## 3 Results
### Mechanical Properties of the Ti\({}_{49.1}\)Ni\({}_{50.9}\) Alloy  
Table 1 and Figure 4 present the averaged data of the Ti\({}_{49.1}\)Ni\({}_{50.9}\) alloy in the CG and UFG states at temperatures of 25, 250, and 400 \({}^{\circ}\)C with a tensile stress of 1 \(\times\) 10\({}^{-3}\) s\({}^{-1}\), including tensile strength (UTS), dislocation yield stress (YS), phase yield strength \(\sigma_{m}\), and relative elongation (El\(\%\)). Analysis of the tensile curves showed that a flat area can be observed on the tensile curves of the samples tested at room temperature at stresses of \(\sigma_{\rm m}\) 350 \(\pm\) 20 MPa due to the reorientation of martensite B19\({}^{\prime}\) under stress. When the test temperature is increased to 250 \({}^{\circ}\)C and higher, this flat area is absent on the tensile curves, which indicates either the blocking of the B2-B19\({}^{\prime}\) transformation or the B2-B19\({}^{\prime}\) transformation simultaneously with plastic deformation. ECAP led to a noticeable increase in tensile strength and yield stress compared with the initial CG state, which is the result of the grinding grain. At room temperature, the tensile curves of the alloy in the CG and UFG states had an extended stage of uniform hardening, which is associated with the possibility of prolonged hardening of the martensitic phase. Tension at room temperature ended with the fracture of the samples without \begin{table}
\begin{tabular}{c c c c c c} \hline
**State** & **Test Temperature** & **UTS, MPa** & **YS, MPa** & \(\sigma_{\rm m}\)**, MPa** & **El,\%** \\ \hline \multirow{3}{*}{CG} & 25 & 1095 \(\pm\) 45 & 480 & 370 & 40 \(\pm\) 7 \\  & 250 & 795 \(\pm\) 30 & 600 & - & 25 \(\pm\) 4 \\  & 400 & 580 \(\pm\) 25 & 545 & - & 31 \(\pm\) 3 \\ \hline \multirow{3}{*}{UFG} & 25 & 1260 \(\pm\) 80 & 1120 & 350 & 35 \(\pm\) 6 \\  & 250 & 1100 \(\pm\) 30 & 950 & - & 32 \(\pm\) 4 \\  & 400 & 910 \(\pm\) 30 & 790 & - & 30 \(\pm\) 2 \\ \hline \multirow{3}{*}{NC} & 25 & 1600 \(\pm\) 80 & 1550 & 420 & 15 \(\pm\) 3 \\  & 400 & 680 \(\pm\) 25 & 600 & - & 45 \(\pm\) 5 \\ \hline \end{tabular}
\end{table} 
Table 1: The results of mechanical tests carried out with the rate \(\epsilon\) = 1 \(\times\) 10\({}^{-3}\) s\({}^{-1}\). UTS: tensile strength; YS: yield stress. Figure 3: TEM images of the microstructure of the Ti\({}_{49.1}\)Ni\({}_{50.9}\) alloy in amorphous-nanocrystalline (**a**) and nanocrystalline (**b**) states. the formation of a neck and localization of deformation. With increasing temperature, the tensile strength and elongation to failure decreased. The HPT of the Ti\({}_{49.1}\)Ni\({}_{50.9}\) alloy led to maximum values of tensile strength of up to 1700 MPa, but at room temperature the material fractured in a brittle manner. An increase in the temperature of the test led to a decrease in strength and the appearance of noticeable plasticity. The NC alloy at 400 \({}^{\circ}\)C had a slightly higher ductility than CG and UFG. Perhaps this is the result of the activation of intergranular slippage. To study the characteristics of mechanical behavior, determine mechanical characteristics at elevated temperatures and determine possible deformation mechanisms, CG and UFG Ti\({}_{49.1}\)Ni\({}_{50.9}\) alloys were tested at various strain rates (Figure 5). The data on the speed sensitivity, presented in Table 2, show that as the temperature of the test increased, the speed sensitivity parameter increased. The parameter of speed sensitivity \(m\) in the UFG state was higher than in the CG state, and with increasing test temperature, \(m\) increased both for the CG and UFG state of the alloy. Based on parameter V, deformation occurred by the mechanism of sliding of dislocations and forest dislocations. With increasing deformation temperature, the \(\Delta\)V/b\({}^{3}\) value increased.