ORIENTATION RELATIONSHIPS BETWEEN GRAINS AND GRAIN-BOUNDARIES IN AL-1 WT-PERCENT GA AT THE BEGINNING OF SECONDARY RECRYSTALLIZATION

The transition from the normal grain growth to the secondary recrystallization (abnormal grain growth) is studied in Al-1 wt% Ga. The orientations of individual grains and grain boundaries are determined with the aid of the selected area channelling method. The area of normal grain growth consists of small uniform grains. In this area almost exclusively twin boundaries are present having low energy and low mobility. Such grain boundaries are not present in the contact area between the abnormally growing large grains and the normal matrix. It is concluded that new grain boundaries with a high mobility are formed during the normal grain growth. Further kinetical selection of such grain boundaries can trigger the onset of the secondary recrystallization.