Recrystallization behavior in 1050 aluminum after cold-rolling

Abstract

Microstractural changes in 1050 aluminum alloy sheets were observed on the same area in a specimen with SEM-EBSD system. Specimens were heat-treated at 823 K for 3.6 ks. The specimen was cold-rolled at a reduction rate of 75% and then annealed at 623 K. Intermittent annealing using a salt bath, Ar ion-polishing and EBSD measurement were repeated. In an area composed of small grains before cold-rolling and an area close to prior grain boundaries, recrystallized grains were formed at the early stage of annealing. Strain induced grain boundary migration (SIBM) was observed in the latter area, although the reduction rate is much higher than those reported in the literatures. The prior grain boundary did not spontaneously migrate but migrated with a growth of dislocation cell formed nearby the boundary. The recrystallized grain formed through the SIBM mechanism has a low angle boundary as an interface between the mother grain, which was immobile. The low angle boundary changed into a high angle boundary after the mother grain was made inroads by other recrystallized grains. Low angle boundaries are not always immobile but migrate in some cases remaining behind a low strained area, and encounters other boundary to form a recrystallized grain.