Effects of aging heat treatment on microstructure and corrosion behavior of friction surfacing treated Al–Zn–Mg–Cu matrix composite

The effect of artificial aging heat treatment on the microstructure and corrosion behavior of Al–Zn–Mg–Cu matrix composite was studied. Nickel-aluminide reinforcement was fabricated in-situ during the stir casting process of Al–Zn–Mg–Cu alloy. After friction surfacing of the consumable rod of an as-cast composite on AA1050 substrate and post-processing artificial aging heat treatment at 125 °C for 18 h, significant grain growth was observed in the nickel-free sample. Moreover, the presence of nickel-aluminide reinforcement in the microstructure of composite resulted in the formation of bimodal microstructure. The presence of nickel-rich particles and the strengthening mechanism through precipitates could help increase the hardness and strength in the nickel-containing sample. After artificial aging heat treatment, the shear strength and hardness of composite containing nickel-aluminide increased by 24% and 13%, respectively, more than those of the aluminum matrix. Before aging heat treatment, the pitting corrosion resistance was significantly improved by the presence of nickel-containing particles. After aging heat treatment due to the adsorption of more significant amount of soluble copper by nickel-rich particles in the nickel-containing sample, corrosion resistance decreased by 39% compared to that of the nickel-free sample.