MECHANISMS OF CONTINUOUS RECRYSTALLIZATION IN AN AL-ZR-SI ALLOY

Microstructural evolution in an AlZrSi alloy has been investigated with the goal of elucidating the mechanisms responsible for formation of high-angle grain boundaries by continuous, recovery-type processes during concurrent straining and annealing. The primary method of investigation was TEM characterization of the microstructure and microtexture after cold rolling, after annealing, and after concurrent straining and annealing. The cold-rolled microstructure consists of layers parallel to the rolling plane; only low-angle boundaries are present within each layer withadjacent layers are separated by high-angle boundaries. During annealing, the subgrain size increases but the subgrain boundary misorientations are not significantly changed and the high-angle boundaries are relatively immobile. In contrast, concurrent straining and annealing of the cold-rolled material causes a gradual increase in the misorientation of some of the original low-angle boundaries, implying subgrain rotation. Ultimately, high-angle boundaries evolve by subgrain rotation from the subgrain boundaries originally present within each layer. The observations are interpreted in terms of several mechanisms previously proposed for microstructural evolution during concurrent straining and annealing. © 1991.