High-temperature mechanical properties of medium-entropy carbide ceramics have attracted significant attention.Tailoring the microstructure is an effective way to improve these high-temperature mechanical properties,which can be affected by the evolution of the enthalpy and entropy,as well as by lattice distortion and sluggish diffusion.In this study,the effects of equiatomic Zr/(Ti,Nb)substitution(Zr content of 10-40 at％)on the microstructure and high-temperature strength of(Ti,Zr,Nb)C medium-entropy ceramics were investigated.The grain size of the(Ti,Zr,Nb)C medium-entropy ceramics was refined from 9.4±3.7 to 1.1±0.4 μm with an increase in the Zr content from 10.0 to 33.3 at％.A further increase in the Zr content to 40 at％resulted in a slight increase in the grain size.At 1900℃,the(Ti,Zr,Nb)C medium-entropy ceramics with the Zr contents of 33.3 and 40 at％exhibited ultra-high flexural strengths of 875±43 and 843±71 MPa,respectively,which were higher than those of the transition metal carbides previously reported under similar conditions.Furthermore,relatively smooth grain boundaries,which were detected at a test temperature of 1000℃,transformed into curved and serrated boundaries as the temperature increased to 1900℃,which may be considered the primary reason for the improved high-temperature flexural strength.The associated mechanism was analyzed and discussed in detail.

Qingqing YANG;Xingang WANG;Weichao BAO;Ping WU;Xiaofei WANG;Xiaojie GUO;Cheng ZHANG;Guojun ZHANG;Danyu JLANG

State Key Laboratory of High Performance Ceramics and Superfine Microstructure,Shanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai 200050,China;School of Materials Science and Engineering,Shanghai Institute of Technology,Shanghai 201418,China;Institute of Functional Materials,Donghua University,Shanghai 201620,China

先进陶瓷（英文版）

[1]Qingqing YANG;Xingang WANG;Weichao BAO;Ping WU;Xiaofei WANG;Xiaojie GUO;Cheng ZHANG;Guojun ZHANG;Danyu JLANG-.Influence of equiatomic Zr/(Ti,Nb)substitution on microstructure and ultra-high strength of(Ti,Zr,Nb)C medium-entropy ceramics at 1900℃)[J].先进陶瓷（英文版）,2022(09):1457-1465

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