He, P.

Klimenkov, M.

Lindau, R.

Möslang, A.

English

KITopen

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association www.kit.eduMicrostructure- property correlation of 13.5%Cr nanostructured ODS steels for fusion applicationKarlsruhe Institute of TechnologyInstitute for Applied Materials (IAM)Karlsruhe, GermanyP.He, M. Klimenkov, R. Lindau, A. Möslang1 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM) Introduction- Requirements for structural material in fusion reactor- Reduced-activation F/M steels and ODS RAFM steels- Development of ODS RAF steels Experimental- Fabrication route- Analytical TEM (EDX and EELS) Microstructure- Bimodal grain size distribution- Chemical composition of coarse precipitates and ODS particles- Influence of Ti content on the mean particle size Mechanical properties- Hardness, tensile property, Charpy impact property SummaryOutline2 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Divertor: 10 dpa/a, 10-15 MW/m2Nanostructured RAF(M)-ODS-steels~300 - 800 °CBlanket: 30 dpa/year,  2.5MW/m2Reduced-activationferritic-martensitic steels: EUROFER (9Cr-WVTa) 250-550 °C EUROFER-ODS 250-650 °CMaterial challenges in Fusion ReactorAlloy Heat C Si Mn Cr V W Ta  Y2O3   EUROFER E 83699 0.12 0.06 0.42 8.87 0.19 1.10 0.14 + 0.3 or 0.5  RAFM-ODS (EUROFER-ODS)3 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Priority:Low activation capabilityReduced Activation Structural Materials:RAFM Steel ODS-RAFM Steel-200 -100 0 100 200 300 4000246810EUROFER 97 Impact Energy A v [J]Test Temperature [°C]ODS-Eurofer, 0.3 wt.-% Y2O3 HIP, as-received HIP + 1100°C 30' + 750°C 2h plate, L-T, 980°C 30' + 750°C 2h plate, T-L, 980°C 30' + 750°C 2h plate, L-T, 1100°C 30' + 750°C 2h plate, T-L, 1100°C 30' + 750°C 2h  PM2000, L-T, ENEA  ROFER 97hipped. EUROFER ODSTMT. EUROFER ODSPriority:Superior high temperature ductility Promising impact property4 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM) ODS steels are candidate materials for several Gen.IV reactor concepts  Sodium-Cooled Fast Reactor (SFR) :  cladding, in-core, out-of-core Super-Critical Water-Cooled Reactor (SCWR): cladding, in-core, out-of core  Very –High-Temperature Reactor (VHTR):  in-core, out-of-core ODS steels are candidate structural materials for future DEMO reactor Trends: 12-20 Cr ODS ferritic steels for higher operating temperature (higher thermal efficiency)Superior tensile and creep strength compared to 9Cr ODSBetter HT corrosion resistance Good radiation resistanceInferior impact property and ductilityExperimental Steels for Higher Operating Temperatures5 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Basic composition of 13.5% Cr ODS ferritic steelsRAF Steels:Replace critical alloying elements e.g. Mo  W99.1%0.00.02.013.5159/0K1299.5%0.30.42.013.5159/5K699.1%0.30.32.013.5159/4K599.9%0.30.22.013.5159/3K499.5%0.30.02.013.5159/1K2DensityY2O3TiWCrHeatCapsel-No.This work aims to investigate Ti dependency of microstructure and mechanical properties for ferritic ODS steels Theoretical density: for pure metal: ρ=m/vfor alloys:        1/ρ= ω1 %/ρ1 + ω2 %/ρ2 +ω3 %/ρ36 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Mechanical Alloying(MA)Hot IsostaticPressingHot RollingMA powderSteel canAttrition MillHeat TreatmentY2O3PowderSteelPowderHot ExtrusionElementalPowders orFabrication route7 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Mechanical alloying processZOZ Simoloyer CM01View into milling container MA: under H2, 1000/4'/700/1'/24h, Glove-Box HIP: 1150°C, 100 MPa, 2.5h Anealing: 1050°C, 2h, VacuumCapsules after HIP8 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Microstructure by SEM No visible porosity after HIP in all alloys  high density Elongated coarse precipitates align preferentially along GB in all ODS steels after HIP, eliminated by annealing Spherical precipitates (100-300nm in diameter) in all ODS steels in both conditions Grain structure (especially nano grains) is not clearly visible due to etching problem1µmODS-0 Ti: as-hipped ODS-0 Ti: after annealingODS-0.4 Ti: as-hipped ODS-0.4 Ti: after annealing9 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Bimodal grain size by TEMODS-0 Ti: as-hipped ODS-0.4 Ti: as-hipped• Bimodal grain size distribution in all Ti-containing ODS steels  • Coarse grain ~1-8µm free of dislocations; nano grains ~200-800 nm with much higher dislocation density (darker contrast)• It is very stable and resistant to annealing• It is assumed to caused by recrystallization and abnormal grain growth during HIP.10 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Chemical composition of precipitates• TEM: Tecnai F20 S (200keV) - GIF 200• STEM-HAADF technique was used for imagingand analyical investigations• EDX and EELS experiments were performed in the STEM  mode• EELS investigations were performed on coarseprecipitates and ODS particles as an excellent complement for the detection of light elements.11 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Chemical composition of precipitates• Darker contrast in BF while brighter in HAADF• Size:1-3 µm in length, 0.1-0.2 µm in thickness• EDX and EELS experiments were performed at the position located near to the edge• Cr carbideODS-0 Ti: as-hippedBF imageHAADF imageEDX profileEELS profile12 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Chemical composition of precipitates• Spherical precipitate (50-300 nm in diameter) in the non-Ti ODS steel are proven to be Cr oxide.ODS-0 Ti: as-hippedHAADF imageEDX profileEELS profileEDX SpectrumEELS Spectrum13 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Chemical composition of precipitates• Spherical precipitate (100-300 nm in diameter) in the 0.4%Ti ODS steel are proven to be Ti oxide.• Only a few Al oxides were found with a similar size and contrast.ODS-0.4 Ti: as-hippedHAADF imageEDX profileEDX profileEDX SpectrumEELS Spectrum14 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Chemical composition of ODS particles• In non-Ti ODS steel, ODS particles visible as spherical dots with similar contrast to that of the matrix in BF image mainly consist of Y and O.• In 0.4Ti ODS steel, ODS particles are visible as dark dots consist of Y-Ti-O. A non negligible Al is also detected in some particles.• Al contamination may result from MA process.EDX profileEDX profileEDX SpectrumEELS SpectrumODS-0 Ti: as-hippedBF imageHAADF imageODS-0.4 Ti: as-hipped15 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Ti dependence of ODS particle size • Ti addition is effective in particle size refinement• The optimum effect is obtained with 0.3% Ti in terms of narrow range and the smallest mean particle size• Further increase in Ti may increase the amount of coarse Ti oxides.0 2 4 6 8 10 12 14 16 18 20020406080100120140 Particle NumberParticle Size [nm](a) 13.5Cr2W0.3Y2O30 2 4 6 8 10 12 14 16 18 20020406080100120140(b) 13.5Cr2W0.3Y2O30.2TiParticle NumberParticle Size [nm]0 2 4 6 8 10 12 14 16 18 20020406080100120140(c) 13.5Cr2W0.3Y2O30.3TiParticle NumberParticle Size [nm]0 2 4 6 8 10 12 14 16 18 20020406080100120140(d) 13.5Cr2W0.3Y2O30.4TiParticle NumberParticle Size [nm]0% Ti 0. % Ti0.3% Ti 0.4% Ti16 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Mechanical property- Vickers Hardness • ODS steels significantly increase the hardness by 160%.• Generally hardness increases with increasing Ti content.• Annealing leads to a decrease for base steel  recovery and recrystallizationdislocation density↓ grain size ↑• All ODS alloys exhibit hardness increment after annealing dissolution of Cr carbides during annealing and enhanced Cr solid solutionbase steel 0 Ti ODS 0.2 Ti ODS 0.3 Ti ODS 0.4 Ti ODS20µm20µmAs-hippedAfter annealing17 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Mechanical property- Tensile Property Base steel13.5%Cr ODS• ODS ferritic steels show more profound strengthening effect compared to 9%Cr ODS• 0.3Ti ODS steel shows best tensile strength over the test temperature range with lowest high temperature ductility• 0-Ti ODS steel exhibits satisfactory strength up to 500°C and show a steep drop in strength at higher temperature; comparable ductility to ODS Eurofer18 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Mechanical properties - Impact Propertiesbase steel0 Ti ODS0.2-0.4 Ti ODS• Base steel exhibits similar USE with 2nd Gen.ODSEurofer• 0-Ti ODS steel shows comparable USE of 5.8 J and lower DBTT with the hipped ODS Eurofer • Ti-containing ODS steels show inferior impact property (USE < 2J) There is always trade-off between strengthand fracture property! Appropriate Thermal Mechanical Treatment ☺19 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)Summary Fully dense materials were received after HIP. All Ti-containing ODS steelsexhibit a bimodal grain size distribution even after annealing.  Precipitates: coarse precipitates and fine ODS particles- elongated Cr carbides in all as-hipped ODS samples; eliminated by annealing- Spherical Cr oxide for the 0-Ti ODS steel; spherical Ti oxides (a few Al oxides) for0.4Ti ODS in as-hipped state as well as in after-annealing state- ODS particles consist of Y and O for 0Ti ODS and Y-Ti-O in 0.4Ti ODS (Y-Ti-Al-O). 0.3Ti ODS exhibits the optimum effect in particle size refinement highestultimate tensile strength Mechanical properties- Superior hardness and tensile strength. Increase with increasing Ti content.- weaker impact properties for all Ti-containing ODS steels (USE<2 J); 0 Ti ODS steelshows comparable USE (5.8J) with 1st Gen. ODS Eurofer and satisfactory tensilestrength up to 500°C. Future work aims to improve high temperature ductility and impact properties.20 | Pei He | Aussois, France                                                        April 4-8, 2011 Institute for Applied Materials (IAM)

Microstructure-property correlation of 13.5%Cr nanostructured ODS steels for fusion application

https://publikationen.bibliothek.kit.edu/230085960/3815974

Microstructure-property correlation of 13.5%Cr nanostructured ODS steels for fusion application

Abstract

Similar works

Full text

Available Versions

KITopen