J. Mater. Sci. Technol. ›› 2022, Vol. 121: 181-189.DOI: 10.1016/j.jmst.2021.12.063

• Research Article • Previous Articles     Next Articles

Regulating the formation ability and mechanical properties of high-entropy transition metal carbides by carbon stoichiometry

Juntao Songa,b, Guiqing Chena, Huimin Xiangb, Fuzhi Daib, Shun Donga, Wenbo Hana,*(), Xinghong Zhanga, Yanchun Zhoub,*()   

  1. aScience and Technology on Advanced Composite in Special Environments Laboratory, Harbin Institute of Technology, Harbin, 150080, China
    bScience and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology, Beijing, 100076, China
  • Received:2021-11-16 Revised:2021-12-22 Accepted:2021-12-23 Published:2022-09-10 Online:2022-03-17
  • Contact: Wenbo Han,Yanchun Zhou
  • About author:yczhou@alum.imr.ac.cn (Y. Zhou).
    *E-mail addresses: wbhan@hit.edu.cn (W. Han),

Abstract:

Tremendous efforts have been dedicated to promote the formation ability of high-entropy transition metal carbides. However, the majority of methods for the synthesis of high-entropy transition metal carbides still face the challenges of high temperature, low efficiency, additional longtime post-treatment and uncontrollable properties. To cope with these challenges, high-entropy transition metal carbides with regulatable carbon stoichiometry (HE TMCx) were designed and synthesized, achieving improved ability for single phase solid solutions formation, promoting of sintering and controllable mechanical properties. Two typical composition series, i.e., easily synthesized (Zr0.25Hf0.25Ta0.25Nb0.25)C (ZHTNC) and difficultly synthesized (Zr0.25Hf0.25Ta0.25Ti0.25)C (ZHTTC) are selected to demonstrate the promoting formation ability of single phase solid solutions from carbon stoichiometry deviations. Single phase high-entropy ZHTTC, which has been proven difficult in forming a single phase solid solution, can be prepared with the decrease of C/TM ratio under 2000 °C; while the high-entropy ZHTNC, which has been proven easy in forming a single phase solid solution, can be synthesized at lower temperatures with the decrease of C/TM ratio. The synergistic effect of entropy stabilization and reduced chemical bond strength gaining from carbon stoichiometry deviations is responsible for the formation of single phase solid solutions and the promoted sintering of HE TMCx. For example, the relative density of bulk (Zr0.25Hf0.25Ta0.25Nb0.25)Cx (SPS-ZHTNCx) increases from 90.98% to 94.25% with decreasing the C/TM atomic ratio from 0.9 to 0.74. More importantly, the room temperature flexural strength, fracture toughness and brittleness index of SPS-ZHTNCx can be tuned in the range of 384 MPa-419 MPa, 4.41 MPa⋅m1/2-4.73 MPa⋅m1/2 and 3.679 μm-1/2-4.083 μm-1/2, respectively. Thus, the HE TMCx prepared by adjusting the ratio of carbon to refractory transition metal oxides have great potential for achieving low temperature synthesis, promoted sintering and tunable properties.

Key words: Carbon stoichiometry, High-entropy ceramics, Transition metal carbide, Low temperature synthesis, Tunable mechanical properties