Abstract
Low-cycle fatigue experiments emphasizing the ratchetting are performed on the carbide-free bainitic (CFB) rail steel under different heat-treatment conditions. The effects of microstructure and retained austenite (RA) on the ratchetting-fatigue interaction are investigated through macroscopic and microscopic characterizations. The results indicate that the CFB rail steel exhibits a non-saturated and strain amplitude-dependent cyclic softening feature and shows different ratchetting behaviors and failure modes at various stress levels. Ratchetting promotes the development of stable dislocation substructure and the transformation of blocky RA. The fatigue resistance of 1380 grade CFB steel under the online controlled cooling conditions is better than that of 1280 grade CFB steel under the air-cooling condition.
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