Chemisorption-facilitated dislocation emission and motion, and induced nucleation of brittle nanocrack

Abstract

Using a special TEM constant deflection device, the change in dislocation configuration ahead of a loaded crack tip before and after adsorption of Hg atoms and the initiation of liquid metal-induced nanocracks (LMIC) have been observed. The results show that chemisorption of Hg atoms can facilitate dislocation emission, multiplication and motion. Nanocracks will be initiated in the dislocation-free zone (DFZ) or at the crack tip when chemisorption-facilitated dislocation emission, multiplication and motion reach a critical condition. On the basis of the available experimental evidence concerning liquid metal embrittlement (LME), a new mechanism for this phenomenon is considered. This involves the fact that the decrease in surface energy induced by chemisorption of Hg atoms results in a reduction in the critical stress intensity factors for dislocation emission and the resistance for dislocation motion. On the other hand, the plastic work andK _IC will decrease with the decrease in the surface energy.