Temperature dependence of electroplastic effect on reducing the ultimate stress in Ti–6Al–2Zr–1Mo–1V alloy during tension

Abstract

To investigate the electroplastic effect of Ti–6Al–2Zr–1Mo–1V alloy (TA15 alloy) at different temperatures, the uniaxial tension tests assisted with the pulsed current and temperature matched tension tests without current were performed at the temperature ranging from 200 °C to 800 °C in this study. The results demonstrated that the electroplastic effect of TA15 alloy became appreciable as the temperature approached 600 °C, namely that the pulsed current contributed about 12% reduction in ultimate stress with respect to that of temperature matched test when the temperature was higher than 600 °C. The microstructure observation showed that the pulsed current reduced the ultimate stress by enhancing dislocation recovery and α→β phase transformation. These electroplastic effects for reducing the ultimate stress were related on temperature. When the temperature was higher than 700 °C, the effect of pulsed current on ultimate stress drop changed from promoting dislocation motion to accelerating the nucleation and growth of softer β phase by accelerating the diffusion of Mo, V elements enriched in the β phase. The electroplastic mechanism was considered as the ‘local heat spot’. The higher energy surrounding the defects could reduce a resistance to move an ion core for titanium, which may have a significant effect on dislocation motion and element diffusion promoted by pulsed current.