First-principles study on solid solution embrittlement effect of Ga in Al_3.8Ga_0.2 alloy

The structural properties, mechanical properties and electronic structure of Al_3.8Ga_0.2 crystal have been investigated by using the virtual crystal approximation (VCA) based on the density functional theory (DFT). The lattice constants, elastic constants, elastic modulus, poisson's ratio, anisotropic index and density of states (DOS) of three Al_3.8Ga_0.2 crystal structures are analyzed in this work and that of pure Al crystal are also calculated as comparison. The results show that 5% solid solubility of Ga atoms in Al crystal structure caused about 10% pure Al volume shrinkage; Three structures of Al_3.8Ga_0.2 exhibited thermodynamic stability and mechanical stability; The solid solution of Ga enables Al-Ga alloy to have higher resistance to linear compression along the [001] direction and shear deformation resistance along the (100) crystal plane; Al_3.8Ga_0.2 crystal structures have stronger fracture resistance, plastic deformation resistance and elastic deformation resistance than that of pure Al. Mechanical calculation results show that possibility of embrittlement after the solid solutuion of Ga atom in Al-Ga alloy, and Al_3.8Ga_0.2 crystal structures exhibit mechanical anisotropy; According to the electronic structures analysis, the DOS of three Al_3.8Ga_0.2 structures are higher than pure Al at the Fermi level, and have stronger activity than pure Al. (paper)