Modelling recovery and recrystallisation during annealing of AA 5754 aluminium alloy

Abstract

A microstructure model taking into account recovery and recrystallisation has been developed to predict the yield stress and the recrystallised grain size during continuous annealing of cold rolled AA 5754 sheet alloy. Using isothermal annealing tests, recovery and recrystallisation kinetics were quantified as a function of temperature and cold reduction. The model was formulated employing the internal state variable approach with the following three state variables: dislocation density, volume fraction recrystallised, and grain size. A rule of mixtures is adopted to separate the effect of recovery and recrystallisation in the overall softening. Model validation has been carried out by comparing the predicted softening curves with those obtained in continuous heating tests replicating heating rates of industrial continuous annealing lines. The model can be applied to non-isothermal processing routes of industrial cold rolled AA 5754 with thickness reduction in the range 40-80%.