Formation of 3D interconnected multiphase heterostructures from CoCrFeMnNi high-entropy alloy via liquid metal dealloying using Cu–Ag melts

Liquid metal dealloying has emerged as an effective process to fabricate three-dimensional (3D) interconnected heterostructures, yet the control of element dissolution in complex alloys remains limited. In this study, binary Cu–Ag melts were employed to regulate the dealloying behavior of a CoCrFeMnNi high-entropy alloy (HEA) precursor. Microstructural analyses revealed distinct differences in dealloying kinetics between Cu 80 Ag 20 and Cu 40 Ag 60 melts at 800–950 °C. In Cu 80 Ag 20 , grain-boundary-driven inhomogeneous reactions resulted in abnormal ligament morphologies at 950 °C, whereas Cu 40 Ag 60 promoted faster and more uniform reaction layers, with linear growth of ligament thickness. At extended times, 3D interconnected heterostructures consisting of CoCrFeNi-rich ligaments and melt-derived lamellar phases were obtained. The addition of Ag suppressed the dissolution of precursor elements, except for Mn, owing to their low solubility and immiscibility in Ag. X-ray diffraction results confirmed the formation of three distinct FCC phases, consistent with observed microstructures and composition analyses. Thermodynamic calculations using Thermo-Calc further supported the observed near-equilibrium dissolution behavior and formation into multiple FCC phases. Notably, the resulting heterostructure processed in Cu 40 Ag 60 at 950 °C exhibited a marginal decrease in hardness (∼4.7%) while achieving a 3.2-fold increase in electrical conductivity compared to the precursor. This work demonstrates that tailoring melt composition suppresses catastrophic precursor dissolution. It further enables the design of 3D interconnected heterostructured HEA composites with controlled architectures.