Effect of the Transition Group Metals (M = Sc, Ti, V, Zr, and Cr) on Mechanical Properties of S-AlCuMg Phase: A First-Principles Study

To further enhance the mechanical properties of the S-AlCuMg (Al2CuMg) phase in 2xxx Al alloys, we investigated the effects of five different transition metal elements (M = Sc, Ti, V, Zr, and Cr) on the Al2CuMg phase using first-principles calculations. The results show that the addition of these five elements effectively reduces the formation enthalpy of the Al2CuMg phase, thereby improving its energy stability. Among them, substitution of Mg-1 sites with transition metal elements results in the lowest Delta H (Sc-Mg-1 = - 0.230 eV/atom, Ti-Mg-1 = - 0.202 eV/atom,V-Mg-1 = - 0.163 eV/atom, Zr-Mg-1 = - 0.223 eV/atom, and Cr-Mg-1 = - 0.128 eV/atom) and the highest E-coh (Sc-Mg-1 = - 3.392 eV/atom, Ti-Mg-1 = - 3.428 eV/atom,V-Mg-1 = - 3.438 eV/atom, Zr-Mg-1 = - 3.466 eV/atom, and Cr-Mg-1 = - 3.359 eV/atom) for Al2CuMgM. In terms of mechanical properties, the doping elements significantly improve the toughness and hardness of the Al2CuMg phase. Notably, the effect of Cr is the most pronounced (B = 82.435 GPa, G = 44.308 GPa, E = 112.727 GPa, H-V = 6.652 GPa, and Pugh's ratio = 0.272). The addition of Cr to the Al2CuMg phase enhances its mechanical properties, primarily by weakening the strength of metal bonds in the Al2CuMg phase, which in turn improves the overall toughness of Al2CuMgM. This study provides a theoretical foundation for understanding the influence of transition metal doping on the mechanical properties of the S-AlCuMg phase, offering valuable insights for the development of high-performance 2xxx Al alloys.