Al grain boundary segregations in doped intermetallic NiAl and their effect on brittleness at room temperature

Abstract

The nature of intermetallic NiAl brittleness is investigated by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and electron energy-loss fine structure (EELFS) means. It is found that the reason for this phenomenon is the ordering of intermetallic NiAl, accompanied by the formation of aluminum structural segregations at grain boundaries. Doping with 0.1 wt % La transforms the atomic and electronic structures of grain boundaries, eliminating NiAl intergranular fracturing at room temperature. Doping is accompanied by Fermi level shifts and an increase in conduction electron density n_eff. These factors are responsible for the lower covalence of interatomic bonds in pure intermetallic NiAl. The effect A1 segregations have on the critical deformation of the generating grain boundary fracture in NiAl is discussed.