Observations of Contraction Twin Boundaries of High-Purity Titanium during Dynamic Loading

Abstract

High-purity titanium has been subjected to dynamic compression with a strain rate of 103 s−1 to activate {112-2} and {112-4} contraction twins. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) were performed to observe the morphologies and twin boundaries of the contraction twins. The results show that {112-2} twins are the predominant twinning mode, as well as the formation of {112-4} twins due to the change in local stress state at the intersection region of {112-2} twin variants or {112-2} twin and grain boundary. The TEM and HRTEM observations reveal that (0001)‖(1122-) facets and (0001)‖(1121-) facets formed along the {112-2} and {112-4} twin boundaries, respectively. According to the theory of interfacial defects, the propagation of the {112-2} twin boundary was discussed with (b3, 3h{112-2}) and (b1, h{112-2}) twinning disconnections, as well as the growth process of the {112-4} twin boundary.