A generalized electro-thermo-mechanical framework for electrically assisted tube forming: Case study on TA18 titanium alloy

Abstract

Titanium alloy (TA18) tubes have good mechanical properties such high strength,hardness and yield strength ratio, but in thin-walled tubes, cracking on the exterior and shrinking on the interior are common during conventional bending processes, and often accompanied by significant springback upon unloading. This study introduces an electro assisted precision forming process to overcome these defects. Electrically assisted deformation (EAD) offers a promising pathway to improve the formability of high-strength alloys, yet the scientific understanding of its electro-thermo-mechanical coupling effects remains incomplete. This study systematically investigates the electric pulse-assisted tensile and bending behavior of TA18 titanium alloy tubes. A response surface methodology is used to optimize key electric parameters (current density, frequency, duty cycle), while microstructural mechanisms are examined through EBSD and TEM analyses. The results reveal that electric pulses not only reduce flow stress but also refine grains and enhance phase transformation, thereby improving plasticity. A modified Johnson–Cook model is developed to quantitatively capture the EAD behavior, which is validated through finite element simulations of bending processes. Meanwhile the optimal pulsed current parameters (6.41 A/mm², 258.3 Hz, 56.2 %) significantly released the deformation stress of the titanium alloy, enhanced the ductility, minimized elastic springback during forming, and improved the sectional distortion rate and thickness reduction of the TA18 tube material, markedly enhancing forming precision. Furthermore, a modified Johnson-Cook constitutive model for TA18 titanium alloy considering the Electro Assisted Deformation (EAD) was established, which accurately predicted the experimental outcomes. This case study provides a generalized framework for understanding the interaction between electric pulses, microstructure evolution, and deformation behavior in electrically assisted forming, with implications for other difficult-to-form alloys.