OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 1 2022 Thus, it has been established that an increase in the strain rate reduces the degree of transformation of austenite into martensite and does not affect its kinetics. When analyzing phase transformations occurring under the infl uence of deformations and low temperatures in steel 10Cr14Mn14Ni4Ti at different strain rates, the following was revealed. As a result of cooling below 20 °C, two martensitic phases α- and ε-martensite appear. As the temperature decreases, the amount of these phases increases, but does not exceed 12 % for ε-martensite and 8 % for α-martensite (Figure 4). During low-temperature deformation of steel 10Cr14Mn14Ti, as the temperature decreases, the amount of austenite and ε-martensite decreases, and α-martensite increases. It should be noted that in the temperature range of deformation from 20 °C to –100 °C, the intensity of formation of α-martensite is low and, apparently, in this temperature range, the transformation occurs according to the scheme γ→ε→α, and with a further decrease in temperature, the amount of α-phase increases sharply. With an increase in the strain rate, the transformation of austenite into martensite decreases (Figure 5). Fig. 4. Dependence of martensitic transformations in steel 10Cr14Mn14Ti on test temperature Fig. 5. Dependence of martensitic transformations in steel 10Cr14Mn14Ni4Ti on the strain rate at a test temperature of –196 °C It is shown that a decrease in the amount of secondary structural phases α- and ε-with an increase in the strain rate of metastable austenitic steels can be associated with sample heating. The authors of [4, 13–17] showed that high-speed deformation leads to a sharp increase in temperature on the shear planes. Areas of high-temperature heating, as a rule, are grouped in thin shear layers, as a result neighboring zones are heated slowly. It follows that the decrease in the amount of martensitic phases associated with an increase in the strain rate can be explained by an increase in the temperature of the samples due to the heat released during deformation. At the same time, an increase in the proportion of the α-phase with an increase in the strain rate may be due to the fact that the samples were stretched under isothermal conditions. Thus, during isothermal tension, an increase in the strain rate leads to an increase in the proportion of α-martensite formed, and when the sample is heated, it prevents the formation of secondary structural phases.
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