The atomic mechanisms of twin boundary migration in copper under externally applied mechanical loads and during thermal annealing were investigated utilizing molecular dynamics computer simulations. The migration dynamics of the incoherent Σ = 3[110](112) twin boundary, pinned between two Σ = 3[110](111) twin boundaries, was determined. A three-dimensional structural model was described for the junction between intersecting coherent and incoherent twin boundaries, and migration velocities were calculated under thermal annealing conditions. It was shown that the coherent twin boundary (CTB)/ITB junction resulted in breaking the crystal symmetry by creation of either an edge dislocation or a mixed (edge/screw) at the intersection. These two types of defects could lead to pronounced differences in the observed migration (and hence annealing) rates of ICT/CTB junctions. The annealing rate resulting from the migration of incoherent twin boundaries with a mixed dislocation was found to be more than twice that of the edge dislocation. The mechanism of incoherent twin boundary motion was shown to be governed by successive kink-like motion of neighbouring atomic columns, each of which was shifted by ¼[110], followed by structural relaxation to accommodate boundary motion.

Structure and Motion of Junctions between Coherent and Incoherent Twin Boundaries in Copper. J.A.Brown, N.M.Ghoniem: Acta Materialia, 2009, 57[15], 4454-62