Effect of hot extrusion and subsequent T6 treatment on the microstructure evolution and tensile properties of an Al-6Si-2Cu-0.5Mg alloy

In this work, an Al-6Si-2Cu-0.5Mg alloy was subjected to hot extrusion at various temperatures (400 °C, 450 °C and 500 °C) followed by subsequent T6 heat treatment, and the effect of aforementioned thermal-mechanical treatment on the microstructure evolution and tensile properties was systematically investigated. Microstructure observed suggested that both eutectic Si particles and primary intermetallic particles (Q phase) were refined by hot extrusion. Further T6 treatment led to the dissolution of the Q phase and the formation of nano-precipitates. Tensile test revealed that the alloy extruded at 450 °C (after T6 treatment) exhibited the best combination of strength and ductility. Increasing or decreasing the extrusion temperature resulted in the deterioration of ductility. The effect of the extrusion temperature and T6 treatment on the mechanical properties was discussed based on the microstructure evolution.