Initial stages of recrystallization in aluminium containing both large and small particles

The recrystallization behaviour has been studied in a dispersion strengthened aluminiumalumina alloy containing a bimodal distribution of fine alumina particles (<0.1 /μm) and coarse FeAl₃ particles (0.2–4 μm). The formation and growth of recrystallization nuclei were studied by in situ annealing in a high voltage electron microscope, conventional transmission electron microscopy and light microscopy. The parameters studied were the initial grain size and the degree of deformation (50 and 90% reduction in thickness by cold-rolling). It was found that recrystallization nuclei formed preferentially at the initial grain boundaries and at deformation bands; the effect of such sites was enhanced by the FeAl₃ particles which, however, in isolation were not strong nucleation sites. The recrystallization kinetics in the aluminium-alumina alloy were retarded or accelerated due to the presence of alumina or FeAl₃ particles respectively. However, the FeAl₃ particles did not lead to a significant grain refinement ; the recrystallized grain size of the aluminium-alumina alloy was large. Finally, the structural and kinetic observations are discussed and related to results from a previous study of the initial stages of recrystallization of aluminium of commercial purity.