Hot deformation behavior, processing maps and microstructure evolution of extruded SiC/AZ80 magnesium matrix composites

The hot deformation behavior of SiC/AZ80 composites, fabricated using stir casting followed by hot extrusion, was carried out through isothermal compression tests at strain rates between 0.001 and 10 s -1 and temperatures ranging from 250 °C to 400 °C. The true stress-strain curves demonstrated true stress increased rapidly with the increase of the true strain and then stabilized or decreased slightly after the true stress reaches the peak value. The peak stress levels increased as the deformation temperature decreased and the strain rate increased. The flow behavior was precisely described using the sine-hyperbolic Arrhenius equation, with the composite showing an average stress exponent of 4.52 and activation energy of 130 kJ/mol. These findings suggest that dislocation climb might be the dominant deformation mechanism. Processing maps were developed to identify stable and unstable deformation regions, enabling the optimization of processing parameters to promote uniform deformation and prevent material failure. The microstructural evolution indicates that dynamic recrystallization (DRX) is the dominant mechanism; however, at a higher strain rate of 10 s -1 , a transition from DRX to dynamic recovery (DRV) occurs due to the insufficient softening mechanisms.