constitutive behavior of az31 magnesium tube processed by severe plastic deformation

In this study, the evolution of parallel tubular channel angular pressing (ptcap) as a severe plastic deformation process on the hot deformation behavior of the extruded az31 magnesium tube was investigated. after four passes, a more refined and homogeneous microstructure was achieved. to understand constitutive behavior, hot tensile tests were carried out on four passes of specimens at temperatures of 350, 400, and 450ºc with strain rates of 0.0001, 0.001, and 0.01 s^-1. the dependence of flow stress on strain rate and temperature was investigated by the zener-hollomon equation and the activation energy was found to be around 131.26 kj/mol. effect of strain was included in the constitutive equation by applying material constants. based on the constitutive model, the stress-strain curves of ptcap processed tubes were extracted and compared with the experimental curves. the results indicate good agreement between experimental and predicted flow curves by considering the softening effect.