Assessment of deviatoric lattice strain uncertainty for polychromatic X-ray microdiffraction experiments

X-ray microdiffraction is a powerful technique for conducting high-spatial-resolution lattice strain measurements. However, there has been limited validation of the technique to date. An experiment was conducted at the Advanced Light Source to assess the uncertainty of deviatoric lattice strains measured using polychromatic X-ray microdiffraction. It is shown that the measurement uncertainty is different for each component of the deviatoric lattice strain tensor. Monte Carlo simulations of the experiment are used to explain the differences in uncertainty. The simulations point to the existence of spurious deformation modes that arise erroneously in the strain calculation owing to measurement noise and limited pole figure coverage. Methods for reducing measurement uncertainty are proposed.