Effects of Neutron Irradiation on Tensile Properties in High-Purity Fe–Cr Alloys

Abstract

The tensile properties of high‐ and low‐purity Fe–9, –18 and –30Cr alloys irradiated by neutrons up to a dose of 5 × 1024 n/m2 (E >1 MeV) at 613, 673, or 763 K have been examined. The yield strength and the ultimate strength are increased and the elongation is decreased by irradiation. The enhancement of these strengths due to the irradiation has a tendency to increase with chromium and impurity content. Large stress drops are often observed, especially at 763 K, in stress–strain curves of high‐purity and high‐chromium‐content alloys except for Fe–9Cr alloys. Irradiation‐induced precipitates, with 2% larger interplanar spacings than the α′‐phase, on dislocation loops are more easily formed in the specimens of higher chromium content and higher purity. The precipitates are formed even in the irradiated Fe–9Cr alloy of high purity. The stress drop behaviour during the tensile tests is predominant in the specimens of higher chromium content and higher purity.

Mechanical Property of F82H Steel Doped with Boron and Nitrogen

“…The effects of neutron irradiation on tensile deformation, DBTT, and microstructures of F82H and the other ferritic/martensitic steels were reported. [1][2][3][4][5][6] Radiation hardening occurred mainly at irradiation temperatures lower than about 400 C, and it increased with decreasing irradiation temperature up to about 250 C. The issue of helium accumulation on mechanical properties has been an ongoing concern. Recently, the effect of helium production on radiation hardening has been examining and the large enhancement of hardening due to helium from 600 appm to 10000 appm is detected in the tensile testing for 9Cr martensitic steels EM10 and T91 implanted by cyclotron experiments.…”

Radiation hardening and -embrittlement due to He production in F82H steel irradiated at 250°C in JMTR

“…The structural materials must not only withstand radiation damage, but also accommodate helium atoms due to transmutation process. The effects of neutron irradiation on tensile deformation, DBTT, and microstructures of F82H and the other ferritic/martensitic steels were reported previously [1][2][3][4][5][6][7][8][9][10][11][12][13]. In fission data, radiation hardening occurred mainly at irradiation temperatures lower than about 400°C, and it increased with decreasing irradiation temperature up to about 250°C.…”

“…The effects of helium production and displacement damage on DBTT in ferritic/martensitic steels were reported by several researchers [5,9,10,16,29,30,40,41]. The DBTT of ferritic/martensitic steels depends on the chromium content, and other impurities and the formation of precipitates such as a 0 -phase [2,3,39,40] and M 6 C [41]. A relatively large shift in DBTT, 70°C, due to helium production about 20 appm was shown in a previous study using JLF-1 doped with natural boron [10], however the result did not take into account the chemical effect of boron on the shift in DBTT in the irradiated specimen and the real shift in DBTT should be a smaller value.…”

Effects of Helium Production and Heat Treatment on Neutron Irradiation Hardening of F82H Steels Irradiated with Neutrons

“…Therefore, the effects of neutron irradiation on tensile deformation, ductile to brittle transition temperature (DBTT), and microstructures of F82H and the other ferritic/martensitic steels have been extensively investigated. [1][2][3][4][5][6][7][8][9][10][11][12][13] On the course of these research activities, hardening and upward shift of DBTT induced by neutron bombardment have been commonly regarded as crucial problems. Radiation hardening occurs mainly at irradiation temperatures lower than about 400 C, and it increased with decreasing irradiation temperature down to about 250 C. The DBTT tends to increase with decreasing irradiation temperature as well, and the shift increases largely at 250 C. The issue of helium accumulation effects on these properties has been an ongoing concern.…”