Using Density Functional Theory (DFT) calculations and Monte-Carlo (MC) simulations, we investigate the recently reported magnetic transition in B2 Al–Cr–Co alloys. The Cr sublattice is alloyed with different amounts of Co in the antiferromagnetic (AFM) B2 AlCr binary alloy and the resulting exchange interactions are analyzed within the Heisenberg Hamiltonian framework. DFT results reveal that at low Co concentrations the system favors the AFM order, while at high Co contents a transition to the ferromagnetic (FM) state is observed. Within the FM stability field, the Curie temperature (TC), obtained within the mean-field approximation, is below ∼160 K and decreases with Co concentration. The calculated exchange parameters evolve systematically with Co content, and the trends are consistent with the DFT total energies. The magnetic configurations obtained from MC simulations follow the DFT results at low Cr levels but predict a spin-glass behavior for alloys containing more than 40 at. % Co on Cr sublattice. These findings provide a fundamental understanding of how the chemistry-driven changes in exchange interactions affect magnetism in the B2 Al–Cr–Co alloys.

Incoherent interfaces are ubiquitous in materials, yet their interfacial properties remain poorly understood. Due to the high computational cost, density functional theory (DFT) studies are typically restricted to coherent or semicoherent interfaces. In this work, we propose a novel approach to estimate incoherent interfacial energies within a DFT-accessible supercell size. Based on the so-called “incoherent γ-surface” concept, we first develop a classical-model-potential-based framework to capture the evolution of the one-dimensional (1D) incoherent γ-surface with increasing cell size. The method is then extended to the Ni/Ni3Nb interface in a quasi-1D configuration, and further to a fully two-dimensional case of the Cu–Nb incoherent interface possessing very different lattice mismatches along the two in-plane directions. All investigated systems exhibit a consistent smoothing behavior of the γ-surface with increasing cell size. Moreover, the average value of the incoherent γ-surface is demonstrated to be a robust estimator for the incoherent interfacial energy, which is shown to converge rapidly even at small cell sizes. This work extends the applicability of first-principles methods to ideal incoherent interfaces and deepens the understanding of the coherent versus incoherent γ-surface concepts.

Stacking fault energies and critical resolved shear stresses (CRSSs) of different slip systems are predicted as a function of chemical composition for Mg solid solutions by accounting for chemical disorder, using the exact muffin-tin orbitals method involving coherent potential approximation and the semi-discrete variational Peierls–Nabarro model. A correlation between the stability of local atomic structure and stacking fault energies is established to understand the mechanisms behind the varied influences of alloying species. While addition of Ni, Co, Ti, and Ag (Sn, Ca, and Y) are demonstrated to significantly increase (decrease) the unstable stacking fault energy (γus) of prismatic and pyramidal 〈a〉 slip, Al, Li, and Zn yield relatively small influence. In addition, Sn, Ca, and Li decrease significantly both the intrinsic stacking fault energy (γisf) and γus of pyramidal 〈c+a〉 slip. The varied influences of alloying species on stacking fault energies of prismatic/pyramidal 〈a〉 and pyramidal 〈c+a〉 slip are demonstrated to strongly correlate with the local structural stability of the body-centered orthorhombic and triclinic structure, respectively. The counterbalance between the influence of volume change and chemical composition on the local structural stability dominates the alloying effect on γisf and γus. Furthermore, the predicted dislocation core structure and CRSSs of both basal and non-basal slips based on the calculated stacking fault energies and elastic parameters are in line with the available experimental findings. Among the studied alloying species, addition of Ca, Li, Sn, and Y are found to significantly reduce the difference of CRSS between basal and non-basal slips of Mg alloys. The present advances provide a solid basis for understanding the atomic mechanisms of plastic deformation and intelligent design of high-performance Mg alloys.

Using ab initio Density Functional Theory (DFT) calculations, we investigate the electronic structure, phase stability, and magnetic properties of equiatomic binary alloys between Al and 3d magnetic transition elements (Cr, Mn, Fe, Co, and Ni). Thermodynamically, all five binary aluminides are more stable in the ordered B2 phase than in the disordered body centered cubic phase, and Co is found to be the strongest B2 forming element with Al. The AlCo and AlNi compounds with B2 structure are verified to be non-magnetic, whereas AlFe turns out to be weakly magnetic, which is consistent with other DFT calculations employing similar exchange-correlation approximations. Magnetic simulations based on the Heisenberg Hamiltonian predict an antiferromagnetic ground state for the hypothetical B2 AlCr, which is also confirmed by direct DFT calculations. Doping AlCr with Co leads to an antiferromagnetic to ferromagnetic transition, where ferromagnetism is to a large extent attributed to Cr atoms. The phase stability and magnetic trends are explained using electronic structure arguments. The present findings contribute to a deeper understanding of the phase stability and magnetic properties of AlX binary alloys, providing insights into the formation mechanisms of the B2 structure with 3d magnetic transition metals.

The underlying mechanism of co-segregation of alloying elements at the grain boundary and its influence on mechanical properties are elaborated in Mg-Zn-Ca alloys by integrated experimental characterizations and ab initio calculations. Significant co-segregation of Zn and Ca at the grain boundary is detected in the Mg-Zn-Ca ternary alloy, leading to an important contribution to the simultaneous improvement of strength and ductility. The relatively strong electronic interactions between Zn and Ca are demonstrated to promote the formation of Zn-Ca ionic bonds and greatly decrease the segregation energy. It, in combination with the atomic-size-related preferred occupations of Zn and Ca, primarily contributes to their significant co-segregation at the grain boundary. The obvious co-segregation of Zn and Ca remarkably decreases grain size, significantly contributing to the improved strength. In addition, coarse twins and the associated cracking are efficiently suppressed in plastic deformation owing to the decreased grain size. Furthermore, the co-segregation significantly increases grain boundary cohesion strength and decreases grain boundary energy, which can delay the initiation of grain boundary cracks and accommodate high stress to activate non-basal slips. In addition, the high-angle grain boundaries stabilized by alloying element co-segregation promote the transmission of non-basal slip pairs and stress relaxation at the grain boundary and improve ductility ultimately. The present advances enhance the understanding required for evading the strength and ductility trade-off in Mg alloys by tailoring alloying element segregation. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

In this work, valence electron concentration (VEC), thermodynamic calculation (CALPHAD), and first-principles method were combined to predict the phase formation of (CrMnFeCoNi)100-xWx (x = 0-16) HEAs. Based on the predicted results and insight, five (CrMnFeCoNi)100-xWx (x = 0, 4, 8, 12, 16) HEAs were prepared by experiment. The phase composition, microstructure, and mechanical properties of the selected five HEAs were studied systematically by experiment. The experimental results on the phase formation agree very well with those of the theoretical prediction. The experimental results show that the yield strength of the (CrMnFeCoNi)100-xWx increases by approximately three times with the addition of 16 at.

In this study, novel non-equiatomic CoCrFeMnNi-based medium- and high-entropy alloys (M/HEAs) were designed to activate distinct deformation mechanisms, including twinning-induced plasticity (TWIP) and/or transformation-induced plasticity (TRIP). Tensile tests were performed at 298 and 173 K. A variety of ex-situ multiscale characterization techniques, strengthening modeling, thermodynamic modeling (CALPHAD method), and ab initio density functional theory (DFT) calculations were employed to investigate the structural and microstructural evolution, enabling accurate identification of the strengthening and active deformation mechanisms operating in the M/HEAs. Strengthening modeling revealed that grain boundary strengthening was the primary contributor to yield strength at both temperatures. A key finding of this study is that a controlled FCCHCP martensitic transformation, associated with TRIP, enhances the strength-ductility balance even when the resulting HCP phase reaches similar to 50% volume fraction. This demonstrates that TRIP-enabled metastability engineering is a promising strategy for designing high-performance M/HEAs for next-generation structural applications in energy, aerospace, and defense.

Understanding the electronic, lattice, and magnetic contributions to the magnetocaloric effect in magnetic materials can help to elucidate and optimize their performance. In this work, the structural and magnetocaloric properties of Al-Mn-Ni alloy are experimentally determined and theoretically analyzed based on ab initio calculations. The dominating B2 phase associated with the Mn-rich sublattice is found to be responsible for the observed magnetocaloric properties. The magnetic entropy change, refrigerant capacity, and adiabatic temperature change are evaluated. Through the analysis of the data, we find that for the B2 phase, changing from ferromagnetic to paramagnetic configurations results in a pronounced elastic hardening despite the volume expansion. The decrease in lattice entropy is significant and contributes negatively to the magnetic and electronic entropy changes. Our work emphasizes the critical role of the lattice sector in the magnetocaloric effect, and provides an in-depth understanding of the individual entropy terms in magnetic solid solutions.

This study employs ab initio density functional theory (DFT) combined with the exact muffin-tin orbitals (EMTO) method and coherent potential approximation (CPA) to systematically investigate the structural and mechanical properties of TiVNbMo-based refractory high-entropy alloys (RHEAs) doped with 4d transition metals (Zr, Rh, Ag). Equiatomic TiVNbMoM (M = Zr, Rh, Ag) and non-equiatomic Ti(1-x)VNbMoMx, TiV(1-x)NbMoMx, TiVNb(1-x)MoMx and TiVNbMo(1-x)Mx (with M = Zr, Rh, Ag; 0 <= x <= 1), were analyzed to evaluate phase stability, lattice parameters, elastic constants, and mechanical moduli. Results confirm the dominance of the body-centered cubic (bcc) phase in all equiatomic alloys, with valence electron concentration (VEC = 4.8-6.2) and atomic size difference (delta = 3.65%-6.18%) aligning with solid-solution formation criteria. However, Zr doping reduces bcc stability by lowering average d-electron occupancy, while Rh and Ag retain bcc dominance. Zirconium significantly expands the lattice parameter, whereas Rh reduces it. Mechanical analysis reveals that Rh enhances hardness in Rh-rich compositions, while Zr substitution at Ti sites improves ductility. All systems exhibit ductility (B/G > 1.75; nu > 0.31). This study provides the first theoretical exploration of Rh and Ag doping effects on TiVNbMo RHEAs, demonstrating Rh's unparalleled hardening capability and Zr's dual role in lattice expansion and ductility enhancement. These findings, validated against experimental lattice constants and hardness, as well as theoretical elastic constants and moduli, require further experimental studies to confirm and extend the theoretical predictions.

We investigate how the Al content in Alx(Mn0.76Co0.24)1-x (x = 0.45, 0.50, 0.55) alloys and the Mn/Co ratio in Al0.50MnyCo0.50-y (y = 0.36, 0.38, 0.40) alloys affect the magnetic properties. Structural and magnetic investigations by experiments, Thermo-Calc, and ab initio calculations show a dual-phase microstructure containing different fractions of a paramagnetic body-centered cubic (BCC) solid solution and a ferromagnetic B2 phase. The BCC/B2 phase fraction is sensitive to the Al content which strongly affects the saturation magnetization, magnetic transition temperature, and magnetocaloric properties. The magnetocaloric properties of the Al0.50Mn0.38Co0.12 alloy show peak values around 430 K with a magnetic entropy change of 0.71 Jkg- 1K-1, an adiabatic temperature change of 0.40 K, and a refrigeration capacity of 25.56 Jkg- 1 under a magnetic field of 650 kAm- 1 (0.82 T). These results open new possibilities for identifying promising medium-entropy alloys for magnetocaloric applications.

Using first principle alloy theory, we calculate the basal stacking fault energies as a function of chemical composition for a series of Mg binary alloys by accounting for the chemical disorder in solid solution. We show that while the basal stacking fault energies significantly increase with the addition of Co, Ni, Ag, and Li, they obviously decline upon alloying with Sn, Y, Ca, and Al. In contrast, Zn and Ti exhibit negligible influence on the basal stacking fault energy of I1 and I2 fault. The varied influence of alloying species on basal stacking fault energies are demonstrated to predominately determined by the volume- and composition-dependent relative phase stability between face-centered cubic and hexagonal close-packed structure. The influence of alloy species predicted in solid solution are obviously different from those computed for segregated ones, underlining the significance of chemical disorder to the intrinsic energy barriers of Mg solid solutions.

Addition of Gd with relatively large solubility is demonstrated to significantly reduce the coefficient of thermal expansion (CTE), while improving obviously the mechanical properties of Mg matrix. A good combination of low CTE, high strength and ductility is obtained at Gd content of - 10.6 wt%. According to first-principle predictions for Mg-Gd solid solutions, the decreased CTE upon alloying with Gd is predominately determined by the reduction of lattice vibrational contribution. This reduction emerges basically from the weakened anharmonic effect, which is represented by the decreased Gr & uuml;neisen parameter. The refined grain size and solution of Gd in bulk matrix predominate the increased strength of Mg-Gd alloys. The segregation of Gd at grain boundary is found to yield important impact on the refined grain size. Furthermore, while the obvious reduction of ductility at relatively high Gd contents is related to the precipitation of coarse Mg5Gd phase, the high ductility achieved at relatively low Gd contents is closely correlated with the activation of non-basal slips. It emerges fundamentally from the varied influence of Gd on the unstable stacking fault energy of basal and non-basal slips. The present advances enhance the understanding of designing innovative Mg alloys with tunable thermal expansion and mechanical properties.

An emerging trend in advanced thermal barrier coatings is the development of high-entropy ceramics. This study explores a Yb-rich high-entropy rare-earth zirconate synthesized though reverse coprecipitation. The x-ray diffraction and Raman spectrum analysis confirm a homogeneous defective fluorite structure without elemental segregation or secondary phases. The ceramic exhibits a coefficient of thermal expansion of 5.94 × 10−6 K−1 at room temperature, increasing to 11.70 × 10−6 K−1 at 1773 K. The Vickers hardness is measured to be 16.7 GPa. The ab initio calculations confirm the experimental findings, revealing significant local lattice distortion with a broad distribution of metal–oxygen bond lengths and strong nonlocal charge overlap. The substitution of Ce3+, Nd3+, Sm3+, and Eu3+ for Yb3+ forming weaker Ce-O, Nd-O, Sm-O, and Eu-O bonds, which reduce the crystal lattice energy and increase the ion relaxation under thermal vibration, thereby improves the coefficient of thermal expansion of the Yb2Zr2O7 ceramic. This work highlights the key role of bond engineering and lattice distortion in tuning thermal expansion characteristics, providing a robust framework for the rational design of high-entropy materials with optimized properties for high-temperature applications.

The structural, elastic and electronic properties of the ternary transition metal nitrides alloys TaxHf1-xN at (0<x<1) in the rock-salt structure are investigated by ab initio calculations. The calculations were performed using the first-principles Exact Muffin-Tin Orbitals method using full charge density technique within the framework of density functional theory. The compositional disorder is treated within the coherent potential approximation. The estimated formation enthalpy indicates that Ta0.5Hf0.5N is thermodynamically the most stable alloy. The obtained lattice parameters of the TaxHf1-xN alloys are in good agreement with other available theoretical and experimental values. The predicted elastic stiffness constants C-11, C-12 and C-44 indicate that the TaxHf1-xN alloys are mechanically stable and the addition of Ta increases their ductility. The Ta0.7Hf0.3N found to be hardest alloy. The correlation between Pettifor's criterion (C-12-C-44) normalized by bulk modulus B and Pugh's ratio G/B with increasing the degree of alloying x allowed us to predict that the critical value (G/B)=0.53, which correspond to x around 0.6 +/- 0.05, marks the brittle to ductile transition.

To our knowledge, no magnetic B2 phase in the Al–Mn system of near-equiatomic compositions has been reported so far. Here, we investigate the structural and magnetic characteristics of Al45Mn41.8X13.2 (X = Fe, Co or Ni) alloys. We demonstrate that adding 13.2 atomic percent magnetic 3d metal to AlMn stabilizes a ferromagnetic B2 structure, where Al and X occupy different sublattices. We employ density functional theory calculations and experimental characterizations to underscore the role of the late 3d metals for the phase stability of the quasi-ordered ternary systems. We show that these alloys possess large local magnetic moments primarily due to Mn atoms partitioned to the Al-free sublattice. The revealed magneto-chemical effect opens alternative routes for tailoring the magnetic properties of B2 intermetallic compounds for various magnetic applications.

Gold (Au) segregation at Pt grain boundaries (GBs) plays an important role in the properties of Pt-based alloys. It was reported that close-packed GBs and open GBs exhibit different segregation behaviors, and their origin is still unclear. Based on the density functional theory as implemented in the exact muffin-tin orbitals method and the full charge density technique, we investigate the impact of bulk composition and temperature on the segregation behaviors of the Σ3(111)[11¯0], Σ5(310)[001], and Σ9(221)[11¯0] symmetric tilt GBs in Pt–Au alloys. It is revealed that the segregation driving forces are correlated with the large local volume near the GB and the miscibility gap in Pt–Au alloys. At finite temperatures when the configurational entropy is considered, a competition between the chemical driving force and the configurational entropy is responsible for the segregation anisotropy in Pt–Au alloys. The bulk composition has a small effect on the segregation energy but strongly impacts the equilibrium concentration profiles at finite temperatures. The present study provides a theoretical analysis for the segregation anisotropy, and the methodology utilized in this work can be generalized to other binary or multi-component dilute or concentrated alloys while the composition variation is involved.

The nonstoichiometric Fe2P-type FeMn(1-x)Vx(P0.5Si0.5)1-x alloys (x = 0, 0.01, 0.02, and 0.03) have been investigated as potential candidates for magnetic refrigeration near room temperature. The magnetic ordering temperature decreases with increasing FeV concentration x, which can be ascribed to decreased ferromagnetic coupling strength between the magnetic atoms. The strong magnetoelastic coupling in these alloys results in large values of the isothermal entropy change (ASM); 15.7 J/(kg K), at 2 T magnetic field for the x = 0 alloy. ASM decreases with increasing x. Results from M & ouml;ssbauer spectroscopy reveal that the average hyperfine field (in the ferromagnetic state) and average center shift (in the paramagnetic state) have the same decreasing trend as ASM. The thermal hysteresis (AThyst) of the magnetic phase transition decreases with increasing x, while the mechanical stability of the alloys improves due to the reduced lattice volume change across the magnetoelastic phase transition. The adiabatic temperature change ATad, which highly depends on AThyst, is 1.7 K at 1.9 T applied field for the x = 0.02 alloy.

Recently, we reported an antiferromagnetic ground state for equiatomic Al-Cr in the B2 structure. Here, by a joint theoretical–experimental study, we investigate the effect of Co additions to the Al-Cr alloy with the aim to synthesize a ferromagnetic B2 phase. Al50Cr38Co12 (at.%) is prepared by arc melting from high-purity raw materials and solidifies into a combination of a Co-enriched B2 phase, a Co-depleted BCC phase, and an Al8Cr5 intermetallic phase. The as-cast alloy is ferromagnetic with a Curie point of 260 K, primarily due to the presence of about 54% B2 phase. Subsequent annealing decreases the fraction of the B2 phase to 27% with depletion of Cr from 20.2 at.% to 16.1 at.%, which leads to a reduction in its ferromagnetic behavior. Calculations based on Density Functional Theory (DFT) predict a corresponding decrease in the total magnetic moment and Curie temperature of the B2 phase by annealing. The present findings highlight the roles of Cr and Co in facilitating the formation of a metastable ferromagnetic B2 phase in this alloy.

The formation energy of the coherent interface between the primary strengthening phase gamma '' and gamma matrix in Inconel 718 alloy is investigated using ab initio calculations. We begin by examining the interface energy of the ordered Ni/Ni3Nb system. A negligible interface energy (1 mJ/m2) is obtained for the nonmagnetic state, which is explained by a nearest-neighbor layer interaction model. Allowing for spin polarization within both face-centered cubic (FCC) and D022 structures increases the interface energy to 181 mJ/m2. The strong magnetic dependence of the formation energy of the ordered Ni/Ni3Nb interface arises primarily from the different magnetic behavior of Ni in FCC and D022 phases. A detailed analysis of the site preference of minor elements in the gamma '' phase shows that Fe and Cr occupy the Ni-site, while Al, Mo, and Ti tend to occupy the Nb-site. The coherent interface energy of the gamma/gamma '' interface is predicted to be 257 mJ/m2 for the paramagnetic state and 255 mJ/m2 for the ferromagnetic state. The closeness of these formation energies reflects a similar magnetic response from both phases. The sensitivity of the gamma/gamma '' interface energy to variations in the gamma and gamma '' compositions is also investigated. Only small variations are revealed for the reported composition intervals. Our predictions serve as input for further theoretical simulations and as a reference for experimental investigations.

First, we discuss a common feature of single-phase pure metals and amorphous and high-entropy alloys: the maximum value of hardness corresponding to a valence electron count (VEC) value of around 6.5–7. This correlation is explained by the coincidence that by subtracting the number of sp valence electrons (Nsp = 2) from the VEC we obtain the maximal number of unpaired d electrons, Nd = 4.5–5 in the 3d, 4d, and 5d rows of transition elements. These unpaired d electrons form orbital overlap bonding, which is stronger than the isotropic metallic bonds of a delocalized electron cloud. The more unpaired d electrons there are, the higher the bonding strength. Second, we will discuss the hardness formulas derived from cohesion energy and shear modulus. We will demonstrate that both types of formulas originate in the electrostatic energy density of metallic bonds, expressing a 1/R4 dependence. Finally, we show that only two parameters are sufficient to estimate hardness: the atomic radius and the cohesion-based valence. In the case of alloys, our formula gives a lower bound on the hardness only. It is not suitable for calculation of the hardness increase caused by solid solution, grain size, precipitation, and phase mixture.