Effect of structure of high entropy CrFeCoNiCu alloys produced by EB PVD on their strength and dissipative properties

Highlights: • Thin foils of high-entropy CrFeCoNiCu_x (x = 0…3) alloys were prepared by EB PVD. • Effect of substrate temperature on the phase composition of the foils is studied. • Single-FCC structure transforms into dual-phase one at temperatures above 925 K. • Dual-phase foils show high values of both hardness and plasticity. • CrFeCoNiCu coatings with dual-phase structure exhibit high damping capacity. -- Abstract: Thin (up to 100 µm) foils and coatings of high-entropy CrFeCoNiCu_x (x = 0...3.0) alloys (HEAs) were produced at different temperatures in the 525…1275 K range by electron-beam evaporation of ingots. It is shown that CrFeCoNiCu_x (where x > 0.3) condensates deposited at a temperature above 925 K have a dual-phase structure consisting of two FCC phases, while those deposited at a temperature below this value exhibit a single-FCC structure. It is also found that annealing of the deposited single-phase CrFeCoNiCu_x (x = 0.3…3.0) condensates at temperatures above 925 K results in the transition into a dual-FCC phase state. Yet, condensates with the copper content x < 0.3 remain stable at heating up to high temperatures (up to 1300 K). The transition from single-phase condensates into dual-phase condensates occurs through the formation of the metastable Cr-enriched phase. The effect of the condensate structure on their mechanical and dissipative properties is considered. The single-phase condensates exhibit increased microhardness, as compared to the cast alloy. The microhardness of the two-phase condensates is lower than in single-phase ones but still higher than in the cast ingot. HEA-based vacuum condensates in both single-phase and two-phase states show high values of damping capacity, which are comparable with those of highly damping materials, such as AZ31B-F magnesium alloys.