AUTHOR=Jia Yuefei , Zhang Liangbo , Li Peiyou , Ma Xindi , Xu Long , Wu Shiwei , Jia Yandong , Wang Gang 

TITLE=Microstructure and Mechanical Properties of Nb–Ti–V–Zr Refractory Medium-Entropy Alloys

JOURNAL=Frontiers in Materials

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.00172

DOI=10.3389/fmats.2020.00172

ISSN=2296-8016

ABSTRACT=<p>Low-density refractory medium entropy alloys (NbTiVZr, Nb<sub>0.</sub>5TiVZr, and NbTiV) were produced by vacuum arc melting, then heat-treated at 1,200°C for 1 h, water quenched, and finally annealed at 500°C for 0.5 h. Their respective microstructures, elevated-temperature (600–1,000°C) mechanical properties, and thermal expansion behavior were then investigated. All the alloys are characterized by a BCC structure with a grain size of c. 85–135 μm. The results demonstrated that NbTiVZr alloy exhibits relatively high yield strength and specific strength at 600, 800, and 1,000°C. Moreover, a low coefficient of thermal expansion was also obtained for this alloy when the temperature was below 750°C. This study provides guidance for the engineering application of low-density refractory medium entropy alloys at elevated temperatures.</p>