Mechanism of embrittlement of al alloy by liquid metal (GA)

The liquid metal-induced embrittlement (LME) of 7075 Al alloy by Ga was investigated by using modified wedge open loaded (WOL) specimens. The results showed that the adsorption of Ga atoms could facilitate local plastic deformation of the base metal and there was an observable concave plastic zone at the notch tip. A microcrack then initiated when the plastic deformation reached a critical condition. The threshold stress intensity of LME under tensile applied stress is 1.7 MPa m(1/2). When the specimens are loaded in the opposite direction, the stress is compressive at the notch rip and is tensile some distance away from the notch tip. Ga atoms diffused to the tensile zone and resulted in microcrack initiation. The microcrack propagated outwards in the tensile stress zone and was arrested at the compressive stress zone near the notch tip. The nominal compressive threshold stress intensity K-IC*(L) is equal to 3.5 MPa m(1/2). The fracture surfaces of LME for ail the specimens are intergranular. (C) 1999 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.