Formability and mechanism of ultra-thin titanium foil under the elevated temperature and high strain rate in electromagnetic forming

Electromagnetic forming (EMF) is a high-speed forming process with significant potential for manufacturing bipolar plates. However, titanium's low conductivity requires the use of a driver sheet in traditional EMF, limiting its formability improvement. This study proposed a novel electromagnetic forming method with independent loading of the magnetic field and current (EMF-ILMFC), enabling separate application of electromagnetic force and Joule heating. The dynamic deformation behavior of ultra-thin titanium was investigated using three different loading methods: quasi-static (QS), electromagnetic bulging with driver sheets (EMB-DS), and electromagnetic bulging with the new method (EMB-ILMFC). The study revealed that the forming limit under EMB-ILMFC was significantly higher than under EMB-DS and QS, with a maximum improvement of 139.1%. Numerical simulations and experimental analyses were conducted to elucidate the thermal effects on formability during dynamic deformation. The results indicate that thermal effects reduce flow stress, extend the duration of inertia and high strain rates, and thereby improve the formability of titanium.