An atom probe field ion microscope study of boron decorated boundaries in Ni 3Al

Abstract

Ni/sub 3/Al based alloys have recently come into prominence because of their potential for high temperature applications. However, the stoichiometric binary Ni/sub 3/Al intermetallic material is inherently brittle and therefore difficult to fabricate. Boron additions to substoichiometric (<25% aluminum) alloys substantially improve the ductility and alter the fracture mode to a transgranular failure. The reasons that boron has such a dramatic effect on the failure mode is currently under widespread investigation by a variety of techniques. Atom probe field ion microscopy (APFIM) is an excellent technique for studying the microstructure and chemistry in these materials -2). While Auger spectroscopy (AES) can analyze boundaries which can be made to fail intergranularly, the APFIM has the advantage that it can analyze all boundaries, including the ductile ones. Additionally, APFIM can quantify the chemistry of local areas, such as boundaries, for all elements. In this paper, the degree of boron segregation to 3 types of boundaries, - an antiphase boundary (APB), a twin boundary, and a high angle grain boundary, - will be presented.