Thixoforming of AM50 magnesium alloy

Abstract

To obtain AM50 magnesium alloy slurry with fine microstructure, a new process including equal channel angular extrusion (ECAE) and partial remelting treatment has been developed. The evolution of grains from the ECAE-formed AM50 alloy in the semi-solid stage has been studied. Furthermore, thixoforming of ECAE-formed AM50 alloy was conducted, and the mechanical properties of thixoformed components were investigated. Instead of involving dendritic in the as-cast alloy, the microstructure of alloy produced by ECAE contained plenty of recrystallized grains along the deformation direction. During the partial remelting, the liquid phase penetrates not only to the grain boundaries but also to the inside of solid grains. An increase in reheating temperature leads to a corresponding enhanced liquid fracture, and the result improved the degree of spheroidization. Prolonged the holding time, both the solid grains and intragranular liquid droplets had undergone coarsening. The tensile properties of thixoformed from ECAE state are much higher than those from as-cast state. The research encourages the belief that magnesium alloy semi-solid billet with fine and spheroidal grains, which is suitable for semi-solid processing, could be obtained by the combination of ECAE and partial remelting.