Modification of eutectic silicon and β-Al5FeSi phases in as-cast ADC12 alloys by using samarium addition

The effects of Sm additions (0, 0.5 wt.%, 1.0 wt.% and 1.5 wt.%) on the eutectic Si and beta-Al5FeSi phases of ADC12 as-cast alloys were studied by optical microscopy (OM), scanning electron microscopy (SEM) and differential thermal analysis (DTA). The experimental results showed that Sm was an effective modifying agent for the eutectic Si of ADC12 alloy, when 1.0 wt.%-1.5 wt.% Sm was added to the alloy, the coarse acicular eutectic Si was modified into fine particle or short rod structure. Moreover, the appropriate addition of Sm (about 1.0 wt.%) had marked effects on shortening the length of needle-like beta-Al5FeSi phase. Whereas, Sm was less effective on modifying the needle-like beta-iron to the Chinese script or spherical alpha-iron phase. The modification mechanism was also discussed.