The annealing kinetics of cold-rolled AA5182 and AA5657 aluminum alloy sheets have been investigated and compared. The microstructures of a series of partially recrystallized samples are characterized by electron back scattered diffraction and key stereological parameters including volume fraction recrystallized, interfacial areas and contiguity are determined. The overall recrystallization kinetics as well as the nucleation and growth rates are thereby quantified. The results reveal that the nuclei develop in clusters. This matches well with the observation of a low kinetics exponent n =2 in AA5182. Much more surprising is that n is 2.8 in AA5657, even though the nucleation is clustered. Also, it is higher than almost all recrystallization kinetics investigations which generally find values significantly below 3.Effects of nucleation rate, spatial distribution of nuclei and growth rate are discussed and used in a quantitative analysis of recrystallization kinetics in the two alloys.
The efficiency of large second phase particles to stimulate nucleation of recrystallization in commercially cold rolled (25%) AA5182 aluminium sheet is investigated by laboratory multimodal X-ray tomography. The spatial distributions of 11434 particles and 742 nuclei are determined nondestructively in 3D in the same sample volume. Our work confirms that particle stimulated nucleation is the dominant nucleation mechanism, but it is also found that PSN nuclei stimulated from small particles and non-PSN nuclei can grow to large sizes. These results and the observed orientation distributions of the PSN and other nuclei are discussed in relation to existing theories. IMPACT STATEMENT The efficiency of the nucleation mechanism called particle stimulated nucleation is quantified in 3D by a non-destructive experimental approach.
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