Abnormal growth relationship between Si and other phases in undercooled Al-Cu-Si alloy

The dependence of the growth relationship between Si and other two phases on undercooling was investigated in terms of microstructural characteristics in Al77.2Cu13.6Si9.2 ternary alloy. As undercooling increases, the independent growth of faceted Si phase and the cooperative growth of Al and theta phases are replaced by the attaching growth of Al phase on faceted Si phase in the ternary eutectic. At the same time, theta phase and a small amount of non-faceted Si phase tend to grow cooperatively in both pseudobinary and ternary eutectics. Once undercooling exceeds a critical value, the independent nucleation and growth of the three non-faceted phases result in anomalous ternary eutectic. (C) 2012 Elsevier B.V. All rights reserved.