Investigating the effects of a Ga layer on an Al grain boundary by a first-principles computational tensile test

We have performed a first-principles computational tensile test on an Al grain boundary (GB) with a Ga layer. The tensile strength, the toughness and the Griffith energy for the Ga-layer segregated GB are, respectively, 17%, 19% and 23% lower than those of the clean GB, which indicates that the GB is weakened. A closely-packed Ga cluster is formed following the breaking of some Ga-Ga bonds at a certain tensile strain, leading to the formation of a void-like structure in the GB. It is suggested that the GB weakening is directly associated with the formed void-like structure, which makes the applied stress concentrate mainly on the Ga cluster. The final fracture occurs inside the Ga layer. The weakened GB may contribute to the Ga-induced Al GB embrittlement.