ACOUSTIC-EMISSION ASSOCIATED WITH THE FRACTURE OF AL AND AL-ALLOY EMBRITTLED BY LIQUID GALLIUM

Liquid gallium embrittlement of Al and Al alloy (2017 duralmin) specimens was studied using acoustic emission (AE) techniques. AE signals were always detected from each specimen when they were wetted with Ga in either the presence or the absence of tensile stress. This seems to indicate that even in the absence of external stress, the Ga atoms adsorbed on the specimen surface could penetrate the interior, probably through grain boundaries, and that those moved atoms might form microcracks. In the tensile tests for 2017 duralmin and 99% Al specimens, AE signals of high amplitude were detected, and they were attributed to the formation and propagation of macrocracks. AE signals observed in duralmin were markedly different from those in 99% Al. This difference is discussed in connection with the corresponding fracture surfaces.