Microstructure change of duplex stainless steels after thermal aging and electron beam irradiation

Duplex stainless steel has been used as a structural material for light water reactors. It is well known that the thermal aging during operation causes spinodal decomposition to Cr-rich (α') phase and Fe-rich (α) phase in the ferrite phase, resulting in brittlement. In order to understand the mechanism of this phenomena and the effect of irradiation, a duplex model alloy (Fe-25Cr-10Ni-2.5Mo-1Mn) prepared by arc melting and thermally aged in the appropriate condition was subjected to accelerated irradiation by a multi-beam ultra-high voltage electron microscope and partially an ion accelerator in this study. Spinodal decomposition of Fe and Cr was confirmed in the model alloy aged at 450 °C. In addition, the electron beam irradiation to aged model alloy resulted in the decrease in the amplitude of spinodal decomposition. From this experiment, it was suggested that spinodal decomposition could be suppressed by accelerated irradiation.