| Microstructure evolution during equal channel angular extrusion at 400 œC was studied in a cast 1421Al alloy. The structural changes were investigated by using transmission and scanning electron microscopes incorporating an orientation imaging microscopy. The microstructure evolution is characterized by the development of new fine grains with a size of about 2 µm primarily at triple junctions and near original grain boundaries, leading to the formation of necklace-like microstructure. The interlayers consisting of new fine grains do enlarge with increasing the total strain that results in a gradual rise of the volume fraction occupied by fine grains. The mechanism for the fine-grained microstructure evolution is discussed as a kind of continuous dynamic recrystallization. |
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