Optimization of casting means and heat treatment routines for improving mechanical and corrosion resistance properties of A356-0.54Sc casting alloy

Abstract

In this paper, the effect of different casting means and heat treatment routines on the mechanical and corrosion resistance properties of A356-0.54Sc casting alloy was comprehensively studied. Three different molds, including graphite mold, steel mold, and copper mold, were employed. Both the grain size and secondary dendrite arm space of primary α-(Al) in the casting A356-0.54Sc alloy with copper mold are the finest. Three different heat treatments, i.e., T4, T5, and T6, were then applied. With the T4 treatment, the eutectic (Si) particles transferred from the as-cast fibrous structure to the isolated spherical one, leading to a significant increase in ductility. After aging, the alloys in the T6 state always own the best strength properties. The strong heredity of microstructures from the casting stage to the subsequent heat treatments was observed. Moreover, the corrosion resistance of alloys was studied by the salt-spray corrosion experiments. The experiments showed that the pitting corrosion mostly occurs in the interface between the eutectic (Si) and primary α-(Al). It was finally concluded that the alloys casted using the copper mold and treated with the T6 routine maintain the best comprehensive mechanical properties after corrosion, while the alloys casted using the graphite mold are with the best corrosion resistance.