Anomalously large deformation of 12Cr18Ni10Ti austenitic steel irradiated to 55 dpa at 310 °C in the BN-350 reactor

Whereas most previous irradiation studies conducted at lower neutron exposures in the range 100–400 °C have consistently produced strengthening and strongly reduced ductility in stainless steels, it now appears possible that higher exposures may lead to a reversal in ductility loss for some steels. A new radiation-induced phenomenon has been observed in 12Cr18Ni10Ti stainless steel irradiated to 55 dpa. It involves a ‘moving wave of plastic deformation’ at 20 °C that produces ‘anomalously’ high values of engineering ductility, especially when compared to deformation occurring at lower neutron exposures. Using the technique of digital optical extensometry the ‘true stress σ–true strain ε’ curves were obtained. It was shown that a moving wave of plastic deformation occurs as a result of an increase in the intensity of strain hardening, dσ/dε(ε). The increase in strain hardening is thought to arise from an irradiation-induced increase in the propensity of the γ → α martensitic transformation.