Microstructure of irradiated ferritic/martensitic steels in relation to mechanical properties

Schaeublin, R.; Gelles, D.S.; Victoria, M.

doi:10.1016/s0022-3115(02)01034-6

Cited by 74 publications

(35 citation statements)

References 11 publications

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“…It was also reported by Schaeublin that the irradiation hardening of proton-irradiated F82H-IEA could not be explained by the irradiation-induced dislocation loops, and it was suggested the effects were due to very fine precipitates, which were observed as black spots. 4) In addition to these, the effect of precipitates on grain boundaries on hardness was reported by Ohmura by comparing nano-hardness versus micro-hardness over Fe-C alloys. 5) These investigations suggested the possibility that precipitation under irradiation could have a large impact on mechanical properties.…”

Section: Introductionmentioning

confidence: 94%

Irradiation Effects on Precipitation in Reduced-Activation Ferritic/Martensitic Steels

Tanigawa¹,

Sakasegawa²,

Klueh

2005

Mater. Trans.

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It was previously reported that reduced-activation ferritic/martensitic steels (RAFs), such as F82H-IEA and its heat treatment variant, ORNL9Cr-2WVTa, JLF-1 and 2%Ni-doped F82H, show a variety of changes in ductile-brittle transition temperature (DBTT) and yield stress after irradiation at 573 K up to 5 dpa. These differences could not be interpreted as an effect of irradiation hardening caused by dislocation loop formation. In this paper, the effects of irradiation on precipitation of RAFs were investigated to determine how these effects might affect the mechanical properties. The precipitation behavior of the irradiated steels was examined by weight analysis, X-ray diffraction analysis and chemical analysis on extraction residues. These analyses suggested that irradiation caused (1) an increase of the amount of precipitates (mainly M 23 C 6 ), (2) an increase of Cr and decrease of W contained in precipitates, and (3) the disappearance of MX (TaC) in ORNL9Cr and JLF-1.

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Section: Introductionmentioning

confidence: 94%

Irradiation Effects on Precipitation in Reduced-Activation Ferritic/Martensitic Steels

Tanigawa¹,

Sakasegawa²,

Klueh

2005

Mater. Trans.

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“…Microhardness tests were performed on the specimens at different irradiation doses and the obtained results were related to the strength of the unirradiated material. TEM specimens prepared with special technique [9] were investigated in a JEOL2010 electron microscope with LaB 6 gun, high tilt lens, operated at 200 kV. The microstructure of the irradiated samples was analyzed using the bright field, dark field and weak beam conditions.…”

Section: Methodsmentioning

confidence: 99%

“…However, the damage accumulation in ferritic/martensitic steel with bcc structure is less than in other metals such as stainless steel or pure fcc metals [8]. After high energy proton/neutron irradiations to low doses, transmission electron microscopy observation reveals in F/M steel F82H unidentified defects the so-called 'black dot' [7,8] possibly interstitial clusters, with sizes ranging from 1 to 2 nm [9,10]. In another ferritic/martensitic steel, Optimax, the irradiation induced hardening reduces the total elongation and shifts the DBTT value to higher temperatures, which is due to the formation of nanocavities and small sized defect clusters [14].…”

Section: Introductionmentioning

confidence: 99%

Effect of irradiation on the microstructure and the mechanical properties of oxide dispersion strengthened low activation ferritic/martensitic steel

Ramar

Baluc

Schäublin

2007

Journal of Nuclear Materials

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“…Note that the typical value of a for dislocation networks is <0.1, [29][30][31] as they are considered to be weak obstacles to the moving dislocations segments. Further, it has been shown that, for a random array of obstacles, the value of the barrier strength coefficient is~70 pct of that assumed for a periodic array [32,33] (based on microstructural observations), and results show that the dislocation distribution is rather nonuniform in T91.…”

Section: Role Of Internal Stressmentioning

confidence: 99%

Improved Creep Behavior of Ferritic-Martensitic Alloy T91 by Subgrain Boundary Density Enhancement

Gupta

Was

2007

Metall Mater Trans A

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The objective of this study was to increase the creep strength of the ferritic-martensitic (F-M) alloy T91 by enhancing the subgrain boundary density. A thermomechanical treatment involving a 5 pct compression treatment, followed by an annealing treatment at 1050°C for 1 hour, then air cooling, and a tempering treatment at 800°C for 0.66 hours, then another air cooling, resulted in an increase in the subgrain boundary density of~39 pct, without altering any of the other microstructural features. Creep tests were conducted on both as-received (AR) and subgrain-boundary-enhanced (SGBE) conditions of the F-M alloy T91, over a temperature range of 500°C to 600°C and in the stress range of 150 to 255 MPa in argon. The T91-AR exhibited a higher creep rate than the T91-SGBE by a factor of~2.0 to 8.0. The ratio of time to rupture for the T91-SGBE compared to the T91-AR varied from 1.0 to 5.0. In general, higher ratios were seen at higher stresses. Creep behavior was analyzed on the basis of the Orowan equation, according to which creep rate is controlled by the mobile dislocation density and dislocation velocity. Internal stress calculations performed on both conditions showed a higher internal stress in the T91-SGBE by~10 MPa. Analysis of the sources of internal stress suggest that the higher value for the SGBE condition is due to subgrain boundary density enhancement. The SGBE condition exhibited a temperature-increment benefit of between 8°C and 26°C, such that the creep strength realized for the T91-SGBE was similar to that realized for the T91-AR, but at a higher temperature. The temperature-increment benefit increased exponentially with applied stress but less so with temperature.

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Microstructure of irradiated ferritic/martensitic steels in relation to mechanical properties

Cited by 74 publications

References 11 publications

Irradiation Effects on Precipitation in Reduced-Activation Ferritic/Martensitic Steels

Irradiation Effects on Precipitation in Reduced-Activation Ferritic/Martensitic Steels

Effect of irradiation on the microstructure and the mechanical properties of oxide dispersion strengthened low activation ferritic/martensitic steel

Improved Creep Behavior of Ferritic-Martensitic Alloy T91 by Subgrain Boundary Density Enhancement

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