Characterization of the microscale/nanoscale hierarchical microstructure of an as-cast CrMnFeNiCu high-entropy alloy with promising mechanical properties

Abstract

In this study, we investigated the evolution of a hierarchical multiphase structure in an as-cast CrMnFeNiCu high-entropy alloy (HEA). Thermodynamic calculations were performed to better understand and clarify the phase transformation of CrMnFeNiCu that occurs when molten metal is cooled to lower temperatures. The as-cast structural analysis at the micron- and nanoscale, and thermodynamic calculations, revealed that the hierarchical microstructure consisted of Cr+Fe-rich body-centered cubic (BCC)+ 2 face-centered cubic (FCC) (Cr+Fe+Ni-rich FCC and Cu+Mn-rich FCC) phases, which were further strengthened by nanoscale precipitates. Furthermore, transmission electron microscopy (TEM) studies revealed that the nanoscale precipitates maintained coherent interfaces, a similar lattice constant, and an inverse trend of chemical composition with regard to their matrix. The micro/nanoscale hierarchically structured as-cast CrMnFeNiCu alloy exhibited exceptional mechanical properties with a yield stress of ∼587.5 ± 20.3 MPa, ultimate tensile stress of ∼990.1 ± 15.4 MPa, and a reasonable elongation of ∼28.7 ± 4.6%. The proposed as-cast alloy exhibited superior mechanical properties compared with those of other as-cast HEAs.