Effects of Sc content on the microstructure of As-Cast Al-7 wt.% Si alloys
The effects of Sc content on the microstructure of as-cast Al-Si alloys were investigated by adding 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.4 wt.% Sc to hypoeutectic Al-7 wt.% Si alloys. The results show that there are significant changes in the microstructure when the Sc content is increased to 0.15%. The volume fraction of the primary {alpha}-Al phase increased nearly monotonically with increasing Sc content in the as-cast state. As the Sc content increased, the average length of the eutectic Si in the as-cast Al-7Si-xSc alloy decreased sharply from 150 {mu}m (without Sc content) to 20 {mu}m (0.4 wt.% Sc content). The Sc atoms are concentrated in the interdendritic regions. A fish-bone structure composed of Al, Si, Sc, and Fe, which might be the Fe-rich phase precipitated on the AlSc{sub 2}Si{sub 2} (V-phase) was detected adjacent to the grain boundary by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). - Highlights: Black-Right-Pointing-Pointer Significant changes in the microstructure when the Sc content is increased to 0.15%. Black-Right-Pointing-Pointer Volume fraction of the primary a-Al phase increased with increasing Sc content. Black-Right-Pointing-Pointer Average length of Si decreased sharply from 150 to 20 {mu}m with increasing Sc content. Black-Right-Pointing-Pointer The Sc atoms are concentrated in the interdendritic regions.