Cooling behaviour and microstructure of rapidly solidified Ag-Cu alloys

Abstract

A systematic experimental approach has been used to study rapid sotidification of Ag-Cu alloys with 23, 28.1 (eutectic), and 33 wt-%Cu using a levitation casting technique. The cooling curves were recorded during each experimental run and the microstructure was examined. Different cooling rates were obtained ranging from 3.2 × 10⁴ to 10 × 10⁴ K S^-l, with nucleation undercoolings of 35–132 K, while growth undercooting was in the range 12–52 K. Under these conditions, the microstructure did not exhibit any lamellar structure. Instead, several other structures were obtained mainly, microsegregationfree, banding, columnar, and equiaxed dendritic structures. A correlation was made between each type of structure, the cooting rate, and the nucleation undercooling. The results are discussed and compared with previous work.