Protrusions at migrating high-angle grain boundaries were observed following partial recrystallization of high-purity body-centred cubic refractory metals. Their morphology was similar to that previously observed in Al and was in good agreement with the predictions of a kinetic model based upon the sinusoidal variation of the local driving pressure along the boundary. The heterogeneous dislocation structure intersecting the boundary was considered to cause this sinusoidal variation and, therefore, the growth of protrusions in the high-purity metals.

Observations of Grain Boundary Protrusions in Static Recrystallization of High-Purity BCC Metals. M.A.Martorano, H.R.Z.Sandim, M.A.Fortes, A.F.Padilha: Scripta Materialia, 2007, 56[10], 903-6