Exceptional thermal stability of nanostructured FeCoNiCrCu high entropy alloy facilitated by unusual grain boundary segregation

Nanocrystalline metals often suffer from grain coarsening at elevated temperatures, which deteriorates their mechanical properties. One important strategy to retard grain growth is solute segregation at grain boundaries, which can reduce excess Gibbs free energy of grain boundaries and thus impede their motion. The strategy has been widely utilized in binary and ternary alloy systems to stabilize their nanostructures. In present work, we report superior thermal stability of nanostructured FeCoNiCrCu high entropy alloy film prepared by ion beam deposition. In contrast to Cu segregation at grain boundaries when the alloy is fabricated by solidification, the nanostructured FeCoNiCrCu film fabricated via ion beam deposition exhibits segregation of Cr at the boundaries. The segregation of Cr persists at grain boundaries even at high annealing temperature and effectively prevents grain growth. This study indicates that multi-elemental alloys can provide plenty of opportunities to obtain nanostructured alloys with high thermal stability.