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Transformations of structure, phase composition, and mechanical properties of 45Cr26Ni33Si2Nb2 alloy during hightemperature (800-1100 °C) tests for longterm strength are investigated. The formation of the G phase of Ni 16 Si 7 Nb 6 was revealed, and the temperature range of its stability was determined. The cor� relation of strength properties with the formation of the G phase at intercrystalline boundaries is found.

The properties of materials of the heat-exchange equipment components of the fast breeder reactor BN-600 after 130000–170000 h of operation at 500–550°C are studied. The effect of long-term aging on the strength, ductility, impact strength, and fracture toughness of 18Cr-9Ni steel (type 304 stainless steel) and its welds is examined. The mechanisms that give rise to changes in the mechanical properties are analyzed on the basis of microstructural and fractographic studies. The predicted degradation of material properties is estimated as a function of operating temperature and time.

A mathematical model of the kinetics of ferrite formation in the structure of pipe steels is developed. It allows for predicting the structural parameters of ferrite as a function of chemical composition, features of the structure of the initial austenite, and cooling mode after hot rolling.

The durability and plasticity of Kh18N9 steel was experimentally studied after its service for 170000 h at temperatures of 500–550°C in various components of an intermediate heat exchanger of a reactor facility. The properties of austenitic metal and the aged metal during operation were compared. The effect of thermal aging on durability and durable plasticity of Kh18N9 steel was simulated.

The microstructure of a Ti-killed interstitial free (IF) steel has been examined through TEM observations after simple-shear/simple-shear strain-path changes, in connection with the crystallographic orientation of the examined grains. A partial disappearance of prestrain microstructures is shown to cause the stagnation of work hardening at earlier stages of reversed loading during Bauschinger simple shear sequences. Under progressing reversed deformation, a fragmentation of the grains of unstable orientations still slows down the work-hardening rate. A strong localization of plastic flow within microbands following an orthogonal strain-path change is shown to occur within the grains containing well-developed prestrain dislocation boundaries and belonging to certain orientation groups.

Effects of molybdenum replacement by tungsten in steels of the bainitic, martensitic, and martensitic–ferritic classes containing 2.5%, 8% and 11% Cr, respectively, were investigated. The phase composition and structure of the bainitic steels were varied by changing the cooling rates from the austenitization temperature (from values typical for normalization up to V=3.3 × 10−2°C/s) and then tempering. The steels were irradiated to a fluence of 4×10 23 n / m 2 (⩾0.5 MeV) at 270°C and to fluences of 1.3×1023 and 1.2×10 24 n / m 2 (⩾0.5 MeV) at 70°C. The 2.5Cr–1.4WV and 8Cr–1.5WV steels have shown lower values of the shifts in ductile–brittle transition temperature (DBTT) under irradiation in comparison with corresponding Cr–Mo steels. Radiation embrittlement at elevated irradiation temperature was lowest in bainitic 2.5Cr–1.4WV steel and martensitic–ferritic 11Cr–1.5WV steel. The positive effect of molybdenum replacement by tungsten at irradiation temperature ∼300°C is reversed at Tirr=70∘C.

The deformability and fracture appearance of neutron irradiated Ti–Zr alloy were investigated. It was shown that irradiation at 200–250°C resulted in a drastic decrease of uniform elongation. The material irradiated at 350°C and over was characterized by high deformability. The dimple ductile transgranular fracture was found to be typical for the examined material both in initial state and after the low temperature irradiation. Elements of ductile intergranular fracture were observed in the material after neutron irradiation at 400°C.