Mechanical Properties of Work-hardened Pure Titanium Foils Pre-treated by Short-time Continuous Electric Current

The mechanical properties of work-hardened pure titanium foils pre-treated by short-time continuous electric current were studied. Tensile tests were conducted for the foils pre-treated at different temperatures. A laser speckle-based digital image correlation (DIC) technique was utilized for a full-field strain measurement. The accuracy of the DIC system was confirmed by the correlation with the measurement from a video extensometer. The continuous electric current was kept for around 1 min to pre-treat the foils at different temperatures. The mechanical properties of the foils affected by the continuous electric current were discussed in terms of stress-strain curves and strain field. The results showed that the foils indicated non-uniform temperature distribution along length direction while the strain localized at the area with higher temperatures. The stress indicated the same profiles for the foils without pre-treatment and pre-treated at 160 and 300°C. In the meanwhile, the stress decreased while the fracture strain increased when the pre-treating temperature achieved 450°C, revealing an increase of ductility of the foils pre-treated at a higher temperature. The full-strain field and strain distribution showed that the width of the area with localized strain increased with increasing pre-treating temperature. The Lankford coefficient was calculated based on the obtained strain field, showing an increasing-decreasing tendency with increasing pre-treating temperatures.