An irradiation experiment on copper alloys in the Fast Flux Test Facility (FFTF) at 43O*C has been compieted. Four exposure levels were reached with the ...
250
Journal
of Nuclear
Materials
179-181
(1991) 250-253 North-Holland
neutron-induced changes in density and electrical of copper alloys at 16 to 98 dpa and 430 OC *
conductivity
F.A. Garner Pacific Northwest
Laboratory,
P.O. Box 999, Richland,
WA 99352, USA
H.R. Brager We.vfinghowe
Hanford Company,
Richland,
WA 99352, USA
K.R. Anderson Universi[y of Illinois. Urbana, IL 61801, USA
An irradiation experiment on copper alloys in the Fast Flux Test Facility (FFTF) at 43O*C has been compieted. Four exposure levels were reached with the maximum at 98 dpa. Immersion density measurements of a wide variety of copper alloys show swelling values ranging from 1 to 64% at 98 dpa. Copper that is dispersion-strengthened with 0.25% Al,O, (designated A125) appears to be the most swelling resistant and promising high conductivity alloy. The steady-state swelling rate of relatively simple copper alloys was found to be - 0.5%/dpa at 430 *C. Both the swelling and conductivity changes of the pure copper reference alloy were found to be very reproducible.
1. Introduction Copper
alloys
Test Facility
are being
to investigate
irradiated their
in the
potential
Fast
Flux
for high
heat
in fusion reactors. The program consists of several generations of irradiation experiments described in detail elsewhere [l]. The first generation experiment has now been completed after reaching 1.6 x 1O23 n cm-* (E > 0.1 MeV), which for pure copper in the FFTF spectrum corresponds to - 98 dpa. Earlier publications have described the results for some alloy subsets of this experiment at damage levels of 16, 47, and 63 dpa and a reported temperature of - 450°C [2-41. An improved calculation of the gamma heating for this experiment leads to a better estimate of 430,” C. In this paper the swelling data for all alloys and dose levels of the first generation experiment are presented. Also presented are measurements of electrical conductivity for the pure copper reference alloy, and some copper alloys with low solute levels. Alloy compositions and thermomechanical conditions are presented in table 1 along with a summary of the swelling data, measured by immersion density. The experimental details have been presented in earlier papers j2-4). flux
applications
2. Results and discussion Fig. 1 shows those alloys exhibiting the largest amounts of swelling. Pure zone-refined copper reaches 56% at 98 dpa, exhibiting a very small incubation period * Prepared
for the US Department DE-ACO6-76RL0 1830.
0022-3115/91/$03.50
of Energy
under Contract
0 1991 - Elsevier Science Publishers
for swelling. Cu-0.1 wt% Ag initially swells at a rate of - l%/dpa but then decreases to the O.S%fdpa exhibited by pure copper and Cu-5 wt% Ni. Cu-5 wt% Al appears to swell in a manner very much like Cu-0.1 wt% Ag. The Cu-1.8 wt% Ni-0.3 wt% Be alloys in the cold worked and aged and in the annealed and aged conditions swell less than pure copper and exhibit more pronounced transient regimes of swelling. While it appears that this alloy is initially approaching the OS%/dpa swelling rate, there is some indication that a lower swelling rate may be developing above 47 dpa. Two other precipitation-strengthened alloys, MZC and Cu-2.0 wt% Be are shown in fig. 2. Note that cold working before aging accelerates swelling in both CuBeNi and CuBe. Radiation-induced redistribution of solutes can lead to changes in alloy density, sometimes manifested as a densification (see annealed CuBe in fig. 2) and sometimes masquerading as void swelling. MZC is an example of the latter case and has been shown to have insufficient voidage at 16 and 63 dpa to account for the apparent swelling observed [3,4]. The most swelling-resistant alloy in this first generation experiment was the dispersion-strengthened CuA125 alloy. It was the resistance of this alloy to swelling that led to the initiation of the 1.5 and 2.0 Generation series of FFTF irradiation experiments, [I] both of which focus on various types of dispersion-strengthened alloys. Pure copper has been used as a standard reference materiai in the various generations of the FFTF copper studies [l]. It is therefore of interest to assess the reproducibility of its response to irradiation. For this
B.V. (North-Holland)
copper
Cu-2.OBe
CuBe (I/2
HT and AT are industry
Cu-0.2SAl Cu-0.25AI
CuA125 (CW) CuA125 (CWA)
a> I/2
Cu-O.F)Cr-O.lZr-0.05Mg
MZC
designations
(asAI,C),) (asAla0,)
cu-2.oBe
CuBe (AT)
HT)
Cu-1.8Ni-0.3Be
CuNiBe (AT) a)
in MOTA/FFTF
and tempered
90% CW, aged (0.5 h at 470 o C) 20% cw 20% CW + aged (1 hat 550°C)
Annealed Annealed Annealed 20% cw 20% CW 20% CW and aged (3hat480OC) Annealed and aged (3hat480OC) 20: CW and aged (2hat320°C) Annealed and aged (2hat320“C)
Condition
for half-hard
alloys irradiated
cu (99.999) Cu-5Ni Cu-SAI Cu-O.lAg mu-0.3Ag-O.~P-O.O~Mg Cu-l.SNi-0.3Be
(wt%)
Alloy Composition
commercial
Cu (MARZ) Cu-5Ni Cu-5AI CuAg CuAgP CuNiBe (I/2 HT) a)
Alloy
Table 1 Swelling of various
and annealed
dpa: n/cm’
450 ’ C
and tempered,
(E 3 0.1 MeV):
Swelling (W)
at approximately
respectively.
-
1.03 0.13
- 0.66
-0.18
0.29
1.70
16.6 7.9
6.5 2.15
16 2.5 x 1022
0.04,1.45,
1.85
- 0.43, - 0.25
- 0.18, 0.05, 0.52
+0.12
5.15, 7.90 0.28
-0.24,
1.09,1.61
5.73,6.59
22.3, 24.6
30.1, 31.3, 33.2 27.7, 31.8 46.8,45.8, 39.4 47.4 17.1
63 1.0x 102’
0.79 0.23,0.36,0.86
-0.45,
0.18, 1.11, 1.71
3.05
13.9,14.6
35.4, 38.2 160,162
22.2,23.3
47 7.7x 1022
x
lo*’
1.5, 3.3
2.9 1.3
1.4, 2.0
4.4, 7.1
13.2
23.4, 31.1
55.8 52.9 66.0 63.9 24.0
98 1.6
F. A. Garner et al. / Neutron-induced changes of copper alloys
252
purpose we have chosen to examine its swelling and electrical conductivity in this and other irradiation experiments. Fig. 3 shows a comparison of swelling observed in five separate irradiation tests conducted in three different reactors. It appears that pure copper exhibits a relatively reproducible behavior, exhibiting a very small incubation period for swelling, followed by steady-state swelling at - 0.5%/dpa over a temperature range of at least 385-430 o C. The major transmutation product in copper is nickel and its production rate is very dependent on neutron spectra [S]. Fig. 5 also shows, however, that Cu-5% Ni swells in a manner not very different from that of pure copper, so transmutation to nickel is not expected to affect the bulk swelling behavior of copper very much, although it may affect some details of the microstructure. Nickel additions to copper do have a substantial impact on the electrical conductivity, however. Both nickel and the second major transmutant, zinc, strongly depress the conductivity of copper [5,6]. Void swelling
PURE COPPER
40 SWELLING % 30
20
0
COLD-WORKED
0
4 NEUTRON
Fig. 1. Swelling
8 FLUENCE.
12
16 n cm-*
AND AGED
20
24 x
lo:22
(E ) 0.1 MeVl
observed in a variety of copper alloys irradiated in FFTF at 430 o C.
CuBe
0 Cold-Worked Very Few Voids
Swelling, % Av/vo
at16dpa -0
25
50
75
0
100
I
I
I
I
25
50
75
100
125
Displacements per Atom
Fig. 2. Swelling of CuBe and MZC at 430 o C.
Cu-5Ni
Pure Copper 60
Swelling, % A v/v,
40
/I
A
EBR-II, 385°C
0
EBR-II, 400°C
x
FFTF, 411-414”C
30
Fig. 3. Comparison of swelling behavior at - 400°C of pure copper and G-5
wt% Ni in various
irradiation
experiments
[8-111.
F.A. Garner et al. / Neutron-induced changes
ofcopperalloys
253
(a) 80 2
60
-
8 40
Pure Copper o Generation 1.0, 430 “C l
20
-
o Generations 1.5 and 2.0 a Frost and Kennedy, 385 “C, EBR-II
t Trend Line of Pure Copper at -400 “C
80 $
(b)
60
8 40
0 Cu Ag P
t 0
Fig.
0
20
40
60
Displacements
per Atom
80
100
4. (a) Neutron-induced changes in electrical conductivity of pure copper in various irradiation experiments (b) conductivity changes observed in CuAg and CuAgP in the First Generation Experiment.
also decreases the conductivity (51. Fig. 4a shows that fast reactor irradiations of copper at 385%43O’C yield conductivity changes that are very consistent. Since the neutron spectra of EBR-II and FFTF are very similar, the consistency is not unexpected. Also shown in fig. 4a is conductivity data derived at 529” C [7]. Since the swelling at this temperature is only 1.8% [8], most of the observed conductivity loss arises from transmutation to nickel and zinc, a process independent of temperature., In most solute-modified alloys radiation-induced redistribution of solutes can lead to modifications in conductivity [4,5], particularly if the solute levels are relatively large. There are two alloys in the first generation study involving relatively low levels of solute, CuAg and CuAgP. Note in fig. 4b that the addition of solutes to CuAg and CuAgP lowered the preirradiation conductivity from 101% IACS to 97 and 96% IACS, respectively, but this decrease in conductivity is maintained with little change throughout the first generation experiment, indicating that these solutes probably stay in solution. 3. Conclusions A wide range of swelling response can be attained in copper alloys, varying from long-term suppression of swelling to near-immediate attainment of the steadystate swelling rate, which for a variety of simple copper alloys appears to be O.S%/dpa at - 400 o C. The most
[2,4,6,7];
promising alloy for further study is the dispersionstrengthened alloy CuA125. The response of the pure copper reference alloy appears to be very reproducible from one irradiation test to another.
References
(11 F.A. Garner et al., Overview of Copper Irradiation Programs, Fusion Reactor Materials Semiannual Progress Report, DOE/ER-0313/6 (1989) pp. 351-356. [2] H.R. Brager, H.L. Heinisch and F.A. Garner, J. Nucl. Mater. 133 & 134 (1985) 676. (31 H.R. Brager, J. Nucl. Mater. 141-143 (1986) 79. [4] H.R. Brager, J. Nucl. Mater. 141-143 (1986) 163. [5] F.A. Gamer, H.L. Heinisch, R.L. Simons and F.M. Mann, Radiat. Eff. and Defects in Solids 113 (1990) 229. [6] H.M. Frost and J.C. Kennedy, J. Nucl. Mater. 141-143 (1986) 169. [7] K.R. Anderson, F.A. Garner, M.L. Hamilton and J.F. Stubbins, ibid. ref. [I], pp. 357-369. [8] F.A. Garner, H.R. Brager and K.R. Anderson, in Fusion Reactor Materials Semiannual Progress Report, DOE/ ER-0313/7 (1989) pp. 225-231. [9] R.J. Livak, H.M. Frost, T.G. Zocco, J.C. Kennedy and L.W. Hobbs, J. Nucl. Mater. 141-143 (1986) 160. [lo] M. Ames, G. Kohse, T.-S. Lee, N.J. Grant and O.K. Harling, J. Nucl. Mater. 141-143 (1986) 174. [ll] S.J. Zinkle and K. Farrell, J. Nucl. Mater. 168 (1989) 262.
