Achieving strength-ductility synergy in additive manufactured α+β titanium alloys through multi-scale microstructure regulation

Additive manufactured high-temperature titanium alloys typically exhibit poor plasticity and crack sensitivity. In this work, a novel strategy incorporating high-melting-point, low-diffusivity tungsten (W) as a microstructural modifier was designed for Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy, with subsequent processing by laser powder bed fusion. At the mesoscale, the columnar prior β-grains of the alloys transformed to fine equiaxed-elongated morphology and formed a bimodal structure. Microscale characterization revealed that the α’ phases were refined while the brittle α’/β interfaces were replaced with more ductile boundaries. Notably, the modified alloys achieved an outstanding tensile strength of 1717.6 MPa along with an improved elongation of 4.4%, which is attributed to the synergistic effects of grain structure and interface optimization. The present work proposes a promising approach for regulating the microstructure and mechanical properties of high-temperature titanium alloys by refractory elements.