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 alloys. Nevertheless, the critical Y2O3 content required to achieve an optimal strength–ductility balance in L-PBF Ti6Al4V has not been systematically determined. To address these critical gaps, this study, for the first time, systematically investigates the effect of various Y2O3 contents on the microstructural evolution 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 increases. 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 10.7%. This study proposes an innovative rare-earth strengthening method for refining the microstructure of L-PBF-fabricated titanium alloys and comprehensively enhancing their mechanical properties.