The design and optimization of mechanically hard soft magnetic materials, which combine high hardness with magnetically soft properties, represent a critical frontier in materials science for advanced technological applications. To address this challenge, a data-driven framework is presented for exploring the vast compositional space of high-entropy alloys (HEAs) and identifying candidates optimized for multifunctionality. The study employs a comprehensive dataset of 1 842 628 density functional theory calculations, comprising 45 886 quaternary and 414 771 quinary equimolar HEAs derived from 42 elements. Using ensemble learning, predictive models are integrated to capture the relationships between composition, crystal structure, mechanical, and magnetic properties. This framework offers a robust pathway for accelerating the discovery of next-generation alloys with high hardness and magnetic softness, highlighting the transformative impact of data-driven strategies in material design.

In this study, we investigate the precipitation kinetics of Cu in 15–5 PH maraging stainless steel during high-temperature thermal treatments in the fully austenitic state. This provides direct evidence that Cu precipitation can occur in the austenite phase of martensitic or ferritic steels. The kinetics of Cu precipitation in austenite are examined at 700 and 800 °C using in situ synchrotron small-angle and wide-angle X-ray scattering, complemented by atom probe tomography investigations to analyze the precipitates, particularly their chemistry, following heat treatment. The resulting experimental data, which include the evolution of size, volume fraction, number density and chemical composition, are used to inform precipitation kinetics modelling using the Langer-Schwartz-Kampmann-Wagner (LSKW) approach coupled with CALPHAD thermodynamic and kinetic databases. The simulations accurately capture the experimental data by adjusting the interfacial energy in an inverse modelling approach. The insight that Cu precipitation occurs in austenite and subsequently in martensite paves the way for design of hierarchical structures with a bi-modal particle size distribution of Cu precipitates with varying crystal structures and compositions. Additionally, the validated LSKW modelling approach establishes a foundation for designing Cu-alloyed high-performance steels, taking into account various manufacturing routes.

Anneal hardening has been commonly observed in single-phase solid solutions, including face-centered cubic (FCC) alloys containing transitional-metal elements. However, the underlying mechanisms governing this effect have remained unclear due to a lack of direct evidence. In this study, we utilize multi-scale in-situ characterizations to thoroughly investigate the microstructural evolution during annealing of an MP35 N (Co35Ni35Cr24Mo6, at %) alloy. Our findings reveal negligible differences in the crystal structure, grain boundary (GB) character, and dislocation structure before and after annealing at 550 °C. However, in-situ transmission electron microscopy heating experiments and atomic-resolution energy-dispersive spectroscopy mappings disclose that the 550 °C annealing promotes nanoscale segregation of Mo into GBs, driven by the reduced GB energy. These segregated Mo atoms engage in strong charge exchanges with neighboring atoms, enhancing the GB's cohesive strength and improving the resistance to dislocation motion due to the increased strain field near the GBs. Consequently, the GB strengthening effect is enhanced, leading to significant anneal hardening in the fine-grained sample (3.2 μm) with Mo segregation, while no hardening is observed in the coarse-grained sample (202.2 μm) lacking Mo segregation. Furthermore, we demonstrate that annealing at higher temperatures triggers an interfacial phase transition from the FCC to a μ phase through spinodal decomposition accompanied by significant dislocation recovery, which paradoxically weakens the anneal hardening effect. These findings provide deeper insights into the anneal hardening phenomena and offer valuable guidance for optimizing cold working and heat treatment processes in the further development of high-performance structural alloys.

Vanadium-based materials have great potential for advancing novel hydrogen storage technology. To address the limited gravimetric hydrogen storage capacity of V, incorporating light alloying elements has been proposed. In this study, the hydrogen storage capacities of V1−xAlx (x = 0, 0.1, 0.2, 0.3, and 0.4) solid solutions are investigated by employing first-principles calculations. Our results indicate that both the stability and hydrogen storage capacity of V1−xAlx hydrides decrease with an increase in Al content due to a reduction of chemical contribution, consistent with experimental results. The chemical bond analysis, Bader charge, and projected density of states investigation reveal that the Al-H antibonding states appear at the Fermi level and net H-H antibonding states surrounding Al form due to the transfer of excessive electrons from Al to H. To further explore the relationship between chemical bonding and desorption enthalpy, over 20 face-centered cubic (FCC) metal dihydrides are selected. It is found that the desorption enthalpies correlate weakly with the metal-hydrogen (M-H) bond strength and positively with M-H antibonding states below the Fermi level. Our study reveals the mechanism of interactions between chemical bonds and hydrogen storage properties in metal hydrides, providing valuable insights for the future design of hydrogen storage materials.

This study explores the dynamic strain aging mechanism in medium-Mn steel, emphasizing its interplay with the kinetics of strain-induced martensite transformation (SIMT). By tracking the migration of each Portevine-Le Châtelier band, we investigated the complex dynamics of SIMT and its impact on the mechanical behavior. Characteristics of stress serrations are closely related to the dynamic propagation behavior of PLC bands. The ε martensite, being softer than austenite, contributes negligibly to the work hardening rate, while plays a key role in coordinating plastic deformation. The α′ martensite with the hardest value of 6.08 GPa, locally pins the mobile dislocations, triggering the stress serrations in the stress-strain curve. However, as α′ martensite grows, the pinning effect on dislocations diminishes substantially. We delimited a critical size of α′ martensite, about 350 nm, beyond which it loses the ability to pin dislocations and instead begins to undergo plastic deformation. Therefore, the serrations intensity is closely governed by the nucleation and growth rates of α′ martensite: a nucleation-dominant regime intensifies serrations, while a growth-dominant regime reduces them. The deep learning of the effect of SIMT kinetics on DSA mechanism is pivotal for understanding the mechanical stability and ductility of medium-Mn steels under strain.

Refractory high-entropy alloys (HEAs) show promise for novel hydrogen storage technology, but addressing their limited gravimetric hydrogen storage capacity necessitates exploration of light alloying elements including Mg and Al. Here, we employ density-functional theory to investigate the hydrogen desorption energetics of Ti0.325V0.275Zr0.125Nb0.275 alloy and the impact of doping with Mg and Al. Our analysis reveals that Mg and Al addition thermodynamically destabilize the Ti0.325V0.275Zr0.125Nb0.275-hydride and lower its storage capacity. The observed destabilization is attributed to reduced chemical contributions to the desorption enthalpy in the Mg and Al-doped hydrides. Detailed examination of the electronic density of states, electron localization function, and crystal orbital Hamilton population analysis unveils fundamental features of chemical bonding in these hydrides. Notably, H-H antibonding states occur for hydrogen atoms located in the nearest-neighbor interstices of Mg and Al atoms. Charge transfer facilitates formation of these antibonding states. This comprehensive analysis enhances our understanding of the intricate interplay between electronic structure, hydrogen desorption energetics, and chemical bonding in HEA hydrides, offering valuable insights for the design and optimization of advanced hydrogen storage materials.

Solid-state magnetic refrigeration, based on the magnetocaloric effect, is a promising, highly energy-efficient, and environmentally friendly cooling technology. High-entropy metallic glasses (HE-MGs) have attracted increasing interests due to their excellent magneto-caloric properties across a wide temperature range. In this work, we successfully prepared three rare-earth (RE) based HE-MGs microwires and investigated their structural and magnetocaloric properties. The Gd25Dy25Co25Al25, Tb20Gd20Dy20Co20Al20, and Ho20Gd20Dy20Co20Al20 microwires exhibit an amorphous structure with good glass forming ability. They undergo a second-order phase transition from ferromagnetic to paramagnetic states around Curie temperatures of ∼61 K, ∼63 K, and ∼ 47 K, respectively. The peak magnetic entropy change (-ΔSM) for these HE-MGs microwires range from 8.2 J kg−1 K−1 to 10.2 J kg−1 K−1 under a 5 T magnetic field change. Furthermore, the refrigeration capacities of these microwires are evaluated to be between 504 J kg−1 and 507 J kg−1 (5 T), demonstrating their exceptional cooling efficiency. Additionally, this study provides valuable insights for the further research and development of RE-containing HE-MGs, paying the way for optimized materials tailored for advanced magnetic refrigeration applications.

This paper presents a systematic investigation of the microstructure and magnetocaloric properties of melt-extracted Sm20Gd20Dy20Co20Al20 high-entropy microwires. The fabricated wires exhibited an amorphous structure, and the temperature interval of the undercooled liquid Delta T was 45 K. The microwires underwent a second-order magnetic transition from a ferromagnetic to a paramagnetic state near the Curie temperature (T-C=52 K). The maximum magnetic entropy change (-Delta S-M(max)), the relative cooling power and the refrigeration capacity reached 6.34 J.kg(-1).K-1, 422.09 J.kg(-1) and 332.94 J.kg(-1), respectively, under a magnetic field change of 5 T. In addition, the temperature-averaged entropy changes with two temperature lifts (3 and 10 K) were 6.32 and 6.27 J.kg(-1).K-1, respectively. The good magnetocaloric performance highlights the significant potential for the Sm20Gd20Dy20Co20Al20 microwires to be used as magnetic refrigerant materials in low-temperature region applications. This work will serve as a valuable reference for future investigations on low-temperature high-entropy magnetocaloric materials.

The application of structural metals in extreme environments necessitates materials with superior mechanical properties. Mo-doped FeCoCrNi high-entropy alloys (HEAs) have emerged as potential candidates for use in such demanding environments. This study investigates the hightemperature performance of FeCoCrNiMox HEAs with varying Mo contents (x = 0, 0.1, 0.3, and 0.5) prepared by laser powder bed fusion additive manufacturing. The mechanical properties were evaluated at room and 600 degrees C temperatures, and the microstructures were characterized using scanning electron microscopy, electron backscatter diffraction, energy dispersive X-ray spectroscopy, and transmission electron microscopy. The intrinsic dislocation cell patterning, solid-solution strengthening, nanoprecipitation, and twinning effects collectively modulated the plastic deformation behavior of the samples. The high-temperature mechanical performance was comprehensively analyzed in conjunction with ab initio calculations and molecular dynamics simulations to reveal the origin of the experimentally observed strength-ductility synergy of FeCoCrNiMo0.3. This study has significant implications for FeCoCrNiMox HEAs and extends our understanding of the structural origins of the exceptional mechanical properties of additively manufactured HEAs.

Molybdenum (Mo) has been recognized as an essential alloying element of the MP35N (Co35.4Cr22.9Ni35.5Mo6.2, at.%) superalloy for enhancing strength and corrosion resistance. However, a full understanding of the addition of Mo on microstructure and mechanical properties of the Mo-free parent alloy is lacking. In this work, we consider five (Co37.7Cr24.4Ni37.9)100-xMox (x = 0, 0.7, 2.0, 3.2, and 6.2) alloys, and reveal that yield/tensile strength and ductility are continuously increased for these alloys with increasing Mo content while a single-phase face-centered cubic structure remains unchanged. It is found that strong solid solution strengthening (SSS) is a main domain to the improved yield strength, whereas grain boundaries are found to soften by the Mo addition. The first-principles calculations demonstrate that a severe local lattice distortion contributes to the enhanced SSS, and the grain boundary softening effect is mostly associated with the decreased shear modulus. Both first-principles calculations and scanning transmission electron microscopy observations reveal that the stacking fault energy (SFE) reduces by the Mo addition. The calculated SFE value decreases from 0.4 mJ/m2 to-11.8 mJ/m2 at 0 K as Mo content increases from 0 at.% to 6.2 at.%, and experimentally measured values of SFE at room temperature for both samples are about 18 mJ/m2 and 9 mJ/m2, respectively. The reduction of SFE promoted the generation of stacking faults and deformation twins, which sustain a high strain hardening rate, thus postponing necking instability and enhancing tensile strength and elongation.