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TEXTURE OF NIOBIUM SHEET 3 MM THICKNESS

TEXTURE OF NIOBIUM SHEET 3 MM THICKNESS. RF SUPERCONDUCTING MATERIALS WORKSHOP FERMILAB, 23 AND 24 MAY 2007 PETER R. JEPSON PRINCIPAL SCIENTIST H.C. STARCK INC. NEWTON, MA. TEXTURE ANALYSIS BY EBSD. ELECTRON BACK-SCATTERING DIFFRACTION SEM equipped with video camera Channelling

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TEXTURE OF NIOBIUM SHEET 3 MM THICKNESS

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  1. TEXTURE OF NIOBIUM SHEET3 MM THICKNESS RF SUPERCONDUCTING MATERIALS WORKSHOP FERMILAB, 23 AND 24 MAY 2007 PETER R. JEPSON PRINCIPAL SCIENTIST H.C. STARCK INC. NEWTON, MA

  2. TEXTURE ANALYSIS BY EBSD • ELECTRON BACK-SCATTERING DIFFRACTION • SEM equipped with video camera • Channelling • Kikuchi patterns • Yields grain-by-grain information

  3. AREA EXAMINED BY EBSD • Cross-section (through-thickness) reveals more information than planar section • Sample is small, and outside actual part • Full-thickness • Top/bottom symmetry • Step size (square grid): 1/3 average linear intercept • 8 microns • 90 steps horizontally, 375 vertically • 34,000 points at 20 per second: scanning time 30 minutes

  4. COLOUR SCHEMES • Colours are relative to ND, which is vertical in all maps shown 15 DEG 20 DEG 20 DEG ALL EULER TRICOL 15 DEG

  5. HOW BEST TO DESCRIBE TEXTURE QUALITATIVELY • GRAIN MAPS, relative to ND, RD and TD, show • Prominent components (eg. 100 // ND) • Through-thickness gradient • Banding and other inhomogeneities ND ND RD TD

  6. OPTICAL MICROSCOPY PHOTOS FROM FERMILAB TD-06-048

  7. POLE FIGURES AND INVERSE POLE FIGURES

  8. SYMMETRY OF POLE FIGURES 2-FOLD 4-FOLD

  9. QUANTIFICATION OF TEXTURE(FROM GRAIN MAPS) SURFACE • BASED ON HALF-THICKNESS • STRENGTH OF EACH COMPONENT • AREA % WITH <15° MISORIENTATION • THROUGH-THICKNESS GRADIENT • BEST FIT • % PER MM • BANDING FACTOR • AVERAGE RESIDUAL FROM BEST-FIT LINE • % MID-THICK SURFACE MID-THICK

  10. 3 mm NIOBIUM SHEET A

  11. B ND X Z

  12. C ND X Z

  13. D

  14. SUMMARY • Texture control is important for large-scale production • Repeatable forming • Repeatable response to surface treatments • Maybe also for reliable performance • Texture can be quantified, and therefore specified • Controlled texture (and fine grain) is possible in 3 mm high-RRR Nb sheet.

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