Micro-Mechanical Characterization of Hydrides in Zr-2.5 wt% Nb - - PowerPoint PPT Presentation

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Micro-Mechanical Characterization of Hydrides in Zr-2.5 wt% Nb - - PowerPoint PPT Presentation

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Micro-Mechanical Characterization of Hydrides in Zr-2.5 wt% Nb Pressure Tube Material Vineet Bhakhri, Wenjing Li, Cameron Howard, Sean Hanlon, Chris Dixon, Clinton Mayhew, Colin Judge, Sterling St Lawrence Canadian Nuclear Laboratories, Chalk

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Micro-Mechanical Characterization of Hydrides in Zr-2.5 wt% Nb Pressure Tube Material

Vineet Bhakhri, Wenjing Li, Cameron Howard, Sean Hanlon, Chris Dixon, Clinton Mayhew, Colin Judge, Sterling St Lawrence

May 22, 2019 Canadian Nuclear Laboratories, Chalk River (ON), Canada, K0J 1P0

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Outline

➢ Introduction (Mechanical properties of Zirconium Hydrides) ➢ Test Material ➢ Experimental Results (Micro-mechanical Testing) ➢ Post-deformation TEM Analyses Results ➢ Conclusion

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Introduction (Mechanical Behaviour of Bulk Hydrides)

  • K. G. Barraclough, C.J. Beevers, “The Deformation and Fracture of Hydrides Based on the d-

Phase, Part I”, Journal of Materials Science 4 (1968) 518

  • Extremely brittle in tension up to 500C
  • In Compression: No measurable plastic

deformation up to 100C

  • Dislocation-based slip plasticity between

100C to 500C

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Introduction (Acoustic Emission Coupled Mechanical Testing)

  • Small radial hydrides (length < 25 mm) required ~ 4% plastic

strain to fracture under uniaxial loading at 25C

  • Room-temperature hydride fracture strain decreased with

increasing length.

  • Tri-axial stress state further decreased the hydride fracture

strain to 1% or less at ambient temperature conditions.

  • Longer hydrides (length > 50 mm) failed at a critical stress (644

± 45 MPa)

  • Brittle-to-Ductile transition behaviour between 120C to 140C

under uniaxial loading.

L.A. Simpson, “Criteria for Fracture Initiation at Hydrides in Zirconium-2.5 Pct Niobium Alloy”, Metallurgical Transactions A 12 (1981) 2113 M.P. Puls, “Effects of Crack Tip Stress States and Hydride-Matrix Internal Stresses on Delayed Hydride Cracking”, Metallurgical Transactions A 21(1990) 2905 M.P. Puls, “Fracture Initiation at Hydrides in Zirconium”, Metallurgical Transactions A 22(1991) 2327

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Micro-mechanical Testing of Zirconium Hydrides

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Test Material: Hydrided Pressure Tube Offcuts

Transverse tensile specimens, Hydrided & Thermo-mechanically cycled

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72 ppm 118 ppm

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Results: Pure Matrix Configuration

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Results: Pure Matrix Configuration

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Results: “Pure” Hydride Configuration

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Results: “Pure” Hydride Configuration

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Results (Pure Hydride Configuration)

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Results (Matrix-Hydride-Matrix Configuration)

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Results (Matrix-Hydride-Matrix Configuration)

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Results (Matrix-Hydride-Matrix Configuration)

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Circumferential Matrix Radial Matrix Pure Circumferential Hydride Pure Radial Hydride M-H-M (Circumferential) M-H-M (Radial)

Results (Summary)

*Configurations with Error Bars (2-4 Experiments) ** Configurations without Error Bars (1 Experiment)

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Results (Summary)

*Configurations with Error Bars (2-4 Experiments) ** Configurations without Error Bars (1 Experiment)

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𝟐𝟐𝟐 𝟐𝟐ഥ 𝟑

Twins

Post-deformation TEM Structural Analyses (Circumferential Hydride)

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Post-deformation TEM Structural Analyses

Orientation Relationship ഥ 𝟐ഥ 𝟐 𝟐 𝒒// ഥ 𝟐𝟐ഥ 𝟐 𝒖

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Post-deformation TEM Structural Analyses

𝟐𝟐𝟐 𝟐𝟐𝟏 Activated Slip System

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Conclusions

➢ Pure Matrix Configuration

  • Strength: Circumferential Matrix > Radial Matrix
  • Plastic Strain to Failure: Radial Matrix > Circumferential Matrix

➢ Pure Hydride Configuration

  • Strength: Circumferential Hydride > Radial Hydride
  • Plastic Strain to Failure: Radial Hydride > Circumferential Hydride
  • TEM analyses of post-deformed pure circumferential hydride revealed extensive

twining and dislocation slip. ➢ Matrix-Hydride-Matrix (M-H-M) Configuration

  • Strength: M-H-M (Circumferential Hydride ) > M-H-M (Radial Hydride)
  • Plastic Strain to Failure: (M-H-M) Radial Hydride > M-H-M) Circumferential Hydride
  • Co-deformation of hydride and matrix phases displayed extensive plastic

deformation of both the phases prior to final fracture.

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On-going Work

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Acknowledgement

CANDU OWNERS GROUP (COG) for providing financial support this work.

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Results (Matrix-Hydride-Matrix Configuration)

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