Effects of RE on Iron-Phase Morphology in As-Cast Al-7Si-0.3Mg Alloy Containing 1.2%Fe

Abstract

In this work, the effects of the addition amount of rear earth on iron phase morphology of Al-7Si-0.3Mg alloy with 1.2%Fe were studied by Optical microscopy (OM), X-ray diffraction (XRD) and electron probe (EPMA). The results showed that: (1) the defined amount of RE addition can significantly inhibit the needle-like iron phase in Al-Si alloy. RE can make the needle-like β-Fe thick thinning, and some even blow or bending. When the addition of RE is 0.36%～0.48%, the modification effect to needle-like β-Fe phase are best. In high iron Al-Si alloys modified by RE, a small amount of bone-like Fe-rich compounds caused by Re were found. (2) after adding excess of RE (RE%>0.48%), a deterioration phenomenon emerged with the formation of large amount of needle-like and plate-like (AlSiRE) intermetallic compounds.