ZrO_2を含有したムライトの1200℃での疲労と破壊靱性値

概要

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The static and dynamic fatigues of 72 and 74 mass% Al_2O_3 mullite ceramics containing 10 vol% ZrO_2(72-10Z, 74A-10Z)were measured at 1200℃, and the fracture toughness was evaluated from the size of a slow crack growth(SCG)region. The crack growth parameters N obtained by the static fatigue technique were 15 for 72A-10Z and 37 for 74A-10Z. On the other hand, the N values obtained by the dynamic fatigue technique were 23 for 72A-10Z and 30 for 74A-10Z. Fracture toughness(K_<IC>), obtained by the controlled surface flaw(CSF)method after the static fatigue measurement, was 2.5 MPa・m^<1/2> for 72A-10Z or 1.6 MPa・m^<1/2> for 74A-10Z, and was negligibly affected by the addition of ZrO_2. The fracture toughness of 72A-10Z obtained after the dynamic fatigue measurement varied considerably with stressing rate. The fracture toughness obtained through static and dynamic fatigue measurements showed the rising R-curve behavior. Enhanced fracture toughness and R-curve behavior in 72A-10Z were attributed to the fracture of rodlike crystals and/or the viscoelastic flow of the glassy phase in the grain boundary.
1998-05-01