Microstructural stability and aging behavior of refractory high entropy alloys at intermediate temperatures

Several body-centered-cubic (BCC) refractory high entropy alloys (HEAs), i.e., HfNbTaTiZr, NbTaTiZr, HfNbTiZr and NbTiZr, were annealed at intermediate temperatures for 100 h, and their microstructures and aging behaviors were studied in detail. All these HEAs start to decompose into multiple phases at around 500 degrees C, but reenter the single-phase region at significantly different temperatures which were determined to be 90 0, 10 0 0, 110 0 and above 1300 degrees C for HfNbTiZr, NbTiZr, HfNbTaTiZr and NbTaTiZr, respectively. Our analysis indicates that the onset decomposition temperature in these four HEAs is closely related to the elemental diffusion rates while the ending decomposition temperature is strongly dependent on the elemental melting points. Our findings are important not only for understanding phase stability of HEAs in general, but also for adjusting processing parameters to optimize mechanical properties of these HEAs. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study examined the microstructures and aging behaviors of several refractory high entropy alloys annealed at intermediate temperatures. The alloys exhibited decomposition into multiple phases at around 500 degrees C, but reentered the single-phase region at different temperatures. The onset decomposition temperature was found to be influenced by the elemental diffusion rates, while the ending decomposition temperature was strongly dependent on the elemental melting points.