Effect of environment on the brittle-to-ductile transition of pre-cracked NiAl single and polycrystals

Hydrogen diffusion and solubility measurements on NiAl single and polycrystals have been performed as well as fracture toughness tests in various environments and after high-temperature charging. It was found that internal hydrogen lowers the grain boundary strength, while external hydrogen promotes stable crack growth in a small temperature region around the brittle-to-ductile transition temperature.