Efficient fabrication of high-performance ZK61 magnesium alloy hat-shaped thin-walled part: Tailoring heterogeneous structure via multi-DoF forming and heat treatment

• An innovative integrated process is proposed for high-performance ZK61 alloy hat-shaped thin-walled part fabrication. • Microstructure and mechanical properties of multi-DoF formed magnesium alloy hat-shaped thin-walled part are investigated. • Heterogeneous structure is well-maintained after short-term aging and excellent strength-ductility synergy is achieved. This study proposes an innovative integrated process combining multi‑degrees of freedom (multi‑DoF) forming with short‑term aging treatment for efficiently fabricating high-performance ZK61 magnesium alloy hat-shaped thin-walled part. Multi-DoF forming results in significant grain refinement and evident heterogeneous structure, especially at high strain area of web and thin wall. Texture transformation from basal and pyramid textures into prismatic texture is observed at the web and thin wall. The web at high strain rate area displays moderate mechanical properties, and thin wall displays the optimum mechanical properties, which is mainly attributed to grain refinement and heterogeneous structure. Subsequent conventional T6 treatment results in grain coarsening, dislocation annihilation and heterogeneous structure disappearance, while short‑term aging treatment not only simultaneously retains fine grains and heterogeneous structure, but also promotes uniform precipitation of nano‑scale second phases. Consequently, only marginal improvements of strength and ductility are observed after conventional T6 treatment, but significant improvement of strength increased by around 72 MPa in yield strength and 43 MPa in ultimate tensile strength and roughly the same ductility are achieved after short-term aging treatment compared to conventional T6 treatment, which is mainly attributed to the retainment of heterogeneous structure. The increase of precipitation strengthening counteracts the decrease of grain boundary and dislocation strengthening after conventional T6 treatment, while the increase of precipitation strengthening is significantly higher than the decrease of grain boundary and dislocation strengthening after short-term aging treatment. It is hoped that this work can provide a new method of efficiently fabricating high-performance magnesium alloy thin-walled part.