Time evolution of sigma 3 annealing twins in secondary recrystallized nickel

Samples of commercially pure nickel have been annealed in air at 0.68T(m) (900degreesC) for 1, 2 and 3 h in order to study the relationship between the grain growth characteristics and grain boundary misorientation, particularly annealing twins (Sigma 3). Orientation mapping by electron backscatter diffraction was used to obtain the experimental data. Anomalous grain growth was observed in commercially pure nickel after each of the anneals. The main findings are as follows. The texture was mainly {100}<001> and {112}<111> and it was more pronounced in coarse-grained areas than in fine-grained areas. The length fraction of Sigma 3s (annealing twins) increased with annealing time and therefore with the level of anomalous grain growth. Two to three twins per grain were sited in coarse-grained regions whereas less than one twin per grain was sited in fine-grained regions. It is suggested that the nucleation and growth of twinning is mechanistically linked to anomalous grain growth.