On interaction of twinning disconnections with obstacles in hcp metals

Mechanical twinning is important mode of plastic deformation in the metals with hcp crystal structure. (e.g. magnesium and titanium alloys). Migration of twin boundaries are often mediated by disconnections. Disconnections are interfacial defects, which combine dislocation and step character. Mechanisms of interaction between disconnections gliding on the {1 0 -1 1} and {1 0 -1 2} twin boundaries and obstacles will be the subject of proposed presentation. Several types of interactions will be considered: interaction with unshearable obstacle, interaction between disconnections and interaction with stacking faults. The nucleation of non-invariant plane facets on the twin boundaries as results of the interaction will be demonstrated as well as disconnection-mediated mechanism of stacking fault growth inside twins.