First-principles study on alloying stability, electronic structure, and mechanical properties of Al-based intermetallics

Abstract

First-principles calculations were performed to study on alloying stability, electronic structure, and mechanical properties of Al-based intermetallic compounds (AlCu 3, AlCu 2Zr, and AlZr 3). The calculated results show that the lattice parameters obtained after full relaxation of crystalline cells are consistent with experimental data. The calculation of cohesive energies indicated that the structure stability of these Al-based intermetallics will become higher with increasing Zr element in crystal. The calculations of formation energies showed that AlCu 2Zr has the strongest alloying ability, followed by AlZr 3 and finally the AlCu 3. The further analysis find out that single-crystal elastic constants at zero-pressure satisfy the requirement of mechanical stability for cubic crystals. The calculations on the ratio of bulk modulus to shear modulus reveal that AlCu 2Zr can exhibit a good ductility, followed by AlCu 3, whereas AlZr 3 can have a poor ductility; however, for stiffness, these intermetallics show a converse order. The calculations on Poisson's ratio show that AlCu 3 is much more anisotropic than the other two intermetallics. In addition, calculations on densities of states indicate that the valence bonds of these intermetallics are attributed to the valence electrons of Cu 3d states for AlCu 3, Cu 3d, and Zr 4d states for AlCu 2Zr, and Al 3s, Zr 5s and 4d states for AlZr 3, respectively; in particular, the electronic structure of the AlZr 3 shows the strongest hybridization, leading to the worst ductility.