ICME approach to explore equiatomic and non-equiatomic single phase BCC refractory high entropy alloys

摘要

High entropy alloys made from refractory metals, commonly known as refractory high entropy alloys (RHEAs) are potential candidates for high-temperature applications beyond the temperature regime (>1873 K) of conventional nickel based super alloys. In the present investigation, integrated computational materials engineering (ICME) framework consisting of detailed CALPHAD (CALculation of PHase Diagram) modeling and experimental investigation have been carried out to design both equiatomic and non-equiatomic RHEA composition exhibiting thermodynamically stable single-phase BCC/B2 solid solution. Starting with 126 equiatomic compositions, the CALPHAD calculations reveal only two equiatomic (MoNbTaVW and CrMoReVW) alloys having single phase BCC solid solution at 1000K. Further, low temperature (1000-400 K) CALPHAD assessment on 2902 non-equiatomic alloys reveal the formation of 54 single phase RHEAs based on MoNbTaVW at 400 K and 86 single phase RHEAs based on CrMoReVW at 800 K. In order to validate the CALPHAD predictions, one equiatomic, one non-equiatomic CrMoReVW alloy and six non-equiatomic MoNbTaVW alloys were synthesized and characterized using X-Ray diffraction, scanning electron microscopy and transmission electron microscopy. All of them show single phase solid solution with an excellent combination of microhardness (5.33-17.64 GPa) and elastic modulus (188-474 GPa) thus proving high fidelity of the CALPHAD approach in predicting phase stability of HEAs. To summarize, ICME approach involving CALPHAD modeling aids in accelerated design and development of existing RHEAs and discover new RHEAs showing potential for high-temperature applications. (C) 2019 Elsevier B.V. All rights reserved.