Molecular dynamics simulations were used to apply shear to the twinned microstructure of an hexagonal close-packed metal, as represented by a Finnis-Sinclair type potential for Zr. The twinned microstructure resulted from a simulated martensitic phase transition from the high-temperature phase, and therefore contained some boundary defects. The 60º twin boundary could be regarded as being a (10•1) symmetrical tilt boundary with partial twin boundary dislocations. These were sessile, but acted as sources for the boundary steps which permitted the boundary to migrate. When the twinning deformation mechanism was exhausted, the partial twin boundary dislocations remained as lattice dislocations and could move under further shear.

Atomistic Simulation of Shear in a Martensitic Twinned Microstructure. U.Pinsook, G.J.Ackland: Physical Review B, 2000, 62[9], 5427-34