Transmission electron microscopic observations of embrittlement of an aluminum alloy by liquid metal

Change in dislocation configuration ahead of a loaded crack tip of Al alloy 7075 (UNS A97075) before and after adsorbing Hg-3at% Ga atoms, and initiat ion of liquid-metal-induced microcracking have been observed in a transmiss ion electron microscope (TEM) using a special TEM constant-deflection devic e with precracked foil. Results showed that chemisorption of liquid metal a toms can facilitate dislocation emission multiplication and motion. A micro crack initiated in the dislocation free zone or at the crack tip and propag ated by a cleavage mode when the chemisorption-facilitated local plasticity developed to a critical level.