Effects of aging heat treatment on microstructure and corrosion behavior of friction surfacing treated Al-Zn-Mg-Cu matrix composite
(Department of Materials Engineering, Babol Noshirvani University of Technology, Shariati Avenue 47148-71167, Babol, Iran)
Abstract: 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.
Key words: aluminum matrix composite; nickel-aluminide reinforcement; friction surfacing; artificial aging heat treatment; corrosion behavior