Decoupling the effect of orientation on additively manufactured metals by lattice engineering

The properties of additively manufactured solid metal parts are sensitive to the build direction due to changes in microstructure. Here, we show that the mechanical properties of topologically engineered metal lattices remain largely independent of the build orientation. Cubical samples of solid and sheet-based gyroid lattice were fabricated from Inconel718 alloy using laser powder bed fusion. The specimens were tilted at different angles from 0(degrees) to 45(degrees) to study the effect of build direction on the microstructure and the mechanical properties of solid and lattice samples. Scanning electron microscopy (SEM) and optical microscopy were used to examine the microstructural features including the grains and the melt pool geometries. The results show that the melt pool dimensions, and the grain orientations are affected by the build direction in the solid and the lattice specimens. While the mechanical properties of solid samples are strongly dependent on the build orientation, the lattices show similar mechanical behavior irrespective of the build direction. These findings show that the topology dominates in controlling the properties of metal lattices. The results have implications in designing 3D printed cellular structures with reproducible properties that are immune to the build orientation.