Kinetic Measurement of the Martensitic Transformation in Y-TZP Samll Particles

采用油中团聚法制备了500 μ m的球形小试样，研究了氧化钇掺杂氧化锆的马氏体相变动力学。主要研究结果如下：1。小的球形试样允许通过快速冷却和加热处理来研究转变动力学。快速淬火导致含有少量氧化钇的氧化锆在室温下形成一个高度亚稳的四方相，而氧化锆在通常的冷却速率下会发生转变。这表明马氏体相变是一个热活化过程。在中等温度下，亚稳t相发生等温转变。在TTT图上用C曲线描述其动力学，其上限为450ºC，下限为350ºC。亚稳t相在亚零度冷却过程中发生突变。Ms温度位于-1 - 18+-6 - <s:1> C.4。从上述观察可以证实，亚稳t相根据热处理的不同，既经历等温转变，也经历非热转变。现有的马氏体成核理论无法解释这种现象。

Kinetics of the martensitic transformation of yttria doped zirconia was studied on small spherical specimens of 500 mum size prepared by the agglomeration method in oil. The main results obtained are as follows :1. Small spherical specimens allowed to study the transformation kinetics by rapid cooling and heating treatments. Rapid quenching resulted in a highly metastable tetragonal phase at room temperature for the zirconia containing small amount of yttria which normally transform during the usual cooling rate for a bulk specimen. The fact suggested that the martensitic transformation involves a thermally activated process.2. The metastable t-phase underwent isothermal transformation when held at an intermediate temperature. The kinetics was described by a C-curve in the TTT diagram with an upper limit at 450ﾟC and a nose at 350ﾟC.3. The metastable t-phase undergoes a burst transformation during subzero-cooling. The Ms temperature was located at-1 18+-6ﾟC.4. From the above observation, it was verified that the metastable t-phase undergoes both isothermal and athermal transformations depending on the heat treatment. Such phenomenon cannot be explained by the existing theories of the nucleation of martensite.