Bimetallic Al–Fe composites with tailored properties produced by cold spray additive manufacturing

Cold spray enables multi-material additive manufacturing through solid-state bonding, thereby reducing intermetallic formation and thermal residual stresses typical of fusion-based manufacturing routes. This study establishes a composition–structure–property framework for cold sprayed Al–Fe bimetallic composites produced by online powder mixing by varying Fe content from 0 to 100 vol% and relating retained composition to microstructure and mechanical response. The mixed deposits formed dense Al-rich matrices containing dispersed Fe splats, while retained composition deviated from the nominal feedstock composition at higher Fe contents. Porosity decreased from ∼0.8% in pure Al to ≤ 0.25% in the mixed deposits, and the flattening ratio of Al splats increased with Fe addition, indicating enhanced matrix deformation. Mechanical properties were governed by retained Fe content: elastic modulus increased from 32 to 61 GPa, while yield/tensile strengths rose from ∼40/55 to ∼77/94 MPa, approaching saturation beyond ∼23–28 vol% retained Fe. Ductility exhibited a non-monotonic trend, reaching a maximum in Al–25Fe (∼5% fracture elongation) and decreasing at higher Fe contents as clustering and interface-controlled fracture became more pronounced. Overall, retained composition and spatial distribution governed the balance between strengthening and damage mechanisms, defining an intermediate Fe regime that provides the most favorable mechanical performance.