Two different modelling approaches to predict the microstructure and properties of age hardenable aluminium alloys after non-isothermal heat treatments have been presented. These models have been applied to make predictions for aerospace aluminium alloys joined by friction stir welding. The hardness model is based on a semi-empirical method that requires calibration with data from isothermal heat treatments. A thermal model is used to predict the temperature evolution during the welding process. The model has been shown to give a good prediction of the observed hardness profile, correctly predicting the position of the hardness minimum. The numerical precipitate evolution model is based on the framework of Kampmann and Wagner. Given the temperature profile and initial precipitate parameters, this model predicts how the precipitates evolve. It accounts for transformation of metastable to equilibrium phases, and includes a prediction of both grain boundary and grain interior precipitate distributions. It has been shown that bimodal particle size distributions are predicted to evolve during welding, resulting from the mixture of coarsened particles from the original parent material and new particles formed on post-weld cooling. The model shows that the particle size in the HAZ after welding is sensitive to small changes in peak temperature during the weld cycle. The precipitate evolution model still requires further refinement. However, it already shows promise as a tool to design improved welding practices. Future developments will include linking the microstructural predictions to models for important complex properties such as fracture toughness.
Microstructural modelling for friction stir welding of aluminium alloys
ICAMMP, International Conference on Advances in Materials and Materials Processing 2006, 2006 ; 450-456
Materials and Manufacturing Processes ; 22 , 3/4
2007
7 Seiten, 9 Bilder, 1 Tabelle, 16 Quellen
Conference paper
English
Friction Stir Welding of Aluminium-Alloys
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