Effects of alloying elements on elastic properties of Ni3Al by first-principles calculations

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.