<p>7003 aluminum alloy offers high strength and formability, ideal for vehicle structures. Studying its impact behavior and modeling can broaden its applications. Under high-speed impact, the flow stress of the cast 7003-T6 aluminum alloy is significantly higher than that under quasi-static loading. With strain rate below 4100 s⁻¹, the flow stress increases gradually after yielding, whereas at 4100 s⁻¹, it peaks at a strain of about 0.12 before decreasing. During deformation, the grains are elongated into fibrous structures, with some regions exhibiting shear deformation characteristics where the primary and secondary shear bands converge and propagate toward specimen center. Simultaneously, high-speed impact induces high-density dislocations that accumulate at grain boundaries, eventually forming dislocation tangles and geometrically necessary dislocations. An optimized model is developed by modifying the strain hardening term and strain rate sensitivity coefficient in the Johnson–Cook (J–C) constitutive model, along with incorporating an adiabatic temperature rise correction term, achieving prediction errors within ± 10% (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(R\)</EquationSource> </InlineEquation> = 0.991, <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(AARE\)</EquationSource> </InlineEquation> = 1.3%). Based on the established modified J–C model and considering the thermo-mechanical coupling, a VUMAT subroutine is developed and implemented in ABAQUS/Explicit. The simulated stress–strain curves and strain wave–time curves agree well with the data from experiments and constitutive model predictions.</p>