摘要
利用热膨胀方法,研究了冷却速度对热压烧结的ZrO2陶瓷(含2mol%Y2O3稳定剂)正方相(t)到单斜相(m)转变的影响.结果表明:冷却速度可以改变t-ZrO2相含量,这与t→m转变受热激活控制有关.随冷却速度增加相变开始Ms下降,结束点Mf上升.TEM观察表明m相的长大速度较钢铁中马氏体慢得多.电子束照射下诱发m相生长说明新相长大必须越过一个能垒.
The effeCt of cooling rate on transition from tetragonal (t) to monoclinic (m) structure in zirconia stabilized with Zmol% yttria is investigated by means of thermal expansion analysis and X-raydiffraction. Experimental results show that the volume fraction of t phase is greatly dependent on the coolingrate, the larger the cooling rate, the smaller the volume' fraction of t phase. The t→m transformation can be completely inhibited when the cooling rate of 100℃ / min is employed. Moreover, the transformation point of t→m and t→m is affected by cooling and heating rate, respectively . The starting point of t→m transformation (Ms) decreases with increasing cooling rate, the ending POint (Mf) increases with increasing colting rate.Both the starting point (As) and ending point (Af) of m→t transformation increases with increasing heating rate. The deviation between the thermal expansion data and X-ray diffraction is also analysed. Present results further demonstrate that the production of m phase in ZrO2 (2mol%Y2O2) is obviously time-dependent and associated with the process of thermal activation. The compound composed of oxygen vacancy and oxygen ion might be responsible for the short-range diffusion. In situ observation of the growing speed of m phase reveals that the growing speed is highly anisotropic, the growing speed along the transverse direction equals 0. 1μm / s and there exists an energy barrier for growth which should be overcomed. (Correspondent:ZHU Welzhong, Department of Metallic Science and Technology, Harbin Institute of Technology,Harbinl 50006)
出处
《材料研究学报》
EI
CAS
CSCD
1994年第1期56-60,共5页
Chinese Journal of Materials Research
关键词
冷却速度
氧化锆陶瓷
colling rate
t →m transformation
zirconia