Penetration of liquid gallium into the grain boundaries of aluminium: a synchrotron radiation microtomographic investigation

The penetration of liquid metals into the grain boundaries of polycrystalline solid metals is a precursor process triggering liquid metal embrittlement for some specific metal couples. Synchrotron radiation X-ray microtomography is used to investigate the penetration of liquid gallium into the grain boundaries of aluminium. The large difference in absorption coefficients between Ga and Al allows micrometer thick liquid Ga films to be observed as they are wetting grain boundaries of Al. The effects of annealing are presented and discussed. This technique opens the way for in-situ measurements of the kinetics of liquid metal penetration in materials. It might also be used to visualise and analyse the three-dimensional grain structure of a metallic polycrystal.