Electrically Assisted Forming (EAF) technology has obvious advantages in material forming. To develop an effective constitutive model considering electrical effects, room temperature and electrically assisted quasi-static uniaxial tensile tests were conducted using ultrathin nickel-based superalloy plates with a thickness of 0.25 mm. The research focused on the two most widely recognized effects: the Joule thermal and the electric athermal effects. The mechanism of current action can be divided into two scenarios: one considering the Joule thermal effect only, and the other considering both effects simultaneously. Two basic constitutive models, namely the Modified-Hollomon model and the Johnson-Cook (J-C) model, were selected to be optimized through the classification of two different situations, and four optimized constitutive models were proposed. It was found that the J-C model with simultaneous consideration of the Joule thermal effect and electric athermal effect had the best prediction effect by comparing the results of these four models. Finally, the accuracy of the optimization model was verified by finite element simulation of the electrically assisted stretching optimization model. The results show that the constitutive model can effectively predict the temperature effect caused by the Joule heat effect and the athermal effect of current on the material.

The systematic investigation of the mechanical properties and microstructure evolution process of ultra-thin-walled Inconel 718 capillary brazing joints is of great significance because of the exceptionally high demands on its application. To achieve this objective, this study investigates the impact of three distinct brazing temperatures and five typical grain sizes on the brazed joints’mechanical properties and microstructure evolution process. Microstructural evolution analysis was conducted based on Electron Back Scatter Diffraction (EBSD), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), and Focused Ion Beam (FIB). Besides, the mechanical properties and fracture behavior were studied based on the uniaxial tension tests and in-situ tension tests. The findings reveal that the brazing joint’s strength is higher for the fine-grain capillary than the coarse-grain one, primarily due to the formation of a dense branch structure composed of G-phase in the brazing seam. The effects of grain size, such as pinning and splitting, are amplified at higher brazing temperatures. Additionally, micro-cracks initiate around brittle intermetallic compounds and propagate through the eutectic zone, leading to a cleavage fracture mode. The fracture stress of fine-grain specimens is higher than that of coarse-grain due to the complex micro-crack path. Therefore, this study contributes significantly to the literature by highlighting the crucial impact of grain size on the brazing properties of ultra-thin-walled Inconel 718 structures.