Microstructure and mechanical properties of ferritic/martensitic steel EP-823 after neutron irradiation to high doses in BOR-60

Mechanical properties and microstructure of ferritic/martensitic (F/M) steel EP-823 were investigated following irradiation in BOR-60 to 63 dpa at 365–680 °C. Up to ∼460 °C irradiated EP-823 was found to fracture in a brittle mode at low strength levels, but no significant change in mechanical properties occurred at temperatures >460 °C. When compared to EP-450 often used in Russia it is observed that EP-823 is rather more brittle, with the primary microstructural difference being the formation of M2X in EP-823 instead of α′ precipitates in EP-450. On the other hand, EP-823 appears to be somewhat more resistant to void swelling. Both of these attributes are thought to arise primarily from the higher silicon content of EP-823.