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

在油中凝聚法制备的500微米球形小样品上，研究了Y掺杂氧化锆的马氏体相变动力学。主要研究结果如下：1.通过快速冷却和加热处理，研究了球状小试件的相变动力学。快速淬火导致含有少量氧化钛的氧化锆在室温下形成高度亚稳的四方相，在块体样品的通常冷却速度下通常会发生转变。这一事实表明，马氏体相变涉及一个热激活过程。在中温条件下，亚稳t相发生等温转变。动力学曲线为C曲线，上限为450ﾟC，鼻端温度为350ﾟC.3。亚稳t相在零下冷却过程中经历了一次猝发转变。MS温度位于-118-6ﾟC.4。通过以上观察，证实了亚稳t相在不同的热处理条件下都经历了等温和非等温转变。这种现象不能用现有的马氏体形核理论来解释。

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.