Effects of heat treatment on the microstructure, impact toughness and fracture strength of Al-6Si-2Cu cast alloy

Al-Si-Cu cast alloy is widely used for the production of components like rims, engine and gear parts due to excellent combination of high strength/weight ratio, high impact toughness, very good castability and tensile strength. The microstructures, impact toughness and fracture strength of Al-6Si-2Cu cast alloy were studied after heat treatment. The as-cast microstructure was thermally modified. CuAl2 particles in as-cast structure totally dissolved in the interdendritic region after solution treatment. The thermal modified microstructure consists of uniformly distributed α-Al grains and interdendritic network of fine eutectic silicon. The alloy exhibited improved impact toughness in solutionized and overaged conditions when compared to peakaged condition. Evaluation of fracture strength at solutionized and ageing conditions showed that peak ageing increases the fracture strength significantly compared to solutionized and overaged condition. The tensile fracture surfaces mainly exhibit the dimples and shear type dimples pattern.