Influence of texture on twin boundary cracks in fatigued austenitic stainless steel

It is well-known that crack initiation in fatigued austenitic steel (316L) specimens is dominated at lower deformation amplitudes by twin boundaries (TBs). For medium plastic strain amplitudes, it is shown here that the propagation of short cracks starting at TBs can be explained when both the surface tractions caused by elastic anisotropy as well as the related slip processes are considered. This conclusion has been obtained from grain orientation measurements along damaged TBs using the electron backscatter diffraction technique in the scanning electron microscope. The frequency of the damaged TBs strongly depends on the meso-texture given by the distribution of 60° 〈111〉 rotation axes of the twins in the pole figure. The texture was determined by automatic orientation mapping. Specimens, which were machined transverse to the rolling direction of the plate, show more damaged TBs than those machined parallel. Consequently, the risk of TB cracks can be reduced by favorable alignment of the specimens with respect to the rolling direction.