In situ observation of triple junction motion during recovery of heavily deformed aluminum

Microstructural evolution during in situ annealing of heavily cold-rolled aluminum has been studied by transmission electron microscopy, confirming that an important recovery mechanism is migration of triple junctions formed by three lamellar boundaries (Y-junctions). The migrating Y-junctions are pinned by deformation-induced interconnecting and lamellar boundaries, which slow down the recovery process and lead to a stop-go migration pattern.

This pinning mechanism stabilizes the deformation microstructure, i.e. the structure is stabilized by balancing the driving and pinning forces controlling the rate of triple junction motion. As a consequence, recovery and the subsequent recrystallization are strongly retarded. The mechanisms underlying Y-junction motion and its pinning are analyzed and discussed.