Abstract
First principles calculations are performed to study the effects of alloying elements (X = Al, Si, Sc, V, Cr, Mn, Cu, Zn, Y, Mo, Ta, W and Re) on the phase stability and elastic properties of TiZrHfNb refractory high entropy alloys. Both equimolar and non-equimolar alloys are considered. It is shown that the calculated lattice parameters, phase stability and elastic moduli of equimolar TiZrHfNbX are consistent with the available experimental and theoretical results. The substitutions of alloying elements at Ti, Zr, and Hf sites with various contents show similar effects on the phase stability and elastic properties of the TiZrHfNb-based alloys. The substitutions on Nb site are found to generally decrease the stability of body centered cubic phase. Close connections between the charge densities at the Wigner-Seitz cell boundary and the bulk moduli of TiZrHfNb-based alloys are found. The present results provide a quantitative model for exploring the phase stability and elastic properties of TiZrHfNb-based alloys from the electronic structure viewpoint.
Highlights
To explore the effect of alloying element X on the phase stability of equimolar TiZrHfNb, in Fig. 2 we show the calculated equilibrium Wigner-Seitz radii, the energies of the fcc and hcp phases relative to that of the bcc phase, and the equilibrium bulk moduli
We observe that the variations of the equilibrium Wigner-Seitz radii of equimolar TiZrHfNbX alloys follow the same trend as the atomic radii of the alloying elements X
We have studied the phase stability and elastic properties of TiZrHfNb based refractory high entropy alloys (HEAs) based on first-principle alloy theory
Summary
Due to the multi-principal element character and the slow diffusion kinetics, high entropy alloys (HEAs) often occur in single/dual phase with simple crystal structures. By comparing the calculated results between SQS and CPA on HEAs, the local lattice distortions were found to have small effect on the lattice parameters and elastic constants [19,26] and for these properties CPA turned out to be an efficient approach to describe the HEAs from first principles Various parameters, such as the atomic size difference [27,28], valence electron concentrations (VEC) [7,29,30], entropy of mixing and enthalpy of mixing between alloying elements [27], are used to predict the phase stability of HEAs. The VEC is found to have connections with the ductility of HEAs. The VEC is found to have connections with the ductility of HEAs When it is b4.5, the RHEAs consisting of IV, V, and VI metals are intrinsically ductile [7].
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