Micro-friction stir welding of thin aluminum sheets requires precise control of heat generation and axial force, as insufficient heat input may result in insufficient material plasticization, while excessive heat can lead to local thinning, surface defects, or loss of dimensional stability. In this study, a finite element simulation was developed to investigate the thermomechanical response during micro-FSW of 0.6 mm thick 6061-T651 aluminum alloy sheets. The model was used to evaluate the influence of tool rotational speed and feed rate on the temperature field and downward force during welding. The tool employed featured a pin with a diameter of 3 mm and a length of 0.4 mm while the tool shoulder was 10mm. The results indicated that the optimal temperature and force for the used material were achieved at a rotation speed of 750 rpm and a feed rate of 400 mm/min. These results suggest that numerical simulation is a useful approach for reducing experimental time and selecting initial conditions for micro-FSW trials.

Therefore, the study establishes a safe operating window for micro-FSW on 0.6 thick 6061-T651 aluminum alloy sheets, as in case of such thin metal sheets, a slight change in rotation speed or feed rate can abruptly shift the process from a stable state to one with significant defects.