<p>Friction stir consolidation (FSC) is a solid-state manufacturing technique that transforms metal powders, chips, or scraps into dense, solid blocks through intense plastic deformation and solid-state bonding. This study investigates the effect of material arrangement during the FSC process of Cu/Al (Case #1) and Al/Cu (Case #2) multi-material billets on their metallurgical and mechanical properties. The microstructure and chemical composition were analyzed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The hardness of the billets was evaluated through Vickers microhardness testing. The findings reveal that the properties of the consolidated billets are significantly influenced by the initial material placement. In Case #1, where Al was positioned above Cu, a well-formed bowl-shaped weld with an observable diffusion zone containing intermetallic compounds was identified at the interface. Conversely, in Case #2, no diffusion was observed between Al and Cu at the interface, resulting in an unsound weld. This study highlights the importance of material arrangement in optimizing the interface properties of multi-material billets produced by FSC.</p>