Nucleation of recrystallization in compressed aluminium: studies by electron microscopy and Kikuchi diffraction

Abstract

Following the earlier investigation of recrystallization of aluminium by Bellier and Doherty [1] by transmission Kossel diffraction, the details of the nucleation process were studied by transmission electron microscopy and Kikuchi electron diffraction. This showed that nucleation appeared to occur via a sub-grain coalescence process that occurred selectively at deformation bands and at deformation band, grain boundary junctions. Nucleation occurred only at grain boundaries and at deformation bands. The condition for continued growth, of enlarged sub-grains of length 2L, along the grain boundary L>2r(γ _s/γ _g) where γ _s is the sub-boundary energy and γ _g the grain-boundary energy, was found to be obeyed. The values of the stored energy calculated from the measured sub-grain sizes and misorientations were less than the reported experimental value, indicating that in as-deformed aluminium the dislocation arrays in the sub-boundaries may not have the lowest energy structure assumed in the calculation.