首页|On phase stability of Mo-Nb-Ta-W refractory high entropy alloys

On phase stability of Mo-Nb-Ta-W refractory high entropy alloys

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  • NSTL
  • Elsevier
Refractory high entropy alloys (RHEAs) emerge as promising candidate materials for ultrahigh-temperature applications. Accurate phase stability is the prerequisite for design of high-performance RHEAs, but still missing in the literature due to the big challenge in experiments. In this paper, the reliable 3rd-generation Gibbs energy expressions for pure Mo, Nb, Ta and W were firstly evaluated by integrating the physical based Segmented Regression model with thermal vacancy description from 0 K to high temperatures. The thermodynamic database of the Mo-Nb-Ta-W quaternary system was then developed by combining the established 3rdgeneration Gibbs energies with the phase equilibrium and thermodynamic data by using the CALPHAD (CALculation of PHAse Diagram) approach. The calculated phase equilibria, thermodynamic properties as well as the A2/B2 ordering transition behaviors show good agreement with those from experimental determination and theoretical calculation. The phase constitutes and elemental distributions in an equiatomic MoNbTaW as-cast alloy were experimentally investigated and compared with the non-equilibrium solidification simulations to further verify the database reliability. The high-throughput mapping of phase stability within the compositiontemperature space in various Mo-Nb-Ta-W alloys was then constructed by applying thermodynamic calculations. The alloying effects on the formation of B2 phase were systematically analyzed. The Mo-Nb-Ta-W alloys have a wide temperature region with a single A2 phase, while the A2 + B2 phase regions exist at very low temperatures. It is highly anticipated that the present accurate 3rd-generation thermodynamic database provides an important basis for efficient design and development of novel Mo-Nb-Ta-W RHEAs.

Mo-Nb-Ta-W RHEAsPhase stability3rd-generation thermodynamic descriptionsA2B2 phase transitionNon-equilibrium solidificationTHERMODYNAMIC PROPERTIESSOLID-SOLUTIONMECHANICAL-PROPERTIES0 KVACANCY FORMATIONHEAT-CAPACITYLIQUIDMICROSTRUCTURETRANSITIONPREDICTION

Zhang, Enkuan、Tang, Ying、Wen, Mingwen、Obaied, Abdulmonem、Roslyakova, Irina、Zhang, Lijun

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Hebei Univ Technol

Ruhr Univ Bochum

Cent South Univ

2022

10.1016/j.ijrmhm.2022.105780

International Journal of Refractory Metals & Hard Materials

International Journal of Refractory Metals & Hard Materials

SCI
ISSN：0263-4368
年,卷(期)：2022.103
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