C-TYPE DISLOCATIONS EMITTED FROM CRACKS INTRODUCED IN A THIN FOIL OF LANI5

The nature of dislocations emitted from cracks introduced in a thin fo il of LaNi5 has been characterized by means of transmission electron m icroscopy. Dislocations emitted from cracks are determined to be of th e c-type (b (Burgers vector)=[0001]) moving on {10 (1) over bar 0} pri sm planes. Although grown-in dislocations of the a-type (b=1/3[11 (2) over bar 0]) locate near cracks where the emission of c-type dislocati ons occurred, these a-type dislocations are not observed in motion, in dicating the difficulty in the motion of a-type dislocations. The impl ications of these results for controlling the extent of cracking durin g cycles of hydriding-dehydriding of alloys based on LaNi5 are discuss ed. (C) 1998 Elsevier Science S.A.