Temperature-dependent mechanical and long crack behavior of zirconium diboride-silicon carbide composite

详细信息	查看全文 | 推荐本文 |

• 作者：Marc W. Bird^a ; Robert P. Aune^a ; Alfred F. Thomas^a ; Paul F. Becher^b ; Kenneth W. White^a ; ^{kwwhite@uh.edu}
• 关键词：Fracture ; Toughness ; Mechanical properties ; Composites ; Diborides ; UHTC
• 刊名：Journal of the European Ceramic Society
• 出版年：2012
• 期刊代码：53_09552219
• 类别：ms
• 出版时间：September, 2012
• 卷：32
• 期：12
• 页码：3453-3462
• 文件大小：2117 K

摘要

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 掳C. Long crack propagation studies were conducted up to 1400 掳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 掳C with no visible plastic deformation prior to fracture. Similar stiffness decreases were observed with a transition temperature range of 1100-1200 掳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 掳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 掳C with K_R rise from 0.1 to 0.5 MPa鈭歮. Beyond 1000 掳C fracture mechanism transitions to include creep zone development ahead of crack tip with wake zone toughening vanishing.