Synergic grain boundary segregation and precipitation in W- and W-Mo-containing high-entropy borides

• Published in: Journal of the European Ceramic Society Vol. 41; no. 10; pp. 5380 - 5387
• Main Authors: Wang, Chunyang, Qin, Mingde, Lei, Tianjiao, He, Yubin, Kisslinger, Kim, Rupert, Timothy J., Luo, Jian, Xin, Huolin L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01-08-2021; Elsevier
• Subjects: Grain boundary; High-entropy borides; High-entropy ceramics; NANOSCIENCE AND NANOTECHNOLOGY; Precipitation; Segregation; High-entropy borides; High-entropy ceramics; Precipitation; Segregation; Grain boundary
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2021.04.004

The structures of W- and W-Mo-containing high-entropy borides (HEBs) are systematically studied by combining atomic-resolution transmission electron microscopy imaging, electron diffraction, and chemical analysis. We reveal that W or W-Mo addition in HEBs leads to segregation of these elements to the grain boundaries (GBs). In the meantime, W- or W-Mo-rich precipitates also form along the GBs. Crystallographic analysis and atomic-scale imaging show that the GB precipitates in both W- and W-Mo-containing HEBs have a cube-on-cube orientation relationship with the matrix. With further strain analysis, the coherency of the precipitate/matrix interface is validated. Nanoindentation tests show that the simultaneous GB segregation and coherent precipitation, as a supplement to the grain hardening, provide additional hardening of the HEBs. Our work provides an in-depth understanding of the GB segregation and precipitation behaviors of HEBs. It suggests that GB engineering could be potentially used for optimizing the performance of high-entropy ceramics.