Abstract
Crack initiation in AISI 316 stainless steel has been investigated.
Persistent Slip bands (PSBs) were characterized using Scanning Electron
Microscopy (SEM) and Atomic Force Microscopy (AFM). PSBs on the surface
of the material increase the surface roughness and result in crack
initiation. EBSD data from near the crack initiation region were used to
correlate the global and local misorientations of the grains, plastic
deformation, and Schmid Factor with the fatigue life of specimens. The
crack initiation region was found to have the highest misorientations.
The region near crack initiation was found to have more plastic
deformation, which was severe in specimens loaded with higher stresses.
The Kernel Average Misorientation (KAM) and Grain Reference Orientation
Deviation (GROD) maps from the EBSD data were investigated for specimens
that failed at different fatigue cycles. It was found that the
interaction of high dislocation density, substructuring and
misorientation of low-angle grain boundaries in the region of plastic
deformation resulted in the fatigue crack initiation.