Ti-6Al-4V powder characteristics in laser powder bed fusion: The effect on tensile and fatigue behavior

Abstract

This work investigates the effects of powder characteristics, particularly particle size distribution (PSD), on the micro-/defect-structure, tensile, and fatigue properties of Grade 23 Ti-6Al-4V specimens as well as how these effects are influenced by the build location and specimens’ surface finish. Two batches of plasma atomized Ti-6Al-4V powder feedstock with two different PSDs of 15–45 µm (fine) and 15–53 µm (coarse) were used for fabrication. Both batches exhibited excellent rheological properties with moderate improvement noted in the fine batch. The influence of PSDs was shown to be small on the resulting microstructure and surface roughness of the specimens, while significant on the volumetric defect distribution. In addition, machined specimens fabricated from coarse powder exhibited somewhat enhanced ductility, smaller defects, and some improvements in the fatigue properties as compared to the fine powder specimens. These variations were correlated with lower tendency of spattering in coarse powder. Process-induced silicon-rich spatters, which were detrimental to both tensile and fatigue properties, were more prevalent in the specimens built from the fine powder batch, and were ascribed to the rapid decomposition of SiO2. Owing to the highly spherical particles and the resulting excellent flowability of both batches, defect content and mechanical properties did not show strong location dependency.