Microstructure and martensitic transformation of selective laser melted NiTi shape memory parts

Additive Manufacturing allows to design and realize 3D parts, integrating additional functionalities offered by the interaction between complex shapes and the material properties. Results can be even more appealing when functional materials, like Shape Memory Alloys, are printed: new opportunities for smart devices can be opened. In the present bulk and lattice structures of Nitinol were additively manufactured with a Seletive Laser Melting. A pulsed laser, which is more suitable for manufacturing thin parts, was selected to process the initial powder. The selection of the process parameters, like laser power and exposure time, was performed for maximizing the relative density. Furthermore, the microstructure and the martensitic transformation temperatures were analyzed through Xrays diffraction and differential scanning calorimetry, respectively. A comparison between the initial powder and SLMed parts was also considered. Finally, the mechanical properties of Niti builts under compression were tested for both bulk and lattice structures.