Ultra-fast bake-hardening response of Al-Mg-Si-Cu-Zn alloys with the assistance of heterogeneous nucleation

Mg-Si clusters or precipitates can make Al-Mg-Si alloys stronger, but the low bake-hardening response severely restricts their wide application in the automotive field. Here, we report a new strategy to significantly enhance the bake-hardening response of Al-Mg-Si-Cu-Zn alloys to the highest value of 167 MPa, compared with values of traditional 6xxx series alloys (such as, AA6016, AA6111 and AA6022). The ultra-fast bake-hardening response is mainly obtained by the synergy of homogeneous/heterogeneous nucleation of Zn-containing precipitates during the heat treatments. The process discovered here is amenable to large-scale automotive industrial production at low cost, and might be applicable to other Al alloy systems.