Enhanced mechanical properties of C-doped CuFeMnNi high entropy alloy by modulating phase decomposition

Abstract

High-entropy alloys (HEAs) with the face-centered cubic structure usually exhibit decent ductility, but their poor yield strength and expensive raw materials still limit their industrial application. In this work, the low-cost carbon-doped CuFeMnNi HEAs have been processed by homogenization annealing, cold rolling, and subsequent annealing at 600 °C–1000 °C. The recrystallization degree, recrystallization grain size and carbide size of the alloy with phase decomposition were successfully regulated by utilizing the incompatibility and the difference of melting point of Cu and Fe. The annealed HEAs exhibit a series of excellent mechanical properties, and the yield strength increase from 405 ± 8 MPa to 1102 ± 8 MPa, while the satisfactory uniform elongation is maintained. The variations in the yield strength are attributed to the fact that strengthening mechanisms gradually changes from grain boundary strengthening and solid solution strengthening to dislocation strengthening and carbides Orowan strengthening with the decrease of annealing temperatures. In particular, the dissolution of high carbon content into the matrix promotes the appearance of short-range order, thus changing the dislocation slip mode, and further evolving into the well-developed microbands, which is beneficial to the improvement of strain hardening ability. These insights provide a new paradigm for the design of high-performance and low-cost Fe–Cu alloy and Cu-HEAs by modulating phase decomposition.