Based on exact muffin-tin orbitals (EMTO) and coherent potential approximation (CPA), we investigate the effects of Mo content on the mechanical properties of CrFeCoNiMo_x (0.1 ≤ x ≤ 0.3) high-entropy alloys (HEAs) with a face-centered-cubic (fcc) crystal structure; relevant physical parameters are calculated as a function of Mo content. The results indicate that the theoretical predictions of lattice constant, elastic constants, shear modulus, and Young's modulus are in good agreement with the available experimental data, which proves the validity of the applied approach. CrFeCoNiMo_0.26 HEA has better ductility and plasticity with respect to other HEAs with different Mo contents because it has the minimum elastic moduli and Vickers hardness, and has the maximum Pugh's ratio and anisotropy factors, etc. CrFeCoNiMo_0.2 HEA has better plasticity compared with CrFeCoNiMo_0.1 and CrFeCoNiMo_0.3 HEAs due to its minimum energy factor and maximum dislocation width. Screw dislocation is more likely to nucleate in CrFeCoNiMo_x (0.1 ≤ x ≤ 0.3) HEAs than edge dislocation. The present studies are helpful to explore the excellent mechanical properties of CrFeCoNiMo_x (0.1 ≤ x ≤ 0.3) HEAs during experiments.

In this work, the hot deformation behavior of 30Cr4MoNiV ultra-high-strength steel is investigated by isothermal compression tests using the Gleeble-3500 thermal simulation machine (Dynamic Systems Inc., New York, NY, USA) at a temperature range of 1173–1373 K under the strain rate of 0.01–10 s⁻¹. A constitutive equation with strain-dependent constants and processing maps suitable for 30Cr4MoNiV ultra-high-strength steel are established. The results show that the combination of the hyperbolic sine function and the Zener-Hollomon parameter can accurately represent the influences of deformation temperature, strain rate, and strain on the flow stress of the 30Cr4MoNiV ultra-high-strength steel. The applicability of plastic instability criteria such as m, $\dot{m}$, S, $\dot{S}$ and the instability parameter ξ are analyzed, the stability and instability regions are clarified accurately, and the optimized processing regions are given in the stability regions. The optimized regions are verified by the uniform equiaxed grains, and the plastic instability is validated by dynamic strain aging and the microstructure of the voids.

Frist-principles calculations combined with exact muffin-tin orbitals (EMTO) and coherent potential approximation (CPA) methods are conducted to investigate the effects of Cu content on mechanical properties of CrFeCoNiCu_x (0 ≤ x ≤ 0.3) high-entropy alloys (HEAs), and the dependencies of relevant physical parameters on Cu content in HEAs are shown and discussed in this work. It is found that the equilibrium lattice constant increases linearly and the elastic constant decreases gradually with increasing Cu content, and the crystal structure of CrFeCoNiCu_x (0 ≤ x ≤ 0.3) HEAs can preserve mechanical stability according to the stability criterion of cubic crystals. From the general trend, adding Cu atoms to CrFeCoNi-based HEAs will reduce elastic moduli, Vickers hardness, and yield strength, whereas ductility and plasticity of HEAs show the opposite trend. Also, three different dislocations, including screw, edge, and mixed dislocations, and twins are more likely to occur in HEAs with high Cu content because energy factors decrease steadily and dislocation widths increase gradually with increasing Cu content. The present results provide valuable theoretical verification for further research on the mechanical properties of CrFeCoNiCu_x (0 ≤ x ≤ 0.3) HEAs.

SPE water electrolysis is a promising method of hydrogen production owing to its multiple strengths, including its high efficiency, high product purity and excellent adaptability. However, the overpotential of the oxygen evolution reaction process and consumption of Ir during charging in SPE water electrolysis will inevitably result in large energy loss and then high cost. Under these circumstances, we propose a novel 40IrO ₂ /Co _x Sn _{(1− x )} O ₂ ( x = 0.1, 0.2, 0.3) anode catalyst, where the Co _x Sn _{(1− x )} O ₂ support is synthesized by a hydrothermal method and IrO ₂ is synthesized by a modified Adams fusion method. After modifying the component of Co _x Sn _{(1− x )} O ₂ , the 40IrO ₂ /Co _x Sn _{(1− x )} O ₂ exhibits an increased specific surface area, electrical conductivity and surface active sites. Moreover, a single cell is fabricated by Pt/C as cathode catalyst, 40IrO ₂ /Co _x Sn _{(1− x )} O ₂ as anode catalyst and Nafion 117 membrane as electrolyte. The 40IrO ₂ /Co _0.2 Sn _0.8 O ₂ exhibits the lowest overpotential (1.748 V at 1000 mA cm ⁻² ), and only 0.18 mV h ⁻¹ of voltage increased for 100 h durability test at 1000 mA cm ⁻² . Consequently, Co _x Sn _{(1− x )} O ₂ is a promising anode electrocatalyst support for an SPE water electrolyzer.