Powder metallurgical fabrication processes for NiTi shape memory alloy parts

NiTi components with reproducible and stable shape memory properties are attractive for various technical applications (e.g. couplings). With the aim of producing NiTi components on an industrial scale, near-net-shape fabrication routes are preferred considering the limited machinability of NiTi alloys. Powder metallurgy (PM) is known to provide the possibility of material-saving and automated fabrication of at least semi-finished products as well as net-shape components. As promising PM routes hot isostatic pressing (HIP) and metal injection moulding (MIM) were used for the fabrication of NiTi compacts. Microstructural investigations, chemical analysis, X-ray diffraction (XRD) measurements and also differential scanning calometry (DSC) measurements were performed in order to characterize the produced parts. Additionally, the mechanical properties of HIPed samples were measured by tensile tests at room temperature. The components from both fabrication routes show reversible austenite↔martensite transformations which are a prerequisite for shape memory effects.