Deformed microstructure of ferritic-martensitic steel EK-181

Abstract

The mechanical properties of heat-resistant low-activated 12% Cr ferritic-martensitic steel EK-181 are investigated during tensile tests at T = 20 °C and in the temperature range close to the operating temperatures of the nuclear reactor (T = 650 and 720 °C) after traditional heat (THT) and high-temperature thermomechanical treatments (HTMT). It is shown that the strength properties of steel after HTMT exceed the corresponding values after THT. The features of the steel microstructure near the neck of the samples deformed by tension at these temperatures using two processing methods are studied. It is shown that plastic deformation at T = 20 °C leads to the curvature and fragmentation of martensitic lamellae and the formation of new low-angle boundaries. Deformation near the operating temperature range contributes to the development of dynamic polygonization, recrystallization and increase in density and size of the precipitates. After HTMT these processes are less intensive compared to the structural state after THT. This is due to the higher density of nanosized precipitates of V(C, N) and the increased dislocation density after HTMT.The mechanical properties of heat-resistant low-activated 12% Cr ferritic-martensitic steel EK-181 are investigated during tensile tests at T = 20 °C and in the temperature range close to the operating temperatures of the nuclear reactor (T = 650 and 720 °C) after traditional heat (THT) and high-temperature thermomechanical treatments (HTMT). It is shown that the strength properties of steel after HTMT exceed the corresponding values after THT. The features of the steel microstructure near the neck of the samples deformed by tension at these temperatures using two processing methods are studied. It is shown that plastic deformation at T = 20 °C leads to the curvature and fragmentation of martensitic lamellae and the formation of new low-angle boundaries. Deformation near the operating temperature range contributes to the development of dynamic polygonization, recrystallization and increase in density and size of the precipitates. After HTMT these processes are less intensive compared to the structural sta...