Effects of Neutron and Electron Irradiation on Low-manganese Steels

Abstract

The interaction between solute atoms and defects was studied by means of tensile test and transmission electron microscopy. The defects were produced by neutron irradiation at 200°C to a fluence of 6.4×10¹⁸ n/cm² (E_n>1 MeV) and electron irradiation at 650 kV electron microscope to a fluence of 7×10²¹ e/cm².
Radiation hardening and radiation embrittlement occured by neutron irradiation. The yield stress increased and the total elongation decreased with the increase of manganese content. Dislocation loops were observed on iron, but they were not detected on manganese alloys. Therefore, it will be considered that the defects would be trapped by manganese atoms and then formed complex with carbon atoms. On electron irradiation defects were not observed also on the manganese alloys, however, the defect clusters, presumably interstitial type, appeared above 325°C and grew during post-irradiation annealing. The annealing behavior was similar for the neutron and electron irradiated specimens.
The radiation hardening could be explained as that manganese atoms trap carbon atoms and interstitial atoms during irradiation and then form fine complexes, which would act as the obstacles for dislocation motion.