Brittle-to-ductile transition and high-temperature deformation in ZrO2(Y2O3) and Al2O3 ceramics as evaluated by small punch test

Abstract

Temperature dependence of fracture behavior in two representative oxide ceramics, 3 mol%Y2O3-partially stabilized ZrO2 and pure Al2O3, was investigated to explore the high-temperature deformation mechanisms associated with ceramic superplasticity. Both the zirconia and alumina ceramics were found to show apparent brittle to ductile transitions. The transition temperatures (BDTT) were determined by means of the Small Punch (SP) test. Linear relationships were obtained between the BDTT and the logarithmic deforming rate in both ceramics. The high-temperature deformation mechanisms were discussed on the basis of the relationship between BDTT and deforming rate, and they were found to be intrinsically the same both in the present zirconia and alumina ceramics. Superplasticity can be easily achieved in tetragonal zirconia ceramics mainly because of the stability of the fine-grained microstructures. High ductility and even superplasticity can be achieved also in alumina, provided that its grain growth can be suppressed during deformation at high temperature.