Effect of in-situ submicron Al3Ti particles on grain refinement and strengthening of Al–Zn–Mg–Cu-based alloy

Abstract

Extensive research has been conducted to improve the efficiency for grain refinement of aluminum cast alloys. Herein, we propose a novel strategy to significantly reduce the cast grain size using in-situ submicron Al₃Ti particles. The ZnO nanoparticles with enhanced wettability via mechanical stirring process provide finely dispersed $\alpha$-Al₂O₃ particles, which serve as heterogeneous nucleation sites for primary Al₃Ti particles. A large number of primary Al₃Ti nuclei are formed from the $\alpha$-Al₂O₃ particles without coarsening even under a relatively slow cooling rate. As a consequence, the size of Al₃Ti particles was reduced to approximately 600 nm, resulting in the fine cast grain size of approximately 20 $\mu m$. Furthermore, a sheet made of the refined cast alloy has reduced recrystallized grain size and simultaneously improved strength and ductility.