Achieving excellent strength and plasticity of aluminum alloy through refining and densifying precipitates

Abstract

Strength and plasticity are basic mechanical properties for wrought Al alloys, and generally exhibit a trade-off relationship. Herein through analyzing the respective effects of precipitates on yield strength and strain hardening, we proposed and quantitatively analyzed a strategy for synchronously strengthening and plasticizing Al alloys by refining and densifying the precipitates, defined as RDP effect. The precipitates were highly refined and densified in three high-Zn 7xxx alloys in order to verify the validity of the RDP effect. The tensile tests show that the high-Zn Al alloys possess ultra-high strength and good plasticity compared to the traditional Al alloys. Further analysis reveals that the densification of precipitates mainly contributes to the ultra-high strength, accounting for over 75%, while the refinement of precipitates suppresses the dislocation annihilation, thus increasing the strain-hardening capacity. Together, these two factors finally contribute to the excellent strength and plasticity matching. This finding will provide strong support for the positive impact of RDP effect on improving the balance between strength and ductility. Besides, this strategy may be considered as an effective one for simultaneously improving the strength and plasticity in high-performance Al alloys.