-
Options for yield strength Options for yield strength
enhancement of Alenhancement of Al--stabilisedstabilised
1st Linear Collider Detector (ILC/CLIC) Magnet Workshop
enhancement of Alenhancement of
Al--stabilisedstabilisedsuperconductorssuperconductors
S. Sgobba
CERN, CH-1211 Geneva
-
• The present CMS conductor:
□ materials and developments□ state of stress, safety
factors
• Toward an improved conductor
reinforcement alloy EN AW-6082 or EN AW-7020?
Outline of the talkOutline of the talk
□ reinforcement alloy EN AW-6082 or EN AW-7020? □ replacement of
pure Al stabilizer by cold drawn Al-0.1wt%Ni□ weldability
• Comparison of mechanical properties and equivalent RRR of the
improved conductor
• Limits and perspective of alternative solutions for yield
strength enhancement
-
The present CMS conductor,The present CMS conductor,materials
and geometrymaterials and geometry
Insert ReinforcementReinforcement
Al 99.998 % stabilizer
32 strands Rutherford typesuperconducting cable
⇐ EN AW-6082 T6 continuous extrusions ⇒
Nominal current 20 kAInsert ReinforcementReinforcement Nominal
current 20 kASuperconducting strand type NbTi- Cu stabilized
Strand Cu/SC ratio 1.1
Number of strands 32
Strand diameter 1.28 mm
Rutherford cable cross section 20.68 mm x 2.34 mm
Insert cross section 30 mm x 21.6 mm
High Purity Aluminum stabilizer Al 99.998 %
RRR aluminum at 0 T, annealed > 1500
Reinforcement material EN AW-6082
Conductor cross section 64 mm x 21.6 mm
Quantity produced 21 lengths x 2600 m
-
The present CMS conductor,The present CMS conductor,billet on
billet extrusion of the reinforcementbillet on billet extrusion of
the reinforcement
Schematic representation of the extrusion line (S. Sequeira
Tavares, S. Sgobba, An improved billet on billet extrusion process
of continuous aluminium alloy shapes for cryogenic applications in
the Compact Muon Solenoid experiment, J. of Mat. Proc. Technology
143–144 (2003) 584–590)
-
The present CMS conductor,The present CMS conductor,EB weldingEB
welding
Electron Beam (EB) welding seams
-
The present CMS conductor,The present CMS conductor,curing
cyclecuring cycle
-
The present CMS conductor,The present CMS conductor,tensile and
electrical propertiestensile and electrical properties
B. Curé et al., “Mechanical Properties of the CMS Conductor”,
IEEE Trans. Appl. Superconduc., vol. 14, no. 2, pp. 530-533, June
2004
-
Toward an improved conductor,Toward an improved
conductor,material selectionmaterial selection
Replace by:
o a higher strength Al-alloyo extrudableo weldableo compatible
with a cryogenic
applicationo maintaining high ductility and o maintaining high
ductility and
strength at 4.2 Ko even after a curing cycle
Replace by:
o cold drawn Al-0.1wt%Ni alloyo developed for the ATLAS thin
solenoid superconductor (A. Yamamoto et al., Development towards
Ultra-thin Superconducting Solenoid Magnet for High Energy Particle
Detectors, Nuclear Physics B (Proc. Suppl.) 78 (1999), pp.565-570)
o enhanced mechanical strength o without excessive degradation in
RRR compared to pure Al
-
Toward an improved conductor,Toward an improved
conductor,reinforcementreinforcement
Extrudable,weldable
-
Candidate alloy:
o EN AW-7020 (Al-Zn4.5Mg1 alloy), equivalent of EN AW-7005o
Extrudable and weldable
Toward an improved conductor,Toward an improved
conductor,reinforcementreinforcement
o High ductility and strength at 4.2 K even after curing?
o Sections of 18±0.4 mm x 24±0.4 mm supplied byOtto Fuchs
/DE
o Lengths of 3 m to 6 mo Two different T6-type tempers
(designation .71 and .72
according to DIN 17007)
-
0
100
200
300
400
500
600
700
800
900
Rp0.2 Rm A
Rp
0.2
/MP
a, R
m /M
Pa,
A ×
1000
.71 temper, as received
.72 temper, as received
.71 temper, cured
.72 temper, cured
RT
EN AW-6082 T6 (cured)
EN AW-6082 T51EN AW-6082 T6 (cured)
Rp0.2 Rm A
0
100
200
300
400
500
600
700
800
900
Rp0.2 Rm A
Rp
0.2
/MP
a, R
m /M
Pa,
A ×
1000 4.2 K
EN AW-6082 T6 (cured)
EN AW-7020.72, cured, at 4.2 K
Rp0.2 = 677 MPa Rm = 817 MPa
-
EN AW-7020.72, cured, at RT
3.1cured)-as T61 6082AW (EN
cured)-as .72 7020AW (EN
2.0
2.0
=p
p
R
R
EN AW-7020.72, cured, at 4.2 K
6.1cured)-as T61 6082AW (EN
cured)-as .72 7020AW (EN
2.0
2.0
=p
p
R
R
EN AW-7020.72, cured, at RT and 4.2 K
Toward an improved conductor,Toward an improved conductor,safety
factorssafety factors
2.1cured)-as T61 6082AW (EN
cured)-as .72 7020AW (EN=
m
m
R
R
Safety factors:
EN AW-7020.72 ⇒ 3 (677 MPa/225 MPa)EN AW-6082 T61 ⇒ 1.9 (428
MPa/225 MPa)
with respect to the actual 4 T design strength at 4.2 K
-
From 4 T to 6 T:
Toward an improved conductor,Toward an improved conductor,safety
factorssafety factors
From 4 T to 5 T:
“It seems difficult, respecting construction codes, to exceed a
hoop strain of 0.15%. In the case of CMS, this corresponds to a
maximum Von Mises stress of 140 MPa, requiring alloys with Rp0.2
> 210 MPa and Rm > 420 MPa at 4.2 K. Thus one can tentatively
conclude that the
225 MPa ⇒⇒⇒⇒ 506 MPa
EN AW-7020.72 ⇒ 1.3 (677 MPa/506 MPa)EN AW-6082 T61 ⇒ 0.84 (428
MPa/506 MPa)
with respect to a design strength at 4.2 K (ceteris paribus)
225 MPa ⇒⇒⇒⇒ 350 MPa
EN AW-7020.72 ⇒ 1.92 (677 MPa/350 MPa)EN AW-6082 T61 ⇒ 1.22 (428
MPa/350 MPa)
with respect to a design strength at 4.2 K (ceteris paribus)
Thus one can tentatively conclude that the selected alloys EN
AW-6082-T51 for the reinforcement and EN AW-5083-H321 for the
mandrels are perfectly suitable for a 5-T coil”
A. Hervé et al., Experience Gained from the Construction, Test
and Operation of the Large 4-T CMS Coil, paper presented at MT20
(2007)
-
Candidate alloy:
v Al99.998 ⇒ Al-0.1wt%Ni v developed for the ATLAS thin
solenoid superconductorv aiming an Rp0.2 = 85 MPa at
4.2 K after curing
Toward an improved conductor,Toward an improved
conductor,stabilizerstabilizer
A. Yamamoto et al., Nuclear Physics B 78 (1999), pp.
565-570;Wada et al., IEEE Trans. Appl. Superconduc., vol. 10, pp.
373-376, March 2000
v Al-0.1wt%Ni is a work-hardenable alloy
v softens only partially with curing cycles
v compromise strength/RRR
-
ATLAS coil curing: ATLAS coil curing: 130 130 °°CC--15 h15 h
Effect of CMS coil Effect of CMS coil curing (including a curing
(including a 135 135 °°CC--50 h 50 h plateau)?plateau)?
AlAl--0.1wt%Ni0.1wt%Ni
Toward an improved conductor,Toward an improved
conductor,stabilizerstabilizer
AlAl--0.1wt%Ni, from K. Wada et al., IEEE Trans. Appl. 0.1wt%Ni,
from K. Wada et al., IEEE Trans. Appl. Superconduc., vol. 10, pp.
1012Superconduc., vol. 10, pp. 1012--1015, March 20001015, March
2000
plateau)?plateau)?
-
200
250
300
350
400
Rp
0.2
/MP
a, R
m /M
Pa,
A /%
RT, as drawnRT, cured4.2 K, as drawn4.2 K, cured
20 % to 23 % typical reduction in area
Toward an improved conductor,Toward an improved
conductor,stabilizerstabilizer
0
50
100
150
200
Rp0.2 Rm A
Rp
0.2
/MP
a, R
m /M
Pa,
A /%
AlAl--0.1wt%Ni, CMS0.1wt%Ni, CMS--type curing, at 4.2type
curing, at 4.2 K: Rp0.2 = 82K: Rp0.2 = 82±±7 MPa7 MPa
-
Four roll shaping processFour roll shaping process(courtesy of
Outokumpu /IT)(courtesy of Outokumpu /IT)
-
allowed 11.3 % reduction in area
Toward an improved conductor,Toward an improved
conductor,stabilizerstabilizer
-
30
40
50
60
Str
eng
th /M
Pa;
Har
dn
ess
As received
After roll shaping
EN AW 1199 Aluminum
0
20
40
60
80
100
120
140
0 20 40 60 80
Reduction by cold rolling /%
Str
eng
th /M
Pa,
Elo
ng
atio
n /%
Tensile strength /MPa
Yield strength /MPa
Elongation /%
Toward an improved conductor,Toward an improved
conductor,stabilizerstabilizer
0
10
20
30
Yield strength/MPa
Tensile strength/MPa
Hardness /HBS
Str
eng
th /M
Pa;
Har
dn
ess
-
Toward an improved conductor,Toward an improved conductor,global
tensile properties of a rollglobal tensile properties of a
roll--shaped insertshaped insert
Global and local tests, a comparison
100
120
140
Str
eng
th /M
Pa;
elo
ng
atio
n /%
Yield Strength /MPaUltimate Tensile Strength /MPaElongation
/%
0
20
40
60
80
As received Roll shaped, test 1 Roll shaped, test 2
Str
eng
th /M
Pa;
elo
ng
atio
n /%
-
Toward an improved conductor,Toward an improved
conductor,weldabilityweldability
Al-0.1wt%Ni EN AW-7020
acc. /kV =120intensity /mA =9.26cath. curr /A =1.35working
distance /mm =150 adv. speed /mm·s-1 =16.7X,Y scanning
-
Comparison of properties,Comparison of properties,basis for a
comparison of 4.2 K propertiesbasis for a comparison of 4.2 K
properties
70207020 SSSS AlNiinsertAlNiinserti
iicc σσσσ +==∑
Equivalent stress σc acting on the improved full conductor:
σAlNiinsert = stress in the insertσAlNiinsertσ7020 = stress in
the reinforcementSAlNiinsert = cross sectional area of the
insertS7020 = cross sectional area of the reinforcement
Contribution of the Rutherford to the yield neglected
(conservative in the case of roll shaped inserts)
-
Comparison of properties,Comparison of properties,basis for a
comparison of 4.2 K propertiesbasis for a comparison of 4.2 K
properties
706 MPa600
700
800
900
1000
stre
ss /M
Pa
EN AW-7020.72 as cured, sample 10
Al-0.1wt%Ni as cured, sample 4
weighted average
104 MPa0
100
200
300
400
500
0 0.005 0.01 0.015
strain
stre
ss /M
Pa
424 MPa
-
Comparison of properties,Comparison of properties,basis for a
comparison of 4.2 K propertiesbasis for a comparison of 4.2 K
properties
At 4.2 K, as CMS-cured state:
Minimum yield strength of the full conductor, evaluated at the
0.2% yield point of the reinforcement,
•for EN AW-7020.72 + Al-0.1wt%Ni = 400 MPa•for EN AW-6082 (T6) +
Al99.998 = 258 MPa [1]
Equivalent RRR = 420 (RRR of the as-cured Al 0.1wt%Ni = 900 x
cross sectional ratio of the insert [1])
[1] B. Curé et al., “Mechanical Properties of the CMS
Conductor”, IEEE Trans. Appl. Superconduc., vol. 14, no. 2, pp.
530-533, June 2004
-
Comparison of properties,Comparison of properties,basis for a
comparison of 4.2 K propertiesbasis for a comparison of 4.2 K
properties
200
250
300
350
400
Rp
0.2
/MP
a, R
m /M
Pa,
A /%
RT, as drawnRT, cured4.2 K, as drawn4.2 K, cured
0
50
100
150
200
Rp0.2 Rm A
Rp
0.2
/MP
a, R
m /M
Pa,
A /%
AlAl--0.1wt%Ni, CMS0.1wt%Ni, CMS--type curing, at RT: Rp0.2 =
59type curing, at RT: Rp0.2 = 59±±2 MPa2 MPa⇒⇒⇒⇒⇒⇒⇒⇒ RRR RRR ≈≈
900900
-
Progress of Al-stabilized SC
A. Yamamoto, “Advances in Superconducting Magnets for Particle
Physics”, IEEE Trans. Appl. Superconduc., vol. 14, no. 2, pp.
477-484, June 2004.
-
Comparison of properties,Comparison of properties,basis for a
comparison of 4.2 K propertiesbasis for a comparison of 4.2 K
properties
ATLAS CS
Bess PCMS
Improved CMS
150200250300350400450500
Eq
uiv
alen
t yi
eld
str
eng
th /M
Pa
ATLAS CS
050
100150
0 400 800 1200 1600
RRR
Eq
uiv
alen
t yi
eld
str
eng
th /M
Pa
-
Composite AlComposite Al--based pure metal based pure metal
conductorsconductors
High purity aluminum composite conductors with Al-alloy matrix
developed in the 90ies
o C.E. Oberly and J.C. Ho (Wright Res. & Dev. Center,
Wright-Patterson AFB, OH), The origin and future of composite
aluminium conductors, Magnetics, IEEE Transactions on, 27 (1991)
458-463
o K.T. Hartwig and R.J. DeFrese, Mechanical and Electrical
Testing of Aluminum Cryoconductors, Adv. Cryo. Engr., 36A (1990)
709-715
o M. K. Premkumar, , F. R. Billman, D. J. Chakrabarti, R. K.
Dawless, A. R. Austen, Composite aluminum
5N Al, RRR=1500 Al-Fe-Ce from PM, VHP
Typical properties at 20 K:YS ≥ 165 MPaUTS ≥ 276 MPao M. K.
Premkumar, , F. R. Billman, D. J. Chakrabarti, R. K. Dawless, A. R.
Austen, Composite aluminum
conductor for high current density applications at cryogenic
temperatures, Advances in cryogenic engineering – Materials, 36
(1990) 733-740
o J. C. Ho, C. E. Oberly, H. L. Gegel, W. M. Griffith, J. T.
Morgan, A new aluminum-base alloy with potential cryogenic
applications, Advances in cryogenic engineering – Materials, 32
(1986) 437-442
UTS ≥ 276 MPa1.5 % ≤ A ≤ 8 %
-
Composite AlComposite Al--based pure metal based pure metal
conductorsconductors
Limiting mechanical strain of 0.1 % to 0.2 %
350 MPa, RRR 400 to 500in magnetic fields up to 10 T
Current densities not cited: "couldcarry much higher current
densitiesthan the practical 2·108 A/m2 of lightweight SC"
-
AlAl--stabilisedstabilised NbTiNbTi multifilament
SCmultifilament SC
o M. Young, E. Gregory, E. Adam and W. Marancik, Fabrication and
Properties of an aluminum-stabilized NbTi Multifilament
Superconductor
o S. Murase, , Y. Koike, Y. Nakayama, T. Toyoda, E. Suzuki, K.
Mendelssohn, Aluminum stabilized Nb--Ti superconducting wires,
Proceedings of the fifth international cryogenic engineering
conference, Kyoto, Japan, 7 May 1974, IPC Science and Technology
Press Ltd., Guildford, Eng. (1974)
Embedding in EN AW-1100 or EN AW-6061 (EN AW-5052 reported)
High purity Al "tube", RRR = 1700
RRR = 320Critical currentdensity at 5 T = 1630 A/mm2
-
AlAl--stabilisedstabilised NbNb33Sn multifilament SCSn
multifilament SC
M. Thöner, H. Krauth, J. Rudolf, A. Szulczyk, Aluminium
Stabilized Nb3Sn Superconductors, Adv. Cryog. Eng. Mat. 34 (1988)
507
Reacted "monolith" (80000 filaments in a CuSn matrix)
High purity Al (RRR = 2500 to 5000)
Duratherm reinforcement
Al added after the reaction treatmentSimultaneous extrusion with
reactedNb3SnLength up to 100 m (limited by lengthof reacted
Nb3Sn)RRR = 580 for the "80000" versionYS = 186 MPa at RT, idem
Duratherm reinforcement(Co-Ni-Cr alloy)
-
AluminiumAluminium alloy DSalloy DS--AlAl--550550
High temperature compression strength(according to Hellum and
Luton, proc. ESA Symp. 1990)
100
200
300
400
500
600
0.2%
pro
of s
tres
s /M
Pa 3% Alumina
7% Alumina
15% Alumina
Mechanical properties at 4.2 Kafter a 10 h thermal treatment
600
700
800None
150 °C-10h
250 °C-10h
•S. SGOBBA, G. MARTIN and T. KURTYKA: Mechanical Properties of a
New Dispersion Strengthened Aluminium Alloy for Use at Very Low
Temperatures, Proceedings of the 5th European Conference on
Advanced Materials, Processes and Applications, Maastricht 21-23
April 1997, vol. 1, p. 251-254
0
0 100 200 300 400 500
T / °C
0
100
200
300
400
500
600
E /GPa Yield stress /MPa UTS /MPa elongation at breakx 10 /%
250 °C-10h
350 °C-10h
-
••Aluminium alloy DSAluminium alloy DS--AlAl--550550Particle
size, 2 nm to 10 nmParticle spacing, 80 nmExpected RRR, less than
10
-
ConclusionsConclusions
Toward a High Strength, High RRR Conductor:Toward a High
Strength, High RRR Conductor:
⇒⇒ Selection of high performance, Selection of high performance,
extrudableextrudable reinforcement and insert reinforcement and
insert alloysalloys
⇒⇒ PotentialPotential suitabilitysuitability of the of the
alloysalloys demonstrateddemonstrated, compatible , compatible
withwith curingcuring
⇒⇒ Good aGood aptitudeptitude of the CMS insert to be cold
reduced by roll shapingof the CMS insert to be cold reduced by roll
shaping⇒⇒ Good aGood aptitudeptitude of the CMS insert to be cold
reduced by roll shapingof the CMS insert to be cold reduced by roll
shaping
⇒⇒ Intrinsic and heterogeneous Intrinsic and heterogeneous
weldabilityweldability of the alloys demonstratedof the alloys
demonstrated
Alternative solutions:Alternative solutions:
⇒ Not fully industrially confirmedNot fully industrially
confirmed⇒⇒ Dispersion Dispersion strengthenedstrengthened or
composite Alor composite Al--basedbased alloysalloys alternative
alternative
to Alto Al--0.1wt%Ni 0.1wt%Ni shouldshould bebe the the
objectobject of a of a carefulcareful design design
-
Toward an improved conductor,Toward an improved
conductor,reinforcementreinforcement
S. Sequeira Tavares, S. Sgobba, J. of Mat. Proc.
Technology143–144 (2003) 584–590