Effect of Crucible Materials and Oxides on Static Undercooling in Molten Nickel.

Abstract

Using fused silica and alumina crucibles, an investigation on the static undercooling behavior of nickel, with and without the addition of oxides, was conducted. The effects of the crucible materials and of the oxides on the undercooling and solidified structure were investigated. The degree of undercooling reached 192 K using the fused silica crucible, and decreased to an average of 55 K using the alumina crucible. With the addition of alumina powder to the nickel, the lowest undercoolings were obtained. Considering a modified planar disregistry between nickel and alumina might explain why alumina acts as a good heterogeneous nucleation catalyst in molten nickel. The addition of the alumina powder did not significantly refine the solidified structure of the specimens. The finest structures were obtained in the specimens with added NiO and Co3O4 powders which had almost no effect on the undercooling.