Improved microstructures of AZ31 magnesium alloy by semi-solid extrusion

The microstructure evolution and mechanical properties of AZ31 magnesium alloy during semi-solid extrusion (SSE) has been studied and compared with traditional extrusion (TE). The results show that non-equilibrium crystallization and plastic deformation occur simultaneously in the semi-solid extrusion process. Throughout the SSE process, the nucleation rate of new fine grains is significantly higher than that of the TE, which is the result of combined nucleation of crystallization and dynamic recrystallization. Twinning can be hardly activated during the SSE process, because the restraint between deformed grains is largely reduced due to the good fluidity of the semi-solid Mg alloy. The Mg alloys extruded by the SSE is characterized for homogeneous microstructure with fine grain size, weakened texture and improved mechanical properties.