Strong solid solution strengthening caused by severe lattice distortion in body-centered cubic refractory high-entropy alloys

Atomic size misfit is one of the origins of solid-solution strengthening in alloys. In this study, we reported a strong solid-solution strengthening via tuning the atomic size misfit in the single-phase body-centered cubic TiZrVNb-based refractory high-entropy alloys (HEAs). The results suggest that the yield strength of the cast samples significantly increased from 680 MPa to 998 MPa with increasing the largest atomic radius Zr content. Among them, the Ti₃₅Zr₁₅V₂₅Nb₂₅ HEA exhibits the best combination of high yield strength of 918 MPa and ductility of 16 %. The solid-solution strengthening causes the 318 MPa strength increment as the atomic size misfit increases from 3.43 % to 4.95 %, where the contribution of atomic size misfit reaches 77 %. Strong solid-solution strengthening mainly originates from the enhanced lattice distortion acting as a strong barrier to dislocation motion, where the resultant high-density dislocations and the activated multiple slip systems lead to the outstanding strain-hardening capacity of the HEAs.