Hot deformation behavior of SiCp/AZ91 magnesium matrix composite fabricated by stir casting

The uniaxial compressive deformation behavior of a 10 vol.% SiC particulate reinforced AZ91 magnesium matrix composite (SiCp/AZ91) fabricated by stir casting is investigated at elevated temperature (250-400 °C). Peak stresses and flow stresses decrease as temperatures increase and strain rates decrease. The extent of dynamic recrystallization (DRX) becomes less as temperatures decrease at 250-350 °C or strain rates increase, and recrystallization occurs mainly within the intergranular regions rich of particles. Dynamic recrystallization accomplishes at 400 °C even at the strain rate of 1 s^-1. An analysis of the effective stress dependence on strain rate and temperature gives a stress exponent of n = 5 and a true activation energy of Q = 99 kJ/kJ. The value of Q is close to the value for grain boundary diffusion in Mg. It is concluded that the deformation mechanism of SiCp/AZ91 composite during hot compression is controlled by the dislocation climb.