Density of annealing twins

Abstract

Recrystallization studies were carried out in a photoemission electron microscope (PEEM) on OF copper and also on nickel and aluminium bronze. Grain sizes and prior cold work were varied over a wide range. The twin density, when expressed as the number of coherent twin interfaces per unit area, is found to correlate well witha parameter reflecting dislocation density. However, the inverse relationship between recrystallized grain size and twin density is not as simple as originally thought. The results show a large scatter which seems to be associated with the variation in recrystallization temperature incurred during heating runs in the PEEM. These variations, although not affecting final grain size, may have a considerable influence on the twin density. The results suggest that twins form because the reorientated matrix provides an easier reaction path for arapid reduction in dislocation density and not because the twinning process may lead to a reduction in interfacial energy.