Achieving superior strength-ductility synergy in AlCoCrFeNi-based eutectic high-entropy alloys through tailored Ti additions

Achieving an optimal balance between strength and ductility remains a critical challenge in the development of advanced structural materials. In this work, the microstructure and mechanical properties of the eutectic high-entropy alloy system Al_1.25-xCoCrFeNi3Tiₓ were systematically tailored by adjusting the Ti content (x = 0.05–0.5). With increasing Ti addition, the microstructure transitions from a lamellar/irregular eutectic structure to a petal-like morphology. The alloy with x = 0.2 exhibits a combination of tensile strength (1311 MPa) and ductility (17% elongation). This enhancement is attributed to the synergistic effects of solid-solution strengthening, interfacial strengthening, and back-stress hardening. However, excessive Ti content leads to a loss in ductility, resulting from the coalescence of microcracks at brittle nanoscale interfacial phases. These findings provide valuable insights into the role of Ti in balancing strength and ductility, offering guidance for the design of high-performance eutectic high-entropy alloys.