The structural stability and mechanical properties of doped Al2Cu precipitates with different elements by first-principles calculations

Abstract

The Al2Cu precipitates (θ phase) is an important strengthening phase of Al- Cu alloy, which has a significant effect on the comprehensive mechanical properties of the material. This study employed first-principles calculations based on density functional theory to investigate the effects of doped elements X (X = Fe, Mn, Mg, Sc, and Zr) on the structural stability, mechanical properties, and electronic structure of the θ phase. The calculations of forming energy, cohesive energy, and phonon spectrum show that different doping elements have different substitution sites for Al or Cu in θ phase, and the doped θ phase has good structural stability. The calculation results of elastic constants show that doping Fe can enhance the hardness and stiffness of θ phase, reduced Mn content can improve its ductility, while the introduction of Mg can improve the shear modulus of θ phase. Sc is the most effective element to improve the anisotropy of θ phase, and the addition of Zr can makes θ phase better ductility. By electronic structure analysis, it is found that the incorporation of doping elements promotes covalent interactions with Al and Cu atoms, thus enhancing the stability of the θ phase. Charge density and Bader charge analysis reveal that the Fe and Mn atoms experience electron gain in the doped θ phase, whereas the Mg, Sc, and Zr atoms undergo electron loss. The results of this study provide useful information for the composition design and performance optimization of Al-Cu alloys.