The Effect of Particle Content, Particle Distribution, and Cold Deformation on the Recrystallization of Low Oxide Al-Al2O3 Products

The recrystallization of dispersion-strengthened Al-Al2O3 products containing 0.6 and 1.2 wt % Al2O3 was followed by optical and transmission electron microscopy and by hardness measurements. The recrystallization was retarded compared to aluminium and the important structural parameters were the oxide content (proportional to the reciprocal particle spacing) and the distribution of oxide particles either as a uniform distribution or as a regular three-dimensional network.

From the microstructures after cold work and after recovery it is suggested that particle-retarded recrystallization may be caused by pinning, during the recovery stage, of sub-boundaries and of individual dislocations. The hypothesis of retardation of recrystallization as due to particle-enhanced homogenization of dislocation structures during deformation is not supported by the microstructural observations.

In the product containing 0.6 wt% Al2O3 the recrystallization was markedly retarded after 50% cold reduction, whereas the retardation was small after 80 and 90% reduction. An increase in the degree of cold deformation may reduce the critical size of the recrystallization nuclei, and thus the retarding effect of particles during nucleation may be reduced or disappear.

It is therefore suggested that the degree of cold deformation and the particle spacing may be interdependent parameters when determining the recrystallization behaviour of dispersion-strengthened products.