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Work hardening of Cu-based conductors bydeformation under cryogenic conditions

Leibniz−Institut

für Festkörper− und

Werkstoffforschung

Dresden

F. Thiel,

J. Freudenberger, A. Kau�mann, D. Rafaja

IFW Dresden, Institut für Metallische Werksto�eHelmholtzstr. 20, 01069 Dresden

TU Bergakademie Freiberg,Institut für Werksto�wissenschaftGustav-Zeuner-Str. 5, 09599 Freiberg

TU Dresden, Institut für Werksto�wissenschaft01062 Dresden

Karlsruher Institut für Technologie,Institut für Angewandte Materialien - Werksto�kunde76128 Karlsruhe

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developmental range of highstrength conductors for pulsedfield magnets

Cu

UTSσ

50 100510

0.5

1.0

1.5

0.5

1.0

1.5

at RTconductivity

[ % IACS ]

[ GPa ]

fatigue strengthafter N=5000

[ GPa ]

[ % ]elongation

High electricalconductivity

(Joule heating)heat capacity

high tensile strength(Lorentz force)

η

σUTS

sufficient ductility(rectangular crosssection and coilwinding)

σUTS

A t

σUTS

% IACS

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strength vs. conductivity

J. Freudenberger High Strength Cu-based conductor Ma-terials, In: Copper Alloys, Nova (2011)

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microstructure of Cu-Ag

hardening mechanisms

I solid solution hardening

I precipitation hardening

I phase boundary hardening

I work hardening

20 40 60 80Ag concentration [ m.-% ]

0

500

1000

Tem

pera

ture

[°C

]

Cu Ag

779.1°C8% 91.2%

961.9°C

1084.9°C

71.9%

(Cu)

(Ag)

S

continuous precipitates(140-160 HV)

discontinuous precipitates(80-100 HV)

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thermo-mechanical treatment

casting

homogenisation850◦C/5h/Ar

rotary swaging750◦Cϕ > 2 for dynamicrecrystallisation

precipitation reaction400◦C/18h/Ar

wire drawingup to ϕ = 4.7

300K

77K

wiredrawingof

pure

copper

activation of an additionalhardening mechanism

I twin boundary hardening

A. Kaufmann, Dissertation, TU Dresden (2014)

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thermo-mechanical treatment

casting

homogenisation850◦C/5h/Ar

rotary swaging750◦Cϕ > 2 for dynamicrecrystallisation

precipitation reaction400◦C/18h/Ar

wire drawingup to ϕ = 4.7

300K

77K

wiredrawingof

pure

copper

activation of an additionalhardening mechanism

I twin boundary hardening

A. Kaufmann, Dissertation, TU Dresden (2014)

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evolution of the microstructureof CuAg5Zr0.3

deformation at room temperature

I mixed <100> <111> �bre texture at large strainsI no formation of deformation twins

100 µm

CuAg5Zr0.3 CuAg5Zr0.3

30 µm

deformation at cryogenic temperature

I mixed <100> <111> �bre texture at large strainsI smaller grains when compared to RT deformationI deformation induced formation of twins

CuAg5Zr0.3

100 µm

CuAg5Zr0.3

30 µm

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evolution of the microstructureof CuAg5Zr0.3

deformation at room temperature

I mixed <100> <111> �bre texture at large strainsI no formation of deformation twins

100 µm

CuAg5Zr0.3 CuAg5Zr0.3

30 µm

deformation at cryogenic temperature

I mixed <100> <111> �bre texture at large strainsI smaller grains when compared to RT deformationI deformation induced formation of twins

CuAg5Zr0.3

100 µm

CuAg5Zr0.3

30 µm

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mechanical and electricalproperties of Cu-Ag5-Zr0.3

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texture in CuAg5Zr0.3 at largedeformation strain

RT deformation CT deformation

.0.480.46

0.32

0.40

[111]

[011]

0.50.49

[001]

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summary & outlook

I deformation under cryogenic condition:I wire drawing of CuAg5Zr0.3 is possibleI texture with mixed <100> <111> �bre texture in wire axisI initiates deformation twins in CuAg5Zr0.3I results in higher strength and lower conductivity when

compared to room temperature deformation

I twin density is lowering at very large deformation strains

I texture evolution not bene�cial for achieving high strength

AcknowledgementFR 1714/2-1

FR 1714/5-1

many thanks to: Enrico Knauer, Dirk Seifert,Hans-Peter Trinks, Sigfried Neumann, MichaelFrey, Kerstin Schröder, Christiane Mix, HansjörgKlauÿ, Tino Wolf and Ludwig Schultz