Formation of fragmented structure in Armco-iron under fatigue crack surface

Cyclic cracking of annealed Armco-iron specimens in the three-dot bending scheme has been obtained and TEM investigations of areas under the fatigue fracture surface have been carried out. The formation of different dislocation structures in Armco-iron depending on a distance to the cycle crack surface is studied. The dislocation density dependence on the distance to the fatigue fracture surface is determined. The formation of the fragmented structure in the immediate vicinity of the fatigue crack surface is revealed.