Abstract
Refractory high-entropy alloys are considered as potential structural materials for elevated temperature applications. To obtain refractory high-entropy alloys with high strength, different amounts of Si were added into the NbMoTiVW refractory high-entropy alloys. The effects of Si on the phase constitution, microstructure characteristics and mechanical properties of NbMoTiVWSix alloys were investigated. Results show that when the addition of Si is 0, 0.025 and 0.05 (molar ratio), the alloys are consisted of primary BCC and secondary BCC in the intergranular area. When the addition of Si is increased to 0.075 and 0.1, eutectic structure including silicide phase and secondary BCC phase is formed. The primary BCC phase shows dendritic morphology, and is refined by adding Si. The volume fraction of intergranular area is increased from 12.22% to 18.13% when the addition of Si increases from 0 to 0.1. The ultimate compressive strength of the NbMoTiVW alloy is improved from 2,242 MPa to 2,532 MPa. Its yield strength is also improved by the addition of Si, and the yield strength of NbMoTiVWSi0.1 reaches maximum of 2,298 MPa. However, the fracture strain of the alloy is decreased from 15.31% to 12.02%. The fracture mechanism of the alloys is changed from mixed fracture of ductile and quasi-cleavage to cleavage fracture with increasing of Si. The strengthening of alloys is attributed to the refinement of primary BCC phase, volume fraction increment of secondary BCC phase, and formation of eutectic structure by addition of Si.
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Acknowledgements
This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 52001114, 51825401), Cultivation Program for Outstanding Young Teacher in Henan Province (Grant Nos. 21420152, 2021GGJS064), Scientific Research Fund of State Key Laboratory of Materials Processing and Die & Mould Technology (Grant No. P2020-023), Program for Guangdong Introducing Innovative and Entrepreneurial Teams (Grant No. 2016ZT06G025), and the Project of Science and Technology in Henan Province (Grant No. 192102210011).
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Qin Xu Ph.D, Associated Professor and Master Supervisor, Vice Director of Department of Materials Forming and Controlling Engineering in Henan University of technology. She mainly engages in advanced material solidification theory and casting technology, including titanium aluminum alloys, niobium silicon alloys, and high entropy alloys. To date, she has published more than 60 technical papers and a book, authorized 8 patents of invention.
Qi Wang Born in 1987, Ph.D, Lecturer. His research interests mainly focus on the melting and solidification process of titanium-based alloys and Nb-Si based ultrahigh temperature alloys.
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Xu, Q., Wang, Q., Chen, Dz. et al. Microstructure characteristics and mechanical properties of NbMoTiVWSix refractory high-entropy alloys. China Foundry 19, 495–502 (2022). https://doi.org/10.1007/s41230-022-1206-z
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DOI: https://doi.org/10.1007/s41230-022-1206-z