熱膨張測定によるY₂O₃-PSZの変態挙動の研究

抄録

The behavior of tetragonal (t)-monoclinic (m) transformation in partially stabilized zirconia (PSZ) containing yttria from 0 to 6 mol% was investigated by means of dilatometry. The results are as follows:
(1) The transformation temperature (T₀^m−t) decreases lineally with increasing Y₂O₃ content. The present data almost coincide with the result by Ruh et al..
(2) By using the relationship between T₀^m−t and Y₂O₃ mol% as a conversion curve, the equilibrium concentration of t-phase in alloys annealed at 1600°C (1873 K), 1700°C (1973 K) and 1800°C (2073 K) was determined from their T₀^m−t, and it was found that the solubility limit of Y₂O₃ in t-phase increased with rising temperature.
(3) The as-annealed PSZ was composed of (t+c) phases, but the m\ ightleftharpoonst transformation took place more and more easily by cyclic heating. These transformations can proceed isothermally with release of the transformation-induced internal stress by the aid of slow speed cracking.
(4) The t\ ightharpoonupm transformation is suppressed by rapid cooling, but the m\ ightharpoonupt transformation is not much affected by the heating rate.