The multi-scale Si-containing phases-assisted improvement in the microstructure and mechanical properties of Al–Mg-xSi-Cu-Zn alloys

Abstract

The wide application of Al–Mg–Si alloys in automobile industry requires good formability, high strength and high bake-hardening response. Herein, this study presents a strategy to improve the comprehensive mechanical properties of Al–Mg-xSi-Cu-Zn alloys assisted by the designed multi-scale Si-containing phases. The results show that with increasing Si content from 0.55 to 1.08 wt%, not only the transformation rate of β-Al5FeSi to α-Al12(Fe,Mn)3Si during the homogeneous treatment can be increased, but also the number density and homogenization distribution level of the multi-scale Si-containing phases (i.e., β-Al5FeSi, α-Al12(Fe,Mn)3Si, Mg2Si, Q and Si phases) can be improved by the optimized thermomechanical processing route. These improvements further result in the fine-grained microstructure and enhanced average r, elongation and strengths. The positive effects change greatly with the changes of type, morphology, number density and distribution of the multi-scale particles. The related mechanisms of forming multi-scale particles and high formability have been discussed in this paper.