Influence of annealing on interfacial microstructure and corrosion behavior of Al/ZE42/Al composite plate

The microstructures and morphologies of Al/ZE42/Al composite plates were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Corrosion rates of the Al/ZE42/Al composite plates at different temperatures and held for different time were also measured in salt water immersion test, and the influence of annealing on interfacial microstructure of Al/ZE42/Al composite plates and corrosion behaviors in 5.0 wt% NaCl aqueous solution were investigated. The results show that element diffusion of Mg, Al, Zn, Y and Er occur in Al/ZE42/Al composite plate interfacial region after annealing. The interfacial diffusion layer has two reaction layers. Mg17Al12 phase is in one reaction layer near ZE42 magnesium alloy, while Al3Mg2 phase in the other reaction layer close to Al plate. With annealing temperature and holding time increasing, the thickness of ZE42/Al interfacial diffusion layer increases, and meanwhile recrystallization occurs in ZE42 magnesium alloy. Annealing cannot improve corrosion resistance of the Al/ZE42/Al composite plate, but it can increase corrosion rate. The corrosion mechanism of the Al/ZE42/Al composite plate is the aggravation of galvanic corrosion which occurs from edge to internal of the plate. © 2016, Science Press. All right reserved.