Effects of SiC_p on microstructures of semi-solid extruded AZ91D magnesium alloys in recrystallization process

AZ91D and 8.5vol.% SiCp/AZ91D magnesium matrix composites were fabricated by a semi-solid extruded processing method, and treated with solution and aging heat treatment. The effects of SiCp on the microstructures of the semi-solid extruded AZ91D magnesium alloy during recrystallization were studied by observing and analyzing the microstructure evolution during extrusions and heat treatments. The results show that the addition of SiCp inhibits the dynamic recrystallization of AZ91D during the semi-solid extrusion with only 26% of the volume fraction of recrystallization. Furthermore, the addition of SiCp refines the sizes of grains and second phases, and upgrades the volume fraction of second phase. After solution and aging treatment, the recrystallization continues, and the addition of SiCp promotes the recrystallization and the recrystallized microstructure is much more stable. Meanwhile, the sizes of grains and second phases continue to be refined, and the volume fraction of second phases continues to increase.