COMPUTER-SIMULATION OF TWINNING DISLOCATION IN MAGNESIUM USING A MANY-BODY POTENTIAL

Twinning is an important plastic deformation mechanism in the response of h.c.p. metals to applied stress, and in the present paper the atomic processes associated with {101BAR1}, {101BAR2},{112BAR1} and {112BAR2} twinning in Mg are considered. The technique of atomic-scale computer modelling has been used, with atomic interactions described by the many-body potential of the Finnis-Sinclair type recently derived by Igarashi, Khantha and Vitek. The atomic structure, energy and stress state of planar twin interfaces, and the structure and energy of twinning dislocations in these boundaries, have been determined. The ease of glide of these dislocations has also been studied. It is found that the energy and mobility are related to the width of the dislocation core rather than to its height. Hence, dislocations in {101BAR2} and {112BAR1} boundaries are wide, have a low energy and are very glissile, whereas those in {101BAR1} and {112BAR2} boundaries have the opposite characteristics. These results support conclusions drawn from earlier modelling which used pair potentials.