Correlating Local Lattice Distortion with Dislocation Pinning in Refractory High-Entropy Alloys

Abstract: Local lattice distortion (LLD) of refractory high-entropy alloys (RHEAs) plays an essential role in mechanical properties and phase stability. However, the random distribution of multi-principal constituents of RHEAs inhibits the comprehension of LLD, although LLD is suggested to couple with chemical short-range-order (SRO). Herein, an analytical model is built to determine the site-to-site LLD of RHEAs by coupling the local lattice sites, the local size ordering in their environments and the global constituent information. By elucidating the size coupling between components, the model demonstrates that LLD exhibits a mechanism similar to the relaxation of metal surfaces. Moreover, it is found that LLD, rather than chemical SRO, serves as the origin of solid-solution strengthening and as a measure of the phase transformation in RHEAs. The scheme provides a comprehensive physical picture and offers a quantitative measurement of LLD at macro and micro scales, laying a foundation for the design of RHEAs.