Processing of the hypoeutectic AlSi9 alloy with twin-roll casting by using copper shells

Abstract. Lightweight design is one of the central topics of the automotive industry since reducing mass can save emissions over the entire life cycle of a component. Nowadays, vehicle structures usually consist of a multi-material design, which poses the additional challenge of joining these different materials. Mechanical joining is the most common way of joining different types of materials. Cast aluminium alloys of the AlSi system have a low ductility, which causes cracks during the mechanical joining process in the joint. One research approach is to achieve a fine microstructure by influencing the solidification rate since this results in increased mechanical properties, specifically the elongation at fracture and yield strength. A very fine microstructure can be achieved by utilizing Twin-roll casting (TRC) which is a continuous casting process in which high solidification rates of more than 100 K/s occur. In this study, the hypoeutectic cast aluminium alloy AlSi9 is processed in the TRC process using copper rollers. The cast strips are investigated regarding the microstructure-property correlation. A variation of the roller materials and cooling conditions allows for an increase in the solidification rate, whereby a defined, fine microstructure can be achieved, which enhances the mechanical properties of the hypoeutectic aluminium casting alloys.