Inter- and intragranular stresses in cyclically-deformed 316 stainless steel

Neutron diffraction was used to study residual stresses in cyclically-deformed 316 LN stainless steel. The tension-compression high-cycle fatigue tests were conducted in air with a frequency of 0.2 Hz. Large intergranular stresses were found to develop in the stainless steel as a result of elastic and plastic anisotropy. These intergranular stresses started to decrease when micro-cracks were initiated at the surface and vanished when the sample reached failure. Cyclic loading also led to the development of intragranular stresses, as evidenced by the broadening of the diffraction peaks. Analysis of the orientation dependence of the measured peak widths indicates that the immobile dislocations generated by fatigue deformation are mostly edge rather than screw type.