First Principles Investigation of the Effects of Chemical Short-Range Ordering Clusters on the Ideal Tensile Strength and Ductility of Aluminum Alloys

As important structural features of the metal materials, chemical short-range ordering clusters play a critical role in the mechanical properties of the materials. They have been discovered in dilute Al-alloy systems and are usually generated by annealing processes at high temperatures or by severe plastic deformation at room temperature. In the present work, systematic first-principle calculations were conducted to evaluate the influences of the chemical short-range ordering clusters L12-Al3Zr on the mechanical properties of the pure Al supercell. Results showed that the mechanical properties including both ideal tensile strength and ductility were improved simultaneously when the chemical short-range ordering clusters L12-Al3Zr were introduced to the pure Al. The larger the volume fraction of chemical short-range ordering clusters L12-Al3Zr, the larger the ideal tensile strength. The deformation charge density, the electron localization function and the density of state were computed to reveal the nature of the strengthening of the chemical short-range ordering clusters L12-Al3Zr on the pure Al supercell. It was found that excellent ideal tensile strength for the Al supercell with the chemical short-range ordering clusters L12-Al3Zr was due to strong charge accumulations and strong electronic interactions between the solute atoms Zr and the host Al atoms. In addition, the Pugh ratio (B/G) and ratio (Wsep/Gdisl) of the work of the separation Wsep to the work of dislocation emission Gdisl were computed to reveal the effect of the chemical short-range ordering clusters L12-Al3Zr on the ductility of the Al supercell. Results showed that the addition of L12-Al3Zr chemical short-range ordering clusters addition to pure Al supercell brought about an increase in ductility as compared to pure Al supercell, which is ascribed to large the Pugh ratio B/G and ratio (Wsep/Gdisl) of the work of the separation Wsep to the work of dislocation emission Gdisl. This work is important for simultaneously improving the tensile strength and ductility of Al alloys.