Low-cycle fatigue behaviour and microstructural evolution of pearlitic and bainitic steels

Microstructural analysis of new bainitic steel subject to heat treatment was performed and directly compared with those achieved from the microstructure of R-260 pearlitic rail steel. Mechanical properties, fracture behaviour, and low-cycle fatigue (LCF) tests of the bainitic steel were also evaluat...

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Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2019-02, Vol.747, p.144-153
Main Authors: Adamczyk-Cieślak, Bogusława, Koralnik, Milena, Kuziak, Roman, Brynk, Tomasz, Zygmunt, Tomasz, Mizera, Jarosław
Format: Article
Language:English
Subjects:
Austenite
Bainitic steel
Crack propagation
Deformation
Fatigue tests
Fracture surfaces
Heat treating
Heat treatment
Low cycle fatigue
Martensite
Martensitic transformations
Mechanical properties
Metal fatigue
Microstructural analysis
Microstructure
Pearlitic steel
Rail steels
Retained austenite
Steel
Structural steels
X-ray diffraction
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Summary:Microstructural analysis of new bainitic steel subject to heat treatment was performed and directly compared with those achieved from the microstructure of R-260 pearlitic rail steel. Mechanical properties, fracture behaviour, and low-cycle fatigue (LCF) tests of the bainitic steel were also evaluated and collated with those achieved from pearlitic rail steel. The LCF tests were performed at room temperature at varying strain amplitudes under total strain control. The basic characteristics of the relationship between the low - cycle fatigue parameters of steels were evaluated based on the Coffin – Manson formula. The obtained test results demonstrate that the two microstructures exhibit different cyclic stress responses, i.e. the cyclic strengthening of pearlitic steel and a cyclic softening in bainitic steel. The variations in the amount of retained austenite in the bainitic structure, before and after LCF, were evaluated by X-ray diffraction and electron transmission microscopy (TEM). The results indicate that during deformation, a partial transformation of the residual austenite into the deformed martensite α' has taken place. Moreover, the quasi-cleavage character of the fracture surface was observed for bainitic steel with a higher deformation degree during the LCF test.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2019.01.043