Coherent precipitation and stability of cuboidal nanoparticles in body-centered-cubic Al0.4Nb0.5Ta0.5TiZr0.8 refractory high entropy alloy

The present work developed a new body-centered-cubic (BCC)-based Al0.4Nb0.5Ta0.5TiZr0.8 refractory high entropy alloy with coherent precipitation. The formation of cuboidal nanoprecipitates with a size of 25-50 nm in an 873 K-aged alloy is ascribed to a moderate lattice misfit. A Zr5Al3 phase also coexists with B2 in a same particle shape due to similar chemical compositions, in which Ti is enriched in B2 but not in Zr5Al3. The BCC/B-2 coherency would be deteriorated with increasing the aging temperature, leaving coarse Zr5Al3 alone. Besides, there exist two kinds of BCC phases due to the segregations of Nb/Ta and Ti/Zr. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

A new body-centered-cubic (BCC)-based refractory high entropy alloy was developed, with coherent precipitation observed. Cuboidal nanoprecipitates were formed in an 873 K-aged alloy, with a moderate lattice misfit. The coexistence of B2 and Zr5Al3 phases was found, with deteriorated coherency observed at higher aging temperatures. Segregations of Nb/Ta and Ti/Zr led to the presence of two kinds of BCC phases.