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I will discuss the resistance to ultrahigh-temperature deformation of boron, boron carbide, Ta0.2Hf0.8C, Zr-Ta multi-boride, tantalum monoboride, and tantalum diboride. The mechanism of ultra-high temperature flexure & strain-driven amorphization in polycrystalline B4C has been analyzed. With RT to 1800 °C mean strength of 650 MPa, boron carbide exhibits ultrahigh flexural strength far exceeding 1000 MPa, accompanied by a change in the deformation mechanism from brittle fracture to plastic at 2000 °C. Depending on the loading rate, B4C showed 1000 - 8400 MPa strength with a plastic stress-strain curve. Even deformation in an elastic manner at 25 mm/min resulted in a strength of 675 MPa, confirming its deformation resistivity. Zr-Ta multiboride ceramic was formed with an artificially created hierarchical superstructure via reaction-driven consolidation of ZrB2, Ta, and amorphous B powders. Due to the formation of the (Zr, Ta)B2 solid solution multiboride ceramic composite exhibited ultra-hardness of 28.6±3.2 GPa at 98 N and 22.6±0.6 GPa at 196 N, and the flexural strength 400 MPa up to 2000 °C [3]. Deformation-resistant Ta0.2Hf0.8C solid-solution ceramic with superior flexural strength at 2000°C showed toughness and a strength of 3.4 ± 0.4 MPa m1/2, 500 ± 20 MPa. The bending tests show that at 1800 °C and after, TaB's loading curves exhibited nonlinear characteristics associated with flaw healing or plasticity (micro-plasticity) contribution.

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Keyword: UHTC, Deformation-resistant carbides and borides , Hardness and toughness, Flexural Strength

Conference: The 38th International Japan-Korea Seminar on Ceramics (2024-10-31 - 2024-11-02)

Funding:

• NIMS AB3080 (多結晶光学材料 Research toward Innovative Optical Materials)

Manuscript type: Not a journal article

MDR DOI: https://doi.org/10.48505/nims.4983

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Updated at: 2024-11-21 16:35:57 +0900

Published on MDR: 2024-11-21 16:35:57 +0900