Mueller Inga, Rementeria Rosalia, Caballero Francisca G, Kuntz Matthias, Sourmail Thomas, Kerscher Eberhard
Department of Mechanical and Process Engineering Materials Testing (AWP), University of Kaiserslautern, Gottlieb-Daimler-Straße, Kaiserslautern 67663, Germany.
Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, Madrid E-28040, Spain.
Materials (Basel). 2016 Oct 14;9(10):831. doi: 10.3390/ma9100831.
The recently developed nanobainitic steels show high strength as well as high ductility. Although this combination seems to be promising for fatigue design, fatigue properties of nanostructured bainitic steels are often surprisingly low. To improve the fatigue behavior, an understanding of the correlation between the nanobainitic microstructure and the fatigue limit is fundamental. Therefore, our hypothesis to predict the fatigue limit was that the main function of the microstructure is not necessarily totally avoiding the initiation of a fatigue crack, but the microstructure has to increase the ability to decelerate or to stop a growing fatigue crack. Thus, the key to understanding the fatigue behavior of nanostructured bainite is to understand the role of the microstructural features that could act as barriers for growing fatigue cracks. To prove this hypothesis, we carried out fatigue tests, crack growth experiments, and correlated these results to the size of microstructural features gained from microstructural analysis by light optical microscope and EBSD-measurements. Finally, we were able to identify microstructural features that influence the fatigue crack growth and the fatigue limit of nanostructured bainitic steels.
最近开发的纳米贝氏体钢具有高强度和高延展性。尽管这种组合在疲劳设计方面似乎很有前景，但纳米结构贝氏体钢的疲劳性能往往出奇地低。为了改善疲劳行为，了解纳米贝氏体微观结构与疲劳极限之间的相关性至关重要。因此，我们预测疲劳极限的假设是，微观结构的主要功能不一定是完全避免疲劳裂纹的萌生，而是微观结构必须提高减速或阻止疲劳裂纹扩展的能力。因此，理解纳米结构贝氏体疲劳行为的关键在于理解那些可以作为疲劳裂纹扩展障碍的微观结构特征的作用。为了验证这一假设，我们进行了疲劳试验、裂纹扩展实验，并将这些结果与通过光学显微镜和电子背散射衍射（EBSD）测量的微观结构分析获得的微观结构特征尺寸相关联。最后，我们能够识别出影响纳米结构贝氏体钢疲劳裂纹扩展和疲劳极限的微观结构特征。
