The effect of spheroidisation heat treatment on the creep resistance of a cast AlSi12CuMgNi piston alloy

The isothermal creep resistance of an overaged AlSi12CuMgNi alloy was studied at 300 °C as a function of solution heat treatment time at 480 °C. The microstructure of the alloy in as cast condition is formed by a three dimensional network of Si lamellae and intermetallic compounds embedded in an age-hardenable α-Al matrix. The solution heat treatment provokes the partial dissolution of Mg-rich intermetallic compounds and the spheroidisation of eutectic Si. These microstructural changes reduce the creep resistance of the alloy with increasing solution heat treatment time. The determination of the load transfer loss during solution heat treatment and an analogy with a modified shear-lag model for metal matrix composites indicate that the largest reduction in creep resistance occurs in the first 20 min-1 h of solution heat treatment.