Papers by Keyword: AA3103

Abstract: The microstructural evolution during annealing of a commercial Al-Mn alloy cold rolled to a high strain was investigated using EBSD and Gallium Enhanced Microscopy. The precipitation of manganese, coarsening of precipitates and tensile properties were monitored at different stages. It was found that during recovery the subgrains grow until they reach the limiting subgrain size when the driving force has been reduced to the same level as the Zener drag from the dispersoids. New grains are nucleated at constituent particles and a few are able to grow. The softening during recovery and the onset of discontinuous recrystallisation are analyzed and discussed in terms of recent theories of recovery and recrystallisation.

Abstract: The complete evolution of solute content and second phases during full-scale industrial processing of AA3103 sheets has been measured. During pre-heating, dispersoids, which appear as plates or small polyhedra grow and the Mn solute content decreases. During subsequent breakdown rolling the dispersoid number-density increases significantly. The measured decrease of solute Mn after hot rolling and coil cooling is attributed to constituent particle growth, whereas the solute depletion during the final back-annealing is mainly caused by the growth of the dispersoids. These observations are compared to the predictions obtained by a semi-physical model for precipitation. Although simulations have been performed without any retro-fitting, for hot rolling the results compare quantitatively well with experiment, while for coil cooling and back annealing the modelled Mn solute depletion is underestimated. The precipitation process is found to be very sensitive to the microstructure, which illustrates the importance of coupling precipitation models with work hardening and softening models to obtain reliable predictions.

Abstract: The softening behaviour during annealing was investigated in cold and hot rolled AA3103 alloys after different heat treatments. It was found that the evolution of boundary spacing determined using gallium enhanced microscopy gives a very good representation of the softening behaviour. The results show that cold rolled Al-Mn alloys soften by continuous growth of the subgrain structure, “continuous recrystallisation”, provided the pre-treatment of the ingots has been made to avoid too high a density of dispersoids and the cold rolling reduction has been very large. The very high strain creates a microstructure with a large fraction of high angle boundaries that are mostly parallel to the sheet surface. A recently developed subgrain growth model which takes the effect of solute drag into account, gives a good description of the softening kinetics. The solute drag is controlled by bulk diffusion of Mn. The simultaneous precipitation of Mn from the solid solution takes place by grain boundary diffusion of the Mn atoms mainly to pre-existing particles. The solute concentration decreases as the inverse of the boundary spacing, which is due to the grain growth mainly in the thickness (normal) direction.

Abstract: A diffusion controlled precipitation model based on classical nucleation and growth theory has been implemented to simulate the precipitation kinetics in a hot rolled supersaturated Al- Mn alloy (AA3103). The modelling approach explicitly includes the effect of concurrent recrystallisation on precipitation and considers the simultaneous evolution and interaction of two precipitate populations that vary significantly in size, i.e. constituent particles and dispersoids. Comparison with experimental results shows that this classical modelling approach predicts incorrect nucleus density and too high precipitation rates, which cannot be simply corrected by parameter fitting. Reasons for this discrepancy are discussed in terms of selection of nucleation sites, the effect of diffusion in a multi-component system, various diffusion paths and the possible influence of precipitate shape and size distribution. The model is subsequently altered by introducing two additional parameters that control the Mn solute concentration at the particle-matrix interface. This more phenomenological model is successful in reproducing the experimental precipitation kinetics, both in deformed and undeformed aluminium matrix, and the effect of concurrent recrystallisation for a wide temperature range.