Microstructure and Mechanical Properties of CoCrCuFeNi High-Entropy Alloys Synthesized by Powder Metallurgy and Spark Plasma Sintering.

CoCrCuFeNi high-entropy alloy (HEA) has distinctive properties such as good ductility and corrosion resistance, whereas its low strength severely limits its engineering applications for structural components. To solve this issue, herein, laminated CoCrCuFeNi HEA was synthesized using a combined powder metallurgy and spark plasma sintering technique. Effects of ball milling durations on powder morphologies, microstructural evolution, mechanical properties and fracture behaviors of the sintered CoCrCuFeNi HEA were investigated. Results show that the average flake diameter of CoCrCuFeNi powders firstly increases (from ~ 60.44 μm to ~ 160.29 μm) but then sharply decreases (~37.59 μm) with the further increase of ball milling duration up to six hours. Microstructure of sintered CoCrCuFeNi HEA exhibits a flake feature with the bimodal structure (i.e., with both fine- and coarse-grained regions). Cu-rich spherical nanoparticles with an average size of ~ 30 nm are uniformly spread in the CoCrCuFeNi matrix. After two-hour ball milling, the yield strength of the sintered HEA is 706.9 MPa and its uniform elongation is 22.2%, which are much higher than those of the original CoCrCuFeNi HEA (i.e., with a yield strength of 569.3 MPa and a uniform elongation of 3.9%). The enhanced mechanical properties are mainly attributed to the formation of bimodal grains, dislocation strengthening and second phase strengthening due to Cr₂O₃ and Cu-rich spherical nanoparticles. [ABSTRACT FROM AUTHOR]