Electrically assisted (EA) forming is a plastic forming technique under the coupling action of multiple energy fields, such as force field, temperature field, and electric field. It is suitable for the forming of difficult-to-deform materials such as nickel-based superalloys. In this paper, uniaxial tensile tests on nickel-based superalloy sheets were carried out using the pulsed current assisted with different parameters. The experimental results show that the flow stress of the material decreased with the increase in the current density under a high-frequency pulsed current, and the Joule heating effect explains the flow stress drop. In the pulsed current application process, the different types of Portevin-Le Chatelier phenomena appeared with the increase in the current density. The decrease in elongation assisted by the pulsed current was explained by analyzing the inhomogeneity of the maximum Joule heating temperature distribution. In addition, the digital image correlation (DIC) analysis was used to analyze the local strain behavior of the pulsed current-assisted tensile process. Under the application of a high-frequency pulse current, the specimen exerted an inhomogeneous temperature increase and local hot pressing stress, which resulted in the inhomogeneous distribution of the local strain.
Keywords: Joule heating; local strain; nickel-based superalloy; pulsed current.