GRAPHENE/ALUMINUM COMPOSITES FABRICATED BY FRICTION STIR PROCESSING: MECHANICAL PROPERTIES AND PRECIPITATE EVOLUTION

In this study, friction stir processing (FSP) was employed to fabricate graphene/aluminum composites. A lateral hole-opening method was utilized to introduce 1.03 vol.% graphene, followed by multiple passes of FSP. The number of passes increased, and graphene was stirred uniformly, but the accumulated heat input resulted in the solid solution of the Mg 2 Si phase, the Mg 2 Si precipitation strengthening effect was reduced, and the mechanical properties of Al alloy decreased. The amount of Mg 2 Si after the 3-pass friction stir process with graphene was less than that without graphene, which indicates that graphene suppresses the precipitation of Mg 2 Si. The tensile strength of Al alloy being 3-pass processed with graphene was lower than that without graphene. Transmission electron microscopy (TEM) observation revealed a novel interface where graphene was adsorbed onto Mg 2 Si. In the interface between graphene and Mg 2 Si, the graphene reacted with Al to produce Al 4 C 3 . The interface between Al 4 C 3 and Mg 2 Si was semi-coherent, with a mismatch of 0.17. This mismatch can reduce the bonding strength at the interface, leading to a decrease in the yield strength of the graphene/aluminum composites.