Systematic study of growth behavior of β-Al9Fe2Si2 in Al alloys with high iron and silicon contents

β-AlFeSi is one of the most common and most damaging intermetallics in aluminum alloys containing silicon. The study of its growth behavior is crucial for alloy design. In this work, Al-8.1Si–5Fe and Al–13Si–3Fe alloys were cast to study the growth of β-AlFeSi. The skirt like β-AlFeSi clusters formed by splitting were discovered, and this phenomenon was found to be mainly caused by thermal stress. By micro to atomic scale electron microscopy studies, a layer-by-layer growth mode along the (001) crystal plane was proposed for β-AlFeSi. In addition, it is found that β-AlFeSi grows along the heat flow, and the preferred growth orientation is determined to be [100]/[010]. Other characteristics of β growth, such as stacking faults and inducing formation of pores, were also reported and discussed.