A numerical simulationNumerical simulation of the continuous twin-roll castingCasting (TRC) process for AA 80118011 aluminum alloyAluminum alloy was conducted to investigate the formation of centerline segregation, a critical defect known to impair downstream formabilityFormability and mechanical propertiesMechanical properties. The study utilized a 3D thermo-fluid model in ProCAST®, with essential temperature-dependent material propertiesProperties, such as phase evolution, calculated by the CompuTherm software package. For predictive accuracyAccuracy, the model was carefully calibrated against experimental data from an industrial castingCasting line. Following validation, a parametric sensitivity analysis quantified the influence of key variables on the defect. The investigation focused on five variations in alloy chemistry (specifically the Fe:Si ratio), two different interfacial heat transferHeat transfer coefficients (IHTC), and two mushy zone permeability models that govern interdendritic fluid flow. Results conclusively demonstrated that the alloy’s chemical compositionChemical composition, particularly the Fe:Si ratio, is the dominant factor, controlling the type and morphology of ironIron-bearing intermetallicIntermetallics phases that precipitate during solidificationSolidification.