The influence of solid solution treatment (SST), artificial aging treatment (AAT), and deep cryogenic-aging treatment (DCAT) on the mechanical properties and microstructure evolution of 6082 aluminum alloy was investigated. The tensile test was performed to obtain the true stress–strain curves through an electronic universal testing machine. The results show that the yield strengths of the SST specimens in all three directions are the lowest, of less than 200 MPa. In addition, the maximum elongation of the SST specimen is over 16% and the value of in-plane anisotropy (IPA) is 5.40%. For the AAT specimen, the yield strengths of the AAT alloy in three directions have distinct improvements, which are beyond 340 MPa. However, the maximum elongation and the IPA were evidently reduced. The yield strength and elongation of the DCAT alloy exhibit a slight enhancement compared with those in the AAT condition, and the corresponding IPA is 0.61%. The studied alloy specimens in all conditions exhibit ductile fracture. The DCAT alloy has the highest density of precipitates with the smallest size. Therefore, the dislocation pinning effect of the DCAT specimens are the strongest, which exhibit the highest yield strength accordingly. In addition, the uniformly distributed precipitates in the matrix with a large ratio of long and short axes can suppress the anisotropy caused by elongated grains.

The stability and mechanical and thermodynamic properties of Al₁₁RE₃ intermetallics (RE = Sc, Y and lanthanide La-Lu) have been investigated by combining first-principles and Debye model calculations. It was found that the formation enthalpies of the Al₁₁RE₃ intermetallics are all negative, indicating that they are stable; moreover, the experimental values of Al₁₁La₃ and Al₁₁Ce₃ are in good agreement with the predicted values, which are −0.40 kJ/mol and −0.38 kJ/mol, respectively. The calculated results of the mechanical properties reveal that the Young’s modulus E and shear modulus G of Al₁₁RE₃ (RE = La, Ce, Pr, Nd and Sm) intermetallics are obviously greater than that of Al, implying that the stiffness, toughness, and tensile strength of them are significantly greater than those of aluminum, and that they, as strengthen phases, can effectively improve the mechanical property of aluminum alloys. The Poisson’s ratio v of Al₁₁Sc₃ (0.37) is the largest, and the heterogeneity is obvious. All the Al₁₁RE₃ intermetallics can enhance the thermostability of the aluminum because of their lower Gibbs free energy F in the range of −5.002~−4.137 eV/atom and thermal expansion coefficient α of Al in the range of 2.34~2.89 × 10⁻⁵/K at 300K, as well as higher entropy and constant volume-specific heat than aluminum at finite temperatures. With an increase in the atomic number, different change trends were observed for the formation enthalpy ΔH_f, bulk modulus B, Young’s modulus E, and shear modulus G. This paper can provide ideas and help for designing a high-performance, heat-resistant aluminum alloy.

Hot compression tests were conducted to explore the deformation behavior of an extruded 7075 aluminum alloy bar at elevated temperatures. Specimens with 0°, 45°, and 90° angles along the extrusion direction were prepared. The compression temperatures were 300 and 400 °C, and the strain rates ranged from 0.001 to 0.1 s⁻¹. The corresponding microstructures were characterized via OM and TEM, and the macroscopic texture was tested using XRD. The results indicated that the strength of the 7075 alloy decreases with higher compression temperatures and is in a proportional relationship with respect to the strain rate. During high-temperature compression, it is easier to stimulate atomic diffusion in the matrix, which can improve thermal activation abilities and facilitate dynamic recovery and dynamic recrystallization. In addition, the coarsening of precipitates also contributed to dynamic softening. When compressed at 300 °C, the stress levels of the 0° specimens ranked first, and those for the 45° specimens were the lowest. When compressed at 400 °C, the flow stresses of the specimens along three directions were comparable. The anisotropic mechanical behavior can be explained by the fiber grains and brass {011} texture component. However, higher temperature deformation leads to recrystallization, which can weaken the anisotropy of mechanical properties.

In this study, we investigated the effects of modified aging treatments on the microstructures and hardness in a commercial 6016 Al alloy through hardness tests and transmission electron microscopy (TEM) observations. The results demonstrate that many fine needle-like β″ phases contribute to the high hardness of peak-aged (T6) alloys. Over-aging treatments lead to the precipitation of lath-like β′, β″/disordered, or B′/disordered composite phases. Moderate over-aging treatment results in the coarsening of grain boundary precipitates (GBPs) and widening of the precipitate-free zone (PFZ), while heavy over-aging treatment triggers the re-precipitation of Cu-containing GBPs and increases the number density of GBPs. A retrogression and re-aging (RRA) treatment precipitates β″, lath-like β′, and disordered phases, while a two-step aging (T78) treatment precipitates β″, B′, and disordered phases. Both the T78 and the RRA treatments lead to the coarsening of GBPs and the widening of PFZs. The decreased hardness during over-aging treatments is attributed to a combination of coarsening intragranular precipitates and/or wider PFZs. The T78 and RRA tempers achieve 95.5% and 94% of the hardness values of the T6 treatment, respectively. The hardness values of the RRA and T78 treated alloys are related to the finer nano-sized precipitates formed during the high temperature process. These precipitates can compensate for the loss of hardness caused by the increase in the widths of the PFZs and the coarsening of the matrix precipitates. The relationship between the hardness and microstructures such as PFZs and precipitates in the matrix during various heat treatments is elucidated.

High strain rate biaxial forging (HSRBF) was performed on AZ31 magnesium alloy to an accumulated strain of ΣΔε = 1.32, the related microstructure, texture and mechanical properties were investigated. It was found that the microstructure evolution can be divided into two steps during HSRBF. In the early forging processes, the refinement of the grain is obvious, the size of ~10 μm can be achieved; this can be attributed to the unique mechanisms including the formation of high density twins ({1012} extension twin and {1011}-{1012} secondary twin) and subsequently twining induced DRX (dynamic recrystallization). The thermal activated temperature increases with the increase of accumulated strain and results in the grain growth. Rolling texture is the main texture in the high strain rate biaxial forged (HSRBFed) alloys, the intensity of which decreases with the accumulated strain. Moreover, the basal pole rotates towards the direction of forging direction (FD) after each forging pass, and a basal texture with basal pole inclining at 15–20° from the rolling direction (RD) is formed in the full recrystallized HSRBFed alloys. The grain refinement and tiled texture are attributed to the excellent strength and ductility of HSRMBFed alloys with full recrystallized structure. As the accumulated strain is ΣΔε = 0.88, the HSRMBFed alloy displays an outstanding combination of mechanical properties, the ultimate tensile strength (UTS) is 331.2 MPa and the elongation is 25.1%.

The tensile properties of rolled 6082-T6 aluminum alloy were tested at a high temperature, and the influences of tensile temperature on its flow stress and anisotropy were studied. The microstructure evolution was characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was concluded that the tensile strength of the studied alloy decreases with increasing temperature. In higher-temperature deformation, the dislocation density decreases alongside the coarsening of precipitates, leading to a decrease in deformation resistance, and increase in the number of dimples and deepening of their sizes, exhibiting good plasticity. The alloy displays anisotropic mechanical properties at 200 °C due to the elongated grains and the orientation of the α-phase. The anisotropy becomes weaker with increasing temperature. There is no evident anisotropy at 400 °C, as the slip systems are activated more easily and the grains begin to recrystallize.