Solidification of undercooled Ag-Cu eutectic alloy with the Sb addition

The Ag-28.1 wt.%Cu alloy without or with a minor addition (0.5 or 1 wt.%) of Sb was undercooled and spontaneously solidified in the encasement of a glass flux. A non-steady-state radial growth from the nucleation site on the sample surface results in two types of structures, anomalous eutectics near the nucleation site and lamellar eutectics in the other part. The large thermal diffusion coefficient of the Ag-Cu eutectic alloy melt and the relatively slow growth velocity should be responsible for the non-steady-state growth. After a little Sb is added, the solidification interface changes from a cellular morphology into a cellular dendrite and then an undeveloped dendrite, and the tip radius decreases. Correspondingly, the recalescence degree and the recalescence rate increase and the granular particles in the anomalous eutectics become larger because the solidification deviates significantly from the equilibrium state. (C) 2008 Elsevier B.V. All rights reserved.