UBC Theses and Dissertations
Mathematical modelling of the microstructural evolution during the hot rolling of AA5083 aluminum alloys Jupp, Simon M.
A mathematical model to predict the through-thickness temperature, strain and strain rate distribution after a single hot rolling stand was developed and applied to two commercially significant alloys, AA5083 and AA5056 aluminum alloys. For the AA5083 aluminum alloy application a microstructure component was added to model the microstructure evolution that occurred in the strip in the time between the roll bite exit and the quench. The deformation model was developed using a commercial finite element package, ABAQUS™, which couples the thermal and deformation phenomena that occur during strip rolling. The model is able to predict the temperature, strain and strain rate distribution at any position in the strip and any time during the roll bite. The microstructure model is a "user-defined" subroutine within ABAQUS™ that uses semi-empirical equations from in the literature quantifying the microstructure (fraction recrystallised) changes that occur between the roll bite exit and the quench. The microstructure model uses roll bite exit values for deformation temperature and strain, as well as the mean strain rate for at the through-thickness locations. The thermal history of the strip in the interpass region is predicted by ABAQUS™ based on convective heat transfer between the strip and the environment. This is used in the microstructure model to predict recrystallisation kinetics. Validation of the model using a literature comparison and industrial data indicated reasonable predictions for temperature, strain and rolling loads. However, the microstructure model using Raghunathan's equation is not able to consistently predict the fraction recrystallised. A sensitivity analysis indicated that the microstructure model used to predict recrystallisation kinetics was extremely sensitive to the deformation temperature as well as the fitting parameters used in the equation.
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