Temperature effects on the elastic and thermodynamic properties of Al1−xLix and Al1−xCrx alloys from first principles

Abstract

Thermal effects on the elastic and thermodynamic properties of face-centered cubic (fcc) Al-Li and Al-Cr alloys are investigated here by means of density-functional theory. We calculate the polycrystalline Young's modulus, Poisson's ratio, bulk modulus and shear modulus as a function of alloying concentration and temperature. The calculated elastic and thermodynamic properties are in good agreement with available experimental data. Increasing temperature lowers the values of the moduli of both alloys. The results show that both alloying elements increase the Young's modulus. In the case of Al-Li alloys, below 8 at.% Li the Young's modulus increases due to solid solution formation. Further improvement of the stiffness at higher concentrations is due to formation of precipitates. Cr increases almost linearly the Young's modulus, which at 10 at.% Cr becomes almost 34% higher than that of pure Al. The formation of precipitates do not affect the value of the elastic moduli at low Cr concentrations. We estimate the solid solution hardening effect in these alloys by combining the Labusch-Nabarro theory with density-functional theory data.