Phase-field simulation for evolution of iron-rich phase during solidification of Al–Si–Fe alloys

Iron is a common impurity element in Al–Si alloys. The existence of Fe promotes the formation of needle-like iron-rich phase, which has an adverse effect on the macroscopic mechanical properties. In this study, the effects of casting temperature, Fe content and melt ultrasonic treatment on the morphology of β-Al9Fe2Si2 were investigated by phase-field simulation and experiment. The results show that when the casting temperature is close to the liquidus temperature, the grain size of the precipitated phase will be refined. The increase of iron content in the alloy will promote the increase of average grain size and volume fraction of iron-rich phase by inhibiting the growth of α-Al grains. In addition, the elevation of both casting temperature and Fe content promotes the transformation of the β-Al9Fe2Si2 from short rod-like to needle-like with large scale. The melt ultrasound inhibits the transformation to β-Al9Fe2Si2 by promoting the nucleation and growth of α-Al8Fe2Si. Melt ultrasound, casting temperature and iron content together cause the change of needle-like iron-rich phase morphology.