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The deformation behavior, microstructure, phase composition, and mechanical and functional properties of Ti-50.9 at.%Ni shape memory alloy during uniaxial compression in the temperature range from 25°C to 1000°C have been analyzed and are discussed herein. It was found that the deformation temperature of 300°C marked a boundary for the transition from the low-to hightemperature type of flow curves; achievement of the steady-state deformation stage was observed across a wide range of deformation temperatures. Following comprehensive analysis of the obtained data, the temperature ranges of the dynamic processes of recovery, polygonization, and recrystallization of the Ti-50.9 at.%Ni alloy were determined. Deformation in the range of dynamic polygonization is accompanied by not only the formation of B2austenite and R-phase, but also the precipitation of fine Ti 3 Ni 4 particles during deformational aging. The highest shape recovery characteristics were obtained after deformation of the Ti-50.9 at.%Ni alloy in the temperature range from 300°C to 600°C.

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In the present work, flow curves of an equiatomic Ti-Ni shape memory alloy after deformation by compression in the temperature range from 100 to 900 °C at a strain rate of 1 s -1 and up to a true strain (e) of 0.9 were obtained. The phase composition, mechanical and functional properties after compression to e = 0.5 were studied. The boundaries of the temperature ranges of the development of dynamic softening processes were determined, as follows: dynamic recovery in 100-300 °C range; dynamic polygonization in 300-500 °C range and dynamic recrystallization above 500 °C. An optimum deformation temperature range in terms of accumulation of high strains and achieving improved functional properties is 300-500 °C. It has also been found that post-deformation annealing at temperatures above the deformation temperature leads to the decrease in the B2-austenite lattice defectness and to a significant increase in shape recovery characteristics.

The issue is devoted to the study of the influence of hafnium on the structure and properties of alloy 1570. Ingots from alloy 1570 were cast into the steel coquille, including those with additives of hafnium 0.1, 0.2 and 0.5 %. To determine the size of the grain structure in the obtained ingots, an Axionovert-40 MAT optical microscope was used, chemical analysis of intermetallic particles was carried out using JEOL 6390A SEM. In addition, for the alloy 1570 and 1570–0.5Hf, the presence of nanoparticles with the L12 structure was studied using transmission electron microscope JEM-2100. Studies showed that hafnium additives make it possible to achieve a significant modification of the cast structure. For example, when introducing hafnium into the initial alloy in an amount of 0.5 % of the total weight, it was possible to achieve a reduction in the average grain size by 2 times. Scanning microscopy data showed that hafnium partially dissolves in particles containing scandium and zirconium as well. The addition of hafnium increases the number of large particles formed during crystallization. Transmission microscopy showed the presence of coherent aluminum matrix nanoparticles in alloy 1570 and having a superstructure of L12, which were most likely formed during intermittent decay during ingot cooling. When 0.5 % Hf was added, no nanoparticles with the L12 superstructure were detected. To explain the latter fact, it is necessary to study the surface of the liquidus of the Al–Hf–Sc system, as well as to study the effect of hafnium on the diffusion coefficient of scandium in aluminum.

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