Functional properties and shape memory effect of Nitinol manufactured via electron beam powder bed fusion
Alexander Fink, Zongwen Fu, Carolin Körner
Abstract
Ti-rich Nitinol (NiTi) is characterized by its functional properties to restore its original shape after deformation due to a temperature-induced reversible martensitic phase transition. In this study, dense Ti-rich Nitinol free of cracks is successfully produced by means of Electron Beam Powder Bed Fusion (PBF-EB). The martensitic phase transition behavior of the as-built NiTi parts and powder is analyzed using Differential Scanning Calorimetry (DSC) analysis. To gain a deep understanding of the DSC results, segregation during solidification is thermodynamically studied (CALPHAD). The PBF-EB-fabricated NiTi shows a microstructure containing fine columnar grains and numerous precipitates, whose influence on the tensile properties at room temperature is discussed. Furthermore, the one-way and two-way shape memory effects of PBE-EB-produced NiTi are investigated using an innovative experimental setup based on thermomechanical training.