Microstructural evolution and dynamic recrystallization model of extruded homogenized AZ31 magnesium alloy during hot deformation

Abstract Using a thermal simulation testing machine, hot compression experiments were carried out on extruded homogenized AZ31 magnesium alloy, and the hot deformation behavior was analyzed. Based on this, the constitutive equation of the alloy is constructed to explore the evolution law of microstructure during hot deformation of the alloy, which could provide theoretical guidance for the reasonable selection of parameter ranges during hot compression of extruded homogenized AZ31 magnesium alloy. The experimental result indicated that the flow stress of the alloy during the hot deformation decreases with increasing temperature, increases with the strain rate increasing, and the real stress–strain curves during deformation show dynamic recrystallization curves. According to the experimental results, the deformation activation energy Q is 126.882 kJ mol −1 and the stress exponent n is 4.36 calculated by the constitutive equation under the given parameters, which confirmed that the glide and climb of dislocations in the climb-controlled regime is the deformation mechanism in this work. Decreasing the compression temperature and increasing the strain rate are helpful to reduce the Zener–Hollomon parameter, control the dynamic recrystallization occurring, and refine grain size to improve the mechanical properties effectively. Moreover, the dynamic recrystallization model of the alloy was constructed using the work hardening rate method and regression method, including dynamic recrystallization critical condition model, dynamic model and grain size model.