Dislocation Pinning in Oxide Dispersion Strengthened Steels

Modeling of Radiation-Induced- 

Dislocation Pinning in Oxide Dispersion 

Strengthened Steels (ODSS) -II 

Satyen Baindur 

Division of Energy Research 

Ottawa Policy Research Associates, Inc. 

This Poster Describes Work in Progress 



Ottawa Policy Research 

Associates Inc.

Oxide Dispersion Strengthened Steels 

ODS Steels are Made by Ball-milling 

Yttrrium and Titanium Oxide Powders 

with Ferritic and Austenitic Steels 

Oxide dispersion stable above 700 C; but precipitation hardened is not. 




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Kimura 2007 SMINS 




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Dispersions are 

nanosized (5nm) 

while grain size is 

about 1 micron 

ODS Steels are Made by Ball-milling 

Yttrrium and Titanium Oxide Powders 

Ferritic, Martensitic and Austenitic Steels 




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Typical TEM Images of Microstructure and Bubble formation in Irradiated ODSS 

Akasaka et al 2004 JNM 




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Egami, Wang, Simonson (Oak 

Ridge), 2006. 




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BUT 

Wang 

2006 




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Corrosion Behavior of ODS Steels with 

different dispersoid concentrations under SCW 




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Jang et al 2007

ODS Steels: Candidate Structural and 

Cladding Materials for Advanced Reactors 

• Questions and Predictive Understanding Required: 

• What aspects of the Dispersed Medium (Y, Ti, Cr, Al, etc oxides) are 

Responsible for the Excellent Irradiation Creep Strength? 

• How does Dispersed Medium interact with the Matrix? 

• How does the Cubic Centered Structure of the Matrix provide 

Irradiation Swelling Resistance? 

• How do the different Dispersed Media interact with each other? 

• Can the composition, temperature, and radiation dose dependence 

of the behavior be explained/predicted? 

• How are Radiation-Induced Dislocations Pinned? 

• How might SCW-ODSS interactions be understood? 




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Multiscale Materials Modeling 

• The Interaction of Materials with Radiation is an intrinsically 

Multiscale Phenomenon: 

• Atomistic Scale Events Metre Scale Effects 

• Picosecond Scale Events Effects at Decade Scale 

• Events at all scales must be integrated in a truly predictive Model, 

but at the right resolution 

• Also: explain events not accessible in experiments: either because 

of time scale (e.g. 60 year reactor life) or difficult to achieve in lab 

(e.g. SCW environment + fast spectrum neutron dose or 

Furnaces at T > 1300 C or Real-time microscopy) 




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Multiscale Processes during Material 

Irradiation 




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Wirth 2005

Multiscale Modeling 

• Could the Oxide Particles be sinks for point defect migration? 

• Could the Oxide Dispersion, as a whole, pin dislocations, as a result 

of lattice mismatches? 

• Could Oxide Dispersion slow Phase segregation? Oxide dispersion 

exhibits phase stability under irradiation (Kimura 2007 SMINS) 

• Could Oxides of Transition Metals preferentially form higher oxides, 

preventing corrosion? Yttrium-Titanium pyrochlores – Y 2 Ti 2 O 7 

formation reported (Kimura 2007 SMINS) 




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Distinct Levels of Multiscale Modeling 

• Atomistic: Electrons are the dynamic objects: QM states of 

electrons determines atomic dynamics: QMC, TBA, 

DFT, LDA 

• Microscopic: Atoms are objects of interest: Interatomic Potentials 

mediated by electrons: Molecular Dynamics methods, with Classical 

Interatomic Potentials derived from DFT 

• Mesoscopic: Grain boundaries, dislocations, are the objects of 

interest; dynamics derived from phenomenological potentials based 

on microscopic level: Dislocation Dynamics - DD 

• Macroscopic: Materials behavior described by ‘constitutive 

equations’ – volume, temperature, stress and strain, etc become 

dynamic variables of interest: Finite Element Modeling FE 

• Sequential or Concurrent (Kaxiras 2005) 




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Dislocation Dynamics 

• Peierls-Nabarro (P-N) Dislocation Model 

– The creation and motion of dislocations mediates the response 

of a crystal to external stress. 

– The P-N model incorporates details of discrete dislocation core 

into continuum framework, and is an inherently multiscale model. 

– Modified P-N model has been used in modeling evolution of the 

precipitate microstructure (Vaithyanathan et. al. 2002) to yield 

phase-field information. 

– Similar model may be applicable for ODSS, which should show 

phase stability – though the size distribution of the precipitate 

microstructure may be more heterogeneous than in ODSS. 




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References 

1. Baindur, S. Materials Challenges for the Supercritical Water-cooled Reactor (SCWR) Bulletin 

of the Canadian Nuclear Society, vol. 29 no.1, March 2008. 

2. Lu, G. and E. Kaxiras, Overview of Multiscale Modeling for Materials, Chapter 22 in 

Handbook of Theoretical and Computational Nanotechnology (Rieth, M. and 

Schommers, W. eds.) 

3. Bullard, J.W., L. Q. Chen, R. K. Kalia, and A. M. Stoneham, Eds. Computational and 

Mathematical Models of Microstructural Evolution Mater. Res. Soc. Proc. 529, Warrendale, 

PA, 1998. 

4. Bulatov,V.V., T. Diaz de la Rubia, R. Phillips, E. Kaxiras, and N. Ghoniem, Eds. Multiscale 

Modeling of Materials. Mater. Res. Soc. Proc. 538, Warrendale, PA, 1999. 

5. Robertson, I.M., D. H. Lassila, B. Devincre, and R. Phillips, Eds. Multiscale Phenomena in 

Materials—Experiments and Modeling Mater. Res. Soc. Proc. 578, Warrendale, PA, 2000. 

6. Vaithyanathan, V., C. Wolverton and L.Q. Chen, Phys. Rev. Lett. 88, no. 12, 125503.1- 

125503-4. 

Acknowledgment: Dr. Beth Opila, The Gordon Research Conference on High Temperature 

Materials, and its sponsors, are thanked for their support. 




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Dislocation Pinning in Oxide Dispersion Strengthened Steels

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