rate less than 0.05 s⁻¹ and at 1150–1200 °C with a strain rate greater than 2 s⁻¹, with excellent efficiency of power dissipation (η > 0.32) and lower values of Kernel Average misorientation (KAM) (1.2386 and 1.3095, respectively). Full article

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

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26 pages, 7608 KB

Open AccessArticle

High-Pressure Torsion and Anodic Oxidation as a Method for Surface Engineering of Ti-13Nb-13Zr Biomedical Alloy

by Dragana R. Mihajlović, Bojan I. Medjo, Jelena B. Bajat and Veljko R. Djokić

Metals 2025, 15(9), 997; https://doi.org/10.3390/met15090997 - 8 Sep 2025

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Abstract

The anodic oxidation technique was used for surface modification, resulting in the creation of a titanium-based nanotube oxide layer on a coarse-grained and ultrafine-grained Ti-13Nb-13Zr alloy. The modified surface morphology was analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray [...] Read more.

The anodic oxidation technique was used for surface modification, resulting in the creation of a titanium-based nanotube oxide layer on a coarse-grained and ultrafine-grained Ti-13Nb-13Zr alloy. The modified surface morphology was analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). The electrochemical impedance spectroscopy (EIS) method was employed to evaluate the corrosion stability of the Ti-13Nb-13Zr alloy before and after anodic oxidation. Corrosion stability was determined by exposing the examined alloy to a solution that simulates environment in the human organism (Ringer’s solution). To examine the titanium-based nanotube oxide layer adhesion on the Ti-13Nb-13Zr alloy’s surface, a scratch test was performed. The hydrophilicity of the modified surface was measured using the contact angle between a drop of Ringer’s solution and the modified surface. The anodic oxidation led to the creation of a nanotube oxide layer on the surface of the Ti-13Nb-13Zr (wt.%) alloy. The impact of the ultrafine-grained structure on the homogeneity of the nanotube oxide layer obtained using anodic oxidation was observed. The ultrafine-grained structure contributed to the increased diameter of the nanotubes, while the combined effect of anodic oxidation and high-pressure torsion significantly increased the roughness of the Ti-13Nb-13Zr alloy’s surface, which is expected to enhance biomechanical compatibility by reducing cytotoxicity, providing a more adaptable modulus of elasticity for human body conditions and ensuring adequate corrosion resistance and hydrophilicity. In this study, it was established that the examined alloy had suitable corrosion resistance for utilization in medicine as a metallic implant in the human body. The scratch test showed acceptable adhesion from the titanium-based nanotube oxide layer created using anodic oxidation. Also, the determination of the surface contact angle showed that the surface after anodic oxidation was more hydrophilic than the surface before anodic oxidation. Full article

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

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16 pages, 5795 KB

Open AccessArticle

The Effect of Mo and Al Substitution in Cryomilled and Cold-Rolled FeNi Alloys

by Valmir Rodrigo da Silva, Øystein Slagtern Fjellvåg, Peter Švec, Peter Švec, Jr., Bjørn Christian Hauback and Stefano Deledda

Metals 2025, 15(9), 996; https://doi.org/10.3390/met15090996 - 8 Sep 2025

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Abstract

The ordered tetragonal FeNi L1₀ phase, tetrataenite, is a promising candidate for rare earth-free permanent magnets due to its competitive magnetic properties and the low cost of the constituent elements. In this work, we have investigated the effect of molybdenum and aluminum [...] Read more.

The ordered tetragonal FeNi L1₀ phase, tetrataenite, is a promising candidate for rare earth-free permanent magnets due to its competitive magnetic properties and the low cost of the constituent elements. In this work, we have investigated the effect of molybdenum and aluminum substitution on the formation of the ordered L1₀ phase. The alloys were prepared with die casting and melt spinning techniques, further processed using cold rolling and cryomilling, and finally annealed below the estimated order–disorder temperature (T_OD). To study the influence of composition and processing of the alloys, structural characterization and microstructural analysis were performed with synchrotron radiation X-ray diffractometry (SR-PXD) and Scanning Transmission Electron Microscopy (STEM), respectively. The presence of tetrataenite in the alloys investigated in this work could not be confirmed. In situ SR-PXD and STEM indicated minimal structural changes in the temperature stability range of the materials. A full-loop hysteresis curve acquired using a vibrating sample magnetometer (VSM) indicated no signs of magnetic hardening of the alloys with the measured coercivity being below 10 Oe, and thus consistent with FeNi without ordering. Full article

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

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15 pages, 3940 KB

Open AccessArticle

Ductile Fracture Prediction for Ti6Al4V Alloy Based on the Shear-Modified GTN Model and Machine Learning

by Tao Shen, Biao Li and Yuxuan Fang

Metals 2025, 15(9), 995; https://doi.org/10.3390/met15090995 - 8 Sep 2025

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Abstract

To investigate the failure behavior of Ti6Al4V alloy under complex stress states, this study designed tensile specimens with different notches to achieve high, medium, and low stress triaxiality conditions. By adjusting the width of the notch spacing of the specimens, the failure mode [...] Read more.

To investigate the failure behavior of Ti6Al4V alloy under complex stress states, this study designed tensile specimens with different notches to achieve high, medium, and low stress triaxiality conditions. By adjusting the width of the notch spacing of the specimens, the failure mode can be transformed from tension-dominated fracture to shear stress-dominated fracture, which enables further examination of the damage model’s effectiveness. A shear-modified Gurson–Tvergaard–Needleman (GTN) model was employed to predict the failure behavior under various stress states. For calibrating the GTN parameters, a machine learning approach was adopted. Back propagation (BP) neural networks were used to construct surrogate models for predicting the fracture strains of three typical specimens, and genetic algorithms (GAs) were integrated for optimization, to minimize the discrepancy in fracture strains between experimental results and finite element analysis (FEA). Finally, an optimal set of parameters was determined. This set of parameters can effectively predict the failure behavior of all specimens, including not only the stress–strain curves, but also the failure modes (fracture locations). Full article

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27 pages, 11331 KB

Open AccessArticle

A Novel Approach to Rockwell and Scratch Adhesion Tests for Hard Coatings Deposited onto Ti6Al4V Substrates

by Emanuele Ghio, Maria Francesca Bonilauri, Giovanni Bolelli, Paolo Colombi and Emanuela Cerri

Metals 2025, 15(9), 994; https://doi.org/10.3390/met15090994 - 8 Sep 2025

Viewed by 236

Abstract

The paper aims to investigate the failure modes induced by the Rockwell indentation test on Diamond-Like Carbon (DLC)-based and AlCrN coatings deposited on rolled and additively manufactured Ti6Al4V substrates with different surface finishes and subjected to two distinct post-process heat treatments, and the [...] Read more.

The paper aims to investigate the failure modes induced by the Rockwell indentation test on Diamond-Like Carbon (DLC)-based and AlCrN coatings deposited on rolled and additively manufactured Ti6Al4V substrates with different surface finishes and subjected to two distinct post-process heat treatments, and the possible correlations with scratch tests. At the magnification required to capture the entire Rockwell imprint, the adhesion class of the investigated DLC-based and AlCrN coatings could be incorrectly classified as HF1. However, higher-magnification observations revealed numerous radial cracks and non-uniformly distributed small delamination areas, changing the adhesion class to HF3. Additionally, roughness values higher than 1 μm hid the presence of radial cracks, which aligned parallel to the deep dales and high peaks of the roughness profile, as investigated by SEM. Likewise, in the scratch test, the rough surface also made the smallest cracks, formed at the critical load L_C1, undetectable. The critical loads for spallation of the coating in the scratch test (L_C2, L_C3) did not show significant correlation with the number of radial cracks formed during Rockwell indentations. Consequently, a quick Rockwell indentation cannot predict the scratch test results. Finally, both DLC-based and the AlCrN coatings exhibited good adhesion to Ti6Al4V substrates, regardless of the microstructure and surface finish of the titanium substrates. SEM-FIB observations revealed that the cracks formed during Rockwell indentation and scratch tests were deflected longitudinally within the underlying layers of the DLC-based coating and in the bottom part of the AlCrN coating, where the N concentration was higher. Full article

(This article belongs to the Special Issue Additive Manufacturing and Characterization of Metallic Alloys and Composites)

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19 pages, 4494 KB

Open AccessReview

Effect of Lanthanum-Cerium Rare Earth Elements on Steel at Atomic Scale: A Review

by Yuhang Liu, Jianguo Zhi, Ziyu Lyu, Chao Gu, Wangcai Diao, Zhibo Qu and Yanping Bao

Metals 2025, 15(9), 993; https://doi.org/10.3390/met15090993 - 8 Sep 2025

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Abstract

Lanthanum-cerium rare earth (RE) elements play a vital role in metallurgy as essential microalloying elements. Their addition significantly modifies inclusion characteristics, enhances mechanical properties, and improves corrosion resistance. This review emphasizes the distinct and synergistic roles of lanthanum (La) and cerium (Ce) in [...] Read more.

Lanthanum-cerium rare earth (RE) elements play a vital role in metallurgy as essential microalloying elements. Their addition significantly modifies inclusion characteristics, enhances mechanical properties, and improves corrosion resistance. This review emphasizes the distinct and synergistic roles of lanthanum (La) and cerium (Ce) in steel at the atomic scale, elucidated through first-principles calculations based on density-functional theory (DFT). The primary focus includes the nucleation mechanisms and characteristics of rare earth inclusions, the solid solution and segregation behavior of rare earth atoms, and their microalloying effects on electronic structure and interfacial bonding. Although both elements form stable inclusions Re₂O₃ and ReAlO₃ and exhibit grain refinement effects, Ce exhibits a unique dual valence state (Ce³⁺/Ce⁴⁺). This results in nucleation behavior and oxide stability for Ce ions that differ slightly from those of La. Both elements alter the electronic structure of the Fe matrix through hybridization with d-orbitals, reducing magnetic moment and enhancing toughness. Compared to other alloying elements, La and Ce exhibit unique behaviors due to their large atomic radii and high chemical reactivity, which influence their solid solubility, segregation tendencies, and interactions with other atoms such as Cr, C, and N. Finally, this paper discusses the challenges that exist when first-principles computational methods are used to study the mechanism of action of RE elements in steel, and proposes measures and methods to address these challenges, aiming to provide an in-depth understanding of the mechanism of action of REs in steel at the microscopic level and to promote the application of computational chemistry in the field of metallurgy. Full article

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

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17 pages, 4181 KB

Open AccessArticle

Fatigue Life Assessment of Railway Rails with Lubrication Holes: Experimental Validation and Finite Element Modelling

by Jose Sainz-Aja, Pablo San Roman, Jose A. Casado, Isidro Carrascal, Borja Arroyo, Diego Ferreño, Raul Moreno, David Peribañez, Hugo Vegas and Soraya Diego

Metals 2025, 15(9), 992; https://doi.org/10.3390/met15090992 - 8 Sep 2025

Viewed by 216

Abstract

This study investigates the fatigue behavior of railway rails with lubrication holes through a finite element modeling approach validated against full-scale laboratory tests. Fatigue tests were conducted on rail coupons subjected to three-point bending with the rail positioned upside-down, replicating the most critical [...] Read more.

This study investigates the fatigue behavior of railway rails with lubrication holes through a finite element modeling approach validated against full-scale laboratory tests. Fatigue tests were conducted on rail coupons subjected to three-point bending with the rail positioned upside-down, replicating the most critical loading configuration. Two finite element models were developed using ANSYS 2024 R2: a reduced model reproducing the laboratory setup, and a more comprehensive model representing a real rail track segment with multiple spans. The first model was calibrated against experimental S–N curve data to ensure consistency with the mechanical behavior observed in tests. The second model was used to evaluate the effect of wheel position, hole diameter, and hole location on the fatigue life of the rail. Simulation results highlight the influence of geometric and load parameters on crack initiation near the hole, providing valuable insights for optimizing hole design and placement in operational conditions. Full article

(This article belongs to the Special Issue Recent Insights into Mechanical Properties of Metallic Alloys)

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27 pages, 8247 KB

Open AccessArticle

Experimental–Numerical Investigation of the Ductile Damage of TRIP 780 Steel

by Rafael Oliveira Santos, Patrick de Paula Coelho, Gabriela Vincze, Fabiane Roberta Freitas da Silva, Rogério Albergaria de Azevedo Junior, Saulo Brinco Diniz and Luciano Pessanha Moreira

Metals 2025, 15(9), 991; https://doi.org/10.3390/met15090991 - 7 Sep 2025

Viewed by 632

Abstract

This study presents a combined experimental–numerical methodology to calibrate the mechanical behavior of an advanced high-strength steel (AHSS) with transformation-induced plasticity (TRIP) effects, incorporating both initial plastic anisotropy and ductile damage. The investigated TRIP 780 grade, widely used in the automotive industry for [...] Read more.

This study presents a combined experimental–numerical methodology to calibrate the mechanical behavior of an advanced high-strength steel (AHSS) with transformation-induced plasticity (TRIP) effects, incorporating both initial plastic anisotropy and ductile damage. The investigated TRIP 780 grade, widely used in the automotive industry for its exceptional strength–ductility balance, exhibits a complex deformation response that demands accurate constitutive modeling for reliable sheet metal forming simulations. The methodology minimizes the number of required specimen geometries without compromising accuracy. Three flat-sheet specimens were employed: standard uniaxial tension (UT) and two double-notched designs reproducing intermediate (ID) and plane strain (PS) modes. Experiments combined digital image correlation with finite element analysis. Hill’s 48 quadratic yield criterion captured the initial anisotropy of the TRIP 780 sheet, while the parameters of a phenomenological ductile damage model were calibrated from the experimental data. The TRIP effect under UT was quantified by X-ray diffraction, showing a decrease in retained austenite from 9.9% (as-received) to 3.2% at 21% equivalent plastic strain. Fractography revealed damage initiation dominated by void nucleation at phase boundaries. The proposed approach yielded stress–strain predictions with R² values exceeding 0.99. This simplified approach offers a cost-effective and experimentally feasible framework for constitutive modeling of AHSS grades, enabling practical applications in advanced sheet forming simulations. Full article

(This article belongs to the Special Issue Advances in Metal Forming and Plasticity)

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15 pages, 3909 KB

Open AccessArticle

Finite Element Simulation of Crystal Plasticity in the Tensile Fracture Behavior of PBF-LB/M CoCrFeNiMn High Entropy Alloy

by Liangliang Wu, Wei Duan, Shuaifeng Zhang, Xiao Yang, Wen Li, Xu Shen, Yan Zhang and Jianxin Zhou

Metals 2025, 15(9), 990; https://doi.org/10.3390/met15090990 - 7 Sep 2025

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Abstract

CoCrFeNiMn high entropy alloy (HEA) fabricated via laser-based powder bed fusion (PBF-LB/M) exhibits exceptional mechanical properties, including high strength, better ductility than titanium alloy, and superior corrosion resistance. This study simulates the intergranular fracture behavior of PBF-LB/M CoCrFeNiMn HEA under tensile loading by [...] Read more.

CoCrFeNiMn high entropy alloy (HEA) fabricated via laser-based powder bed fusion (PBF-LB/M) exhibits exceptional mechanical properties, including high strength, better ductility than titanium alloy, and superior corrosion resistance. This study simulates the intergranular fracture behavior of PBF-LB/M CoCrFeNiMn HEA under tensile loading by embedding cohesive elements with damage mechanisms into polycrystalline representative volume elements based on the crystal plasticity finite element method. The simulation results show good agreement with reported experimental stress–strain curves, demonstrating that the crystal plastic constitutive model combined with the cohesive constitutive model can accurately describe both the macroscopic response behavior and fracture failure behavior of the CoCrFeNiMn HEA. Furthermore, this work investigates the mechanical properties of the HEA in different tensile directions, the improvement of anisotropy through columnar-to-equiaxed grain transition, and the effect of texture strength on crack initiation and propagation. The results show that the polycrystalline CoCrFeNiMn HEA exhibits anisotropic mechanical properties: simulated yield strengths (YSs) are 436.9 MPa (in the scanning direction) and 484.7 MPa (in the building direction), tensile strengths (TSs) reach 639 MPa and 702.5 MPa, and elongations (ELs) are 10.6% and 21.8%, respectively. After equiaxed grain formation, the EL in the scanning direction increased from 10.6% to 17.2%, while the EL in the building direction decreased from 21.8% to 20.3%. Concurrently, the anisotropy coefficients of YS, TS, and EL decreased by 1.8%, 2.2%, and 36.1%, respectively. The cracks initiate at stress concentrations and subsequently propagate along grain boundaries until final fracture. Variations in texture strength significantly influence the crack initiation location and propagation path in the CoCrFeNiMn HEA. Full article

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15 pages, 8787 KB

Open AccessArticle

Point Defects in MoNbTi-Based Refractory Multi-Principal-Element Alloys

by Thai hang Chung, Maciej Oskar Liedke, Saikumaran Ayyappan, Maik Butterling, Riley Craig Ferguson, Adric C. L. Jones, Andreas Wagner, Khalid Hattar, Djamel Kaoumi and Farida A. Selim

Metals 2025, 15(9), 989; https://doi.org/10.3390/met15090989 - 6 Sep 2025

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Abstract

As emergent material candidates for extreme environments, refractory high-entropy alloys (HEAs) or refractory multi-principal-element alloys (RMPEAs) comprising refractory metals feature qualities such as high radiation tolerance, corrosion resistance, and mechanical strength. A set of MoNbTi-based RMPEA samples with Al, Cr, V, and Zr [...] Read more.

As emergent material candidates for extreme environments, refractory high-entropy alloys (HEAs) or refractory multi-principal-element alloys (RMPEAs) comprising refractory metals feature qualities such as high radiation tolerance, corrosion resistance, and mechanical strength. A set of MoNbTi-based RMPEA samples with Al, Cr, V, and Zr additions are prepared by spark plasma sintering and investigated for their response to irradiation using 10 MeV Si⁺ ions with a dose of

1.43 \times 10^{15}

ions/cm². Positron annihilation spectroscopy and transmission electron microscopy are employed as atomic- and meso- scale techniques to reveal how chemical complexity, nanotwinning, and phase fractions play an important role in radiation-induced defect accumulation and damage tolerance. The study provides experimental evidence of nanotwinning acting as an effective sink for radiation-induced point defects. Full article

(This article belongs to the Special Issue Advances in High-Entropy Alloys’ Microstructure, Properties and Preparation)

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19 pages, 10755 KB

Open AccessArticle

Corrosion Performance of (TiAlZrTaNb)N_x High-Entropy Nitrides Thin Films Deposited on 304 Stainless Steel via HiPIMS

by Maria-Camila Castañeda, Oscar Piamba and Jhon Olaya

Metals 2025, 15(9), 988; https://doi.org/10.3390/met15090988 - 6 Sep 2025

Viewed by 303

Abstract

In this study, the electrochemical corrosion behavior of TiAlZrTaNb nitride thin films deposited on 304 stainless steel substrates was investigated. The thin films were synthesized using high-power impulse magnetron sputtering (HiPIMS) and are classified as high-entropy alloys (HEAs). The microstructure, morphology, and chemical [...] Read more.

In this study, the electrochemical corrosion behavior of TiAlZrTaNb nitride thin films deposited on 304 stainless steel substrates was investigated. The thin films were synthesized using high-power impulse magnetron sputtering (HiPIMS) and are classified as high-entropy alloys (HEAs). The microstructure, morphology, and chemical composition of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), respectively. Corrosion resistance was evaluated through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests, employing tap water, acetic acid, and citric acid solutions at room temperature as electrolytes. The results demonstrated that the TiAlZrTaNbN coating exhibits a dense and homogeneous structure with a uniform elemental distribution. XRD analysis revealed the presence of face-centered cubic (FCC) crystalline phases, which significantly contribute to the coating’s corrosion resistance. Furthermore, the coating displayed exceptional corrosion performance in both acetic acid and citric acid electrolytes—simulating food environments with a pH ≤ 4.5—as revealed by a substantial reduction in corrosion current density and a positive shift in corrosion potential. These findings provide valuable insights into the properties of TiAlZrTaNbN coatings and underscore their potential for enhancing the durability of mechanical components employed in the food industry. Full article

(This article belongs to the Section Corrosion and Protection)

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