Phase transformation mediated anomalous plasticity of titanium under severe loading conditions

TQ Li and HX Zong, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 237, 107799 (2023).

DOI: 10.1016/j.ijmecsci.2022.107799

Titanium (Ti) with omega phase is always considered brittle and non- deformable. Therefore, little is known of the role of omega phase in the anomalously high plasticity of titanium alloys undergoing severe plastic deformation. The deformation mechanisms of shocked Ti samples in uniaxial compression and severe shear deformation was investigated by using molecular dynamics (MD) simulations. Results show that anomalous plasticity of Ti is accommodated by a forward and reverse alpha-omega martensitic transformation and subsequent twin-twin interactions, rather than conventional dislocation activity. The dislocation-free deformation mechanism in omega-Ti is due to an energy barrier that favors omega ->alpha martensitic transformation compared to dislocation-based slip. Moreover, the alpha ->omega martensitic transformation process is accompanied by grain/domain refinement, which can be explained by the symmetry change during the phase transformation. This work advances the understanding of the interplay between phase transformation and plastic deformation in titanium under extreme loading conditions.

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