Development of Oxide Dispersion Strengthened Ferritic Steels for FBR Core Application, (I). Improvement of Mechanical Properties by Recrystallization Processing.

Ukai, Shigeharu; Nishida, Takahiro; Okada, Hideya; Okuda, Takanari; Fujiwara, Masayuki; Asabe, Kazutaka

doi:10.3327/jnst.34.256

Cited by 76 publications

(51 citation statements)

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“…6) In the ODS ferritic steels with a basic composition of FeCr-W-Ti-Y 2 O 3 , grain morphology control by recrystallization has been shown to be indispensable not only for softening the material hardened in the process of cold-rolling but also suppressing the strength degradation by grain boundary sliding. [7][8][9][10] As an another approach, phase transformation from ferrite-martensite (α) to austenite (γ ) was demonstrated to be capable method for controlling the grain morphology by using the extruded bars of ODS martensitic steels. 11) In this study, by applying α-γ phase transformation in the ODS martensitic steels, cladding production test is executed using the cold-rolling process at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Development of 9Cr-ODS Martensitic Steel Claddings for Fuel Pins by means of Ferrite to Austenite Phase Transformation

Ukai¹,

Mizuta²,

Fujiwara

et al. 2002

Journal of Nuclear Science and Technology

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147

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For use as fuel cladding of liquid metal fast reactors, Fe-0.12C-9Cr-2W ODS martensitic steel claddings were developed by cold-rolling under the softened ferrite phase induced by slow cooling from austenite phase, subsequently by ferrite to austenite phase transformation to break up substantially elongated grains produced by cold-rolling at the final heat-treatment. The produced claddings showed noticeable improvement in tensile and creep rupture strength that are considerably superior to PNC-FMS and even austenitic PNC316 at higher temperature and extended time to rupture. The strength improvement is mainly attributed to titanium addition in ODS martensitic steels through its reduction of Y 2 O 3 particle size and shortening inter-particles spacing. The behavior of oxide particle size reduction is associated with stoichiometry between Y 2 O 3 and TiO 2 .

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Section: Introductionmentioning

confidence: 99%

Development of 9Cr-ODS Martensitic Steel Claddings for Fuel Pins by means of Ferrite to Austenite Phase Transformation

Ukai¹,

Mizuta²,

Fujiwara

et al. 2002

Journal of Nuclear Science and Technology

Self Cite

147

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“…6,7) It was preliminarily shown that re-crystallization heat-treatment softened the hardened structure and allowed control of the grain morphology in the course of cold-rolling manufacturing of ODS claddings, 8,9) resulting in a superior creep rupture strength in the hoop direction of the claddings. 10) In this study, the creep properties of previously manufactured ODS ferritic steel claddings are investigated for the cases of hoop and longitudinal stress modes.…”

Section: Introductionmentioning

confidence: 99%

Characterization of High Temperature Creep Properties in Recrystallized 12Cr-ODS Ferritic Steel Claddings

Ukai¹,

Okuda

Fujiwara

et al. 2002

Journal of Nuclear Science and Technology

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151

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The high temperature strengthening mechanism of previously manufactured 12Cr-ODS ferritic steel claddings was clarified. In the recrystallized 12Cr-2W-0.3Ti-0.24Y 2 O 3 -ODS ferritic steel cladding, αY 2 TiO 5 type complex oxide formation was responsible for the drastic reduction of oxide particle size and the resulting shortened distance between particles, which led to superior internal creep rupture strength at 973 K because of the high resistance to gliding dislocation. Internal creep deformation was considered to be controlled by the grain boundary sliding associated with grain morphology: the near 11, 9 and 19 coincidence boundaries with a 110 common axis.

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“…5, may be explained either by the coarsening of the microstructure with recrystallization, or by the formation of the brittle Laves phase of Fe 2 W with heat treatment at 923 K. In this case, the latter is more probable because the alloy recrystallizes at temperatures above 1473 K. 15) These decreases are normal in iron-based alloys containing tungsten, but the remarkable decrease in argon is not normal and is associated with the formation of bubbles, together with their segregation at grain boundaries. However, we cannot explain the steep decrease in hydrogen or its existing state in the alloy, as mentioned previously.…”

Section: Effect Of Residual Inert Gas On Impact Strengthmentioning

confidence: 99%

Gas Contamination due to Milling Atmospheres of Mechanical Alloying and Its Effect on Impact Strength

et al. 2005

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This study seeks to clarify the effects of gas contamination from milling atmospheres of mechanical alloying (MA) on mechanical properties. An iron-based dispersion alloy of Fe-13Cr-3W-0.5Ti-0.5Y 2 O 3 (mass%) was selected as the experiment material. We prepared MA powders by milling mixed powders in atmospheres of argon, helium, hydrogen, nitrogen, and vacuum; then we made bulk alloys by groove rolling the MA powders. We then examined atmospheric elements trapped in the MA powders and their releasing processes with heat treatment in vacuum. For bulk alloys, we also examined the high-temperature behavior of residual atmospheric elements and their effects on impact strength as a function of heat-treatment time at 923 K.Experiment results demonstrated that some of the atmospheric element trapped by MA powder was unexpectedly difficult to remove with heat treatment. The content of widely used argon in MA powder, for example, was 0.013 mass%, and the argon was difficult to remove even with treatment at 1473 K, which is considered the maximum allowable temperature. Therefore, most of the argon was introduced into bulk alloy as gas contamination. Nitrogen was effectively reduced with treatment at 1323 K; however, hydrogen could not be sufficiently removed with this treatment. Residual argon and helium in bulk alloys formed bubbles at elevated temperatures and caused density decrease (swelling). Impact strengths of the bulk alloys obtained through milling in argon, hydrogen, nitrogen, and vacuum decreased with increased treatment time; more remarkable decreases were observed in the alloys including argon and hydrogen. We concluded that nitrogen is the most suitable milling atmosphere to be applied as high-temperature materials.

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Development of Oxide Dispersion Strengthened Ferritic Steels for FBR Core Application, (I). Improvement of Mechanical Properties by Recrystallization Processing.

Cited by 76 publications

References 0 publications

Development of 9Cr-ODS Martensitic Steel Claddings for Fuel Pins by means of Ferrite to Austenite Phase Transformation

Development of 9Cr-ODS Martensitic Steel Claddings for Fuel Pins by means of Ferrite to Austenite Phase Transformation

Characterization of High Temperature Creep Properties in Recrystallized 12Cr-ODS Ferritic Steel Claddings

Gas Contamination due to Milling Atmospheres of Mechanical Alloying and Its Effect on Impact Strength

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