Effects of build orientation and sample geometry on the mechanical response of miniature CP-Ti Grade 2 strut samples manufactured by laser powder bed fusion

Abstract

Additive manufacturing can produce a regular three-dimensional mesh containing tiny interconnected wires/struts that form a porous structure. It is reasonable to assume that the properties of these single wires/struts will affect the performance of each unit-cell contained within the porous structure and thereby affect the mechanical properties of the whole porous structure. The effects of strut geometry and build orientation on resulting mechanical properties are examined in this study. Laser powder bed fusion was used to manufacture single strut samples of CP-Ti Grade 2 in the vertical and horizontal orientations with cross-sectional areas ranging from 0.07 mm2 to 2.3 mm2. For samples with cross-sectional areas smaller than 1.5 mm2, the difference in yield strength between the vertical and the horizontal build orientations was 79%, consistent with differences in microstructure scale in these orientations. Build orientation effects were much less pronounced in larger samples where the microstructural scale and features were similar. The presence of surface roughness and process-induced porosity contributed to the significant differences in ductility exhibited in the different orientations. The results indicate that build orientation effects may be significant for as-deposited surfaces and should be considered when designing porous structures consisting of thin struts since these will likely be used with as-deposited surface roughness.