Effects of low-temperature neutron irradiation on the microstructure and tensile properties of duplex 2304 stainless steel and its electron-beam welds

A lean duplex stainless steel material (2304-grade) in its base metal and electron beam (e-beam) welded conditions were studied microstructurally and mechanically as a function of irradiation conditions to evaluate its use as a structural material at low temperatures (60-100 degrees C). Neutron irradiation up to a fluence of 1.40 x 10(19) n/ cm(2) (E > 0.1 MeV) or similar to 0.011 dpa decreased the total elongation of both base metal and e-beam welded samples. Overall, radiation hardening was observed in all the samples. The transversely cut irradiated samples showed some nonuniform quasi-cleavage and shearing in their fracture surfaces, indicating the variance of ductile nature of the two-phased (deformable austenite and harder ferrite) duplex structure. The e-beam welded samples also showed quasi-cleavage fracture, which is a characteristic of radiation-induced embrittlement. These observations of the e-beam welded samples were attributed to the formation of coarse ferrites, grain boundary and intragranular phases such as gamma(2) and gamma(3), and minor impurity phases such as CrN and Cr2N in the weld pool and/or heataffected zone of the samples. Radiation-induced elemental segregation was also identified in the post-irradiated base metal.

Automated summary

The study investigated the microstructural and mechanical properties of a lean duplex stainless steel material (2304-grade) under irradiation conditions, showing radiation hardening and decreased total elongation. Fracture surfaces of irradiated samples exhibited nonuniform quasi-cleavage and shearing, indicative of radiation-induced embrittlement. Furthermore, elemental segregation was identified in the post-irradiated base metal.