Observing the dynamic {10(1)over-bar1} twining process in pure Ti at atomic resolution

The real-time {10 (1) over bar1} twinning process at the crack tip of Ti is captured by carrying out the in situ tension tests in a transmission electron microscope. Both the atomic-resolution observations and the molecular dynamics simulations reveal that the {10 (1) over bar1} twinning deformation is accomplished by the twinning mode corresponding to the b(2) twinning dislocations instead of the conventional b(4) mode. The sessile steps in twin boundaries which induced by pyramidal stacking faults extending across the twin are observed acting as the nucleation sources of b2 twinning dislocations. The nucleation mechanism is verified by determining the Burgers vectors of the sessile steps. (C) 2017 Published by Elsevier Ltd on behalf of Acta Materialia Inc.