Deformation Determined by Electron Backscatter Diffraction (EBSD)

The quality of the EBSD diffraction patterns is a function of many factors, of which an important one is the level of deformation [2]. For this study, nine quality indices were calculated from the analysis of the diffraction patterns or their Hough transform to evaluate the deformation depth. As an attempt to verify the EBSD results, cross-sections of the deformed samples were made using a FIB

To prevent prior or unwanted deformation to influence the measurements, special care was taken during the sample preparation. The samples were annealed and polished up to colloidal silica before being deformed by the grinding paper. Before the final polishing of the deformation profile face of the sample, the deformed surface was nickel plated to avoid any edge deformation effect. The EBSD acquisitions were performed on a Hitachi S-4700 cold-field emitter microscope equipped with an HKL Nordlys II camera. The image analysis software RML-Image [3] was used for the postprocessing of the diffraction patterns. The FIB images were taken on a Hitachi NB-5000 microscope.

Deformation profiles were obtained by dividing the EBSD maps into sections of equal width starting from the deformed surface. Four of the nine quality indices gave satisfactory profiles. Using the 90% deformation point, the depth of deformation was evaluated. Figure 1 shows these measurements and
those from the FIB images. Although the calculations for quality indices are different, the EBSD measured deformation depths for a given grinding paper are similar. However, the deformation depths obtained from the FIB are much smaller than those obtained by EBSD. A possible explanation is that the deformed area seen in the FIB images corresponds to the recrystallization zone and not the complete shear-band layer. However, the FIB images (Figure 2) clearly shows the
heterogeneity of the deformed layer, implying that several measurements are required to properly assess the deformation depth.


The articles and presentations that can be down-loaded from this web site are based upon work done by GFV while employed at Bethlehem Steel (1967-1983), Carpenter Technology (1983-1996), Buehler Ltd. (1996-2009) and Struers (2009-Present) and from the authors consulting work for companies such as, Latrobe Steel, Scot Forge, etc., and from his litigation work. GFV's bylined articles appearing in various issues of the ASM Handbook series have been listed here courtesy of ASM International, Materials Park, Ohio.