Characterization of Al3Zr precipitation via double-step homogenization and recrystallization behavior after subsequent deformation in 2195 Al-Li alloy

Abstract

The processability and final mechanical properties of Al-Li alloys are strongly affected by the uniformity of solute element and the degree of recrystallization, which can be improved via homogenization treatments. It is essential to control the microstructure to achieve the desired properties. In this work, the optimal double-step homogenization (DH) parameters for as-cast 2195 Al-Li alloy were first determined as 460 °C/16 h + 515 °C/20 h according to the comparative analysis, which fitted well with the results predicted by the corresponding kinetics modeling. Compared with the conventional single-step homogenization (SH), DH not only prevented the occurrence of overburning but also provided a more favorable condition for Al3Zr dispersoids to precipitate uniformly. The size and number density of Al3Zr dispersoids in the DH sample are finer and higher than those in the SH sample based on quantitative statistics. Due to the sufficient driving force for nucleation, the precipitate free zone (PFZ) of Al3Zr dispersoids was much narrower after DH. As a result, the DH sample possessed a higher Zener drag pressure, leading to a remarkable inhibition on the continuous evolution of substructures. Therefore, the recrystallization behavior in the DH sample was impeded effectively during the subsequent solution treatment. These findings are expected to provide reliable theoretical guidance for the industrial processing of as-cast 2195 Al-Li alloy.