Local deformation heterogeneity in cyclically deformed interstitial free steel

Heterogeneity of cyclic plastic deformation in interstitial-free steel has been studied through a measurement of local average misorientation using electron back-scattering diffraction technique. It is found that with increase of strain amplitude, the local average misorientation increases linearly within +/- 0.15 to +/- 0.40% and then decreases with further increase of strain amplitude. It is proposed that due to more homogeneous deformation vis-a-vis less generation of geometrically necessary dislocations, misorientation development per cycle becomes almost saturated in the predominantly low cycle fatigue regime. It is also found that the local average misorientation depends upon grain size in such a manner that in small grains, the misorientation is less as compared with large grains.