Grain boundary compositon in NiAl

The high temperature strength and oxidation resistance of many transition metal aluminides makes these intermetallic materials attractive for high temperature applications. However, these aluminides are generally brittle at low temperatures and this restricts their technological applications. However, these aluminides are generally brittle at low temperatures and this restricts their technological applications. It has been demonstrated that the addition of more than 200 ppm of boron to the L12-ordered Ni3Al changes the fracture behavior from intergranular to transgranular and increases the ductility. The B2-ordered NiAl nickel aluminide is particularly attractive because of its low density and high melting temperature. This aluminide also fractures intergranularly at room temperature. However, no improvement in ductility is observed with similar boron additions even though the intergranular fracture is suppressed and there is a significant increase in the yield strength. In this paper, the results of an atom probe field ion microscopy investigation of the compositions of the grain boundaries in undoped and boron-doped NiAl are presented. The suitability of the atom probe field ion microscopy technique for the characterization of boundaries has clearly been demonstrated in many previous investigations including the characterization of boron segregation to grain boundaries and other planar features in Ni3Al