Magnetron-sputtered thin films can differ markedly from their bulk counterparts, highlighting the need to understand how deposition-induced non-equilibrium effects influence their microstructure and stability. Fe-Cr alloys provide a convenient system to model the behavior of stainless steels, but the properties of the films require careful characterization first. In this work, the influence of composition on the microstructure of co-sputtered Fe-Cr thin films is investigated, with a focus on the formation and stability of solid solutions across a range of Cr-to-Fe ratios. Structural analysis was performed using X-ray diffraction (XRD), where a random intercalation model was employed to fit the diffraction data and quantify lattice parameter evolution with composition. These findings were correlated with morphological and compositional analyses via scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS), providing insight into elemental distribution and film homogeneity. These techniques were also employed to assess the effect of a 773 K annealing treatment on sputtered films of different composition. The results reveal a systematic variation in microstructure with composition and demonstrate the compositional limits for stable solid solution formation under thermal load. This work contributes to the understanding of phase behavior and microstructural evolution in Fe-Cr alloy thin films. • Co-sputtered Fe–Cr thin films exhibit metastable body-centered tetragonal phase. • Random intercalation model explains non-Vegard lattice behavior. • The Fe-Cr co-sputtered films form columnar layer with uniform elemental distribution. • σ -phase formation and σ → α transformation kinetics show low activation energies.
Menegus et al. (Fri,) studied this question.