Precipitate evolution and grain size modelling in friction stir welding of AA7449

摘要

The development and application of microstructural models for friction stir welding of aerospace aluminium alloys is presented. These models have been applied to predict the precipitate and grain size evolution in AA7449 aluminium alloy welds performed using the FlexiStir welding system, which permitted in-situ tracking of the microstructure using small angle X-ray scattering (SAXS). A previous model for precipitate evolution during FSW has been augmented by a simple mode to predict grain size in the weld nugget. This model assumes that the dominant recrystallization mechanism during FSW is geometric dynamic recrystallization (GDRX). The grain size model has been tested against experimental data in the literature. Both the precipitate and grain evolution models are demonstrated to give reasonable predictions compared with the available data as well as provide useful insights into the mechanisms controlling microstructural change during FSW that are difficult to obtain by direct measurement.