Nanostructured crystalline-amorphous FeCrCoNi-SiC high-entropy alloy thin film with a superior combination of strength and corrosion resistance

The advancement of ultra-strong and corrosion-resistant high-entropy alloys (HEAs) is pivotal for diverse engineering applications. In this work, magnetron co-sputtering is employed to construct a novel nanostructured crystalline-amorphous FeCrCoNi-SiC (NC C-A HEA-SiC) composite film, featuring FeCoNi-rich nanograins encapsulated by CrSiC-segregated amorphous grain boundaries (GBs). Results show that this nanocomposite film exhibits exceptional compressive yield stress (YS) of ∼3.5 GPa, significantly higher than ∼0.9 GPa in coarse-grained FeCrCoNi (CG HEA) bulk and ∼2.0 GPa in nanocrystalline FeCrCoNi (NC HEA) film. Detailed microstructural analyses unveil that ultrahigh strength with notable plasticity in nanocomposite film stems from co-deformation mechanisms involving initial preserved dislocation activities within nanograins and subsequent amorphous GB crystallization-induced grain coarsening. Additionally, the NC C-A HEA-SiC composite film shows lowest corrosion current density (i_corr) of 2.98 × 10⁻⁸ A/cm² in 3.5 wt% NaCl solution, relative to 1.49 × 10⁻⁷ A/cm² in CG HEA bulk and 5.80 × 10⁻⁸ A/cm² in NC HEA film. The enhanced anti-corrosive performance primarily results from CrSiC-rich amorphous GBs that facilitate the formation of dense protective layer and balance corrosion potential between nanograins and GBs to foster a uniform corrosion process. This work provides valuable insights into designing innovative HEAs with superior mechanical-anticorrosion synergy.