Evolution of Microstructure and Elevated-Temperature Properties during Thermal Exposure with Transition Elements (V, Zr and Mo) in Al–Si 356 Type Cast Alloys

Abstract

Precipitation-hardened AlSi 356 cast alloys are widely used in fabricating the automotive engine parts due to their excellent castability and strength/weight ratio. However, with the increasing demand of the engine service temperature at 250350°C, the mechanical properties of AlSi 356 alloys greatly deteriorate owing to the rapid coarsening of precipitates at elevated temperatures. In this study, individual and combined transition elements (V, Zr and Mo) were introduced into AlSi 356 type cast alloys to form thermally stable dispersoids, and their influences on the strength and creep resistance at 300°C was investigated. During thermal exposure (300°C/100 h) after T7 treatment, the nano-scale ¢A and QA precipitated during aging were transformed to the equilibrium coarse ¢ and Q phases, loosing their contribution to mechanical strength. However, different types of dispersoids formed during the solution treatment were stable during the thermal exposure, resulting in the different but promising contribution to the elevated-temperature properties. The combined additions of V, Zr and Mo showed the highest mechanical and second highest creep properties at 300°C, which possess 22% and 100% improvement on the strength and creep resistance compared to the base alloy.

Recent Progress in Creep-Resistant Aluminum Alloys for Diesel Engine Applications: A Review

“…Li et al [30] carried out compressive creep tests at 300 °C and 50 MPa for 100 h after T7 heat treatment in 356 alloy with individual and combined additions of V, Zr, and Mo. The study showed that the minimum creep rate decreased 67% and 50% for the alloys containing V and V-Zr-Mo, respectively, when they were compared with the base A356 alloy.…”