RADIATION-INDUCED GRAIN-BOUNDARY SEGREGATION IN FERRITIC FE-CR-MN STEELS

Radiation-induced solute redistribution and microstructural evolution in the vicinity of grain boundary (GB) in ferritic Fe-10Cr-xMn-3Al (x = 5, 10, 15) steels were studied by means of electron irradiation up to 10 dpa at 723 K in an HVEM and analytical electron microscopy. In addition, X-ray diffraction analysis was performed for determination of the volume size factor of solutes. The oversized solutes, Mn and Al, were depleted at the GB by the electron irradiation, and the amount of solute segregation (evaluated by the ratio of solute concentration at the GB to the concentration in the matrix of the unirradiated area) decreased with increasing atomic volume, which depend on Mn content in the steel. The GB segregation ratio of Mn, which had a smaller volume size factor relative to that of Al, was lower than that of Al. Those results indicated that radiation-induced segregation of oversized solutes supressed by decreasing their volume size factor. In this context, a new approach for suppression of radiation-induced solute segregation was discussed. On the other hand, the oversized Cr was enriched at the GB as a result of thermal segregation. This Cr segregataion was also enhanced by the irradiation. The GB enrichment of Cr resulted from the formation of chi phase at the GB.