Microstructural effect of elemental additions Zn, Mg, and Pb on Cd–CuCd3 eutectic

AbstractThe 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