Spatial modulation of eutectoid element in melt pool by EB-PBF for constructing high-performance heterogeneous titanium alloys

Abstract

The construction of heterogeneous structures for synergistic enhancement of strength and ductility in metallic materials represents a research hotspot in materials science. Additive manufacturing has achieved progress in fabricating heterogeneous titanium alloys, yet current designs primarily rely on single-phase boundary regulation, lacking multidimensional synergy in controlling precipitate distribution and grain orientation, thus hindering breakthroughs in overcoming the strength-ductility trade-off. Here, we demonstrate the fabrication of high-performance titanium alloys with hierarchical precipitate structure (HPS) via spatial control of eutectoid decomposition during electron beam powder bed fusion (EB-PBF). These structures are characterized by alternating Cu-rich solute matrices and ultrafine-grained (UFG) domains enriched with multi-scale Ti₂Cu precipitates. The alloy achieved an ultimate tensile strength of 1244 MPa, a 37.9 % increase compared to the as-bult Ti6Al4V, while maintaining good ductility (15.7 %). This exceptional mechanical performance is attributed to multi-scale precipitation strengthening facilitated by fine Ti₂Cu dispersions, heterogeneous deformation-induced strengthening across hierarchical domains, and crack deflection accompanied by micro-shear banding, which collectively enhances fracture resistance by dissipating crack propagation energy. Our findings establish a novel pathway for spatially controlled phase decomposition in AM, providing a promising approach for designing damage-tolerant, high-strength titanium alloys. This work opens new avenues for advanced applications in aerospace, biomedical, and structural components.