Influence of Shell Material on the Microstructure and Mechanical Properties of Twin-Roll Cast Al-Si-Mg Alloy

This study is devoted to the influence of shell material on microstructure and mechanical properties of twin-roll cast aluminum alloy of the Al-Si-Mg system. The use of high solidification rates during twin-roll casting can improve the mechanical performance of these alloys. The study involves two pairs of shells, made of hot work tool steel and high-strength copper alloy, and an age-hardening casting aluminum alloy. The solidification conditions are varied by using two different shell materials. The results show that the copper shells had a positive influence on the mechanical performance of the age-hardening casting aluminum alloy. It is demonstrated that the copper shells increased the solidification rate, resulting in a smaller dendrite arm spacing and improved mechanical properties, especially in regard to significantly improved ductility. The steel shells, on the other hand, showed lower solidification rates, resulting in larger dendrite arm spacings and inferior mechanical properties. Additionally, the twin-roll cast material is subjected to heat treatment including solution annealing, water quenching and artificial aging. After the heat treatment characteristics of mechanical properties are distinctly improved. The study also provides insight into the correlation between microstructure parameters and the solidification rate based on microstructure analysis, which is crucial when comparing different tool materials.