Production of niti based shape memory alloys and investigation of their behaviors in different simulated body solutions

Production of NiTi Based Shape Memory Alloys and Investigation of Their Behaviors in Different Simulated Body Solutions In bio-medical applications, NiTi and NiTi-based alloys that show their shape memory effects at body temperature are preferred. In this study, the purpose is to produce NiTi and NiTi-based alloys which transform at body temperature with various chemical rates and electron concentrations and to examine their various physical properties. N45Ti55, Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Sn, Co) , Ni50.8Ti49.2, Ni45.5Ti49.5Cu5, Ni50.5Ti49C00.5 alloys were produced in Arc Melter furnace in this study. After the production of these alloys, the martensitic phase transformation temperatures were determined with Differential-Scanning Calorimeter. The transformation temperature was found to be below the 37 oC (body temperature) in Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Co) alloys; and the transformation temperature of the N45Ti55, Ni48Ti51Sn alloys was found to be over 37oC. Then, the micro and crystal structure analyses of the alloys were made by SEM-EDX (Scannnig Electron Microscopy) and XRD (x-ray diffractogram) device, and it was determined that Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Co), Ni45.5Ti49.5Cu5, Ni50.5Ti49C00.5 alloys, which were in austenite phase at room temperature, included B2 (NiTi) phase and Ti2Ni precipitation phase, and the alloys that were in the martensite phase at room temperature included B19ı (NiTi) phase and Ti2Ni phase. The common phase in both alloy groups is the Ti2Ni phase, and this type of phase is generally seen in NiTi alloys that are rich in titanium (Ti-rich). The ideal alloys which transform at body temperature were determined as NiTiMn. Biocompability of this alloy was investigated by ICP-MS device. The biocompability of alloy was improved by oxidation procedure. In this study, Ringer and salt balanced solution was used as simulated body solution. Oxide and nonoxide alloys put into these solution for one/two week at body temperature and then, element which influenced into solutions were determined. According to experimental results, influence of nickel element was increased for nonoxide alloy, influence of nickel was decreased for oxide alloy. Keywords: Ti-rich, NiTi alloys, body temperature, Ti2Ni phase, austenite, Martensite