Criteria of predicting phase formation for MSi2-Type High-Entropy refractory metal silicides

MSi2-type high-entropy refractory metal silicides (HERMS) have excellent oxidation resistance at medium and high temperatures due to high entropy effect, which is a promising ultrahigh temperature structural material. HERMS have two phase structures, C11(b) and C40, due to allotropic transformation. Compared to C40, C11(b) has better fracture toughness, but it is now difficult to synthesize single-phase C11(b). The first-principle was used to systematically study phase formation ability of HERMS. Formation enthalpy (DHf), mixing enthalpy (Delta H-mix) and mixing enthalpy difference (delta(mix)) were calculated for 504 MSi2-type HERMS structures. delta(mix), VEC and Delta H-mix(C11b) were identified to characterize and predict phase stability of MSi2-type HERMS, in which dmix is a decisive factor, and has general applicability and important guiding significance for material systems with allotropic transformation. The generalized criteria of predicting phase formation for MSi2-type HERMS were proposed. C11b phase formation criterion is VEC > 4.58, delta(mix) < -0.05 eV/atom, Delta HCmix11b < -0.02 eV/atom. C40 phase formation criterion is VEC <= 4.58 and Delta HCmix11b > 0.09 eV/atom. Its accuracy was verified by experimental data to be 100%. This work is of great significance for composition design of HERMS and the further study of C11(b)-type HERMS. (c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The phase formation ability of MSi2-type HERMS was systematically studied, and criteria for predicting phase formation were proposed. The accuracy of the criteria was verified, highlighting their significance for composition design and further research of HERMS.