Research on the constitutive equation of Al₁₈B₄O₃₃w/AZ91D composite during hot deformation

The hot compressive behavior at different temperature (300°C-400°C) and strain rate (0.001 s^-1-0.1 s^-1) of Al₁₈B₄O₃₃ w/AZ91D was investigated by use of Gleeble-1500D thermal simulation testing machine and the constitutive parameters were identified through the experiments. The strain rate sensitivity exponent (m) and apparent activation energy (Q) of the selected composite were determined according to true stress-strain curves. The results show that the flow stress decrease continually after the peak stress because of strain softening caused by whisker rotation and breakage. The exponential form represents high stress regime, the power form represents the low stress regime and the hyperbolic sine form represents all stress regime. The value of m and Q of composite are both higher than the matrix alloy because of the addition of Al₁₈B₄O₃₃ whisker.