Microstructural evolution and formability of Ti-6Al-4V alloy sheet during electropulsing-assisted bending
(1. College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China;
2. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;
3. Engineering Research Center of Advanced Metal Composites Forming Technology and Equipment of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China)
2. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;
3. Engineering Research Center of Advanced Metal Composites Forming Technology and Equipment of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China)
Abstract: The electropulsing-assisted bending test was carried out on Ti-6Al-4V alloy sheet with the effective current density of 0-3.2 A/mm2 and duty ratio of 10%-70%. The results show that the bending forming displacement increased from 9.15 to 15.60 mm with increasing effective current density from 0 to 2.4 A/mm2. The crack changed to be shallow and small at the same time. Besides, the springback angle decreased as the effective current density increased at the bending displacement of 8 mm. Duty ratio also affected bending angle, where 30% duty ratio led to the lowest bending angle of 135.0°. The thermal stability temperature increased with increasing effective current density and varied non-monotonically with duty ratio. In addition, grain coarsening, {0001} texture strengthening and sub-grain development were observed during electropulsing-assisted bending. The electropulsing decreased dislocation density and accelerated dislocation rearrangement, the rearranged and piled-up dislocation inside α grains promoted sub-grain structure formation, which improved the formability. The contribution of athermal effect made the low-temperature formability of Ti-6Al-4V alloy comparable to that at high temperature.
Key words: Ti-6Al-4V alloy sheet; microstructural evolution; formability; electropulsing-assisted bending; springback; dislocation; athermal effect