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 degrees 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 degrees 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 sigma-true strain epsilon' 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, d sigma/d epsilon(epsilon). The increase in strain hardening is thought to arise from an irradiation-induced increase in the propensity of the gamma -> alpha martensitic transformation. (C) 2009 Elsevier B.V. All rights reserved.