The Effect of Hydrogen on the Plastic Deformation of Nickel Single Crystals

AbstractShear stress/shear strain curves for nickel single crystals containing 9 ppm hydrogen (0.045 at.-%) have been compared with those of hydrogen-free crystals over the range −196 to 100°C. The presence of hydrogen causes serrated yielding of the nickel and an increase in the shear stress τIII between − 125 and 0° C, but has no effect on the critical resolved shear stress (C.R.S.S.) at any temperature. These observations are explained in terms of the interaction between dislocations and dissolved hydrogen which is able to diffuse during deformation. It is suggested that hydrogen can lower the stacking-fault energy of nickel from 240 to 155ergs.cm−2.