Abstract
In this study, a type of high-entropy boride (HEB) ceramics ((Ti0.2Zr0.2Nba0.2Hfa0.2Taa0.2)B2) with ∼2vol% oxides and ∼1 vol% porosity was successfully consolidated by spark plasma sintering at 2000°C under a uniaxial load of 50 MPa for 10 min, using self-synthesized high entropy diboride powders from a boro/carbothermal reduction approach. The residual oxides were determined to be m-(Hf,Zr)O2, which were incorporated with minor amounts of boron and carbon. Elastic modulus, Vickers hardness and fracture toughness of HEBs at room temperature were 508.5 GPa, 17.7 ± 0.4 GPa and 4.2 ± 0.2 MPa m1/2, respectively. The as-obtained ceramics possessed excellent flexural strength, particularly at high temperatures. The four-point flexural strengths of HEBs at room temperature, 1600, and 1800°C are 400.4 ± 47.0, 695.9 ± 55.9, and 751.6 ± 23.2 MPa, respectively. Postmortem analysis was conducted on HEB fractured at 1800°C, in the region near their tensile and fracture surfaces, and microstructure observations show that limited dislocation lines were present adjacent to the crack front and edge of the pore, without noticing any trace for dislocation motions. It is the first report on the high-temperature strength of high-entropy diboride ceramics and the strengthening mechanism at high temperatures was also discussed.
摘要
以硼热/碳热还原合成高熵二硼化物粉体为原料, 在2000°C/单轴 加压50 MPa条件下, 经10分钟放电等离子烧结, 成功制备了含有 ∼2 vol%的氧化物和∼1 vol%气孔的高熵(Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)B2陶瓷 (HEBs). 经研究确认, 其中残留氧化物是固溶少量硼和碳的m-(Hf,Zr)O2. 室温下HEBs的弹性模量、维氏硬度和断裂韧性分别为 508.5 GPa、17.7 ± 0.4 GPa和4.2 ± 0.2 MPa m1/2. 烧结得到的HEBs具有 优良的抗弯强度, 特别是其高温强度. HEBs在室温、1600和1800°C下 的四点抗折强度分别为400.4 ± 47.0 MPa、695.9 ± 55.9 MPa和751.6 ± 23.2 MPa. 对1800°C下断裂的HEBs样品进行了失效分析, 在其拉伸和断 裂面附近区域, 仅在裂纹尖端和孔隙边缘发现了数量有限的位错线的 存在, 没有观察到位错运动的痕迹. 本研究首次报道了高熵二硼化物陶 瓷的高温强度, 发现其强度直至1800°C并无衰减, 并对其高温下的强韧 化机制进行了有益的探讨.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (52022072, 51972243, 92060202 and 52202067), the National Key R&D Programs (2021YFB3701400), Hubei Provincial Natural Science Foundation of China (Distinguished Young Scholars 2022CFA042), Independent Innovation Projects of Hubei Longzhong Laboratory (2022ZZ-10), and the Research Fund for Central Universities (2020IVB074 and 2021IVA094). The authors appreciate Dr. Junfeng Gu and Dr. Haiyue Xu for their help with sample preparations.
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All authors participated in the discussion of the results. Zou J conceived the idea of this work. Liu J, Yang QQ and Zou J performed the main experiments. Fu ZY and Wang WM provided resources and helped construct the framework of the manuscript. Yang QQ and Wang XG measured the high-temperature strength. Liu J and Zou J wrote the paper, which was revised by Wang WM and Fu ZY.
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Jie Liu is currently a Master’s student at the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology. Her research focuses on the strengthening mechanisms and properties of high-entropy diboride ceramics.
Qing-Qing Yang is currently a research assistant at the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology. Her research focuses on the microstructure control and ultra-high temperature mechanical properties of high-entropy ceramics.
Ji Zou is a professor at Wuhan University of Technology. He received his PhD degree from Shanghai Institute of Ceramics, Chinese Academy of Sciences. He has been active in the processing-structure-property correlation of ceramics and composites, especially for borides.
Xin-Gang Wang is a senior engineer at Shanghai institute of Ceramics, Chinese Academic of Sciences. He graduated from the same institute and worked from there since then. His current research interests include ceramics for extreme environments and the mechanical performances for coatings and fibers.
Zheng-Yi Fu is a chief professor and an academician of Chinese Academy of Engineering at the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology. He received his PhD degree from Wuhan University of Technology in 1994. His current research interests include advanced ceramics, composites and their bioprocess-in-spired fabrication.
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Liu, J., Yang, QQ., Zou, J. et al. Strong high-entropy diboride ceramics with oxide impurities at 1800°C. Sci. China Mater. 66, 2061–2070 (2023). https://doi.org/10.1007/s40843-022-2287-7
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DOI: https://doi.org/10.1007/s40843-022-2287-7