AlSi2Sc2 intermetallic formation in Al-7Si-0.3Mg-xSc alloys and their effects on as-cast properties

• Published in: Journal of alloys and compounds 2018-01, Vol.731, p.1159-1170
• Main Authors: Pandee, P., Gourlay, C.M., Belyakov, S.A., Patakham, U., Zeng, G., Limmaneevichitr, C.
• Format: Article
• Language: English
• Subjects: Aluminum alloys; Aluminum base alloys; Casting; Grain refinement; Hypoeutectic Al-Si; Mechanical properties; Modification; Scandium; Silicon; Solidification; Studies; Tensile properties; Tensile strength; Ultimate tensile strength
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.10.125

The influences of 0–0.65 wt% Sc additions on microstructure evolution during solidification, and on as-cast tensile properties and fracture behavior have been investigated in Al-7Si-0.3Mg foundry alloys. The results show that the addition of Sc significantly refines both the primary α-Al grain size and the eutectic silicon particle size, and Sc also results in the formation of AlSi2Sc2 in up to two eutectic reactions. The as-cast yield strength was improved by the addition of Sc, however, at high Sc level (0.65 wt%) the ultimate tensile strength decreased, owing to the formation of relatively large AlSi2Sc2 crystals in the Al-AlSi2Sc2 eutectic. The fracture path in the tensile samples is shown to pass through the eutectic AlSi2Sc2 intermetallic and eutectic silicon. The Sc level should not be higher than 0.40 wt% Sc to avoid the deleterious effect of AlSi2Sc2. •Sc refines both the α-Al grain and the eutectic Si in hypoeutectic Al-Si alloy.•Sc results in the formation of AlSi2Sc2 in two eutectic reactions.•The AlSi2Sc2 were significantly larger when they grew in the L→Al+AlSi2Sc2 reaction.•The as-cast yield strength was improved by the addition of Sc.