The evolution of the microstructures and properties of large direct chill (DC)-cast Al-Cu-Mn alloy ingots during homogenization was investigated. The results revealed that the Al-Cu-Mn alloy ingots had severe microsegregation and the main secondary phase was Al₂Cu, with minimal Al₇Cu₂Fe phase. Numerous primary eutectic phases existed in the grain boundary and the main elements were segregated at the interfaces along the interdendritic region. The grain boundaries became discontinuous, residual phases were effectively dissolved into the matrix, and the segregation degree of all elements was reduced dramatically during homogenization. In addition, the homogenized alloys exhibited improved microstructures with finer grain size, higher number density of dislocation networks, higher density of uniformly distributed θ′ or θ phase (Al₂Cu), and higher volume fraction of high-angle grain boundaries compared to the nonhomogenized samples. After the optimal homogenization scheme treated at 535 °C for 10 h, the tensile strength and elongation% were about 24 MPa, 20.5 MPa, and 1.3% higher than those of the specimen without homogenization treatment.

In this work, the effects of Ce content (0.1%, 0.2%, and 0.3 wt%) on the microstructures and mechanical properties of Al-Cu-Li alloys were investigated. The results show that the grains of Al-Cu-Li alloy are refined by adding Ce element. When Ce content is less than 0.1%, the ultimate strength of the alloy increases with the increase of Ce content. However, the ultimate strength of the alloy decreases when Ce content is above 0.1%. For Al-Cu-Li alloy with different Ce content, the aging precipitation of T₁ and θ′ phases play the main strengthening role. When Ce content increases from 0.1 to 0.3%, dynamic recrystallization is promoted during hot deformation. The recrystallization of the alloys is inhibited after T6 treatment with the increase of Ce content, which can be attributed to existence of the Al₈Cu₄Ce phases on the grain boundary. This work provides an economical and convenient method for improving the properties of Al-Cu-Li alloys by Ce addition.

The effects of various rolling reductions (64.7%, 72.1%, 81.4% and 88.2%) on the microstructures and mechanical behaviors of Sc-containing Al-3.2Cu-1.5Li-based alloys were experimentally investigated through XRD, SEM (equipped with EBSD), TEM and the tensile test. The results showed that the grains of hot-rolled and T6-treated alloys are mainly dominated by substructure features, and the addition of the trace Sc element can obviously impede the static and dynamic recrystallization due to the formation of fine and stable nano-Al₃(Sc, Zr) particles. Additionally, the combined effects of fine grains, dispersion, substructure and precipitation strengthening make the alloys with a rolling reduction of 81.4% possess higher tensile properties. With an increase in the rolling reduction, the tensile strength of the alloys increases first and then decreases, while the elongation gradually increases and then reaches a plateau, which was ascribed to the variation in the grain size and substructure features.

The recrystallization and mechanical properties of 7085 alloy and TiC/7085 composites with different nano TiC content (0.1, 0.3, 0.5, and 1 wt%) were investigated in this work. Results showed that as the TiC content increased from 0.1 to 1 wt%, dynamic recrystallization was promoted in which the composites proceeded by hot deformation; after T6 treatment, static recrystallization was hindered. In addition, the ultimate strength of composites first increased and then decreased with the increase of nano TiC particle content from 0.1 to 1 wt%. When the content of nano TiC particles reached 0.5 wt%, the tensile strength of the nanocomposites was improved to 608 MPa, 12% higher than that of 7085 alloy, via the reinforcing particle strengthening mechanism. Due to the grain coarsening and the TiC particle cluster, the ultimate tensile strength of 1 wt% TiC/7085 composite decreased to 585 MPa.

The microstructural evolution of the as-cast large size AA2014 aluminum alloy ingot prepared by direct chill (DC) casting during homogenization was investigated by OM, SEM, EDS, DSC, EBSD, TEM and tensile tests. The results showed that serious dendrite segregation and numerous coarse nonequilibrium eutectics existed in the as-cast alloy were dramatically eliminated, while a small amount of Fe-rich phase was still present along the grain boundaries when the alloys were subjected to the optimized two-step homogenization. Compared with the nonhomogenized alloys, homogenization treatment can effectively reduce grain and second phase particles size, and increase the fraction of precipitates and high angle grain boundaries (HAGBs) during the hot deformation and T6 treatment. Besides, recrystallized grains with random orientation are formed due to dynamic recrystallization (DRX) for the alloys with hot deformation and T6 treatment. Additionally, the strength and elongation of the alloys were simultaneously improved with the application of optimum two-step homogenization because of the more homogeneous structures, finer grain and particles size, higher fraction of HAGBs and fine and uniformly distributed precipitates. The suitable homogenization schedule of the AA2014 aluminum alloy is 490°C × 10 h + 530°C × 8 h.

6 mm thick 2A14 Al alloy plates were friction stir processed with different initial precipitation states of as-cast, homogenization, rolling and T6. The results indicated that FSP can dramatically reduce the grain and particles size and promote the formation of fine recrystallized grains with random orientation in the stirred zone (SZ). No significant influences of the initial precipitation states of base metal (BM) on the grain size, grain boundary characteristic, texture component and texture intensity of SZ were perceived. Rather, the initial precipitation states can evidently affect the morphology and distribution of precipitates and dislocations. The dominant C and A₁* texture components developed in the SZ are correlated with the shear deformation and dynamic recrystallization. And the weakened texture intensity created in the SZ after FSP also signifying that discontinuous dynamic recrystallization might be involved. Compared with the corresponding BM, the SZ fabricated by the BM under as-cast and homogenized states were strengthened arises from the obvious refined grains, uniform dispersed particles and elimination of casting defects caused by FSP, while the softening of SZ were observed for the BM under rolled and T6 states, which are mainly dependent on the reduction of dislocation density and dissolution/coarsening of fine precipitates during FSP.