The band structure, the density of states and optical absorption properties of Cu-doped ZnO were studied by the first-principles generalized gradient approximation plane-wave pseudopotential method based on density functional theory. For the Zn_1-xCu_xO (x = 0, x = 0.0278, x = 0.0417) original structure, geometric optimization and energy calculations were performed and compared with experimental results. With increasing Cu concentration, the band gap of the Zn₁-_xCu_xO decreased due to the shift of the conduction band. Since the impurity level was introduced after Cu doping, the conduction band was moved downwards. Additionally, it was shown that the insertion of a Cu atom leads to a red shift of the optical absorption edge, which was consistent with the experimental results.

High-temperature tensile experiments with tensile rates ranging from 0.01 s⁻¹ to 10 s⁻¹ were carried out at various temperatures ranging from 1000 °C to 1250 °C with a Gleeble-3800 thermal simulation tester to evaluate the physical properties of an as-cast Ni–W–Co–Ta medium–heavy alloy. The microstructure evolution of the alloy during high-temperature stretching was characterized by metallographic microscopy, scanning electron microscopy, and transmission electron microscopy. The results indicated the emergence of multiple slip lines and the parallel arrangement of dislocations in the grain of the alloy after high-temperature stretching, and typical characteristics of plane slipping were observed. The plasticity of the Ni–W–Co–Ta medium–heavy alloy increased, but its strength decreased with an increase in the deformation temperature. In contrast, an increase in the strain rate resulted in a noticeable increase in the strength and plasticity of the medium–heavy alloy. The experiments revealed that the maximum tensile strength of the as-cast Ni–W–Co–Ta medium–heavy alloy was 735 MPa (T = 1000 °C, ${\displaystyle \dot{\mathsf{\epsilon }}}$ = 10 s⁻¹). Additionally, the maximum reduction in area and elongation was 38.1% and 11.8% (T = 1250 °C, $\dot{\mathsf{\epsilon }}$ = 10 s⁻¹), respectively. The mode of fracture after high-temperature tensile deformation was brittle fracturing.

A systematical exploration of the effect of aging time on the microstructure and mechanical properties of cold-rolled Ni-W-Co-Ta medium–heavy alloy with 90% thickness reduction at the aging temperature of 700 °C was performed. The results demonstrate that the volume fraction of the precipitation (Ni₄W), which persists under various aging times, increases from 13.7% (2 h) to 28.7% (32 h) with the extension of aging time. Meanwhile, the microstructure after aging treatment is still dominated by dislocation entanglement and dislocation walls, although the degree of lattice distortion and dislocation density attributed to heavy deformation decreases. The maximum tensile strength, yield strength, and microhardness (2286 MPa, 1989 MPa, 766 HV) of the cold-rolled Ni-W-Co-Ta medium–heavy alloy under the 16 h aging treatment at 700 °C are reached, respectively. The ductile–brittle mixed fracture morphology is maintained in the fracture morphology of the medium–heavy alloy before and after aging treatment.

The influences of rare earth neodymium on microstructure and mechanical properties of as cast and hot rolled AZ31B wrought magnesium alloy were investigated. The results show that the mechanical properties of both as cast and hot rolled AZ31B alloys decrease due to Nd addition. Nd reacts with Al to form Al₂Nd phase when Nd is added. Bulky and brittle Al₂Nd intermetallic degrades the mechanical properties. Moreover, the addition of Nd weakens the grain refining effect of Al on as cast AZ31B alloy, resulting in grain coarsening. Coarse grains also cause the decline of the mechanical properties of as cast AZ31B–Nd alloy. The negative influence of the bulky and brittle intermetallics on mechanical properties of AZ31B alloy can be relieved by large deformation because the intermetallics can be sufficiently broken up during the deformation process.

This paper presents a new formula for calculating the hardness of metallic crystals, resulted from the research on the critical grain size with stable dislocations. The formula is H = 6 kG/[π(1 − ν)e ^η ], where H is the hardness, k the coefficient, G the shear modulus, ν the Poisson’s ratio, η a function of the radius of an atom (r) and the electron density at the atom interface (n). The formula will not only be used to testify the critical grain size with stable dislocations, but also play an important role in the understanding of mechanical properties of nanocrystalline metals.