Temperature Dependences of Mechanical Properties and Fracture Features of Low-Activation Ferritic-Martensitic EK-181 Steel in a Temperature Range from – 196 to 720°C

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).