INFLUENCE OF THE CRYSTALLINE TEXTURE ON THE FATIGUE DAMAGE

摘要

Crack initiation in austenitic steel (316L) specimens fatigued at lower deformation amplitudes is dominated 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 EBSD technique in the SEM. 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. 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 favourable alignment of the specimens with respect to the rolling direction.