FABRICATION OF SHAPE MEMORY ALLOYS USING AFFORDABLE ADDITIVE MANUFACTURING ROUTES
Luhrs, Claudia C.
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The primary objective of this research was to develop paste formulations to enable the fabrication of shape memory alloys (SMA) using low-cost additive manufacturing routes. We focused on determining which precursor particulates, binding agents and post-processing conditions could sinter the 3D printed parts. Nickel-titanium nano/micron-sized particulates along paraffin/alcoholic gel binders were tested as raw materials to produce pastes. Scanning electron and optical microscopy, energy dispersive spectroscopy and X-ray diffractometry were employed to determine the microstructural features in the raw material and final products. Thermal treatments to sinter the parts were performed in a tube furnace or a hot isostatic press. It was found that it is possible to 3D print metal pastes using micrometric particles, gel binders and a modified low-cost polymeric printer. Nanoparticle formulations were found to behave as shear thinning fluids and are not recommended for this application. The post-processing conditions that were successful creating sintered structures used 1000℃ and pressures above 138MPa. The Ni-Ti phases generated deviated from the ideal NiTi stoichiometry, however, were close to those found in commercially available SMA wires. SMAs could be employed to produce actuators and deployment mechanisms in space applications. This research introduces a novel way to fabricate SMAs that could reduce costs and widen the environments where their production could take place.
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