4:55 PM - 5:10 PM
[1C16] FY2017 investigation for improvement of evaluation methods of irradiation effects on reactor pressure vessel and core internals
(3) Correlation between microstructure and yield strength in neutron irradiated austenitic stainless steels
Keywords:Austenitic stainless steel, Neutron irradiation, Atom probe tomography, Transmission electron microscopy, Yield strength
Atom probe and TEM observation were performed on austenitic stainless steel irradiated to about 5 to 47 dpa in a fast reactor (BOR-60).
In the atom probe analysis, nickel and silicon enriched clusters with a size of about 4 nm were observed. In some sample, copper enriched clusters with a size of about 2 nm were observed. The number density of clusters were about 5 × 1023 to 1024 m-3. Nickel and silicon segregated dislocation was observed in materials which highly cold worked before irradiation. In TEM observation, black dots and perfect dislocation loops with a size of about 6 nm were observed. Also, Frank loops with a size of 8 to 10 nm were observed. The number density of those defects were about 1023 m-3 and 5 to 7 × 1022 m-3, respectively. In some samples, γ 'phase with a size of about 6 nm was observed. The number density of γ 'phase was 6 × 1021 m-3. It was confirmed that the increment of yield strength can be estimated from microstructure by using the Orowan mechanism in which the strength factor of cluster is constant as with the 316L stainless steel irradiated in the thermal neutron furnace (JMTR) shown in last year.
In the atom probe analysis, nickel and silicon enriched clusters with a size of about 4 nm were observed. In some sample, copper enriched clusters with a size of about 2 nm were observed. The number density of clusters were about 5 × 1023 to 1024 m-3. Nickel and silicon segregated dislocation was observed in materials which highly cold worked before irradiation. In TEM observation, black dots and perfect dislocation loops with a size of about 6 nm were observed. Also, Frank loops with a size of 8 to 10 nm were observed. The number density of those defects were about 1023 m-3 and 5 to 7 × 1022 m-3, respectively. In some samples, γ 'phase with a size of about 6 nm was observed. The number density of γ 'phase was 6 × 1021 m-3. It was confirmed that the increment of yield strength can be estimated from microstructure by using the Orowan mechanism in which the strength factor of cluster is constant as with the 316L stainless steel irradiated in the thermal neutron furnace (JMTR) shown in last year.