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

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.