The effects of η phases and Al3(Er, Zr) particles pre-precipitation on the hot workability and recrystallization of Al–Zn–Mg–Er–Zr alloy

This paper investigates the impact of pre-precipitated η phases and Al3(Er, Zr) particles on the hot workability and recrystallization behavior of an Al–Zn–Mg–Er–Zr alloy. The optimal pre-precipitation heat treatment prior to hot deformation was obtained by heat treatment under different conditions combined with microstructure analysis. Subsequently, hot compression tests were conducted to establish the processing maps, and the influence of pre-precipitation on the microstructure and the hot workability under various thermal deformation conditions were analyzed. Furthermore, the effect of pre-precipitation of η phases and Al3(Er, Zr) particles on the recrystallization was studied. The results demonstrate that after the optimized pre-precipitation treatment, a multitude of Al3(Er, Zr) particles (∼10 nm) and η phases (∼1 μm) appeared in the alloy. Through this pre-precipitation treatment, the flow stress was significantly reduced, and the hot workability of the alloy was significantly enhanced, particularly at low temperatures and low deformation rates. Moreover, the pre-precipitated η phases facilitated recrystallization, refined grains and hence created a more homogeneous microstructure. Concurrently, during the recrystallization process, the precipitated Al3(Er, Zr) particles impeded grain boundary migration, and thus inhibited the growth of recrystallized grains, contributing to grain refinement.