The plasticity deformation mechanisms caused by nano-indentation of pre-existing coherent twin boundaries in copper was studied using atomistic simulation. Initial plasticity caused by the homogeneous nucleation of threefold symmetry twinning partial loops was observed below the critical twin lamella length of 2.50nm, accompanied by a significant reduction in critical pressure, which indicates that dislocations could originate from perfect coherent twin boundaries. However, the coherent twin boundaries will block the dislocation motion following mechanism of twin boundary migration, resulting in further plastic deformation.

Direct Observation of Dislocations Originating from Perfect Twin Boundaries. J.Sun, L.Fang, K.Sun, J.Han: Scripta Materialia, 2011, 65[6], 501-4