Molecular dynamics simulations of grain boundary migration were performed, where the driving pressure, P, was the excess stored energy due to dislocation structures. This represented recrystallization in metals. Two types of dislocation structure were simulated: tilt dislocation boundaries, where edge dislocations were arranged as parallel arrays, and twist dislocation boundaries, where screw dislocations were arranged in interconnected dislocation networks. The velocity, v, and mobility, M, of the migrating grain boundaries were deduced from the simulations. It was found that v and M were higher in twist-type simulations than in tilt-type simulations, although the activation energies were similar in the two cases. Also, v ∝ P was observed for tilt simulations, where the driving pressure was changed by varying the density of dislocation boundaries, and for twist simulations where the driving pressure was changed by varying the misorientation across dislocation boundaries. However, when the misorientations across edge dislocation boundaries were varied, the simulations showed v ∝ P2. It was suggested that this deviation from the usual v ∝ P relationship was due to local interactions between the grain boundary and nearby individual dislocations. Misorientation variations across grain boundaries were also simulated, but the mobilities exhibited little dependence upon this. The present simulations resulted in mobilities and activation energies that were significantly higher, and somewhat lower than, experimental values, respectively. The present simulations were based upon idealized dislocation structures and suggested that variations in the dislocation structures might play a dominant role in recrystallization dynamics, and that local effects were very important phenomena and were essential for the interpretation of recrystallization mechanisms.

Molecular Dynamics Simulations of Grain Boundary Migration during Recrystallization Employing Tilt and Twist Dislocation Boundaries to Provide the Driving Pressure. R.B.N.Godiksen, S.Schmidt, D.J.Jensen: Modelling and Simulation in Materials Science and Engineering, 2008, 16[6], 065002