Abstract: Friction stir welding(FSW) is highly suitable for the fabrication of Ti/Al structures. However, the effects of process parameters on mass and heat transfer during the FSW of Ti/Al joints, as well as the precise control of interfacial intermetallic compounds(IMCs), still require further investigation. This study, based on fluid dynamics and solid-state diffusion theory, simulates and compares the temperature fields, material flow, and IMCs growth in Ti/Al FSW under different welding speeds. The findings indicate that changes in welding speed have a smaller impact on the peak temperature during the FSW process than on the duration of high-temperature exposure. The model shows that at a welding speed of 15 mm/min, the high-temperature duration is approximately four times longer than at 60 mm/min, although the peak temperature difference at the interface between the two conditions is only about 40 K. The growth of IMCs is primarily influenced by the peak temperature and the duration of high-temperature exposure, with the latter being the main factor for thicker IMCs layers under lower welding speeds. At higher welding speeds, insufficient material flow at the bottom of the weld is the root cause of lack of penetration. The accuracy of the model is validated through experimental temperature measurements, TMAZ boundary assessment, and IMC thickness measurements.

Key words: aluminum/titanium dissimilar friction stir welding, temperature field, computational fluid dynamics model, solid phase diffusion theory, intermetallic compounds