Investigation of structural, physical and biocompability properties of NiTiNbX (X = Ta, V) shape memory alloys

In this study, by adding (at.) 23% Nb element to the NiTi alloy and then Nb, Ta and V elements at different rates to the triple alloy; equal-atomic binary, ternary and quaternary alloy samples were prepared. In this study, different ratios of Nb, Ta and V elements were added to equal atomic NiTi based alloys; binary, ternary and quaternary alloy samples were prepared. Prepared alloys; They were coded as Ni50Ti50 (EB1), Ni27Ti50Nb23 (EB2), Ni27Ti50Nb22Ta1 (E1), Ni27Ti50Nb20Ta3 (E3), Ni27Ti50Nb18Ta5 (E5), Ni27Ti50Nb22V1 (B1), Ni27Ti50Nb21V2 (B2) ve Ni27Ti50Nb18V5 (B5). Some thermodynamic parameters obtained by the phase transformations of the alloys were determined using a differential scanning calorimetry (DSC). All samples exhibited shape memory alloy property. It was determined that the phase transformation temperatures decreased in the alloys added with Nb and V element, while the phase transformation temperature values increased in the alloys added with Ta element. While diffusionless phase transformations occurred between two phases "austenite↔martensite" with different crystal structures, "R- phase" was detected in addition to these transformations in Ta element added alloys. X-ray analyzes were performed for the determination of the crystal structures of the alloys. The presence of B2, B19/, Ti2Ni, ꞵ-Nb and ꞵ-Ta phases were detected by X-ray analysis of the samples. Scanning electron microscopy (SEM) was used to examine the surface morphologies of the samples and EDX analyzes were performed to determine the chemical structure determinations (matrix phases, precipitates and dissociation zones). While martensitic plates were not found in all alloys, the presence of dendritic arms was observed. The microhardness analyzes of the alloys were found by the Vickers test method. While the microhardness value of the equiatomic NiTi alloy was found to be 243 HV0.3, this value increased to an average of 354 HV0.3 with the addition of Nb element, and an average of 380 HV0.3 in the alloys with the addition of Ta element, and 514 HV0.3 with the addition of the V element. Biocompatibility studies of the materials were investigated using potentiodynamic corrosion test and cell culture test methods. While the corrosion resistance of Ta element added alloys was the highest, it was observed that the alloys with the least bacterial colonies on them were shape memory alloys prepared by adding Ta element. As a result, it can be said that NiTiNb-Ta alloys are suitable for implantation in the human body for various purposes.