Recrystallization behaviour of commercial Al-1%Mn alloy

Abstract

The recrystallization behaviour of a commercial Al-1%Mn alley is discussed en the basis of microstructural changes during industrial precessing steps. The main effects result from the extended heat treatment at high temperatures normally used fer direct-chill-cast blocks. The precipitation of finely dispersed second-phase particles within the Al dendrites limits the nucleation of recrystallization to the deformation zone around the coarse primary particles. The formation of new grains at or near the large primary particles involves the migration and dissolution of subgrain boundaries. These reactions are enhanced by the presence of a precipitate-free zone around the primary particles, where the Mn content in solid solution has been reduced by the diffusion of Mn atoms into the particles. A fine final grain size is obtained provided that no decomposition occurs while heating to the annealing temperature, which should be chosen well above the recrystallization temperature of the cold-rolledmaterial.