On cooling rates dependence of microstructure and mechanical properties of refractory high-entropy alloys HfTaTiZr and HfNbTiZr

Structural stability of high entropy alloys (HEAs) at intermediate temperatures during which the config-urational entropy loses its dominance is crucial. In this work, we have scrutinized the effects of cooling rates on the phase stability of the HfTaTiZr(Ta1) and HfNbTiZr (Nb1) refractory HEAs (RHEAs). Ta1 ex-hibited strong microstructure and tensile property dependence on the cooling route, but not Nb1. Ta1 retained the BCC lattice under water quenching but experienced complex phase decomposition upon air and furnace cooling. The different dependence on cooling rates in these RHEAs arises from three main reasons: (i) the wider metastable temperature range in Ta1, (ii) the larger mobility difference between Ta and other constituents, and (iii) the larger electronegativity difference of Nb1. The current work not only sheds new insights into the understanding of the thermal and mechanical stability of HEAs but also provides a new paradigm for the optimization of their overall properties.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study extensively investigated the phase stability of high entropy alloys (HEAs) at intermediate temperatures and found that the effect of cooling rates on refractory HEAs depends on the alloy composition and material properties. This provides a new approach for optimizing the properties of HEAs.