Microstructure-based modeling of residual yield strength and strain hardening after fire exposure of aluminum alloy 5083-H116

Aluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as light rail and marine crafts. The structural performance of such aluminum structures during and after a fire is a major concern. Post-fire evaluation of structural integrity and assessment for structural member replacement requires an understanding of the residual (post-fire) mechanical state of the material. In this work, a model is developed to predict the residual constitutive behavior of AA5083-H116 at room temperature following fire exposure. This model comprises several sub-models to predict (i) microstructural evolution, (ii) residual yield strength, and (iii) residual strain hardening behavior. Time-temperature dependent kinetics models were implemented to predict microstructural evolution, i.e., recovery and recrystallization, during a non-isothermal fire exposure. The residual yield strength is predicted as a function of the subgrain (recovery) and grain (recrystallization) evolution based on kinetic modeling. The residual strain hardening behavior is predicted using the Kocks-Mecking-Estrin law modified to account for the additional dislocation storage and dynamic recovery of subgrains. Constitutive model predictions of residual yield strength and strain hardening show good agreement with experimental data residual yield strength and strain hardening data.