A dramatic decrease of the dislocation velocity in Ni3Al single crystals under the influence of hydrogen

The effect of hydrogen on the average dislocation velocities in Ni3Al single crystals has been investigated by the etch-pit technique. It is found that the velocity is dramatically decreased by the charged high content of hydrogen and that the tension/compression asymmetry of the dislocation velocity is reversed. Detailed observation of the dislocation structure indicates that the motion of edge superkinks is seriously inhibited by hydrogen solutes. These results serve as a strong evidence for the mechanism of hydrogen strengthening in metals. The interaction between the solute H and the edge dislocations also throws a sidelight on the role of kinks in the flow stress anomaly in Ni3Al.