Three-dimensional printing of shape memory alloys

A novel variant of the three-dimensional printing technique has been developed and used to manufacture NiTi parts. Instead of metal powder the process uses granules, which consist of a mixture of metal powder and organic binder. These granules are spread on a working table. Then a solvent is dispensed with a printer head to consolidate a selected area of the granule bed and the table is moved down. The "solvent on granule" printing process is repeated until a three-dimensional green body is obtained. The green part is finally debinded and sintered to obtain a dense and fully metallic part. NiTi parts have been successfully produced by this technique with densities of about 95% of the theoretical density. Detailed information on the microstructure has been obtained by X ray diffraction. Sintered parts exhibit shape memory effect, which has been measured during thermal cycling under tensile stress.