Reduction of springback of Ti6Al4V alloy by high-density and instantaneous pulsed current

Abstract

Ti6Al4V alloy has widely been used in the construction of aircraft parts, such as skins and wall plates owing to its low density, high specific strength, and excellent corrosion resistance. However, its large springback challenges the forming process. In this work, the effects of high-density instantaneous pulsed currents on the springback of Ti6Al4V alloy sheets were investigated by experimental and microscopic analysis. The results suggested a decrease in springback angles of workpiece as a function of discharge voltage. At a voltage reaching 6 kV, the springback was eliminated. For distinguished thermal and electrical effects, the maximum temperature of the specimen and thermal bending was measured at 6 kV. The data revealed a much smaller springback of electropulsing treated (EPT) workpiece when compared to heat-bending workpiece. Thu, the thermal effect was not the only reason leading to reduced springback. The mechanical properties tests of the specimens indicated a slight decrease in the strength of EPT-6kV while showing a significant increase in elongation than the as-received specimen. The microstructural evolution depicted recrystallization of EPT-6kV specimen with phase transformation, declined dislocation density, refined grain, decreased texture strength, and raised low Taylor factor grain content, leading to enhanced deformability. The temperature rise during EPT reduced the flow stress and facilitated the springback reduction. The applied current also promoted α→β phase transition, providing additional stress drop, reduction in dislocation density, and release of stress by recrystallization grain growth, further promoting the springback elimination. Overall, these findings look promising for reducing or eliminating the springback of Ti6Al4V titanium alloys.