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High energy input creates enormous challenges for direct fusion bonding between dissimilar metals in wire‐arc directed energy deposition (DED). Vast differences in material properties, such as those between aluminum and stainless steel, cause significant compatibility issues. Their combination for higher performance is a compelling goal, but attempts are usually limited to nonadditive mechanical fastening. Wire‐based additive for direct fusion has never been attempted, and only powder‐based additive metal fusion manufacturing (AM) has shown any promise. Concentric radial deposition patterns are used in a wire‐arc DED system to produce a layer‐by‐layer in situ bimetallic coupling between AA5356 and SS308L to address this. The additively generated mechanical bond is held together by residual pressure, created by different thermal expansion coefficients between the concentric material bands during cooling. This produces a purely additive yet viable mechanical joint with minimal metallurgical bonding. Destructive testing defines the integrity of the additively coupled unit, with the radial overlap sustaining 732.96 Nm in torsion, 34.17 kN in tension, and a maximum of 475 MPa in compression. Fracture modes confirm the importance of concentric residual loads in creating the mechanically viable joint. Interfacial characterization shows a 300× reduction in crack width for concentrically constrained interfaces with narrowed diffusion zones.