Alloy Design and Properties Optimization of High-Entropy Alloys
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This article reviews the recent work on the high-entropy alloys (HEAs) in our group and others. HEAs usually contain five or more elements, and thus, the phase diagram of HEAs is often not available to be used to design the alloys. We have proposed that the parameters of δ and Ω can be used to predict the phase formation of HEAs, namely Ω ≥ 1.1 and δ ≤ 6.6%, which are required to form solid-solution phases. To test this criterion, alloys of TiZrNbMoV x and CoCrFeNiAlNb x were prepared. Their microstructures mainly consist of simple body-centered cubic solid solutions at low Nb contents. TiZrNbMoV x alloys possess excellent mechanical properties. Bridgman solidification was also used to control the microstructure of the CoCrFeNiAl alloy, and its plasticity was improved to be about 30%. To our surprise, the CoCrFeNiAl HEAs exhibit no apparent ductile-to-brittle transition even when the temperatures are lowered from 298 K to 77 K.
KeywordsLave Phase Withdrawal Velocity Copper Mold Casting Bridgman Solidification Hypereutectic Structure
The authors acknowledge the financial support by the Natural Science Foundation of China (No. 50971019). P.K.L. appreciates the support from the U.S. National Science Foundation (grants DMR-0909037, CMMI-0900271, and CMMI-1100080) and Grant NEUP 119262 from the Department of Energy.
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