Comparative study of hydrogen-induced intergranular fracture behavior in Ni and Cu-Ni alloy at ambient and cryogenic temperatures

In order to clarify the contribution of dislocation-hydrogen interaction on the hydrogen embrittlement (HE) of pure Ni and of Cu-55 wt% Ni binary alloy, slow strain rate tensile (SSRT) tests were conducted at room temperature (RT) and at 77 K on hydrogen-precharged specimens. Regarding the SSRT test at RT, hydrogen increased the flow stress and induced intergranular fracture in both pure Ni and Cu-Ni alloy. Furthermore, based on scanning transmission electron microscopy investigations, it was suggested that the evolution of dislocation structures had been enhanced by hydrogen, but only in the case of pure Ni. At 77 K, the ductility of pure Ni was degraded by hydrogen, whereas that of Cu-Ni alloy was not. The difference in temperature dependence of the dislocation-hydrogen interaction between pure Ni and Cu-Ni alloy was discussed, based on the previously proposed HE mechanisms.