In-situ observations on the annealing behavior of triple junctions in a high purity nickel after slight cold rolling

Off-line in-situ electron back scatter diffraction (EBSD) was used to characterize the annealing behavior of triple junctions in a high purity (99.99 wt.%) nickel which had been cold rolled slightly (the thickness reduction was 5%). The results showed that recrystallization nuclei were developed at some triple junctions during the early stage of annealing at 800℃. All such nuclei exhibit <1 1 1>/60° orientation relationships with the parent grains, and the bounded Σ3 boundaries are found to be incoherent ones. During further annealing, these nuclei are consumed by other growing grains, indicating that their presence is just a release of the strain concentration at the triple junctions and has no substantial effects on the evolution of grain boundary character distribution during annealing. The growing grains are usually those original grains and they are coarsened rapidly via a mechanism of so-called strain induced boundary migration by which high fraction Σ3 boundaries and large-sized Σ3n (n=1, 2, 3…) boundary clusters are introduced.