Twinning and Detwinning Mechanisms in Beta-Ti Alloys
We have investigated {332}<113> twinning and detwinning mechanisms in β-Ti alloys. Microstructure-twinning relations were evaluated in a β-Ti-15Mo (wt.%) alloy by statistical analysis of the evolving twin structure upon deformation by in-situ SEM testing and electron backscattering diffraction (EBSD). We find that most of the primary twins (~80%) correspond to the higher stressed variant and follow Schmid’s law with respect to the macroscopic stress. Detwinning mechanism was evaluated in a multilayered β-Ti-10Mo-xFe (x: 1-3 wt.%) by EBSD. We find that the detwinning process consists of two independent events that occur at two different microstructural regions, i.e. twin tips located at grain interiors and grain boundaries. Both detwinning modes can be explained from a thermodynamic standpoint where the boundary dissociation processes minimize the boundary free energy.