Local Atomic Configuration of Dislocation-Accumulated Grain Boundary and Energetics of Gradual Transition from Low Angle to High Angle Grain Boundary in Pure Aluminum by First-Principles Calculations

Dislocation-accumulated grain boundaries were systematically investigated in terms of local atomic coordinates in the vicinity of grain boundary and energetics on grain boundary evolution by first-principles calculations. Detailed numerical analyses of energy and local atomic configuration at a grain boundary with fixed misorientation angle identified the most stable configurations both for the dislocation-distinctive model and the coincident-site-lattice model with kite-shaped structural units on grain boundary planes. The energy profiles of structural optimization using both initial models indicate that the distinctive dislocations at a grain boundary can be readily converted into kite-shaped structural units without noticeable energy barrier, though they look quite different, and reverse conversion may also be realized under external stress, enabling grain boundaries functioning as dislocation sources and sinks. Systematic calculations for grain boundary with misorientation angles ranging from 5.7° to 53.1° revealed that the interaction energy between dislocation is blunted within a dislocation core region. Furthermore, the energy needed to increase the misorientation angle during severe plastic deformation is quantitatively evaluated.