Superhard bulk high-entropy carbides with enhanced toughness via metastable in-situ particles

• Published in: Nature communications Vol. 14; no. 1; p. 5717
• Main Authors: Hu, Jiaojiao, Yang, Qiankun, Zhu, Shuya, Zhang, Yong, Yan, Dingshun, Gan, Kefu, Li, Zhiming
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.09.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 147/135; 147/137; 639/166/988; 639/301/1023/1024; 639/301/1023/303; Carbides; Crack bridging; Crack tips; Entropy; Fracture toughness; Hardness; Humanities and Social Sciences; Mechanical loading; Metastable state; multidisciplinary; Science; Science (multidisciplinary); Solid solutions; Zirconium dioxide
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-41481-6

Despite the extremely high hardness of recently proposed high-entropy carbides (HECs), the low fracture toughness limits their applications in harsh mechanical environment. Here, we introduce a metastability engineering strategy to achieve superhard HECs with enhanced toughness via in-situ metastable particles. This is realized by developing a (WTaNbZrTi)C HEC showing a solid solution matrix with uniformly dispersed in-situ tetragonal and monoclinic ZrO 2 particles. Apart from a high hardness of 21.0 GPa, the HEC can obtain an enhanced fracture toughness of 5.89 MPa·m 1/2 , significantly exceeding the value predicted by rule of mixture and that of other reported HECs. The toughening effect is primarily attributed to the transformation of the metastable tetragonal ZrO 2 particles under mechanical loading, which promotes crack tip shielding mechanisms including crack deflection, crack bridging and crack branching. The work demonstrates the concept of using in-situ metastable particles for toughening bulk high-entropy ceramics by taking advantage of their compositional flexibility. High-entropy carbides (HECs) with high hardness usually suffer from low fracture toughness. Here, the authors demonstrate a metastability engineering strategy for toughening superhard HECs by introducing in situ metastable ceramic particles, which are transformable under mechanical loading.