Development of high-strength and high-ductility high-entropy alloys via directional solidification: A multifaceted strengthening approach

High-strength and high-ductility alloys are crucial for advanced engineering applications; however, achieving a balanced combination of these two properties remains a significant challenge. Here, we successfully developed an alloy with exceptional mechanical properties through microstructural design and processing optimization. By employing directional solidification, we fabricated an Al_1.25CoCrFeNi_2.8Mo_0.2 dual-phase high-entropy alloy (HEA) that exhibits a distinctive microstructure, which significantly enhances both strength and ductility. The alloy demonstrates superior mechanical performance, with a yield strength of 505 MPa, ultimate tensile strength of 1166 MPa, and uniform elongation of 19 %. Compared with the conventional as-cast HEA, the elongation is increased by 46 %, and the tensile strength is increased by 5 %. The enhanced properties are attributed to a synergistic combination of solid solution strengthening, phase interface strengthening, and precipitation hardening mechanisms. Detailed microstructural analysis reveals that hierarchical stacking fault networks in the face-centered cubic phase facilitate enhanced work hardening. Concurrently, B2-ordered nanoparticles acted as potent obstacles to dislocation motion, resulting in a significant enhancement of the strength. Additionally, the unidirectional lamellar microstructure improves fracture toughness by inhibiting crack propagation. This study underscores the potential of combining advanced metallurgical design with processing techniques to produce high-strength, ductile metallic materials.