13th International Conference on Fracture June 16–21, 2013, Beijing, China Fig. 5 PSB surface observation by SEM and EBSD A specimen with pronounced PSBs was investigated in 3 perpendicular surfaces to have deeper understanding in 3 dimensions of PSB. The 3 surfaces are: original specimen surface, axial cutting surface and cross cutting surface as shown in Fig 6a. All 3 surfaces were prepared by carefully mechanical polish and 4% Nital etching. SEM observations at corner between axial cutting surface and original surface are presented in the Fig 6 b&c and cross section surface in the Fig 6d. Different oriented longitudinal slots were found pronouncedly at both side of corner on the axial cutting surface and original surface. Slots orientation changing takes place at grain boundary. It is reasonable to relate those slots to formation of PSB on the original specimen surface. The figure 6c is the original surface observed with the inlens detector. It is easier to see, that the slots are not deep. It seems these slots are like cylinders. The width of each individual slot is around 0.5 m, the distance between parallel slots varied from 1 m to 3 m and the length of slot is between 2 m to 10 m. On the cross section (Fig. 6d), it appears equiaxe hollows separated or not by a thin wall of matrix (in nanoscale). Hollows are distributed linear in several lines as marked in the yellow square (Fig. 6d). Those lines with hollows are parallel. Equiaxe hollow has size in 0.5 m. Hollow lines observed here have length about 3 m to 5 m. The distance between hollow lines is approximate 2 m. Regarding this hollow deformation at cross section and longitudinal slots found in Fig 6c, it may be constructed a 3D schematic figure of the slots and hollows as Micron Abreast Pipes in Fig.6e However in the fundamental material like ferrite, subsurface irreversible deformation is decreasing according plane stress condition function with distance to the surface a) b) Cross surface Original surface Axial surface
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