: Additive friction stir deposition (AFSD) of Ti/Al dissimilar alloys offers a high-potential route for fabricating lightweight heterogeneous structural, yet it is often hindered by low interfacial friction and deposition instability. In this study, pre-fabricated micro-grooves were introduced on the titanium substrate to modulate interfacial friction and promote material anchoring. This geometric modification successfully suppresses interfacial sliding, enabling the continuous, defect-free deposition of multilayer aluminum builds. Microstructural characterization reveals that the resulting bond is governed by a synergy of mechanical interlocking and localized metallurgical interaction. Transmission electron microscopy (TEM) characterization reveals localized formation of interfacial phases, including Al 18 Ti 2 Mg 3 , Al 2 Cu, and Al 3 Ti. The formation of Al 18 Ti 2 Mg 3 is associated with Mg-Ti co-diffusion, whereas Al 3 Ti forms preferentially in solute-depleted regions. Severe plastic deformation is primarily accommodated by the aluminum, leading to fine equiaxed grains with weak texture, while the titanium substrate largely retains its rolled microstructure. Localized shear deformation within the groove region promotes grain refinement and improves groove filling, thereby enhancing mechanical interlocking. In contrast, incomplete filling of the grooves reduces interfacial integrity. Mechanical testing shows a maximum interfacial strength of 270.3 MPa. Fracture surfaces exhibit aluminum adhesion and ductile dimples in well-bonded regions, whereas poorly bonded regions display features characteristic of brittle failure. These findings provide a strategic framework for interface design in the solid-state additive manufacturing of complex multi-material systems.
Zhang et al. (Mon,) studied this question.