Al–0.7%Mg–0.4%Si–0.2%Cr合金の冷間圧延および焼なまし処理による結晶回転と再結晶

Recrystallization behaviors in an Al–Mg–Si alloy have been intermittently observed by means of SEM-EBSD in detail. A specimen of Al–0.73Mg–0.38Si–0.26Cr alloy was cold-rolled with reduction rate of 30%, then annealed at 673 K. Annealing, ion-polishing and EBSD measurement were repeated and changes in microstructures were observed on the same area in the specimen during annealing up to 4.8 ks. Cold-rolling resulted in lattice rotation along axes parallel to the specimen surface and about perpendicular to the rolling direction. Subgrains formed at a recovery stage have the rotated orientation. Subgrains with low lattice defect densities formed near prior grain boundaries were developed into recrystallized grains through the prior grain migration mechanism. Therefore, the recrystallized grains also have the rotated orientations. In some case, recrystallized grains were formed at interiors of prior grains, and in another case, new grains were formed without orientation relationships among the surrounding prior grains. The recrystallized grain with the prior grain migration mechanism invaded into neighboring prior grains, and the mother grain was invaded by other recrystallized grains. The original and/or rotated orientation of the mother grain was maintained at the outside of the original prior grain.