Xu Haiyue, Ji Wei, Guo Weiming, Li Yulin, Zou Ji, Wang Weimin, Fu Zhengyi
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, China.
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou, 510006, China.
Adv Sci (Weinh). 2022 Feb;9(6):e2104532. doi: 10.1002/advs.202104532. Epub 2022 Jan 2.
Zirconium diboride (ZrB ) is considered as one of the most promising ultra-high temperature materials for the applications in extreme environments. However, the difficulty in fabrication of ZrB limits its industrial applications. In this study, fully dense and grain-refined ZrB is prepared under ultra-high pressure of 15 GPa at low temperature of 1450 °C. The as-prepared ZrB exhibits excellent mechanical and oxidation-resistant properties. Compared with raw powder, the grain size decreases 56%. Compared with high-temperature sintered control specimen beyond 2000 °C, the hardness and fracture toughness increase about 46% and 69%, respectively, the dislocation density increase 3 orders of magnitude, while the grain size considerably decrease 96%. According to work hardening, Hall-Petch and Taylor dislocation hardening effects, the refined grains, substructures, and high dislocation density caused by plastic deformation during sintering can enhance the mechanical properties. The unique structure contributes to a threshold oxidation temperature increase of ≈250 °C relative to the high-temperature sintered ZrB , achieving one of the highest values (1100 °C) among the reported monolithic ultra-high temperature ceramics. A developed densification mechanism of dislocation multiplication with grain refining is proposed and proved to dominate the sintering, which is responsible for simultaneous improvements in mechanical and oxidation-resistant properties.
二硼化锆（ZrB₂）被认为是在极端环境应用中最具前景的超高温材料之一。然而，ZrB₂的制备困难限制了其工业应用。在本研究中，在1450℃的低温和15 GPa的超高压下制备出了完全致密且晶粒细化的ZrB₂。所制备的ZrB₂表现出优异的力学性能和抗氧化性能。与原始粉末相比，晶粒尺寸减小了56%。与在2000℃以上高温烧结的对照样品相比，硬度和断裂韧性分别提高了约46%和69%，位错密度增加了3个数量级，而晶粒尺寸大幅减小了96%。根据加工硬化、霍尔 - 佩奇和泰勒位错硬化效应，烧结过程中塑性变形引起的细化晶粒、亚结构和高位错密度可提高力学性能。这种独特的结构使氧化阈值温度相对于高温烧结的ZrB₂提高了约250℃，达到了所报道的单相超高温陶瓷中的最高值之一（1100℃）。提出并证明了一种位错增殖与晶粒细化相结合的致密化机制主导了烧结过程，这是力学性能和抗氧化性能同时提高的原因。
