Strain controlled fatigue experiments were employed to evaluate automotive-grade interstitial-free ferrite steels. This study demonstrated that the loop-patch structure, dislocation walls and dislocation cells larger than 2μm have no significant effect on fatigue failure. The cracks prefer to grow near grain boundaries while dislocation cells smaller than 2μm tend to develop along the grain boundaries and triple junction of the grains. Once the dislocation cells smaller than 2μm develop from grain boundaries to grain interior, the cracks will propagate near the grain boundaries and through the grain interior simultaneously.

The Study of Crack-Propagation Behaviors and Dislocation Structures in Cyclically Deformed Polycrystalline IF Steel. C.C.Shih, D.H.Yeh, N.J.Ho, H.L.Huang: Materials Science and Engineering A, 2011, 528[21], 6381-6