An Analytic Model to Determine the Interstitial-Solute Energetics and Underlying Mechanism in Refractory High-Entropy Alloys

TL;DR

This paper introduces an analytic model based on tight-binding theory to predict the stability and diffusion of interstitial solutes in refractory high-entropy alloys, addressing the challenge of disorder in local environments.

Contribution

The model provides a quantitative, electronic-level understanding of INS energetics in RHEAs, linking stability to d-band width and valence, aiding alloy design.

Findings

INS energetics depend linearly on d-band width

Valence of INS influences the slope of the energy relationship

Model explains key experimental observations

Abstract

The solution and diffusion of interstitial non-metallic solutes (INSs) like H, He, O, C, N, P, and S is common in refractory high-entropy alloys (RHEAs) and essentially controls the RHEAs properties. However, the disorder local chemical environments of RHEAs hinder the quantitative prediction of the stability and diffusivity of INSs and the understanding of the underlying mechanism. Based on the tight-binding models, we propose an analytic model for determining the stability and diffusivity of INSs in RHEAs, by approximating the bonding length between INSs and their neighbors with the atomic radius of the neighbors in elemental states. This predictive model identifies that the energetics of INSs depends linearly on the d-band width of their neighbors, with the slope determined by the valence of INSs. Our scheme provides an electronic-level understanding of INSs in RHEAs and explains key experimental observations, which can serve as an effective tool for designing advanced RHEAs.