Friction stir processing of Al/SiC composites fabricated by powder metallurgy

Friction stir processing (FSP) was applied to modify the microstructure of sintered Al–SiC composites with particle concentrations ranging from 4 to 16 vol%. Two SiC particle sizes (490N and 800 grades) were examined. Following FSP, the hardness of the 4 and 8 vol% of 490N grade SiC composites increased from 130 HV and 145 HV to 171 HV and 177 HV respectively. The increase was accounted for by the severe deformation occurring during FSP which uniformly distributed the SiC particles. The composites containing 16 vol% SiC could not be fully consolidated using FSP, and contained residual pores and lack of consolidation which originated from the as-received sintered microstructure. The hardness correlated well with the mean inter-particle spacing for the SiC particles in the case of composites containing 4 and 8 vol% SiC.