The Effect of Vanadium on AlFeSi - Intermetallic Phases in a Hypoeutectic Al-Si Foundry Alloy

Abstract

The effect of Vanadium on the Fe-rich alpha- and beta-intermetallic particles in a high purity Al-7wt% foundry alloy was investigated. Needle- and script-like Fe-rich intermetallic particles were successfully identified as beta-Al(4.5)FeSi and alpha-Al8Fe2Si by EBSD and Fe/Si-ratios from EDS. V was found to accumulate in the alpha-phase and the content increased with increasing V-content in the alloy.For the low cooling rate (0.3 K/s) and 0.3wt% Fe alloy the average area fraction of alpha relative alpha + beta increased with increasing V-content in the alloy and the average total area of intermetallics decreased. For the high cooling rate (1.1 K/s) and 0.3wt% Fe alloy the average area fraction of alpha relative alpha + beta was very high and decreased with increasing V-content in the alloy and the average total area of intermetallics increased from 0 to 600ppm V and decreased from 600ppm to 0.2wt% V. Addition of TiB2 grain refiner caused more and larger beta-needles in the 0.2wt% V alloy. The changes were explained to be due to the stabilization of the alpha-phase in the Al-Fe-Si phase diagram by V-additions, similar to the effect of Mn-additions.