Liquid metal embrittlement mechanism

Abstract

Liquid metal embrittlement was studied in the following two aspects. First the first principle and Chen-Nanxian three-dimensional lattice reverse method were employed to obtain the effective potentials for Al-Ga and Ga-Ga. Then with the molecular dynamics simulation, the influence of liquid metal adsorption on dislocation emission was studied. The simulated result shows that after Ga atoms are adsorbed on the crack plane in Al crystal, the critical stress intensity factor decreases, which changes from 0.5 MPam1/2 (without adsorption) to 0.4 MPam1/2 (with adsorption). The reason for the reduction in the critical intensity stress factor is that Ga adsorption reduces the surface energy of the crack plane. Moreover, 7075 Al alloy adsorbing liquid metal (Hg+3atm%Ga) wasin-situ studied in TEM by using a special constant deflection device. The experimental result showed that liquid metal adsorption could facilitate emission, multiplication and motion of dislocations. When this process reached a critical condition, the brittle microcrack was initiated and propagated from the crack tip or in a dislocation free zone.