Temperature Dependences of Mechanical Properties and Fracture Features of Low-Activation Ferritic-Martensitic EK-181 Ste
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erature Dependences of Mechanical Properties and Fracture Features of Low-Activation Ferritic-Martensitic EK-181 Steel in a Temperature Range from –196 to 720°C N. A. Polekhinaa,b,*, I. Yu. Litovchenkoa,b, A. N. Tyumentseva,b, S. A. Akkuzinb, V. M. Chernovc,d, and M. V. Leontyeva-Smirnovac,d aInstitute
of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia b Tomsk State University, Tomsk, 634050 Russia c Bochvar High-Technology Research Institute of Inorganic Materials, Moscow, 123060 Russia dNational Research Nuclear University MEPhI, Moscow, 115409 Russia *e-mail: [email protected] Received November 1, 2017
Abstract—The features of the microstructure, structural-phase transformations, and regularities of the change in the short-term mechanical properties of low-activation 12% chromium ferritic-martensitic steel EK-181 together with the features of its plastic deformation and fracture by the active stretching method in a temperature range from –196 to 720°C are investigated. The high efficiency of dispersive hardening by nanoscale particles V(C, N) provides a weak temperature dependence of the steel strength properties with increasing temperature from 20 to 450°C. A significant increase in the temperature dependence of the steel yield strength is observed in the ductile-to-brittle transition interval (below T ~ 20°C). In a temperature range from –196 to 720°С, the change in the plasticity regularities and the mode of steel fracture are closely related to the features of the temperature dependence of the yield stress and ultimate tensile strength. In the region of temperatures above 0°С (up to ~450°С), these features are determined by the weak temperature dependence of the value of dispersion hardening by nanoscale vanadium carbonitride particles; in the temperature range below 0°С, they are determined by a strong temperature dependence of the thermally activated mobility of dislocations in the crystalline relief (the Peierls barrier, solid solution of impurities). Keywords: ferritic-martensitic steel, reduced activation steel EK-181, microstructure, structural-phase transitions, mechanical properties, fractography, heat resistance, low-temperature embrittlement DOI: 10.1134/S1063778818070098
INTRODUCTION Low-activation (with a rapid decay of the activity) 12% chromium ferritic-martensitic steels are priority construction materials for cores and internals of thermonuclear and nuclear (fast) power reactors of the new generation. To enhance the energy efficiency of reactor plants, it is necessary to expand the operating temperature range of such materials by means of increasing their high-temperature hardening with preservation of a required margin of low-temperature plasticity. To solve these problems, it is necessary to know the peculiarities of the microstructure, regularities of structure-phase transformations, and plastic deformation and fracture of 12% chromium ferritic-martensitic steels in a broad range of temperature of their planned operation, inc
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