锆－4合金高温疲劳断口分形特征二次电子线扫描法研究

Study of Fractal Characteristics of Fatigued Fracture Surfaces at Elevated Temperature in Zircaloy-4 by Secondary Electron Line Scanning

采用二次电子线扫描法研究了锆－４合金ＲＴ、４００℃和６００℃下疲劳断口分形特征，指出锆－４合金疲劳断口是一种与晶粒尺寸相当的材料组织层次上的分形结构；随着断口分形维数的增大，相应的疲劳寿命单调递增。认为相同循环塑性应变幅下，随着试验温度升高，疲劳过程中蠕变作用加强，断口表面蠕变空洞和二次裂纹数量明显增加，断口表面粗糙度增加是疲劳断口分形维数增大的原因。

ractal characteristies of fracture surfaces in Zircaloy-4 specimens fatigued at RT. 400℃ and 600℃ have been investigated by means of secondary electron line scanning. It is believed that the range of validity of fractals for Zircaloy-4 is associated with prominent fractographic features. i.e. with the grain size. The linear relationship of fractal dimension and fatigue lifetime is established. An explanation is given why the fractal dimension increases as the test temperature increasing for Zircaloy-4 at the same cyclic plastic strain amplitude.