Study on Anisotropy in Microstructure and Mechanical Property ofTB6 TitaniumAlloy Fabricated by Laser Directed Energy Deposition

TB6 titanium alloy was fabricated via laser directed energy deposition (LDED), and the anisotropic characteristics of the microstructure and mechanical properties across different sample cross-sections were systematically investigated, the influence of heat treatment on Anisotropy in Microstructure and Mechanical Property were analized. Results indicate that the as-deposited specimen exhibited near-equiaxed grains in the cross-section vertical to the deposition direction, while a columnar/equiaxed grain composite structure was observed in the cross-section parallel to the deposition direction. Both cross-sections displayed a lamellar basketweave microstructure, with the α phase in the cross-section vertical to the deposition direction demonstrating a more elongated morphology. This distinct grain structure and α phase configuration endowed the transverse sample with superior microhardness (389.6 HV), tensile strength (1337 MPa), and reduced elongation (2.9%), exhibiting pronounced mechanical anisotropy compared to the longitudinal sample. Post heat treatment induced coarsening of the lamellar α phase with reduced width heterogeneity, resulting in a significant decrease in the elongation anisotropy index (IPA) from 99.1 (as-deposited) to 33.2. Fractographic analysis revealed a transition from shallow dimples to deep microvoid coalescence, effectively mitigating the mechanical anisotropy.