Stability of ultra-fine 'grain structures' produced by severe deformation

Severe deformation techniques allow metallic alloys to be deformed to ultra-high plastic strains, without any geometrical change to the work piece. They thus offer potential for the cheap production of submicron grained materials, in a bulk form. After processing severely deformed materials do not have conventional, idealized, grain structures, contain significant fractions of low angle boundaries, and are often heterogeneous.

Due to their high stored energy, they are unstable on annealing and in most cases can be thought of as continuously recrystallizing. However, locally discontinuous behaviors are often observed, due to the retained less mobile low angle boundaries, as well as abnormal grain growth at elevated temperatures.

Monte-Carlo-Potts models have been used to show the sensitivity of the annealing behavior to the initial starting structure present after deformation. The effect of coarse (~1µm) particles and fine dispersoid particles are also discussed.