Study on microstructure evolution and wear resistance behavior of in-situ graphene reinforced aluminum matrix composites prepared via friction stir processing

Abstract In-situ graphene reinforced aluminum matrix composites (AMCs) were synthesized by friction stir processing (FSP) using Al5052 alloy and nano-graphite as raw materials. The microstructure, phase composition and wear resistance of AMCs were investigated to elucidate its wear resistance mechanism. The results show that the incorporation of nano-graphite resulted in significant grain refinement of AMCs, with 80.7% of the grain boundaries dominated with high-angle grain boundaries, and 93.2% of the grains were recrystallized grains. The intense shear effect generated in FSP caused the generation of few layers of wrinkled graphene, with the Al4C3 phase detected at the edge. The microhardness of AMCs increased by about 50% and 27% compared to Al5052 base metal (BM) and FSPed Al, respectively. Besides, the average friction coefficient and specific wear rate of AMCs were minimum, which were 0.57 and 15.6 mm3/N·m, respectively. The specific wear rate of AMCs was reduced about 64.9 % as compared to BM, while AMCs were mainly subjected to abrasive wear. The optimal wear resistance of AMCs is due to the dramatic increase in hardness as well as the self-lubricating effect caused by nano-graphite.