Physical modeling of the creep response of an Al–Cu–Mg alloy with a fine microstructure transformed by Friction Stir Processing

The creep response of an Al–Cu–Mg 2024 Aluminum alloy with a refined microstructure produced by Friction Stir Processing (FSP) has been investigated. The material, after FSP, exhibited a strong reduction in creep resistance, attested by higher values of the minimum creep rate, when compared with the base metal (the AA2024 in T3 state). A constitutive model based on a theoretical approach has been then used to correlate microstructural features and creep properties. The model was modified to take into account the microstructure of the transformed alloy, with a fine recrystallized grain size and lower mechanical strength. The hardness variation with creep duration was used to quantify the particle strengthening term. The resulting model gave an excellent description of the experimental results, without requiring any data-fitting of the minimum creep rate experimental data. This achievement represents a substantial advantage over conventional approaches based on phenomenological equations.