Abstract The fatigue dislocation structure in an alloy ferrite steel was studied by the method of electron diffraction contrast analysis. The dislocation structure features in annealed 12CrMo steel variate after 10~7 cycles under cyclic tensile stresses. The main features of fatigue dislocation structure are dislocation jog, dipole, Ioop, deformation band, tangle and banded dislocation structure. Alloy ferrite grains are broken into blocky-like microstructure regions.
