High temperature tensile response of nano-Al₂O₃ reinforced AZ31 nanocomposites

Nano-Al₂O₃ reinforcement's capability to simultaneously enhance the room temperature (25°C) strength and ductility of magnesium alloys has effectively been exploited in ingot metallurgy processed AZ31/1.5Al₂O₃ nanocomposite in this study. Tensile characterization revealed that at high temperature (150-250°C), instead of strengthening, the thermally stable nano-Al₂O₃ reinforcement ironically exacerbated the softening of AZ31 alloy. However, an incredible increment in AZ31 alloy (with grain size of ~2.3μm) ductility (up to 184%) has been achieved in the nanocomposite with increasing temperature due to the incorporation of nano-Al₂O₃ as reinforcement. Microstructural characterization of the nanocomposite revealed that the dynamic recrystallization process has induced a complete recrystallization in AZ31 alloy matrix at a relatively much lower temperature (150°C) with tremendous grain growth near the fracture surface at higher temperature (250°C). Fractography of the nanocomposite revealed that the room temperature mixed ductile mode fracture behavior of AZ31 alloy transformed to a complete ductile mode at high temperature due to the presence of nano-Al₂O₃ particulates.