In situ TEM research of dislocation emission and microcrack nucleation forTi after adsorption by Hg

Using a special constant deflection device, the change in dislocation confi guration ahead of a loaded crack tip for ol-Ti, before and after adsorption of Hg atoms, and the initiations of Hg-induced microcracks have been obser ved in TEM, as well as the in situ extension in TEM without Hg. The results showed that chemisorption of Hg atoms facilitates dislocation emission and motion. When the chemisorption-enhanced dislocation emission and motion de velop into a critical situation, a microcrack in LME nucleates from the mai n crack tip and/or in the dislocation free zone (DFZ), and propagates in cl eavage mode. During in situ extension in TEM without liquid metal, when dis location emission and motion induced by thermal activity and applied stress reach a certain critical condition, microcracks nucleate but do not blunt into a void. (C) 1999 Elsevier Science Ltd.;LVI rights reserved.