On the anomalous hardening during annealing of heavily deformed f.c.c. metals

The anomalous hardening in heavily rolled copper and nickel during thermal treatment is investigated by characterizing deformation and annealing microstructures of the respective metals. Because of the significant dislocation storage in the rolled copper, before the outset of recrystallization significant development of twins that are originated from mechanical micro-twins occurs accompanied by the increasing micro-strain within the metal. The large micro-strain and high density of twin boundaries observed during annealing jointly contribute to the hardening of copper. The peak micro-hardness of nickel is attributed to the strengthening effect of considerable amount of annealing twins that are formed in the process of recrystallization.