PLANE POLARIZED OPTICAL MICROSCOPY STUDIES OF THE STRUCTURE OF HOT-DEFORMED AND PARTIALLY RECRYSTALLIZED ALUMINUM SAMPLES

Pure polycrystalline aluminium samples of average grain size 850-mu-m have been 20 and 40% uniaxially compressed, in both cases at 300 and 400-degrees-C and at true strain rate of 4.6 x 10(-4) s-1. Plane polarized light microscopy, was employed in the study of the deformed and the partially recrystallized states. The microstructure after quenching to room temperature did not show any recrystallized states, instead it revealed an enhanced recovery of subgrain network. Increases in the deformation temperature and the degree of deformation had the effect of "sharpening" the subgrain structure, The subgrain size decreased with the amount of deformation but increased with the deformation temperature. The hot-deformed samples recrystallized after subsequent annealing at 300 and 400-degrees-C with a reduced growth rate due to previous recovery. In samples previously deformed by 20%, nucleation of recrystallized grains was mainly by Strain Induced Boundary Migration (SIBM) at pre-existing grain boundaries and at triple grain boundary intersections The same nucleation mechanism predominated in material 40% hot-deformed. Transition band nucleation was, however, not commonly observed.