Microstructural effect of elemental additions Zn,Mg,and Pb on Cd–CuCd 3 eutectic

The microstructure of unidirectionally solidified Cd–CuCd₃ eutectic monovariant alloys containing elemental additions of Zn, Mg, and Pb was studied. The addition of either Mg or Pb resulted in changes of eutectic morphology, such as curving and branching of CuCd₃ rods, which could be directly attributed to the formation of eutectic cells. The addition of Zn led to microstructural modifications even when the solid/liquid interface was macroscopically flat. Such modifications included an increase of interrod spacing, the stabilisation of a rod morphology at a velocity which produced a mixed blade–rod morphology in the pure eutectic, and the protrusion of CuCd₃ phase at the solid/liquid interface. These modifications were attributed to a change of faceting behaviour of the CuCd₃ phase by the addition of Zn. It is proposed that the formation of lateral facets on the CuCd₃ changed the growth mechanism at the solid/liquid interfaces effecting the modifications described.

MST/1009