This paper describes a simple numerical model for predicting the heat generation in friction stir welding (FSW) from the material hot deformation and thermal properties, the process parameters, and the tool and plate dimensions. The model idealises the deformation zone as a 2D axisymmetric problem, but allowance is made for the effect of translation by averaging the 3D temperature distribution round the tool in the real weld. The model successfully predicts the weld temperature field, and has been applied with minimal re-calibration to aerospace aluminium alloys 2024, 7449 and 6013, which span a wide range of strength. The conditions under the tool are presented as novel maps of flow stress against temperature and strain-rate, giving insight into the relationship between material properties and optimum welding conditions. This highlights the need in FSW for experimental high strain-rate tests close to the solidus temperature. The model is used to illustrate the optimisation of process conditions such as rotation speed in a given alloy, and to demonstrate the sensitivity to key parameters such as contact radius under the shoulder, and the choice of stick or slip conditions. The aim of the model is to provide a predictive capability for FSW temperature fields directly from the material properties and weld conditions, without recourse to complex CFD software. This will enable simpler integration with models for prediction of, for example, the weld microstructure and properties.

In the present study the microstructure and properties of a dissimilar friction stir weld between the magnesium alloy AZ31 and the aluminium alloy 6040 have been investigated. The intermetallic leads to a loss of strength and ductility of the join. In this study optical and scanning electron microscopy as well as energy dispersive spectroscopy (EDS) have been used to analyse the join interface as well as workpiece residues bonded to the joining tool. Dynamic recrystallisation was observed in the stir zone resulting in a substantial reduction in grain size particularly for the Al base material.

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In materials science X‐ray microtomography has evolved as an increasingly utilized technique for characterizing the 3D microstructure of materials. The fundamentals of X‐ray microtomography experimental methods and the reconstruction and data evaluation processes are briefly described. A review of in‐situ synchrotron X‐ray microtomography studies in literature is given. Examples of recent work include in‐situ microtomography investiagtions of metallic foams, in‐situ studies of the sintering of copper particles, and in‐situ investigations of creep damage evolution in composites. Future perspectives of in‐situ X‐ray microtomography studies in materials science are outlined.