Mechanical and electromechanical properties of IBAD-MOCVD-based REBCO coated conductors

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1 superior performance. powerful technology. Mechanical and electromechanical properties of IBAD-MOCVD-based REBCO coated conductors Yifei Zhang International Workshop on Coated Conductors for Applications (CCA) 2014 December 1, 2014 Jeju, Korea SuperPower Inc. is a subsidiary of Furukawa Electric Co. Ltd.

2 Acknowledgements Many thanks to my colleagues at SuperPower Sergey Repnoy Joe Tanski Justin Waterman Aarthi Sundaram John Dackow Drew Hazelton Hisaki Sakamoto All Rights Reserved. Copyright SuperPower Inc

3 Outline 2G HTS wire production at SuperPower Motivation and objectives of this work Mechanical/electromechanical properties under axial tension Delamination strength measurement methods Minimum double bending diameter of wire and joint All Rights Reserved. Copyright SuperPower Inc

2G HTS wire production at SuperPower IBAD-MOCVD based REBCO wire on Hastelloy substrate REBCO formulation: AP (Advanced Pinning) with enhanced in-field performance for B//c, targeting at coil

4 2G HTS wire production at SuperPower IBAD-MOCVD based REBCO wire on Hastelloy substrate REBCO formulation: AP (Advanced Pinning) with enhanced in-field performance for B//c, targeting at coil applications such as high-field magnets, SMES, motors/generators CF (Cable Formulation) for cables, transformers, resistive type SFCL SF wire Ag only or SCS wire with Ag and electroplated Cu stabilizer I c (77K, s.f.)/12mm= a, piece length ~ 300m Variations in width (2-12mm), substrate thickness (50 or 100µm), Ag thickness (1-5µm), Cu thickness (10-115µm), and insulation Product lineup is expanding All Rights Reserved. Copyright SuperPower Inc

5 Motivation and objectives of this work Mechanical/electromechanical properties are key performance to applications Sources of stress: mechanical, thermal, and magnetic High stress(strain) may cause degradation in electrical properties Static tensile or cyclic tensile stress in longitudinal (axial) direction Static tensile or compressive stress in transverse direction (perpendicular to the surfaces) Static compressive stress in transversal direction (parallel to the surfaces) Cleavage or peel stress complex and highly concentrated Bending stress with REBCO under tension or compression Objectives of the work Characterize mechanical/electromechanical behaviors and provide property data to customers Understand relationship between structure/processing and properties and improve mechanical/electromechanical properties Help optimize the wire processes All Rights Reserved. Copyright SuperPower Inc

6 Mechanical/electromechanical properties under tensile stress in longitudinal (axial) direction Mechanical properties Stress-strain relationship under axial tensile load at room temperature and at 77K in liquid nitrogen Basic mechanical properties: elastic modulus (E) and yield stress ( 0.2 ) Electromechanical properties I c measurement under applied axial stress at 77K, compared with zerostress I c Basic electromechanical properties: tensile stress (strain) limit or critical stress (strain), c,0.95 and c,0.95, above which I c drops below 95% of zerostress I c All Rights Reserved. Copyright SuperPower Inc

for tensile testing in LN2 Sample and double

7 Axial tensile testing Shimadzu AG-IC universal testing system Nyilas type double extensometer (GL=50mm) Set-up for tensile testing in LN2 Sample and double extensometer All Rights Reserved. Copyright SuperPower Inc

8 Tensile testing of wire without stabilizer (Ag/Cu) Testing after deposition of REBCO Stress-strain relationship of 12mm wide tape with 50µm thick Hastelloy I c versus stress (strain) relationship at 77K c, MPa, c, % 77K All Rights Reserved. Copyright SuperPower Inc

Tensile testing of bonded wire Bonded wire provides benefits in higher I c, higher mechanical strength, tailored normal state resistivity, and/or improved stability A fully automated system has been

9 Tensile testing of bonded wire Bonded wire provides benefits in higher I c, higher mechanical strength, tailored normal state resistivity, and/or improved stability A fully automated system has been built for fabrication of 2-tape or 3- tape bonded wires Bonded wire in an architecture of 2G/Cu/2G with an initial zero-stress I c (77K, s.f.) of 880A tested Schematic of bonded wire of 2G/Cu/2G E-I characteristic (77K, s.f.) Bonded wire of 2G/Cu/2G All Rights Reserved. Copyright SuperPower Inc

12 Tensile testing of wires with variation in stabilizer I c versus tensile stress relationship at 77K c, 0.95 depends on Cu thickness Wires on 50µm Hastelloy Substrate All Rights Reserved. Copyright SuperPower Inc

13 Tensile testing of wires with variation in stabilizer I c versus tensile strain relationship at 77K c,0.95 is about 0.45%, independent of Cu thickness Wires on 50µm Hastelloy Substrate All Rights Reserved. Copyright SuperPower Inc

14 Tensile testing of wires with variation in stabilizer With a constant c,0.95 of about 0.45%, c, 0.95 depends on E 0.45 which is the slope of the stress-strain in between 0 and 0.45% strain 0.45% All Rights Reserved. Copyright SuperPower Inc

83mm Brass pins 1-e -1 Sample preparation for pin-pull

15 Transverse tensile test pin-pull method (RT) Force gauge Chuck Brass pin Sample X-Y stage G10 base Pin diameter=1.83mm Brass pins 1-e -1 Sample preparation for pin-pull test All Rights Reserved. Copyright SuperPower Inc

Transverse tensile test anvil method (RT and 77K) Upper anvil Lower anvil Contact

Transverse tensile test anvil method with I c Measurement of the transverse tensile strength at room temperature Measurement of the transverse tensile stress dependence of I c at 77K

17 Transverse tensile test anvil method with I c Measurement of the transverse tensile strength at room temperature Measurement of the transverse tensile stress dependence of I c at 77K Stress-displacement curves Transverse tensile test Measurement method is being optimized Set-up for transverse tensile test All Rights Reserved. Copyright SuperPower Inc

Peel test to characterize delamination strength Widely used for testing of peel resistance

results Peel strength (N/cm) determined from peeling load vs.

peeling front), including 90, 180 peel, and T-peel Utilized to study relationship between

18 Peel test to characterize delamination strength Widely used for testing of peel resistance of adhesives, ASTM D-1876 (T-Peel) Steady state peeling process - reliable and reproducible results Peel strength (N/cm) determined from peeling load vs. displacement curve Test can be done at various peeling angles (change in stress state at peeling front), including 90, 180 peel, and T-peel Utilized to study relationship between delamination strength and structure/processing 90 Peel 180 Peel T-Peel All Rights Reserved. Copyright SuperPower Inc

19 Bending test for minimum double bending diameter 77K Set-up for I c measurement in LN2 with wire under bending at various diameters Normalized I c vs. bending diameter for 12mm wide wire with 100 m Cu All Rights Reserved. Copyright SuperPower Inc

20 I c (d) / I c ( ) or R (d) / R ( ) Ratio I c and resistance vs. bending diameter of joints Bending Diameter (mm) I c measured at 77K with spliced wire under bending Lap joint (HTS-HTS) splice of SCS4050 with 40 µm Cu stabilizer R( ) = 10 ~ 20 n with 10 cm overlap length All Rights Reserved. Copyright SuperPower Inc

21 Summary Various testing capabilities have been built or are being established to measure and study mechanical/electromechanical properties of the 2G HTS wires While the stress limit for I c retention under tension at 77K ( c,0.95 ) depends on the Cu/Substrate thickness ratio, the strain limit ( c,0.95 ) is about a constant of 0.45% Weibull analysis based on the result from an anvil test at 77K indicated the transverse tensile strength ( 0.01 ) is about 18 MPa Thank you for your attention! For more information: For questions: info@superpower-inc.com All Rights Reserved. Copyright SuperPower Inc

Detailed studies of tensile and delamination properties of REBCO coated conductors

superior performance. powerful technology. Detailed studies of tensile and delamination properties of REBCO coated conductors Yifei Zhang, Masayasu Kasahara, Aarthi Sundaram, Paul Brownsey, Allan Knoll,