Fig. 10

Simplified model proposed to explain the boundary migration by progressive cellular rings: a) simple glide of dislocations; b) an unstable situation is reached at the corners when dislocations with Burgers vectors rotated by 60^∘ approach one to the other and proceed to an effective climb mechanism. Pairs of dislocations that undergo this climb process are highlighted by green circles just before -in a)- and just after -in b)- the climb process; c) the dislocations at the corners propagate along the sides by a chain of effective climb events, see red circles in b) and corresponding red circles in c); d) a cellular hexagonal-shaped ring is closed and the dislocation number per side is lowered through a three-to-two annihilation reaction, see blue circles in c) and d)