Influence of extinction phenomenon on determination of the orientation distribution function

The influence of the extinction phenomenon on the directly measured pole figures (PF) and calculated orientation distribution function (ODF) is demonstrated for the case of aluminium samples after cold rolling to different reductions and thermal annealing. Pole figures for low index reflections 111, 200, 220 and for high index reflection 222, 400, 420 were measured. An aluminium powder standard sample was also measured. The ODFs were calculated from these PFs data for low and high index reflections separately. The ODF obtained from low index PFs shows systematically lower values of grains orientation density than those obtained from high index PFs. Such inequality of obtained ODFs is attributed to the stronger effect of primary and secondary extinction on the diffraction of low index reflections. The obtained ODFs are also not qualitatively similar. This indicates extinction anisotropy due to the primary extinction coming from recrystallized non equiaxial crystallites.