Indexation and misorientation analysis of low-quality Laue diffraction patterns

A Laue X-ray diffraction pattern indexing scheme, similar to a method previously proposed for convergent beam and backscattered electron diffraction patterns, was implemented. Experimental diffraction patterns are compared with simulated templates corresponding to crystals of prescribed orientations. The orientation of a diffracting volume is determined by maximizing a normalized cross correlation index between experimental and theoretical patterns. The advantages of template matching include (i) elimination of the requirement for extensive peak search/fitting analysis; (ii) the ability to index overlapped diffraction patterns obtained from neighboring grains or second phase particles; and (iii) the ability to confidently index patterns of low quality. A best fit orientation can then be determined by a least-squares fitting approach based on singular value decomposition. The misorientation within a diffracting volume is calculated from 'smeared' and/or 'split' Laue patterns. The methodologies developed are illustrated using micro-Laue diffraction data obtained from the wake of a fatigue crack.