Irradiation Effects on Substructure Related to Irradiation Softening

摘要

The evolution of the dislocation microstructure during irradiation of a deformed Fe-2 1/4 Cr-1Mo ferritic alloy was characterized by two competing processes. At low temperature, the dislocation density increased due to loop formation and interaction. At higher temperature, the dislocation density decreased due to recovery and polygonization of the original tangled cell structure. The transition temperature which separates these two processes decreased with increasing degree of cold work. Radiation induced recovery of the deformation substructure was, however, only marginal compared to purely thermal-induced. The observed transition in microstructure with temperature correlated well with the transition from hardening at low temperatures to softening at high temperatures observed neutron irradiation. The dislocation evolution in cold-worked ferritic alloys is distant from that observed in cold worked austenitic alloys in that cold-worked or annealed starting conditions do not evolve to the same uniform dislocation density in the ferritic alloy as is observed in austenitic alloys. (ERA citation 10:049022)