BORON DISTRIBUTION AT BOUNDARIES IN RAPIDLY SOLIDIFIED Ni₃Al

Abstract
The addition of boron to Ni₃Al produces a fabricable material that has good high temperature properties. The distribution of boron in a rapidly solidified Ni - 24 at.% Al alloy containing 0.24% B was investigated by atom probe field-ion microscopy and transmission electron microscopy. Wire specimens of this material were prepared by a Pendant Drop Melt Extraction technique directly from the liquid phase and produced a wire 40 to 80 µm in diameter with a grain size of 1 to 4 µm. Boron was found to decorate most grain boundaries and some antiphase boundaries. However, the majority of the boron remained in solution in the matrix. A thin boron-enriched phase up to 1.2 nm thick was also observed on most of the grain boundaries. The distribution of this phase was not uniform either along an individual grain boundary or from one boundary to another.