Effect of the CNTs into SiCp-Al interfacial micro-zones on ageing precipitation behavior, microstructure and mechanical properties of SiCp(CNT)/Al–Zn–Mg–Cu composites

For Al–Zn–Mg–Cu matrix composites, the introduction of reinforcements tends to have a significant effect on the aging precipitation behavior of the interfacial micro-zones, which in turn affects the mechanical properties of the composites. In this study, the ageing precipitation behavior, microstructure and mechanical properties of SiCp(CNT)/7075Al composites were systematically investigated, to explore the effect of CNT introduction on SiCp-Al interfacial micro-zones. The results showed that the introduction of SiCp(CNT) hybrid reinforcement could promote the aging precipitation behavior of the composites compared with 7075Al. But the introduction of CNTs leads to a further increase of O content in the composite compared with SiCp due to the adsorption of oxygen by CNTs, leading to more severe segregation of Mg and O, which intensified the degree of adverse interface reactions. This adversely affects the aging precipitation behavior of the interfacial micro-zones and the mechanical properties of the composites. Furthermore, the degree of interface reaction can be effectively regulated by adjusting the heat treatment process of SiCp(CNT)/7075Al composites. Compared with the T6 treatment (solid solution treatment at 475 °C for 1 h, aging treatment at 120 °C for 24 h), the yield strength and ultimate tensile strength of both 15 wt % SiCp/7075Al and SiCp(0.5CNT)/7075Al composites can be increased by more than 100 MPa under the optimal heat treatment process (solid solution treatment at 470 °C for 40 min, aging treatment at 120 °C for 15 h). Moreover, the SiCp(0.5CNT)/7075Al composite showed the best balance between strength and ductility, not only the strength was equivalent to that of SiCp/7075Al, but also the elongation increased by 13.2%. This study can provide guidance and suggestions for regulating the aging precipitation behavior of interfacial micro-zones and mechanical properties of metal matrix composites.