Solid-State Reactive Processing of Al-Fe₃O₄ Nanothermites for In Situ Formation of Soft-Magnetic Fe Nanoparticles in...

We present a solid-state reactive processing (SSRP) route that enables in situ formation and uniform dispersion of metallic Fe nanoparticles within an aluminum matrix through controlled nanothermitic reactions. Using friction-assisted plastic deformation of an Al-Mg alloy embedded with a small fraction (∼4 wt %) of Fe₃O₄ particles, localized heat and shear deformation promote concurrent mechanical mixing, thermal activation, and chemical reduction. The reaction between Fe₃O₄ and Al/Mg produces Fe cores encapsulated by MgO and Al₂O₃-rich shells, effectively suppressing the formation of brittle Fe-Al intermetallics that typically hinder Fe-reinforced Al systems. The resulting microstructure exhibits fine-scale dispersion of core-shell nanoparticles and significant matrix refinement, leading to enhanced hardness and electrical resistivity. This proof-of-concept demonstrates that multistimuli coupling during solid-state processing can activate in situ controlled thermite reactions at moderate temperatures, providing a new pathway for fabricating lightweight, multifunctional metal-oxide nanocomposites.