Effect of friction stir processing on microstructure and friction and wear properties of as-cast SiC_p/ZL101 composites

Friction stir lap welding (FSLW) was used to weld as-cast SiCp/ZL101 composite plate and ZL101 alloy plate to prepare a new brake disc material, and the as-cast SiCp/ZL101 composite plate was modified by friction stir processing (FSP). The microstructure and friction and wear properties of the as-cast SiCp/ZL101 composites after FSP were studied to evaluate the braking performance of the new brake disc material. After FSP, the pores in the SiCp/ZL101 composites are eliminated, and the average size of SiC particles is reduced from 12.8 pm to 3.9 pm. The grains are obviously refined from 8.2 pm to 3.2 pm. The friction coefficient of the as-cast SiCp/ZL101 composites increases firstly and then decreases in the initial stage, and then tends to be stable after 500 s, but the friction coefficient fluctuates greatly. After FSP, the fluctuation ranges of the microhardness and friction coefficient are all reduced, the friction process is stable, and the wear extent is equivalent to about 45% of that of the as-cast SiCp/ZL101 composites. The as-cast SiCp/ZL101 composites are dominated by abrasive wear, showing a fatigue wear characteristic. The FSPed SiCp/ZL101 composites are dominated by oxidation wear, and the size of wear debris is relatively small.