Abstract
Behaviors of the hysteresis loop of low carbon steels in the fatigue process have been studied systematically by the authors using interaction models between dislocations and solute carbon atoms.
In the present study the effect of oversaturated interstitial atoms such as carbon and nitrogen on the hysteresis behavior during fatigue process was investigated especially in the cyclic hardening stage. The samples of 0.1% carbon Al-killed steel with different interstitial solute contents were tested under a constant axial stress amplitude with zero mean stress at a frequency of 30Hz. The experimental results showed that the decrease of the plastic strain amplitude after reaching the peak value was accelarated with the increase of interstitial solute contents. By the analysis based on the Cottrell's pinning theory, it was demonstrated that the cyclic hardening behavior as described above was mainly caused by the migration of interstitial atoms into the highly strained field of dislocation from surrounding matrix under cyclic load.
