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 m1/2. When the specimens are loaded in the opposite direction, the stress is compressive at the notch tip 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 m1/2. The fracture surfaces of LME for all the specimens are intergranular.