The effects of different amounts of segregated Ga (substitutional) on an Al grain boundary were investigated by using a first-principles pseudopotential method. The segregated Ga was found to draw charge from the surrounding Al due to the electronegativity difference between Ga and Al, leading to a charge density reduction between Ga and Al as well as along the Al grain boundary. Such an effect could be enhanced by increasing the Ga segregation amount. With further Ga segregated, in addition to the charge-drawing effect that occurred in the Al–Ga interface, a heterogeneous α-Ga-like phase could form in the grain boundary, which greatly alters the boundary structure. These effects were suggested to be responsible for Ga-induced Al intergranular embrittlement.

First-Principles Study of the Effects of Segregated Ga on an Al Grain Boundary. Y.Zhang, G.H.Lu, T.Wang, S.Deng, X.Shu, M.Kohyama, R.Yamamoto: Journal of Physics - Condensed Matter, 2006, 18[22], 5121-8