WEAK GRAIN-BOUNDARIES IN NI3AL

This study correlates the resistance td intergranular crack initiation with grain boundary character in Ni3Al by comparing the distribution of grain boundary characters at crack initiation sites to that in the general population. Micro-cracks were initiated in Ni3Al by tensile de formation of Ni3Al ribbon/brass bar samples in a pressurized chamber, and the boundary characters were determined using the electron backsca ttering pattern (EBSP) method. It has been found that low-angle and Si gma 3 boundaries are strong, and are resistant to crack initiation; al l high-angle boundaries, including low-Sigma (5 < Sigma < 29) boundari es, are similarly prone to crack initiation, and Sigma 15, Sigma 21, a nd Sigma 29 boundaries are probably some of the weak boundaries in Ni3 Al.