Compositional segregation–driven trimodal architecture in Ti–Fe alloy for enhanced strength–ductility synergy

We present a design strategy that leverages solute segregation—an inherent outcome of solidification—as a controllable mechanism for architecting trimodal microstructures in near-eutectoid Ti–15Fe alloys. Without the need for homogenization, aging of the as-cast alloy induces distinct phase assemblages determined by local Fe concentration: (β+B2) in Fe-rich regions, (β+α) in Fe-poor regions, and single-phase β in intermediate regions. This segregation-driven microstructural architecture forms a network of mechanically dissimilar domains, facilitating strain partitioning and promoting hetero-deformation-induced (HDI) strengthening. As a result, the alloy exhibits a simultaneous increase of more than 200 MPa in yield strength and nearly a twofold increase in fracture strain relative to its homogenized counterpart. The hard B2-bearing regions, typically associated with brittleness when homogeneously distributed, contribute positively when spatially confined within a compliant β matrix, thereby preserving overall mechanical integrity. This approach eliminates the need for homogenization, thereby simplifying processing and reducing energy consumption, while utilizing solidification-induced chemical modulation as an active design variable. The findings establish that chemical heterogeneity, conventionally regarded as a defect to be minimized, can instead be harnessed as a robust and scalable strategy to achieve a synergy between strength and ductility. More broadly, this concept offers a manufacturable pathway for developing hetero-architectured titanium alloys and establishes a general framework for reinterpreting solidification-driven inhomogeneity as a foundation for advanced structural materials design.