Formability of AA7021-T4 Sheet Alloy Under Changing Strain Path Conditions: Experiments and Crystal Plasticity Modeling
Year: 2026
Type: article
Abstract: The formability of AA7021-T4 sheets under changing strain paths was investigated via a novel crystal plasticity model and associated experimentation. The motivation was to advance simulation tools for process design of limited-ductility 7xxx alloys, with important applications in the automotive industry. Pre-strains were applied in biaxial and plane-strain tension using Marciniak tooling, followed by uniaxial tensile testing to failure. Strain measurements were obtained by digital image correlation, while dislocation structures were characterized using high-resolution EBSD. A strain-gradient elasto-plastic self-consistent (SG-EPSC) model incorporating dislocation density-based hardening and backstress from geometrically necessary dislocations (GNDs) was employed to predict stress–strain response and dislocation evolution. Results showed that prestrains normalized by forming limit diagram (FLD) criteria produced comparable residual uniaxial tensile ductility, regardless of whether biaxial or plane-strain tension was applied, despite differences in absolute pre-strain levels. Both experiments and simulations revealed that GND density correlated with remaining ductility better than simple strain magnitude values. These findings indicate that AA7021-T4 retains greater formability under multiaxial strain path changes than expected from FLD-based considerations. The combined experimental–modeling approach demonstrates the value of incorporating microstructure-based variables, such as GNDs, into forming assessments of high-strength aluminum alloys, with implications for their potential use in automotive lightweighting development.
Source: Crystals
Institutions: University of New Hampshire, Brigham Young University
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,534
Awards: GOALI/Collaborative Research: Understanding Multiscale Mechanics of Cyclic Bending under Tension to Improve Elongation-to-Fracture of Hexagonal Metals, GOALI/Collaborative Research: Understanding Multiscale Mechanics of Cyclic Bending under Tension to Improve Elongation-to-Fracture of Hexagonal Metals
OpenAlex ID: W7136602782