Abstract: Al-Zn-Mg-Cu matrix composites reinforced with 0.5wt% GNPs were prepared by vacuum hot pressing sintering and hot extrusion process with Al-Zn-Mg-Cu alloy powder as matrix and graphene as reinforcing phase. The effect of aging treatment on the properties of composites and the strengthening mechanism of graphene on the Al-Zn-Mg-Cu matrix were studied. The results show that the mechanical properties of the composites are the best after aging at 120 ℃ for 24 h, and the tensile strength reaches 505.92 MPa. From the microscopic characterization, it can be seen that the black block second phase in the composite material is the most, mainly graphene and a small amount of precipitated phase after aging at 120 ℃ for 24 h. The reinforced phase graphene is dispersed at the grain boundary of the large grain, which can pin the grain boundary and reduce the merging of the subgrain boundaries, thus hindering the dislocation movement. The MgZn₂ and Mg₂Si phases in the composites aged at 120 ℃ for 24 h are the most. The addition of graphene is also beneficial to the precipitation of the second phase, which is easier to pin the grain boundary and improve the mechanical properties.

Key words: graphene/Al-Zn-Mg-Cu alloy composites, aging heat treatment, mechanical properties, microstructure characterization