High Strength and Excellent Ductility of AZ80 Magnesium Alloy Cabin Component Developed by W-Shaped Channel Extrusion and Subsequent T6 Heat Treatment

The AZ80 magnesium (Mg) alloy cabin component with high strength and excellent ductility was developed by W-shaped channel extrusion (WCE) at 350 °C and subsequent T6 heat treatment. The effect of WCE process on the microstructure and mechanical properties of the alloy was experimentally investigated, and the age-hardening behavior with microstructure evolution during heat treatment was revealed. Due to the introduction of multi-stage asymmetric extrusion and severe shear deformation along the annular channel, the average grain size of the WCE extruded alloy could be effectively refined to 4.7 μm. Besides, the β phase particles were dynamically precipitated from the fine grain boundaries during extrusion, which hindered the grain growth, but worsen the material plasticity. After T6 treatment, the properties of component were eventually improved to a yield strength (YS) of 218 MPa and ultimate tensile strength (UTS) of 344 MPa with elongation (EL) of 14.5%. It was revealed that the rod/lath- and needle-shaped continuous β phase (CP) with finer size precipitated after T6 treatment was more effective in hindering the movement of dislocations and strengthened the alloy than lamellar discontinuous β phase (DP). The dispersed phase precipitated in the grains, the annihilation of dislocations, the uniformly distributed grains and the re-dissolution of β phase particles at initial grain boundaries after T6 treatment greatly contributed to the ductility of alloy. Moreover, the T6 treatment also promoted the basal plane of most grains which were re-arranged to the extrusion direction, which promoted the possibility of non-basal slip activation and further improved the elongation of the alloy. As a result, the UTS and YS of the final component increased by 10% and the EL increased by 7%, respectively.