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 River (ON), Canada, K0J 1P0 May 22, 2019 UNRESTRICTED / ILLIMITÉ -1-
Outline ➢ Introduction (Mechanical properties of Zirconium Hydrides) ➢ Test Material ➢ Experimental Results (Micro-mechanical Testing) ➢ Post-deformation TEM Analyses Results ➢ Conclusion UNRESTRICTED / ILLIMITÉ -2-
Introduction (Mechanical Behaviour of Bulk Hydrides) • Extremely brittle in tension up to 500C • In Compression: No measurable plastic deformation up to 100C • Dislocation-based slip plasticity between 100C to 500C 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 UNRESTRICTED / ILLIMITÉ -3-
Introduction (Acoustic Emission Coupled Mechanical Testing) Small radial hydrides (length < 25 m m) 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 m m) 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 UNRESTRICTED / ILLIMITÉ -4-
Micro-mechanical Testing of Zirconium Hydrides UNRESTRICTED / ILLIMITÉ -5-
Test Material: Hydrided Pressure Tube Offcuts Transverse tensile specimens, Hydrided & Thermo-mechanically cycled UNRESTRICTED / ILLIMITÉ -6-
72 ppm 118 ppm UNRESTRICTED / ILLIMITÉ -7-
Results: Pure Matrix Configuration UNRESTRICTED / ILLIMITÉ -8-
Results: Pure Matrix Configuration UNRESTRICTED / ILLIMITÉ -9-
Results: “Pure” Hydride Configuration UNRESTRICTED / ILLIMITÉ -10- 10
Results: “Pure” Hydride Configuration UNRESTRICTED / ILLIMITÉ -11- 11
Results (Pure Hydride Configuration) UNRESTRICTED / ILLIMITÉ -12- 12
Results (Matrix-Hydride-Matrix Configuration) UNRESTRICTED / ILLIMITÉ -13- 13
Results (Matrix-Hydride-Matrix Configuration) UNRESTRICTED / ILLIMITÉ -14- 14
Results (Matrix-Hydride-Matrix Configuration) UNRESTRICTED / ILLIMITÉ -15- 15
Results (Summary) Pure Circumferential Hydride M-H-M (Circumferential) Circumferential Matrix Pure Radial Hydride M-H-M (Radial) Radial Matrix *Configurations with Error Bars (2-4 Experiments) ** Configurations without Error Bars (1 Experiment) UNRESTRICTED / ILLIMITÉ -16- 16
Results (Summary) *Configurations with Error Bars (2-4 Experiments) ** Configurations without Error Bars (1 Experiment) UNRESTRICTED / ILLIMITÉ -17- 17
Post-deformation TEM Structural Analyses (Circumferential Hydride) 𝟐𝟐ഥ 𝟐𝟐𝟐 𝟑 Twins UNRESTRICTED / ILLIMITÉ -18- UNRESTRICTED / ILLIMITÉ
Post-deformation TEM Structural Analyses ഥ 𝟐ഥ 𝟐 𝟐 𝒒 // ഥ 𝟐𝟐ഥ 𝟐 𝒖 Orientation Relationship UNRESTRICTED / ILLIMITÉ -19- UNRESTRICTED / ILLIMITÉ
Post-deformation TEM Structural Analyses 𝟐𝟐𝟐 𝟐𝟐𝟏 Activated Slip System UNRESTRICTED / ILLIMITÉ -20- UNRESTRICTED / ILLIMITÉ
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. UNRESTRICTED / ILLIMITÉ -21- UNRESTRICTED / ILLIMITÉ
On-going Work UNRESTRICTED / ILLIMITÉ -22- UNRESTRICTED / ILLIMITÉ
Acknowledgement CANDU OWNERS GROUP (COG) for providing financial support this work. UNRESTRICTED / ILLIMITÉ -23-
Results (Matrix-Hydride-Matrix Configuration) UNRESTRICTED / ILLIMITÉ -24-
UNRESTRICTED / ILLIMITÉ -25-
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