Mechanical Response Behavior, Constitutive Modeling and Microstructural Evolution of a 7003-T6 Al Alloy Rolled Plate Under High-Speed Impact Loading

Abstract

The mechanical response behavior, constitutive modeling and microstructural evolution of a 7003-T6 Al alloy rolled plate under various strain rates are systematically studied through high-speed impact test, numerical simulation and microscopic characterization. The results show that the flow stress exhibits a positive SRS, while a negative SRS in the later stage of deformation. When the impacted strain is lower than about 0.21, the plastic deformation is relatively uniform, followed by local shear plastic deformation, which initiates from the edge of the impact surface and then propagates to the center of sample approximately along 25°. Subsequently, local shear deformation occurs at the edge of the other end of the sample. Apparently, the original fibrous grains are continuously fibrillated with the increase of applied strain. The dislocation density increases with the increase of impact strain and strain rate and then evolves into GNDs and cell-like structures. These dislocations with different morphologies gradually evolve into some cellular structures, which eventually lead to a decrease in dislocation density. Due to the adiabatic temperature rise, a small fraction of the previously increased precipitates is dissolved. Furthermore, an optimized JC constitutive model is established by modifying the strain hardening term into a coupled equation of strain and strain rate. The correlation coefficient and average relative error are 97.45% and 1.51%, respectively. Therefore, the evolution of adiabatic temperature rise is obtained by numerical simulation using this optimized model. These results can contribute to the design and optimization of vehicle body structures made by 7003 Al alloy plates.

Keywords: 7003 aluminum alloy, High-speed impact, mechanical response, Microstructure evolution, Adiabatic temperature rise