Atom probe analysis of grain boundaries in rapidly-solidified Ni 3Al

Abstract

The distribution of boron in a rapidly solidified Ni-24 at.% Al alloy containing 0.24 at.% B was investigated by atom probe field-ion microscopy. Boron was found to segregate to both APBs and grain boundaries. Field-ion micrographs revealed that some of the APBs and most of the grain boundaries were decorated with bright spots identified by single atom analysis as boron atoms. A 0.4–1.2 nm thick boron-enriched phase was observed on most of the grain boundaries. The distribution of this phase was not uniform either along a boundary or from boundary to boundary. The degree of long-range order as measured by the atom probe was greater than 0.97. This state of order continued to the interface between the matrix and grain boundary phase.