アルミナのき裂治癒挙動とき裂治癒材の強度特性

抄録

Three point bending specimen was made from commercial alumina and Al₂O₃/SiC composite ceramics. A semielliptical surface crack up to 500μm in diameter (aspect ratio≈0.9) was introduced on the test specimens. Basic crack-healing behavior was systematically studied as a function of crack-healing temperature, environment and crack size. Three point bending strength was measured at room temperature and elevated temperatures up to 1500°C. The crack-healing behavior of monolithic alumina was compared with that of Al₂O₃/SiC. Main conclusions obtained are as follows; (1) Bending strength of pre-cracked specimens of alumina recovered due to crack-healing. A surface crack of 100μm could be healed by the crack-healing above 1400°C for 1h. Difference of annealing environment had no significant effect on the crack-healing behavior of monolithic alumina above 1400°C. (2) The recovery of strength in monolithic alumina was caused by the sintering process or the removal of tensile residual stress near the pre-crack. Above 1400°C, the sintering mechanism is assumed to be dominant, however, below 1300°C, annealing mechanism is dominant. (3) The crack-healing of Al₂O₃/SiC occurs due to oxidation mainly, which is quite different from that of monolithic alumina. (4) The specimens which was crack-healed above 1400°C had similar bending strength to base material up to 1200°C.