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Temperature-dependent mechanical and long crack behavior of zirconium diboride–silicon carbide composite |
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| Authors: | Marc W Bird Robert P Aune Alfred F Thomas Paul F Becher Kenneth W White |
| Affiliation: | 1. Department of Mechanical Engineering, University of Houston, Houston, TX, USA;2. Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, USA;1. Uniformed Services University of the Health Sciences, Bethesda, MD, USA;2. Malaria Research Unit, South African Medical Research Council, Durban, South Africa;3. Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa;4. Malaria Vector Control Specialist, Nelspruit, Mpumalanga, South Africa;5. Africa Fighting Malaria, Washington, DC, USA;6. Africa Fighting Malaria, Durban, South Africa;7. University of Ottawa, Faculty of Law and Medicine, Ottawa, Ontario, Canada;8. National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa;1. Surmet Ceramics Corporation, Buffalo, NY 14207, USA;2. The LNM Institute of Information Technology, Jaipur 302031, India;3. School of Chemical and Biotechnology, Sastra University, Thanjavur 613401, India;4. College of Engineering and Mines, University of Alaska Fairbanks, AK 99775, USA;1. Politecnico di Torino, Department of Applied Science and Technology, INSTM RU PoliTO, LINCE Lab, Corso Duca degli Abruzzi 24, 10129 Torino, Italy;2. Department of Materials Science and Engineering, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA |
| Abstract: | Hot pressed ZrB2–20 vol.% SiC ultra-high temperature ceramic composites have been prepared for strength and fracture investigations. Two composites fabricated under differing hot pressing temperatures with (ZSB) and without (ZS) B4C sintering aids were selected for room temperature modulus of rupture (MOR) strength and single-edge-notch bend (SENB) fracture toughness experiments. Structure property relationships were examined for both composites. MOR and stiffness temperature dependence was also investigated up to 1500 °C. Long crack propagation studies were conducted up to 1400 °C using the double cantilevered beam geometry with half-chevron-notch initiation zones. Residual Boron-rich carbide maximum particle sizes were found to be strength limiting in ZSB billets while SiC controlled strength in ZS billets. Flexure strength decreased linearly with temperature from 1000 to 1500 °C with no visible plastic deformation prior to fracture. Similar stiffness decreases were observed with a transition temperature range of 1100–1200 °C. Long crack studies produced R-curves that show no significant toughening behavior at room temperature with some modest rising R-curve behavior appearing at higher temperatures. These studies also show the plateau toughness increases with temperature up to 1200 °C. This is supported by an observed transition from primarily transgranular fracture at room temperature to primarily intergranular fracture at high temperatures. Wake zone toughening is evident up to 1000 °C with KR rise from 0.1 to 0.5 MPa√m. Beyond 1000 °C fracture mechanism transitions to include creep zone development ahead of crack tip with wake zone toughening vanishing. |
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