Effect of Er Addition on the High Temperature Strength of Al-Si-Cu-Ni-Mg-Fe Piston Alloys

Abstract

In this study, the dependence of Er addition (0-0.49 wt %) on the microstructural evolution and related tensile strength at high temperature (HT) were investigated for the eutectic Al-Si piston alloys. The results showed there were intermetallic compounds of -Al₃CuNi, -Al₇Cu₄Ni, Al₄Cu₂Mg₈Si₇, β-AlFeSi and Al₃(Er, Cu, Fe) (Ni, Si) ₂ identified at T5 states. Herein, the added Er element has led to the formation of the star-like and the irregular-shaped Al₃(Er, Cu, Fe) (Ni, Si) ₂ phase. The phase was stable which showed little change in both size and composition experienced solid solution at HT during the T6 treatment. For the HT strengths (350 ^oC), the T5 state alloys have higher UTSs than those at T6 state, both of which were reduced gradually with the increasing Er contents. The variation of HT strengths caused by the Er addition was explained by the microstructral evolution, namely Al₃(Er, Cu, Fe) (Ni, Si)₂ phase formation