Effects of SiC_(p) on microstructures of semi-solid extruded AZ91D magnesium alloys in recrystallization process

AZ91 D and 8.5 vol.%SiC_(p)/AZ91 D magnesium matrix composites were fabricated by a semi-solid extruded processing method,and treated with solution and aging heat treatment.The effects of SiC_(p)on the microstructures of the semi-solid extruded AZ91 D 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 SiC_(p)inhibits the dynamic recrystallization of AZ91 D during the semi-solid extrusion with only 26% of the volume fraction of recrystallization.Furthermore,the addition of SiC_(p)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 SiC_(p)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.