L-PBF fabricated tools for FSW: effects of geometric design and process parameters on AA6082 joints

This study is focused on the evaluation of mechanical performance and microstructural characteristics of friction stir welded aluminum joints obtained by using additively manufactured tools. In particular, Laser Powder Bed Fusion (L-PBF) technology was used. The joints obtained with printed tools were compared with which welded with a traditionally machined tool. The feasibility and the effect of additive tools were evaluated considering multiple tool geometries and feed rates and the obtained results were analyzed through hardness mapping, tensile testing, and Digital Image Correlation (DIC). As a general result, L-PBF tools demonstrated flatter and more symmetric hardness profiles in the weld cross section and thermo-mechanically affected zones reduced by up to 7 mm compared to the traditional tool. At 700 mm/min, Tool D showed a hardness increase of 10 HV at the nugget. In tensile tests, Tool C at 700 mm/min achieved the highest ultimate tensile strength, outperforming the traditional tool by 9.5%. Regarding the elongation at break, the best result was reached by Tool A at 375 mm/min, surpassing the traditional tool by 3.9%. With the DIC results, an improved deformation control with a more defined strain localization was confirmed in L-PBF tools, particularly on the joints retreating side. Tools B and C exhibited the best combination of strength, ductility, and weld quality, but the microstructure analysis highlighted Tool C as the best refinement and homogenization effect on the microstructure. The findings demonstrate the potential of L-PBF tooling to enhance FSW performance when process parameters and tool design are optimized.