Manufacturing of complex NiTi geometries with LPBF and adapted scanning strategies

Nickel-Titanium (NiTi) is the most important shape memory alloy today as it shows remarkable properties and its characteristics can specifically adjusted to meet particular functionalities. It is possible to realize complex near net shapes with laser powder bed fusion (LPBF) as an additive manufacturing process even for NiTi even though the alloy is not trivial to manufacture conventionally. Specifically designed adapted scanning strategies can create a minimum feature size near the laser beam diameter and more homogenous structures with less defects than conventional scanning strategies. The manufacturing of LPBF-NiTi with adapted scanning strategies enables complex 3D structures with programmable material behavior that is able to follow logic descriptions.

In this contribution, we will present additive manufacturing of NiTi lattice structures with programmable mechanical behavior in terms of stiffness. The results show the potential of manufacturing filigree NiTi structures on conventional LPBF-machines with specifically designed unit cells to meet the desired functional demands. The modification of the structural and functional properties as well as the quality of the structure is possible by means of the selected laser and scan strategy parameters. The chosen unit cell design in combination with the pseudoelasticity of NiTi exhibits a distinct change in stiffness under compression load and elongations of over 20 % without failure.

The results show the potential of additive manufacturing of complex NiTi structures with shape memory properties in the as-built state and the manufacturing and characterization of metallic programmable materials.