Thermodynamic parameters, microstructure, and electrochemical properties of equiatomic TiMoVWCr and TiMoVNbZr high-entropy alloys prepared by vacuum arc remelting

Abstract

This study investigated the thermodynamic parameters, microstructures and electrochemical properties of TiMoVWCr and TiMoVNbZr bio-refractory high-entropy alloys (bio-RHEAs) prepared using the vacuum arc remelting process. The alloys were characterized using field emission scanning electron microscopy, field emission electron probe microanalyzer, X-ray diffraction analysis, and potentiodynamic polarization tests. The determined thermodynamic values of Ω-parameter, atomic size difference and valence electron concentration for the TiMoVWCr and TiMoVNbZr bio-RHEAs were within the range of solid solution formation. A high-temperature stable single BCC1 phase was obtained using the thermodynamic equilibrium calculations for the TiMoVWCr and TiMoVNbZr systems. The TiMoVWCr alloy microstructure comprised a dendrite, an inter-dendrite, and a second phase, while TiMoVNbZr alloy comprised a dendrite and an inter-dendrite. The TiMoVWCr alloy forming the stable single body-centered cubic solid solution demonstrated homogeneous microstructure and high phase stability. Moreover, pitting resistances of TiMoVWCr and TiMoVNbZr bio-RHEAs were remarkably superior to that of ASTM F75 alloy.