Abnormal grain growth in Al of different purity

The transition from normal to abnormal grain growth has been studied in four Al alloys of various purity (2N, 3N, 4N and 5N). The temperature and time for the onset of abnormal grain growth depend strongly on the deformation and homogenization treatment. Generally, the formation of large grains before cold rolling makes easier the transition to abnormal grain growth during the subsequent annealing. The abnormal grain growth can take place only above a certain temperature which decreases with increasing alloy purity. The onset time of the abnormal grain growth decreases with increasing temperature. It can be qualitatively explained by the dissolution of submicron particles of a second phase.