Investigation into microstructure evolution, mechanical properties and corrosion resistance of Al-Zn-Mg-Cu alloy after hot forming quenching integrated process with warm die

The growing severity of environmental challenges has intensified the transportation sector's shift toward lightweight materials for ecological preservation and energy conservation. Among these solutions, high-strength Al-Zn-Mg-Cu series aluminum alloys have emerged as a focal point in materials research, demonstrating exceptional potential for sustainable industrial applications. In this study, the pre-ageing and baking treatment after hot form and quench process (HFQ) with warm die were designed to achieve the balance between strength and corrosion resistance for Al-Zn-Mg-Cu alloy. The findings suggest that pre-HFQ treatment with warm die promotes the generation of high density dislocation, inducing the formation of large-sized grain boundary precipitation (GBP) with high Cu content, and expanding GBP space and precipitation free zone (PFZ), which are responsible for the improvement of corrosion resistance. The maximum corrosion depth was reduced to 21.18 μm form the initial 61.86 μm of the as-received alloy during the accelerated inter-granular corrosion (IGC) test. The EXCO morphology is mainly dominated by slight local IGC and pitting, which is close to the similar condition of retrogression and re-ageing (RRA).High temperature (160 °C) pre-ageing accelerates the nucleation of GP zones, and baking treatment (180 °C/30 min) facilitates the transformation of GP zones to η', which is beneficial to the enhancement of strength.