CHEMISORPTION-FACILITATED DISLOCATION EMISSION AND MOTION, AND INDUCED NUCLEATION OF BRITTLE NANOCRACK

Using a special TEM constant deflection device, the change in dislocat ion configuration ahead of a loaded crack tip before and after adsorpt ion of Hg atoms and the initiation of liquid metal-induced nanocracks (LMIC) have been observed. The results show that chemisorption of Hg a toms can facilitate dislocation emission, multiplication and motion. N anocracks will be initiated in the dislocation-free zone (DFZ) or at t he crack tip when chemisorption-facilitated dislocation emission, mult iplication and motion reach a critical rendition. On the basis of the available experimental evidence concerning liquid metal embrittlement (LME), a new mechanism for this phenomenon is considered. This involve s the fact that the decrease in surface energy induced by chemisorptio n of Hg atoms results in a reduction in the critical stress intensity factors for dislocation emission and the resistance for dislocation mo tion. On the other hand, the plastic work and K-IC will decrease with the decrease in the surface energy.