Synergy of homogeneous/heterogeneous nucleation in Al-Mg-xSi-Cu-Zn alloys with rapid age-hardening response

Abstract

The low age-hardening response dilemma of aluminum alloys is an urgent challenge that needs to be overcome to save costs and improve comprehensive mechanical properties for industrial applications. In this study, we have proposed a novel low-cost strategy to improve the age-hardening response of advanced Al alloys by the synergy of homogeneous/heterogeneous nucleation. The results reveal that nano-precipitates can preferentially nucleate and grow along dislocations due to the rapid diffusion rate of solute atoms assisted by dislocations. Meanwhile, the critical nucleation size of the solute clusters in the pre-aged alloy can be decreased by pre-deformation during the isothermal aging process due to the higher energy for diffusion and higher total strain energy in the matrix. Furthermore, the interaction force between Mg and Zn atoms in the matrix of no dislocation can be enhanced. Accordingly, many fine solute clusters with a high Zn/Mg ratio can also precipitate inside the grain. As a result, remarkable bake-hardening response and excellent strain hardening properties are obtained in the pre-deformed alloys after bake-hardening treatment based on the synergy of homogeneous/heterogeneous nucleation, and the related mechanism has been proposed.