Microstructure and dislocation arrangements in Sanicro 25 steel fatigued at ambient and elevated temperatures
Microstructure and dislocation arrangements in Sanicro 25 steel fatigued at ambient and elevated temperatures
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DOI：
10.1016/j.msea.2016.10.076
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发表时间：
2017-01-05
期刊：
影响因子：
6.4
通讯作者：
Kruml, T.
中科院分区：
文献类型：
--
作者：
Heczko, M.;Polak, J.;Kruml, T.
本文用透射电子显微镜（TEM）研究了高合金耐热Sanicro 25奥氏体钢在室温和700 ℃温度下，在宽应变幅范围内循环应变的显微组织和位错结构。位错的空间排列是使用定向箔技术确定的。确定了位错的特征和伯格斯矢量。结果发现，在室温下，位错滑移的强平面性占主导地位。循环塑性变形局部化为高位错密度的薄带，其结构不同于梯形排列。没有观察到明显的壁位错和沟道位错构型，但条带具有交替的位错富区和位错贫区的特征。显著的塑性应变局部化导致循环软化。在高温循环应变下，交叉滑移的增强导致位错密度的显著增加。与基体相干的纳米尺寸的物体被发现的同时，有证据表明钉扎位错。高位错密度、纳米团簇和滑移位错的均匀分布和相互作用是该材料在高温下异常循环硬化的原因。由于这种硬化，700摄氏度时的饱和循环应力非常高。
Microstructure and dislocation structures in high alloyed heat resistant Sanicro 25 austenitic steel cyclically strained in a wide interval of constant strain amplitudes both at room temperature and at temperature of 700 degrees C were studied by means of transmission electron.microscopy (TEM). The spatial arrangement of dislocations was determined using the technique of oriented foils. The character and the Burgers vectors of dislocations were determined. It was found that at room temperature strong planarity of dislocation slip prevails. Cyclic plastic deformation is localized into thin bands of high dislocation density which have different structure than ladder like arrangement. No distinctive wall and channel dislocation configurations were observed but bands have character of alternating dislocation rich and dislocation poor areas. Pronounced plastic strain localization leads to cyclic softening. In high temperature cyclic straining enhanced cross-slip leads to substantial increase of dislocation density. Objects of nanometer size coherent with the matrix were found simultaneously with the evidence indicating pinning of dislocations. The high dislocation density, its homogeneous distribution and interaction of nanoclusters and gliding dislocations are the cause of exceptional cyclic hardening of this material at high temperatures. Due to this hardening, the saturated cyclic stress at 700 degrees C is remarkably high.