Unsupervised approval criteria for automated EBSP investigation of deformed metals

Unsupervised approval criteria have been investigated for orientations gathered from cold deformed samples (medium to high strain range) using the electron backscattering pattern technique. For such samples, the dislocation cell-size is on the order of the available step-size and pattern quality is generally low. Approval criteria for assessing the validity of measured orientations under these conditions were determined using, as a calibration, channel die cold deformed single crystals of stable orientations. In all cases, approval criteria based on an indexing confidence measure are found to be preferable. Different criteria are suggested, depending on whether the orientation data are subsequently to be used for texture analysis, or for a misorientation angle-based analysis. The latter is illustrated by an investigation of the number of deformation generated high angle boundaries introduced during a 90% cold reduction of a polycrystalline sample.