Hot workability and deformation mechanisms in Mg/nano-Al₂O₃ composite

Abstract

The response of extruded Mg/nano–Al₂O₃ (1 vol.%) composite to hot working in the temperature range 300–500°C and strain rate range 0.0003–10 s⁻¹ has been characterized using processing map and kinetic analysis. The hot working window for the composite occurs at strain rates >0.1 s⁻¹ and the optimum range of temperature is 400-450°C. In this window, the behavior of the composite is similar to that of the matrix and is controlled by the grain boundary self-diffusion. At lower strain rates, however, the composite exhibits much higher apparent activation energy than that for lattice self-diffusion unlike the matrix material. The deformed microstructures revealed that the prior particle boundaries decorated by the nano-Al₂O₃ particles, are stable and do not slide, rotate or migrate but kink after compressive deformation and as such contribute to the high temperature strength of the composite.