Ce—TZP材料的相变增韧

Transformation Toughening in Ce—TZP

本文对Ce—TZP增韧陶瓷材料的相变和断裂行为进行了研究.发现在无外力作用下,尺寸为7.7μm的四方相ZrO_2晶粒在室温下能全部保留.在Ce—TZP材料断裂面没有发现单斜相的ZrO_2存在、但在Ce—TZP材料的微粉中发现有大量的单斜相ZrO_2存在.并且发现随着Ce—TZP材料晶粒的增大,材料的韧性和抗弯强度相应增大,并有极大值.由内耗和DSC的观察分析发现:Ce—TZP材料的四方相ZrO_2到单斜相ZrO_2的转变是可逆的,是典型的马氏体转变.相变内耗峰的温度分别为203K(正转变)和243K(逆转变).转变有明显的滞后现象,并且对应于内耗峰的附近有频率的极小值.即样品模量的软化现象.从而我们认为:Ce—TZP材料的增韧是裂纹尖端应力诱导四方相ZrO_2到单斜相ZrO_2转变的结果,但当裂纹过后裂纹面上又发生了逆转变.Ce—TZP材料的相变机理可能是外力感生界面上位错的运动而引起的.

In this paper, the fracture and transformation behavior of Ce-TZP was investigated. In the absence of applied stress, the tetragonal phase was found to be stable in large-grained (<7.7μm)samples at room temperature. The monoclinic phase was not detected in fracture surface of Ce-TZP, but was discovered in fine powder. There was maximum of fracture toughening and bend strength as the grain size increased. From internal friction and DSC, we discovered the phase transformation of Ce-TZP is reversible. The temperature of internal friction peaks were 203K(T→M) and 243K(M→ T) respectively. There were hysteresis and damping models in this phase transformation. By the result we concluded that the high toughness of this material was due to the occurrence of stress-driven tetragonal-to-monoclinic transformation near the crack tip, which reversed when crack had passed, and the mechanism of phase transfonnation of Ce-TZP was due to vibration of strings of dislocation in phase surface.