Microstructure, Structural-Phase Transformations, and Mechanical Properties of Low-Activation 12% Chromium Ferritic-Martensitic Steel EK-181 Depending on the Treatment Conditions

The results of investigations of the treatment conditions influence on the regularities of structural-phase transformations, microstructure, and mechanical properties of heat-resistant low-activation 12% chromium ferritic-martensitic steel EK-181 are summarized. The physical factors responsible for increasing the yield strength of steel and the relationship of microstructure features to strength and plastic properties are revealed. The regularities of plastic deformation of steel are established. The modes of step-by-step heat treatment (SHT) and high-temperature thermomechanical treatment (HTMT) are presented, which lead to formation of structural states with high values of dispersion and volume fraction of nanoscale particles V(C, N), dislocation density, and internal stresses. These modes provide a significant (by ≈20%) increase in strength properties of steel in a wide temperature range (from –196 to 800°C), while maintaining a sufficient reserve of plasticity and increasing its thermal stability compared with the traditional heat treatment mode (THT).