Microstructural and Mechanical Properties of Y₂O₃ Modified Ti6Al4V Alloy Fabricated by Laser Powder Bed Fusion

A Ti6Al4V alloy fabrication via laser powder bed fusion (L-PBF) leads to the formation of coarse columnar β grains that give rise to anisotropic mechanical properties and inadequate strength. Incorporating the rare earth oxide, yttrium oxide (Y₂O₃), has proven an effective strategy in enhancing the mechanical performance of Ti6Al4V al-loys. This study systematically investigates the effects of various Y₂O₃ contents on the microstructure and mechanical properties of Ti6Al4V alloys fabricated via L-PBF. The results demonstrate that a Y₂O₃ addition of 0.2 wt.% produces β grains and α phases with average sizes of 61.6 and 7.6 μm, respectively. Transmission electron microscopy observations reveal that Y₂O₃ nanoparticles, together with elemental Y nanoparticles formed by reduction, are distributed both within the α-Ti matrix and along phase boundaries. This distribution effectively reinforces grain boundaries and promotes heterogeneous nucleation, thereby refining the microstructure. Mechanical property tests indicate that the alloy strength significantly improves as the Y₂O₃ content in-creases. Specifically, the alloy with 0.2 wt.%Y₂O₃ exhibits a tensile strength of 1106 MPa, a yield strength of 1074 MPa, and an elongation of 10.0%. This study proposes an in-novative rare earth strengthening method for refining the microstructure of L-PBF-fabricated titanium alloys and comprehensively enhancing their mechanical properties.