Abstract: The unique structure and formation mechanism of medium-entropy alloys (MEAs) generally result in better comprehensive properties than traditional alloys. However, the strength-ductility trade-off remains a bottleneck, which limits their applications. In this study, we designed novel high-performance CrNiCux MEAs with a heterophase composition by incorporating a Cu-rich phase, and they were fabricated using laser-directed energy deposition (LDED). The results show that synergistic strengthening from multiple phases significantly improved the mechanical properties of the alloys, resulting in a tensile strength of 675 MPa and a ductility of 34.4%, demonstrating an excellent combination of high tensile strength and ductility. The improved mechanical properties of the CrNiCux medium-entropy alloys are primarily due to the heterophase interfacial strengthening mechanism. In the alloy, numerous semi-coherent and coherent interfaces formed between the Cr-rich phase, Cu-rich phase, and the matrix, creating extensive lattice distortions at the interfaces. An increase in the Cu-rich phase content promoted the interaction between phases, enhancing the strain energy of the alloy and the barrier strength of the interfaces. The calculated τint values, ranging from approximately 5.92-6.69 GPa, are significantly higher than those found in traditional alloys, providing a benchmark for designing new high-performance medium-entropy alloys.

Key words: Laser-directed energy deposition, CrNiCux, Mechanical properties, Heterophase interfacial strengthening