Effect of stirring induced by rotating magnetic field on b-Al5FeSi intermetallic phases during directional solidification in AlSi alloys

Abstract

In AlSi alloys, iron plays an important role and as one of the main impurities causes formation of β-Al5FeSi intermetallics. This study aims to understand the effect of fluid flow on the microstructure and intermetallics in Al-5/7/9 wt.% Si 0.2/0.5/1.0 wt.% Fe alloys directionally solidified under defined thermal and fluid flow conditions (generated trough rotating magnetic field RMF). The solidification experiments were conducted in a special furnace facility Artemis-3 allowing perfectly controlled directional solidification. The results showed that forced flow can cause shortening of the β platelets in dendritic regions and lengthening in eutectics together with increasing their number density. The studies have shown that application of stirring by RMF for AlSi alloys could lead to better results in shortening β-Al5FeSi than lowering Fe content in the range from 1.0 to 0.2 wt.% Fe. It is deduced that melt flowing together with β phases reaches the superheated bulk where intermetallics could be fragmented or remelted, and finally microstructures with shorter β-Al5FeSi and higher number density of β might be obtained.