Integrated study of the influence of casting and heat treatment parameters on microstructures of multiphase multicomponent aluminum alloys

Aluminum-silicon-copper-magnesium casting alloys, such as Al-319, have high strength-to-weight ratio, good machinability, and maintain their strength at moderately elevated temperature. In this study the goal is to understand explicitly how the casting and heat treatment process parameters determine the microstructure/nanostructure and eventually guarantee the desired mechanical properties of cast aluminum alloys for automotive applications. End-chilled plate castings of ternary, quaternary and quinary aluminum alloys have been produced to provide as-cast microstructures representative of a wide range of commercial casting parameters. Coupons from the plates have been heat-treated over a wide range of solution treatment times and given a consistent quench and aging treatment. Selected plates have been instrumented to capture thermal histories during solidification. Optical and electron microscopy have been used to follow the evolution of the as-cast microstructure through solution treatment and aging. Electron microprobe analysis was used to measure solute distribution in the as-cast microstructure and to follow the redistribution of solute during heat treatment. Numerical simulation of heat transfer during solidification and solute redistribution during solidification, post-solidification cooling, and solution heat treatment were compared to the experimental data to develop an integrated understanding of the casting and heat treatment processes in these multi-component and multi-phase alloys.