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arXiv · 2607.16867

Operando observation of strain relaxation in fatigued pearlitic steel

Louis Lesage·Johan Ahlström·Yubin Zhang·Can Yıldırım
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Abstract

Pearlitic steels are the material of choice for railway wheels and rails, where their lamellar ferrite-cementite structure balances cost, strength, and wear resistance. However, in use, cyclic loading combined with frictional heat softens the steel, promoting fatigue and eventual failure. Here we use Dark-Field X-ray Microscopy (DFXM) to follow, operando, the grain-scale response of a fatigued pearlitic colony during annealing up to 550 {\deg}C. Orientation maps reveal negligible lattice rotation and no sub-cell formation, indicating that the cementite lamellae suppress long-range dislocation motion. Strain maps nonetheless show pronounced relaxation: the elastic strain spread narrows by nearly 40%, with recovery starting below 250 {\deg}C, within the operating temperatures of railway wheels. We attribute this relaxation to short-range annihilation of dislocations confined between lamellae, linking grain-scale strain recovery to the macroscopic softening of pearlitic railway steels in service.

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Louis Lesage, Johan Ahlström, Yubin Zhang, Can Yıldırım. 2026-07-18. Operando observation of strain relaxation in fatigued pearlitic steel. https://arxiv.org/abs/2607.16867

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