Investigation on formability and fracture mechanisms of dissimilar DC05/AA5052 sheets in an integrated friction stir-assisted double-sided incremental synchronous forming-bonding process

Abstract

Laminated aluminum alloy-steel (Al-St) sheets exhibit significant potential for use in industrial applications because of their superior mechanical and physical properties. Differences in the intrinsic mechanical properties of these different laminates cause challenges in fabrication and plastic forming. Thermally assisted mechanical joining and forming methods exhibit significant limitations in regulating the formation of Fe-Al intermetallic compounds within Al-St laminates. Cracks can easily occur at the bonding interfaces of these laminates, which severely limits their application. Therefore, a novel forming process is necessary. This study introduces an integrated friction stir-assisted double-sided incremental forming process with synchronous bonding (FS-DSIF&SB) that combines bonding and deformation to fabricate truncated laminated conical components using dissimilar AA5052 and DC05 sheets. A modified fracture criterion, incorporating stress triaxiality, temperature, and strain rate, is developed and implemented using a VUSDFLD subroutine to evaluate ductile damage under diverse thermo-mechanical conditions. Experimental validation using high-temperature tensile tests and forming trials confirm the predictive accuracy of the fracture model. Damage progression reveals that the outer aluminum alloy layer experiences higher damage, leading to fracture. Optimized processing enhanced laminate's formability and variable wall angle compatibility. The findings underscore the process's high formability and demonstrate its potential applicability for multi-material systems and advanced manufacturing scenarios.