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

Abstract 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/B2 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.