First-principles study on the effects of V, Nb, Cd, Ag, Ge and Sb doped in Al2CuMg phase of Al-Zn-Mg-Cu alloy

The S phase (Al2CuMg) is an important strengthening phase for the Al-Zn-Cu-Mg alloys, which are widely used in the aerospace and transportation industries. First-principles calculations based on the density functional theory were used to investigate the effects of doping V, Nb, Cd, Ag, Ge and Sb elements on the S phase. The results demonstrate that Ag atom can spontaneously dope into the S phase. Ge and Sb doping can improve the toughness and plasticity of the S phase. And doping Ge, V or Nb can reduce the anisotropy of the Al2CuMg phase. The hardness of the Nb, V, Cd and Ag doped structures become larger than that of the pristine structure. The results of orbital hybridization in the partial density of states (PDOS) and the distribution in electron density difference (EDD) confirmed that the effect of doping elements and Al atoms has the greatest impact on the performance of the system, and the strength of the covalent bond of the system affects the main aspects of brittleness. This study provides a better theoretical understanding of the doped S phase, providing guidance for improved composition design and performance optimization of Al-Zn-Cu-Mg alloys.