Investigation of boundary migration during grain growth in fully recrystallised high purity nickel

Abstract

The movement of individual boundaries during grain growth after primary recrystallisation in a 96% cold rolled sample of pure nickel has been followed using electron backscatter diffraction maps of the same surface area taken after each of several annealing steps. Particular attention is given to the migration of boundaries with near Σ3 misorientations. During annealing, a small reduction in the length fraction the Σ3 boundaries was observed in the early stages of annealing. Analysis of individual boundaries shows that only those boundary segments with a misorientation angle greater than 4° move during annealing. In addition, the Σ3 boundaries can be divided into two groups: those with misorientations very close to the ideal twin misorientation (‘twin type') and those with a larger deviation to the ideal twin misorientation, but still satisfying the Brandon criterion (‘neighbour type'). Of these, only neighbour type Σ3 boundaries are observed to move during annealing. Some implications of these observations for twin development during grain boundary engineering are discussed.