Study of Phase-Structural Transformations Resulting in Low-Temperature Radiation Embrittlement in Ferritic-Martensitic Steel

The results of investigations of the microstructure and short-time mechanical properties of EP-450 ferritic-martensitic steel and Kh13M2Yu2 + 1.5% TiO₂ dispersion-hardened steel are presented. It is shown that as a result of aging for 25000 h at 400 and 450°C finely dispersed precipitates of the α′-phase are formed in the structure. This increases the strength and decreases the ductility of the steel. The coefficient of hardening by precipitates of the α′-phase in aged dispersion-hardened steel is equal to 2.3. As a result of neutron irradiation at temperature in the interval 285–380°C to maximum dose 56 dpa vacancy pores, dislocation loops, and precipitates of the α′-phase formed in the structure of the EP-450 ferritic-martensitic steel, which also leads to hardening and embrittlement of the steel. The character of the radiation hardening correlates with the dose dependence of the average size and concentration of the formed dislocation loops. The coefficient of hardening of steel EP-450 by dislocation loops and α′-phase precipitates is 1.97 and 2, respectively.