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 singl e crystals has been investigated by the etch-pit technique. It is found tha t the velocity is dramatically decreased by the charged high content of hyd rogen and that the tension/compression asymmetry of the dislocation velocit y is reversed. Detailed observation of the dislocation structure indicates that the motion of edge superkinks is seriously inhibited by hydrogen solut es. 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 stres s anomaly in Ni3Al. (C) 2001 Elsevier Science Ltd. All rights reserved.