Nickel-Titanium is the best-known representative of shape memory alloys. Those have the characteristic of altering under controlled conditions to an externally applied stimulus such as stress, temperature or magnetic field. Additive manufacturing of shape memory alloys is used to overcome the restricted geometrical freedom of conventional manufacturing processes. Laser powder bed fusion (LPBF) allows the manufacturing of complex 3D structures such as filigree lattice structures with exceptional properties, which cannot be realized by conventional manufacturing techniques. Using appropriate processing parameters, it is possible to achieve superelastic properties even in the as-built condition without applying an additional heat-treatment.

In this contribution, the potential of manufacturing different filigree unit cell structures out of NiTi using LPBF is presented. They were produced on conventional LPBF-machines with non-conventional scanning strategies and exhibit superelastic properties in the as-built state. It could be shown that the chosen adapted scanning strategy results in more uniform and thinner struts with a more homogeneous energy input compared to conventional scanning strategies. The resulting properties of the unit cell structures can be adjusted by varying characteristics like the laser parameters, the parameterization of the scanning strategy, and the geometry parameters of the unit cell design. The chosen unit cell designs show an auxetic behavior. When loaded normal to the build direction, the lattice structures exhibit different mechanical behaviors compared to loading them in the direction parallel to the build platform. It is shown that by choosing a suitable combination of parameters, superelastic metallic unit cell structures can withstand elongations up to 20 % without failure in the as-built condition under compressive load in several directions. The results reveal the high potential of further investigations of the interactions between processing parameters, geometry of lattice structures and material characteristics. Withstanding such high deformations can be a game changer in the use of LPBF manufactured NiTi lattice structures in many applications like stents and metamaterials with switchable properties.