Effect of friction stir processing with SiC particles on microstructure and hardness of AZ31

SiC particles were uniformly dispersed into an AZ31 matrix by friction stir processing (FSP). The SiC particles promoted the grain refinement of the AZ31 matrix by FSP. The mean grain size of the stir zone with the SiC particles was obviously smaller than that of the stir zone without the SiC particles. The microhardness of the stir zone with the SiC particles was reached about 80 Hv due to the grain refinement and the distribution of the SiC particles. Additionally, the SiC particle/AZ31 region showed fine grains even at elevated temperatures (∼400 °C) resulting in the pinning effect by the SiC particles. In contrast, the microhardness was significantly decreased attributed to the abnormal grain growth of the FSPed AZ31 without the SiC particles.