The effects of double-step homogenization processes on the precipitation of Al₃Zr dispersoids and the dissolution of the primary phases of 2196 aluminum alloy were studied by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was revealed that first-step homogenization facilitates the nucleation of Al₃Zr, while second-step homogenization results in the dissolution of the primary phases and the growth of Al₃Zr dispersoids. The nanosized θ’ precipitates formed in the first-step homogenization are dissolved after the second-step homogenization. The optimum homogenization process was selected as 400 °C/10 h + 520 °C/24 h, which effectively dissolves the primary phases and promotes the formation of refined distribution of Al3Zr dispersoids. This phenomenon is mainly caused by the highest nucleation rate of the Al₃Zr phase at 400 °C. While reducing the heating rate of the homogenization process can increase the number density of the Al₃Zr dispersoids and reduce the precipitate free zone (PFZ), it does not alleviate the inhomogeneity of the Al₃Zr precipitation. These results are expected to be meaningful for tailoring the industrial homogenization processing of as-cast Al-Cu-Li alloy.

Controlling the formation of the β′ (Al₃Zr) phase is pivotal for regulating the recrystallization and thus the mechanical properties of the spray formed 2195 (Al-Cu-Li) alloy. In a conventional “homogenization-extrusion” process, the precipitation of β′ is severely affected by the presence of the T₁(Al₂CuLi) phase in the as-deposited alloy, leading to an inhomogeneous distribution of the β′ phase. In the present work, we propose a new thermomechanical processing (TMP)—swapping the order of the homogenization and extrusion processes. The microstructures and properties of the new proposed TMP were systematically studied at various stages of the alloy treatment and compared with the out of the conventional TMP. It was revealed that the introduction of the extrusion process on the as-deposited alloy can break the continuous network of primary phases and dissolve the T₁ phase, promoting a uniform distribution of the β′ phase during subsequent two-step homogenization. During solution treatment, the new TMP is more effectively in suppressing the formation of a coarse grain layer at sheet surface, while after final peak aging, the new TMP produces a lower alloy strength but a higher elongation, due mainly to the smaller thickness reduction during deformation. The new proposed TMP technique provides a new insight into regulating the mechanical properties of Al-Cu-Li alloys.

In previous work [1], we analyzed the recrystallization kinetics in cold-rolled AA5657 and AA5182 based on measurements of the volume fraction of recrystallized material, the free (unimpinged) surface area density and the average size of the recrystallizing grains, plus the contiguity between recrystallizing grains, for a series of partially recrystallized samples. In that work, the calculated growth and nucleation rates were used as basis from the analysis. These two properties are derived from the measured parameters, which, as shown in the present work, adds to their uncertainty. In the present paper, we revisit the kinetics using improved stereological data and perform a full microstructural path analysis. The new analysis results are compared to the previous ones and the implications of using the different types of data sets and analytical approach for the interpretation of the kinetics are discussed.