抄録
The diffusionless cubic-to-tetragonal (c-t) transformation was examined in ZrO2-Y2O3 alloys prepared by arc-melting. The alloys with 3∼7 mol% Y2O3 rapidly-cooled from high-temperature cubic phase (c-ZrO2) region were of single tetragonal phase (t-ZrO2) at room temperature, while those containing 8 mol%Y2O3 were fully cubic. The two-phase structure consisting of t-ZrO2 and c-ZrO2 was not found in the rapidly-cooled alloys. The diffusionless c-t transformation accompanied two types of microstructures; the domain structure and the thin plate or lenticular microstructure. The former was initially developed by this transformation in the whole region of samples, and the latter was formed by subsequent cooling for accommodating the strain induced in t-ZrO2. The diffusionless c-t transformation took place above T0 temperature and was always completed. The nature of this transformation is different from that of martensitic transformation as has generally been accepted, and is of the second-order phase transformation.
