Large area friction stir additive manufacturing of intermetallic-free aluminum-steel bimetallic components through interfacial amorphization

Dissimilar metal additive manufacturing of aluminum-steel (AlFe) components offers many opportunities for achieving effective structural lightweighting and multi-functionalities. However, just like direct welding of aluminum alloys to steels, the formation of detrimental intermetallic compounds (IMCs) at the AlFe bimetallic interface has been seen as the major challenge. One recent development in understanding nanoscale shear localization induced alloy amorphization at the AlFe interface has provided a physical basis for developing a modified friction stir additive manufacturing (FSAM) process. This study shows that the modified FSAM is an effective solution for mitigating detrimental IMCs through the development of the nanoscale amorphous phase between the deposited aluminum alloy and steel substrate. The results show that the formation of the nanoscale amorphous metal at the AlFe bimetallic interface leads to the development of ductile fracture features within the aluminum layer in the mechanical tests. Compared to the existing FSAM, the modified FSAM enables a more robust and cost-effective manufacture of AlFe bimetallic structures without introducing detrimental IMCs.