Lattice‐Distortion‐Enhanced Yield Strength in a Refractory High‐Entropy Alloy

Abstract Severe distortion is one of the four core effects in single‐phase high‐entropy alloys (HEAs) and contributes significantly to the yield strength. However, the connection between the atomic‐scale lattice distortion and macro‐scale mechanical properties through experimental verification has yet to be fully achieved, owing to two critical challenges: 1) the difficulty in the development of homogeneous single‐phase solid‐solution HEAs and 2) the ambiguity in describing the lattice distortion and related measurements and calculations. A single‐phase body‐centered‐cubic (BCC) refractory HEA, NbTaTiVZr, using thermodynamic modeling coupled with experimental verifications, is developed. Compared to the previously developed single‐phase NbTaTiV HEA, the NbTaTiVZr HEA shows a higher yield strength and comparable plasticity. The increase in yield strength is systematically and quantitatively studied in terms of lattice distortion using a theoretical model, first‐principles calculations, synchrotron X‐ray/neutron diffraction, atom‐probe tomography, and scanning transmission electron microscopy techniques. These results demonstrate that severe lattice distortion is a core factor for developing high strengths in refractory HEAs.