Overcoming strength–ductility trade-off in shape–performance integrated fabrication by incremental sheet forming

Abstract

The integrated fabrication of accurate forming shapes and micro–macro properties of metal components have promoted carbon neutrality in industrial manufacturing. We found that the multi-stage incremental sheet forming (MISF) process can achieve shape–performance integrated fabrication of thin-walled parts. However, the performance-influencing mechanism of the MISF approach remains unknown, and the methods for mechanical property prediction have received little attention. Therefore, MISF strategies were investigated for a square copper part through experiments, microstructural analysis, and theoretical predictions. The parts formed with different strategies had the same shape, but their strength–ductility synergy increased with the number of stages. In addition, the MISF-produced copper demonstrated an outstanding strength–ductility trade-off, where the yield stress with the optimized strategy was improved to 231.7 MPa, an increase of over 2.6 times compared with that of the raw material, with a uniform elongation of 20.5 %. A microstructural analysis was performed to investigate the material reinforcement mechanism attributable to dislocation accumulation, which decreased with an increasing number of stages. Based on the deformation procedures and microstructure evolution, an efficient theoretical model of the MISF mechanical properties was proposed for the first time using a dislocation-based constitutive function, where the effectiveness was improved by considering the back stress. This work demonstrates the practicality of the shape–performance integrated fabrication of thin-walled parts and sheds light on the application of the MISF technique.