Ultra-High Temperature Mechanical Properties of a Zirconium Diboride-Zirconium Carbide Ceramic


The mechanical properties of a ZrB2-10 vol% ZrC ceramic were measured up to 2300⁰C in an argon atmosphere. Dense billets of ZrB2-9.5 vol% ZrC-0.1 vol% C were produced by hot-pressing at 1900⁰C. The ZrB2 grain size was 4.9 um and ZrC cluster size was 1.8 um. Flexure strength was 695 MPa at ambient, decreasing to 300 MPa at 1600⁰C, increasing to 345 MPa at 1800⁰C and 2000⁰C, and then decreasing to 290 MPa at 2200⁰C and 2300⁰C. Fracture toughness was 4.8 MPa-m 1/2 at room temperature, decreasing to 3.4 MPa-m 1/2 at 1400⁰C, increasing to 4.5 MPa-m 1/2 at 1800⁰C, and decreasing to 3.6 MPa-m 1/2 at 2300⁰C. Elastic modulus calculated from the crosshead displacement was estimated to be 505 GPa at ambient, relatively unchanging to 1200⁰C, then decreasing linearly to 385 GPa at 1600⁰C, more slowly to 345 GPa at 2000⁰C, and then more rapidly to 260 GPa at 2300⁰C. Surface flaws resulting from machining damage were the critical flaw up to 1400⁰C. Above 1400⁰C, plasticity reduced the stress at the crack tip and the surface flaws experienced subcritical crack growth. Above 2000⁰C, microvoid coalescence ahead of the crack tip caused failure.


Materials Science and Engineering

Keywords and Phrases

Carbides; Ceramic materials; Crack propagation; Crack tips; Cracks; Fracture toughness; Hot pressing; Mechanical properties; Argon atmospheres; Critical flaw; Flexure strength; Machining damage; Subcritical crack growth; Ultrahigh temperature; Zirconium carbide; Zirconium diboride; Zirconium compounds

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Article - Journal

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