On the Yield Anisotropy in Laser Powder Bed Fusion-Produced Beta Titanium Alloys

Abstract

Laser powder bed fusion (LPBF)-based additive manufacturing (AM) provides high print resolution which enables design freedom and the fabrication of complex geometries. However, anisotropy is a major challenge that impacts the properties of LPBF materials. In this study, we investigate the mechanical anisotropy of an LPBF-produced BCC Ti-45Nb alloy that exhibits a weakly elongated (near equiaxed) microstructure with no preferred grain orientation. Based on uniaxial tensile tests, profilometry-based indentation plastometry, and microhardness tests along the laser scan and build directions, we find a strong mechanical anisotropy in the randomly oriented LPBF Ti-45Nb alloy. By employing these distinct multi-scale mechanical testing techniques, we delineate the influence of LPBF microstructural features such as grain morphology, cellular structures, melt pool boundaries, and crystallographic texture on the anisotropic behavior. Our work specifically highlights the role of melt interface length on the mechanical (yield) anisotropy.