Structural and phase composition, martensitic transformations, shape memory effect and biocompatibility of Ti – Ni – W alloys

The structure and properties, including biocompatibility of a medical grade alloy based on titanium nickelide alloyed with tungsten, have been studied. The phase composition was determined by X-ray diffraction analysis. Main phases: TiNi; Ti2Ni; TiNi3; Ti3Ni4; pure W. The elemental composition of the microstructure has been studied. It has been established that tungsten is present in the TiNi alloy in the form of individual particles, the average size of which is 1.5 microns. The alloying of TiNi alloys with tungsten shifts the direct martensitic transformation towards lower temperatures. The value of the accumulated deformation of the multiple shape memory effect (mSME) during cooling decreases from 6.5 to 3% with an increase in the tungsten content from 0 and 0.6% (at.). The temperatures of the beginning – end of the shaping during cooling and the temperatures of the beginning – end of the shaping during heating decrease with an increase in the concentration of tungsten. The value of the mSME of monolithic titanium nickelide-based alloys alloyed to 0.2% (at.) W does not deteriorate and remains at a high level, while the degree of incomplete recovery after the 10th cooling-heating cycle under load is close to zero, which indicates the high superelastic properties of Ti50Ni50-xWx alloys (at x = 0; 0.2; 0.4; 0.6). The practical application of Ti – Ni – W alloys in medicine in relation to physical materials science is promising at concentrations up to 0.2% (at.) W. It was found that tungsten alloying of monolithic titanium nickelide samples improves their biocompatibility in relation to 3T3 cells after 72 hours. The hemolysis test showed that Ti50Ni50-xWx alloys (at x = 0; 0.2; 0.4; 0.6) at the indicated alloying concentrations do not have a destructive effect on red blood cells. V. S. Turskaya and E. A. Kushnarev, the students of Tomsk State University, took part in the work.The study is carried out under State Сontract No. FSWM-2020-0022.