The use of STEM microdiffraction for the study of misorientation between subgrains

Abstract

While there have been studies of the relationship between misorientation in worked structures and the development of recrystallisation nuclei, most have lacked accuracy owing to the positional uncertainty of selected area diffraction. However the fine electron probe forming capability required for STEM operation enables diffraction information to be obtained from regions of the order of 20 nm or less in diameter. We have applied this technique to an examination of recrystallisation in situ, where the early stages of grain development are arrested by the presence of particles.The microdiffraction studies were carried out on specimens prepared from an Al-6% Ni alloy which had been given various rolling and annealing treatments. A JEOL JEM 100C/ASID-4D electron microscope was used in the STEM mode with the operating conditions such that the spot size was about 20 nm with a beam divergence of 10-3 rad.For each of the specimens studied, a suitably thin region with a typical subgrain structure was selected and photographed.