The effects of grain boundary on dislocation development for cyclically deformed IF steel

Polycrystalline interstitial-free steels (IF steels) were cyclically deformed at constant total strain amplitude (Δɛ/2) in the range from 0.05% to 0.6%. The transformed speed of loop patches into dislocation cells and walls near grain boundary is faster than that in the grain interior while total strain amplitude is lower than 0.15%. However, the well-known dislocation-free zones (DFZs) near grain boundary are very hard to be found in this study. Additionally, dislocation cells tend to transform into loop-patch structure near grain boundary during high–low strain-controlled fatigue test (two-step fatigue test).