Extraordinary toughening enhancement in nonstoichiometric vanadium carbide

• Published in: Journal of materials science & technology Vol. 97; pp. 176 - 181
• Main Authors: Peng, Chong, Tang, Hu, Geng, Changjian, Liang, Pengjie, Wan, Biao, Ke, Yujiao, Wang, Yuefeng, Jia, Peng, Peng, Wenfeng, Qiao, Lina, Li, Kenan, Yuan, Xiaohong, Zhao, Yucheng, Wang, Mingzhi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 20.01.2022
• Subjects: Amorphous bridging; Coherent interfaces; Nonstoichiometric; Self-toughening; Vanadium carbide; Self-toughening; Vanadium carbide; Amorphous bridging; Nonstoichiometric; Coherent interfaces
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2021.04.057

•VC1-x composites have a quasi-monophasic fcc structure with coherent precipitates.•A doubling of fracture toughness is obtained in VC1-x without any second phase.•VC1-x show an unadulterated transgranular fracture feature, leading to toughening.•Coherent toughening and amorphous bridging toughening make a prodigious toughening. Improving fracture toughness, which has gone through decades, is a long-standing topic and is particularly important for safety-critical applications. In refractory transition metal carbides (RTMCs), remarkable toughening is usually achieved by adding metallic binders, however, resulting in a drastic deterioration of hardness and thermal stability. Here, we report a novel self-toughening strategy for synthesizing high-toughness RTMCs. Using mechanical alloying (MA) and spark plasma sintering (SPS), we synthesized nonstoichiometric VC1-x (0.5 ≤ 1-x ≤ 0.6) with a quasi-monophasic microstructure containing a carbon-rich matrix and carbon-poor precipitates. Significantly, the VC0.5 sintered at 1400°C shows a good trade-off of high hardness of 20.5±0.5 GPa and fracture toughness of 7.1±0.2 MPa m1/2. The fracture toughness of VC0.5 increases by more than 100% accompanied by 7% hardness loss, compared with that of stoichiometric VC. The microstructure characterization and fracture behavior analysis demonstrate that the extraordinary toughening enhancement is attributed to a self-toughening strategy combined with coherency toughening and amorphous bridging toughening, which may offer an efficient pathway for developing high-performance structural ceramics. [Display omitted]