Multiscale modeling of coupling mechanisms in electrically assisted deformation of ultrathin sheets: An example on a nickel-based superalloy. (March 2021)

• Record Type: Journal Article
• Authors: Liu, Y.Z.; Wan, M.; Meng, B.
• Is Part Of: International journal of machine tools & manufacture. Volume 162(2021)
• Publication Date: 2021-03
• Subjects: Nickel-based superalloy -- Electrically assisted microforming -- Grain size effect -- Multiscale constitutive model -- Coupling mechanism; Machine-tools -- Periodicals; Manufacturing processes -- Periodicals; Machines-outils -- Périodiques; Fabrication -- Périodiques; Electronic journals; 621.902
• DOI: 10.1016/j.ijmachtools.2021.103689
• Languages: English
• ISSNs: 0890-6955

Abstract

Abstract: Electrically assisted (EA) forming has ubiquitous merits over room-temperature (RT) forming and thermally aided forming for the fabrication of difficult-to-form microscale products. However, it is difficult to predict the material deformation behavior in the EA microforming process owing to the coupling between the electric current and microstructural size effect. To develop a robust constitutive model that considers the interplay between the electric and grain size effects, RT and EA quasi-static uniaxial tensile tests were performed on ultrathin nickel-based superalloy sheets with a thickness of 0.2 mm and grain sizes ranging from 27.2 to 79.4 μm. The experimental results demonstrated that the Joule heating effect and the normalized flow stress reduction were non-monotonically related to the grain size of the superalloy. The grain size effect in the polycrystalline superalloy was suppressed by the enhanced current density. A multiscale constitutive model that considered multiple strengthening mechanisms was proposed to describe the EA deformation behavior of ultrathin superalloy sheets. The multiscale model was proven to have a desirable predictive ability for the EA drawing force of thin-walled superalloy capillaries. Furthermore, the model revealed that the weakening of the grain size effect with increasing current density in the polycrystalline superalloy was caused by the combined variations in dislocation interaction, shear modulus, and strengthening mechanisms. The abnormal evolution of the surface effect with the current density was captured by the proposed constitutive model, which demonstrates that the electric current can promote the grain size effect in the multicrystalline superalloy. Graphical abstract: Image 1 Highlights: Grain size effect in electrically assisted deformation of ultrathin superalloy sheets was investigated. Dislocation density model was modified and verified to consider grain size and electroplastic effects. Joule heating effect and normalized flow stress reduction are non-monotonically related to grain size. Pulsed current suppresses the grain size effect of polycrystalline, but promotes that for multicrystalline.