In situ observation of fatigue crack retardation in banded ferrite–pearlite microstructure due to crack branching

This paper reports the results of in situ observation of fatigue crack growth in a ferrite–pearlite steel. Stress intensity factor range (ΔK) decreasing/increasing and constant-ΔK fatigue tests have been carried out. In banded pearlite orientation, intense crack branching was observed which leads to fatigue crack retardation. Crack closure during the test was monitored to understand the fatigue crack growth behaviour.