Mechanism and modelling of the electroplastic effect in titanium alloy: From the perspective of dislocation slip

Electrically assisted (EA) forming technology has gained attention for manufacturing the difficult-to-form components of titanium alloy. However, the mechanism of the electroplastic (EP) effect on deformation behaviors remains unclear and the EP effect-coupled constitutive models are scarce, which hinders application of electrical current. In this study, the mechanism of the EP effect on deformation behavior was investigated from pinning, depinning, drag and release stages of dislocation slip. It is found that the thermal EP effect presented in pinning, depinning and release stages, whose mechanism was the same as that in thermally-assisted deformation. In contrast, the athermal EP effect enhanced dislocation pinning and depinning behaviors through promoting solute diffusion to dislocation line and generation of the electrical free energy at pinning points, respectively. While, the athermal EP effect didn't influence the release stage. Then, a physically based EA constitutive model was established. The thermal effect was modelled using thermal activation theory for pinning and depinning stages and Seeger's relation for release stage. The athermal effect on pinning stage was modelled by evaluating solute concentration near mobile dislocations based on electromigration theory and metallic bond dissolution theory. Besides, the athermal effect on depinning stage was modelled by calculating the electrical free energy generated at pinning points based on electrical free energy theory. The model provided good predictive ability and wide application range. Based on the model, the contributions of the thermal and athermal EP effects to flow stress were quantified under various EA deformation conditions.