Stress increase by nanoscale hcp precipitates in HfNbTaTiZr high entropy alloys

HfNbTaTiZr high entropy alloys show a stress increase around 873 K, especially in the single crystals. At 873 K, the bcc single phase is decomposed into the bcc1 and bcc2 phases due to spinodal decomposition with composition modulation along 〈100〉 direction. The bcc1 phase has Zr- and Hf-rich composition, while Nb and Ta are enriched in the bcc2 phase. Next, the hcp phase is precipitated along the bcc1 phase. As a result, the hcp phase is aligned parallel to {100} plane of the bcc phase. The fine hcp phase acts as a strong barrier to the dislocation motion, resulting in the stress increase at 873 K.