A Constitutive Relationship between Fatigue Limit and Microstructure in Nanostructured Bainitic SteelsReport as inadecuate


A Constitutive Relationship between Fatigue Limit and Microstructure in Nanostructured Bainitic Steels


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1

Department of Mechanical and Process Engineering Materials Testing AWP, University of Kaiserslautern, Gottlieb-Daimler-Straße, Kaiserslautern 67663, Germany

2

Spanish National Center for Metallurgical Research CENIM-CSIC, Avda. Gregorio del Amo 8, Madrid E-28040, Spain

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Robert-Bosch GmbH, Materials and Process Engineering Metals, Renningen, Stuttgart 70465, Germany

4

Asco Industries CREAS, Avenue de France, BP 70045, Hagondange Cedex 57301, France





*

Author to whom correspondence should be addressed.



Academic Editor: Yoshiharu Mutoh

Abstract 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. View Full-Text

Keywords: fatigue limit; crack growth; nanostructured bainite; crystallography; EBSD; critical crack length; Kitagawa diagram fatigue limit; crack growth; nanostructured bainite; crystallography; EBSD; critical crack length; Kitagawa diagram





Author: Inga Mueller 1,* , Rosalia Rementeria 2, Francisca G. Caballero 2, Matthias Kuntz 3, Thomas Sourmail 4 and Eberhard Kerscher 1

Source: http://mdpi.com/



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