Effects of Layer Orientation on the Multiaxial Fatigue Behavior of Additively Manufactured Ti-6Al-4V
Additive manufacturing (AM) allows for fabrication of components with complex geometries that cannot be fabricated using conventional manufacturing techniques. These components are often subjected to multiaxial stress states due to their typically complex design accompanied by residual stresses and/or multiaxial external loading. Therefore, understanding the fatigue behavior of AM materials under multiaxial-type loadings is necessary for ensuring reliable in-service component performance. In this study, the effects of layer orientation on the multiaxial fatigue behavior of Ti-6Al-4V fabricated via a laser-powder bed fusion (L-PBF) process was investigated. Tubular thin-walled multiaxial specimens were fabricated in vertical and diagonal orientations with respect to the build plate. Specimens were tested under axial, torsional, in-phase axial/torsional, and 90° out-of-phase axial-torsional cyclic loadings. Upon failure, the crack orientation of vertical and diagonal specimens was correlated to the type of loading, which illustrated the failure mechanism of L-PBF Ti-6Al-4V and justified the variations in the fatigue lives of specimens.