Dislocation arrangements in fatigued iron

Abstract
Observations are reported on the dislocation arrangements in cyclically stressed high purity iron. For a stress amplitude causing failure in 2 × 106 cycles the dislocations were arranged in the form of patches of tiny loops. At higher stress amplitudes the patches became larger with heavily jogged screw dislocations being associated with the loops. A sub-grain structure was also observed in a few areas.