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The effects of alloying elements (Co, Cu, Fe, Ge, Hf, Mg, Mn, Ni, Si, Sr, Ti, V, Y, Zn, and Zr) on elastic properties of Al have been investigated using first-principles calculations within the generalized gradient approximation. A supercell consisting of 31 Al atoms and one solute atom is used. A good agreement is obtained between calculated and available experimental data. Lattice parameters of the studied Al alloys are found to be depended on atomic radii of solute atoms. The elastic properties of polycrystalline aggregates including bulk modulus (B), shear modulus (G), Young’s modulus (E), and the B/G ratio are also determined based on the calculated elastic constants (cij’s). It is found that the bulk modulus of Al alloys decreases with increasing volume due to the addition of alloying elements and the bulk modulus is also related to the total molar volume (Vm) and electron density (nAl31x) with the relationship of nAl31x=1.0594+0.0207√B/Vm. These results are of relevance to tailor the properties of Al alloys.

Abstract: The elastic, phonon and thermodynamic properties of Al12Mg17 have been investigated by first-principles calculations. The obtained structural parameters, phonon dispersion curves and the predicted thermodynamic properties for all the phases studied herein agree well with available experimental data. The temperature-dependent single-crystal elastic constants are also predicted along with the polycrystalline aggregate properties, including bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio. The brittleness of Al12Mg17 that we predict is consistent with experiments, in contrast to the previous calculation showing ductile behavior. Detailed analysis of density of states further explains the present theoretical findings. [Copyright &y& Elsevier]

Abstract: The effects of alloying elements (Cr, Hf, Pt, Y and Zr) on the elastic constants of Ni3Al have been investigated using first-principles calculations within the generalized gradient approximation. The results are compared with the theoretical and experimental data in the literature and analyzed based on volume changes, electron density and pure alloying element''s properties. The calculated enthalpies of formation are used to determine the site preference. It is found that the shear modulus decreases with the additions of alloying elements due to the expansion of the equilibrium volume, wherein Y has the largest effect. It is also observed that the bulk modulus of Ni3Al alloys is strongly related to the total molar volume and electron density, and that the solute atom with high bulk modulus tends to give high bulk modulus of Ni3Al. Based on the calculated results, the change rates of elastic constants due to each alloying element in Ni3Al have been obtained. Our calculations show that Hf prefers the Al sublattice with a negative change rate of the Young''s modulus of Ni3Al, agreeing well with measurements. The predicted Young''s modulus of IC 218 alloy shows a good agreement with available experimental data. [Copyright &y& Elsevier]