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MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARD'3 - 1963
?
LEGAL NOTICE
This report was prepared as an account of
Government sponsored work. Neither the
United States, nor the Commission, nor any
person acting on behalf of the Commission:
A. Makes any warranty or representa-
tion, expressed or implied, with respect to
the accuracy, completeness, or usefulness
of the information contained in this report,
or that the use of any information, appa-
ratus, method, or process disclosed in this
report may not infringe privately owned
rights; or
B. Assumes any liabilities with respect
to the use of, or for damages resulting from
the use of any information, apparatus,
method, or process disclosed in this report.
As used in the above, “person acting on
behalf of the Commission” includes any em-
ployee or contractor of the Commission, or
employee of such contractor, to the extent
that such employee or contractor of the
Commission, or employee of such contractor
prepares, disseminates, or provides access
to, any information pursuant to his employ-
ment or contract with the Commission, or
his employment with such contractor.
d...
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Paper to be presented orally at 8th Annual Conference on Vacuum Metallurgy,
New York City, New York, June 21-23, 1965
OROL -P-1394
JUL 20 1965
HIGH-TËMPERATURE CHEMICAL STABILITY OF REFRACTORY-BASE
ALLOYS IN HIGH VACUUM
· ORNI - AEC - OFFICIAL
CONF-650617-/
D. T. Bourgette
Metals and Ceramics Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee
ABSTRACT
Evaporation losses of refractory-base alloys having the commercial
.
designations T-111, FS-80, FS-85, B-66, C-129Y, and D-43 were determined
for various periods of time at temperatures between 1200 and 1500°C. The .
experimental pressures ranged from 7 x 10-7 to 6 x 10-10 torr.
In general, there were no serious evaporation problems associated with
these alloys, especially at temperatures of 1200 to 1300°C. The alloys that
exhibited the greatest evaporation losses contained the higher vapor-
pressure elements such as vanadium, zirconium, and hafnium. For example,
B-66, the most volatile alloys studied, loet 1.70 mg/cm2 at 1500°C and
7 x 10-9 torr in 316 hr, while at 1200°C and 6 x 10-10 torr a weight loss
of 0.077 mg/cm2 was measured in 513 hr. Vanadium and zirconium losses con-
tributed 95% of the total weight loss. Evaporation occurred only at the ..
surfaces; no subsurface voidis were detected nor did evaporation occur at
any preferential sites, such as grain boundaries or impurity inclusions at
or near the surfaces.
The total weight change in the specimens appeared to be pressure and
composition dependent. At 1200 to 1300°C and 10-7 torr, the niobium-base
alloys FS-80 and D-43, containing only zirconium as the evaporating element,
.
showed a weight gain, while at the same temperature and 10-9 torr a weight
ORNI - AEC - OFFICIAL
*Research sponsored by the U.S. Atomic Energy Commission under contract
with the Union Carbide Corporation. i
BITENT CLEARANCE OBTAINED. RELEASE DE
THE PUBLIC IS APPROVED. PROCEDURES
ARE ON EILE IN THE RECEIVING SECTION
yty
N
1088 was observed. This behavior 18 attributed to interstitial contamination
Tiodisgo-jj- inšÜ
WOJOVOMUO
at 10-7 torr and purification at 10-9 torr. For those alloys containing more
than one evaporating species, such as B-66 and C-129Y, a weight 1088 wae
observed at both the high and low test pressures at 1500°C.
The evaporation
108ses in these cases overshadowed the changes in the interstitiel contents.
Changes in the interstitial concentrations were dependent on the
pressure. At 1500°C and pressures of 10-9 torr or lower, carbon was retained
while oxygen, nitrogen, and hydrogen were evolved. At & higher pressure ..
of 100? torr and 1500°C, carbon was lost while the oxygen and nitrogen con- .
tents showed an increase. It is believed that the reaction of carbon and
oxygen resulted in the loss of carbcis at the higher pressures, while at
10-9 torr insufficient oxygen was present to appreciably reduce the carbon
concentrations.
INTRODUCTION
The importance of refractory alloys in space applications has resulted
in an experimental program designed to determine their compositional
stability in vacuum. In space vacuums ranging from 10-7 to 10-16 torr,
refractory alloy's may become interstitially contaminated at the higher
pressures and purified at the lower pressures when exposed for extended
periods at elevated temperatures. In addition, the concentrations of
other alloying elements may change because of evaporation.
The objective of many researchers in the space power program is to
improve the high-temperature creep strength of various refractory alloys.
The principal method considered is that of changing the interstitial con-
tent and the concentration of minor alloying elements: 1-3: Published
...viiivii n- iitä
ORNI - AEC - OFFICIAL
· ORNI - AEC - OFFICIAL
OINI - AEC - OISICIAL
data, based on tests conducted over short periods, although helpful in
understanding the strengthening mechanisms, do not reveal time-dependent
reactions that might be deleterious. For example, application of such
alloys in space may require thin-walled structural members that must
operate over a design life of 10,000 hr or longer. L088 of interstitial
elements in solution would disturb the equilibrium with interstitial
precipitates. In an effort to reestablish. equilibrium, the precipitates
may dissociate, this resulting in changes in alloy composition and a'
loss of dispersion strengthening.
To assess these potential problems, a study was undertaken to
determine the evaporation behavior and changes in the concentration of
interstitials in the ranges of 2100 to 1500°C and 10-9 to 10-20 torr.
The commercial designation and nominal composition of the alloys
selected for study are listed in Teble 1.
EXPERIMENTAL TROCEDURE
Specimen Preparation
Lanmou
From specimen stock approximately 0.004 to 0.005 in. thick, cylindrical
0.50-in.-diam X 0.75-in.-long evaporation specimens were made by spot welding
in air. The specimens were degreased in acetone and chemically cleaned in a
solution composed of H20, HNO3, HF, and H2SO4. Each specimen was weighed and
the geometric area was determined.
Evaporation Apparatus
Two similar pieces of experimental equipment were used in this investiga-
tion. Both systems allowed for collection of vapor deposits from
ORNL - AEC - OFFICIAL
ORNI – AEC - OFFICIAL
Table 1. Alloys of Interest Investigated in This study
ORNI - AEC - OFFICIAL
Commercial
Designation
Nominal Composition (wt $___
Ta NOW HP Zr v Moy
T-111
.2
FS-80
8
99
60 21
79.9 : 20
1
1
Analyzed Intersti-
tial Content (pom).
C 0 Ñ H
70 57 294
100 180 78 10
40 100 28 2
75 150 60 5
210 97 250
980 63 896

FS-85
28
.
C-12941a)
10
10
10
0.1
0.1
Br 66,
89
5
5
i
1
D-43
89
10
Tal Alloy contained 0.4 wt % Zr as an impurity.
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individually induction-heated specimens held at temperature for various
OINI - AIC - OKSICIAL
periods of time.
The basic difference between the apparatus 18 in the
· ORNI - AIC - OFFICIAL
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pumping systems. The first apparatus, possessing a liquid nitrogen cold .
trap, oil diffusion pump, and mechanical pump combination, allowed for
controlled variation in the pressure by regulating the power to the
diffusion pump. This system was capable of pressures ranging from 10-6 to
10-9 torm at temperature.
The second system incorporated a 15 liter/sec ion pump that was turned
on after a roughing pressure of 10-6 torr was attained using conventional
oil pumps. This system was capable of pressures of 10-9 to 10-10 torr at
temperature, but the pressures were not controllable. The experimental
pressure was the lowest pressure attainable at the desired temperature.
The specimens in both systems were simultaneously heated using a series
. .
connected induction coil.
RESULTS AYID DISCUSSION
Interstitial Stability
:
Results of the pre- and posttest chemical analyses showed that, for
all the alloys studied, the change in the interstitial concentration varied :
with test pressure. At high vacuums of 10-9 torr, the carbon concentrations
remained virtually unchanged. However, the oxygen and nitrogen concentra-
tions at 10-9 torr decreased substantially. At greater pressures of
1 x 10-7 to 6 x 10-7 torr, the oxygen and nitrogen concentrations in the
alloys increased, while the carbon content decreased, and 10 most instances,
these changes were sevire. It 18 postulated that, at the higher pressures,

the increased oxygen and nitrogen concentrations in the alloy resulted from
ORNL - AEC - OFFICIAL
the presence of these elements in the vacuum environments.
ORNI - ACC - OFFICIAL
minister

over
the
When oxygen was available in the environment, a reaction between the
oxygen and the carbon in the alloy occurred. For example, the carbon-to-
oxygen ratio for D-43 alloy decreased with an increase in pressure at
1500°C, as illustrated in Pig. l. Por alloy 18-80, the carbon-to-oxygen
ratio at 2 x 10~9 torr increased with temperature, while at 5 x 10-7 torr,
ORNI - AIC - OFFICIAL
NI - AIC - OFFICIAL.
the carbon-to-oxygen ratio decreased with an increase in temperature.
Purther, after several hundred hours, the carbon-to-oxygen ratios at low
temperatures (2100 to 1200°C) are nearly the same for pressures between
CUOCNC OIST20CM CO
11
5 x 10-7 to 2 x 10-9 torr. This behavior 18 1Uustrated in Fig. 2.
These results indicate that, at temperatures between 1200 and 1500°C
and in ultrahigh vacuums, these alloys viu lose nearly all of the oxygen
(and nitrogen) while retaining nearly all the carbon. On the other hand,
when these types of refractory alloys are subjected to environments con-
taining excessive amounts of oxygen (e.g., at higher pressures), then the
carbon will be decreased.
The Individual analytical test resulto illustrating the behavior
of the interstitial elements are tabulated in Table 2. A comparison
of Table 2 with the initial concentration of interstitials as listed in
Table I will show that, in general, the behavior discussed above 18
relevant to all of the alloys investigated in this study.
..
NQ DI.laio Ditt?OCH GRAM PAMA
.
Metallography
....
When certain refractory-base alloys undergo a severe change in con-
..
centration of interstitial carbon, oxygen, or nitrogen, a corresponding
change in the size and quantity of precipitates containing the se elements:
will also occur. For example, Table'a shows that T-ul alloy lost oxygen
On thens Garasi
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Temperature
Changes in Interstitial
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Carbou Oxygen Nitrogen Hydrogen
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ORNI - AEC - OFFICIAL
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grosely affected. Examination of the corresponding microstructure
ORM - AEC - OFFICIAL
(Fig. 3(a)) shows a comparatively large grain-boundary precipitate
accompanied by clear specimen surfaces. At 5 x 10-7 torr, however, carbon
was lost, while the oxygen and nitrogen concentrations increased.
Figure 3(b) shows that the resulting microstructure contained a very fine
grain-boundary precipitate and that the specimen surfaces were now covered
by a thin film. At 2 x 10~9 torr, the grain-boundary phase 18 believed to
be carbides, while at 5 x 10-7 torr it is believed that both carbides and .
nitrides are present in the grain boundaries because of the increase in
:
nitrogen concentration (Tavle 2). In addition, the film on the surfaces
of the specimen tested at 5 x 10-7 torr is also believed to be a nitride
because of Its etching characteristics.
A similar solid-solution alloy, T-222 (T&-9.6 wt 4 W-2.5 wt% Hf),
containing 0.010 to 0.913 wt% C, exhibits two complex carbides.3 At
1090°C, e tantalum-rich, hexagonal (Ta,W,HT),C precipitates and is stable
to 1316°c. At 1316°C, a hafnium-rich, body-centered cubic (Hf,Ta,w) x
precipitates and 1s stable to 1.540°C. From these results it appears that,
efter several hundred hours at 1500°C, T-111 containing 0.004 to 0.006 wt% C
would precipitate a cerbide phase as 11Justruted in Fig. 3.
Microstructures of niobium-base alloy D-43 (Figs. 4 and 5) show
pressure-dependent variat:lons in the interstitial concentrations et 1300 and
1500°C. At both temperatures, the interstitial elements in the
D-43 alloy exhibited a behavior similar to the interstitials in T-221.
At 1500°C and pressures ranging from 4 x 10-7 to 1 x 10-9 torr, the
microstructures (Fig. 4) and changes in the interstitial concentration
(Table 2) indicated a close relationship between grain-boundary precipitates
and carbon content. As the test pressure was increased over several
IVIJIS10 - DIY - INIO
hundred hours the carbon concentration decreased accompanied by a
.
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precipitates. The sensitivity of D-43 alloy to changes in carbon content
18 more fully illustrated in Fig. 4(c) and (a). Near the end of a
736-hr test, a failure to fill the liquid nitrogen cold trap during a .
36-hr period resulted in an increase in carbon content (Fig. 4(a)] when
compared to a normal 650-hr test (Fig. 4(c)). This 140-ppm increase in
carbon concentration (Fig. 4(a)) resulted in a greater amount of grain-...
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occurred at 1300°C, as illustrated in Fig. 5. In a 376-hr test at .
.
5 x 10-7 torr, the carbon concentration decreased from 980 to 600 ppm,
this resulting in complete disappearance of the grain-boundary phase.
At 1500°C, this complete disappearance of the grain-boundary phase
occurred at a carbon level of 580 ppm, which was attained at 1.5 x 10°7 torr
t.
...
..........
in 650 hr. These results indicate that this phase may be unstable at
lower temperatures. .
No attempts were made to qualitatively identify this grain-boundary......
phase; however, it has been reported46 that. MozC precipitates at grain
boundaries in niobium-base alloys containing relatively high carbon concen-
trations and exhibits an hexagonal structure. Examination of this phase
under polarized light revealed an anisotropic behavior. Although not
conclusive, this is an indication that the grain-boundary phase
illustrated in Figs. 4 and 5 might be Nbạc. Further, Gerken has shown :
that Nb2C 18.a high-temperature phase and that heat treatment at
1200 to 1300°C or a loss of carbon will decrease the amount of this phase
present in the microstructure, a behavior consistent with the results of
this study.
Pollack has also shown that at 1200°C Nb2C is converted to a complex
(N,Zr)c, which appears as the fine "dot" phase in Figs. 4 and 5.
....
ORNI - AEC - OFFICIAL
CRNI - AEC - OFFICIAL
ORNL - AEC - OFFICIAL
...
Verification of these results has been completed at the Oak Ridge National
Laboratory (ORNL), and an electron micrograph illustrating this carbide
conversion 18 presented in Fig. 6.
Metallographic examination to 2000x did not reveal any differences
In etching characteristics, color, or precipitate morphology in specimens
heat treated at 1500 and 1300°C and 10-9 and 10-9 torr. The oxygen and
nitrogen contents were low at 1 x 10-9 and high at 5 x 10-7 (Tables 1 and 2),
and because the metallographic features of the different samples were alike,
it is felt that no oxides or nitrides were present for these test conditions..
The microstructures of the remaining alloys, FS-80, FS-85, C-1297, and
B-66 were similar for the same conditions of time, temperature, and pressure...
At 1500°C, grain growth was severe, the average grain size being approxi-
mately an ASTM-1. No precipitates were detected at magnifications to
1000 X, except in the case of C-1297 at 1500°C and 4 x 10-7 torr. Failure
to fill the liquid nitrogen cold traps resulted in massive precipitates,
which were probably carbides or nitrides, a conclusion based on interstitial
changes (Table 2).
The FS-80 alloy was also tested at the lower temperatures of 1200 and
1300°C. Grain growth was not evident, and the average grain size was an
ASTM-6. Precipitation was evident at 1200 and 1300°C for test pressures
of 107 and 10-9 torr. Hobson has reported that, when 100 ppm O 18
present in the alloy, Zroz will precipitate in FS-80 at 900 to 1100°c.
Evaporation
:
.
.
At the outset of this investigation, a primary concern was evaporation
of the alloys at their service temperatures. It was felt that substantial
evaporation losses would result in 1088 of mechanical strength and adverse changes
ORNI – AEC - OFFICIAL
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Replicated Carbides (Nb-Zr) C in situ. Sample Overetched...
Nb -10% W-1% Zr-0.1c Alloy Annealed 2 hr at 3300°F.
1 Aced 500 hr at 2200°F.
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DINI - AIC - OFFICIAL
in emittance. Therefore, tests were conducted at temperatures slightly
above the intended application temperatures and for times sufficient to
reveal the seriousness of the problem. It was learned that at the
OINI - AIC - ORBISIN
application temperatures no serious evaporation problems would be
encountered in ultrahigh vacuum environments. The results of the
evaporation tests are summarized in Table 3.
In general, a good mass balance was obtained between the weight of
the vapor deposit and the weight lost by the specimen. Errors of
8 to 12% were attributed tu the formation of gaseous products, which
were probably pumped out of the system. In those cases where an
adequate mass balance could not be obtained, the deposit was so light that
the accuracy and precision of the chemical analytical technique led to
uncontrolled errors. The deposits, therefore, could not be identified.
" At 1500°C, all of the investigated alloys (Table 3) lost weight at
both 20-9 and 10-9 torr. However, the weight loss, except in the case...
of D-43 and B-66 alloys, was greater at 10-? torr than at 10-9 torr.
It is postulated that the higher concentration of oxygen and nitrogen
in the environment at the higher pressures resulted in the formation of
volatile metal oxides and nitrides, which were pumped out of the system.
In addition, decarburization, which was discussed previously, added to the
weight loss. For those alloys investigated at lower jemperatures (Table 3),
it was observed that all specimens lost weight at high vacuums of
10-9 to 10-20 torr. At poor vacuums of 5 x 10-7 torr, however, all samples
except B-66 alloy gained weight even though a slight vapor deposit was
observed on the collection tube. The data show that, at temperatures of
2100 to 1300°C and pressures of 4 x 10-7 to 5 x 10-7 torr, the weight
Lost by evaporation of volatile compounds 18 overshadowed by the weight
gain due to the increase in the interstitial concentration at these higher

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Table 3. Results of Evaporation Tests of Refractory-Base Alloys in High Vacuums
...l-.:.
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.-.
Alloy
Temperature
(°c)
Pressure
(torr)
Duration
Specimen
Weight Change
(mg/cm?)
Composition of Deposit
FS-80
-
1500
512
512
100 Zr
100 Zr
.
1300
.
3 x 10-9
6 x 10-7
5 x 10-9
5 x 10-7
1. X 10-9
5 x 10-7
1 x 10-9
493
493
-0.098
-0.130
-0.012
+0.043
-0.024
+0.051
-0.003
1200
1000
1000
ܣܢܵܐ ܇ ܂
300
B-66
.
1500
316
316
7 x 10-9
5 x 10-7
6x 10-10
5 x 10-7
-1.700
-1.600
0.077
-0.024
83.8 8–15.5 Zr-0.45 166 0.25 Mb
82.9 8–12.2 Zr 0.46 MO 0.17 No
93 R-7 Zr
93 V7Zr
.
1200
513
494
T-211
1500
2 x 10-9
5 x 10-7
500
500
-0.079
0.23
92.6 H-5.8 Zr:
100 HP
C-129Y
1500
2 x 10-9
5 x 1007
521
521
1.16
0.56
30.5 RP-8.1 2-21.2 .
61.5 H1—3.7 2r-1.5 Y (b)
FS-85
1500
2 x 10-9
· 5 x 10-7
667
667
-0.066
-0.100
100 Zr
100 Zr
D-43
1500
100 zr(
100 Zr
1 x 10-9
2 x 10-8
1.5 x 10-7
4 X 10°7
1 x 10-9
5 x 10-7
736
650
650
736
376
376
0.029
-0.029
-0.030
+0.019
-0.016
+0.018
100 ZT
100 Zr
1300
Not measurable.
Sample weight uncertain...
(c) Sample weight very low; only one analysis completed.
10
ORNI - AIC - OFFICIAL
The B-66 alloy contains two high vapor-pressure elements, vanadiun
and zirconium, which evaporated at 1500 and 1200°C and .10°7 to 10-10 torr.
The evaporation results (Table 3) showed that system pressure at constant
temperature did not influence the evaporation of oither element. At the
ORNI - ARC - OFFICIAL
different test pressures, the relatives anyunts of vanadium and zirconium
in the vapor deposit were the same. The influence of temperature,
however, is quite obvious in the evaporation results tabulated in Table 3.
The microstructures of the alloys studied did not contain any
i
surface or subsurface voids, broadened grain boundaries, or any other
phenomena that might Indicate localized evaporation. In the case of the
F8-80 alloy, however, certain grain orientations evaporated at greater
rates. This behavior 18 11lustrated in Fig. 7 by the offset in the
surface at the grain boundary.
CONCLUSIONS
:Teman List
The niobium- and tantalum-base alloys investigated in this study
exhibited interstitial instabilities at 1300 to 1500°C under high vacuums.
. At. vacuums of 7 x 10-9 to 6 x 10-10 torr, the instability is a loss of
oxygen, nitrogen, and hydrogen. At 1 x 10-7 and 6 x 10-7 torr, the con-
centration of oxygen and nitrogen increased, but the carbon content
decreased over an extended period of time. At 10-9 torr or lower, the
carbon content remained virtually unchanged. It was concluded that a
carbon-oxygen reaction occurred, this resulting in carbon losses as
carbon monoxide over long testing periods. The gaseous elements were
lost by simply diffusing to the specimen surfaces and desorbing into the
vapor state.
ORNI - AEC - OFFICIAL
ORNI - AC - Off

RNI - AEC - OFFICIAL
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=00035 INCHES
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...Figure 2 Surface drregularity Illustrating
Preferential Evaporation from Certain Crystall a
Orientations in FS-809 at 1500°C and
3x10 9 Torr ( 5790) Mag 20000
Etchent ! 601,0 + 20 Hz Sovet JOHF 110.HCli

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ORNI - ARC - OFFICIAL
Top
INI - AC - OFFICIAL
Metalb evaporation from the alloy surfaces were found to be low. It
was concluded that at temperatures of 1000 to 1300°c no serious evaporation
problems would be encountered in high-vacuum environments. However, it .
was conc.luded that, when high concentrations of hafnium or vanadium are
present in the alloy, exposures of several thousands of hours at 1300 to
ORNI - AC - OPSICIAL
1500°C would result in severe losses of materiale.
· ACKNOWLEDGMCNTS
-
The author 18 indebted to the many service departments in carrying out
various phases of these experiments. The chemical analyses performed by
W. R. Laing of the Analytical Chemistry Division and the metallography of
W. R. Farmer and T. J. Henson proved to be necessary services in the
interpretation of these experiments. The assistance of J. Newsome and
R. L. Taylor in carrying cut the experiments 18 appreciated. Discussions
with H. Inouye of the Metals and Ceramics Division were instrumental in
the formulation of the conclusions reached in this investigation.
Loomad
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ORNI - AEC - OFFICIAL
ORNI - AEC - OSSICIAL
12
REFERENCES
GENI - AIC - OFFICIAL
.
ongea..
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1. R. W. Douglass, Research on the Technology of Tantalum Alloys with
Maximum Strength in the 3000°F to 3500°F Range, Summary Report
March 1 May 31, 1964, NRC Contract No. AF 33( 657)-11255,
Task No. 735101 (June 1964).
2. D. Peckner, "Columbium, A Bright Future, But How Soon," Materials in
Design Engineering 54(7), 107–16 (1961). .
3. R. L. Armon and R. T. Begley, Pllot Froduction and Evaluation of
Tantalum Alloy Sheet, Summary Phase Report - Part II, WANL-PR-M-009
(July 1, 1964).
4. A. C. Barber and P. H. Morton, A Study of the Niobium-Zirconium-Carbon
and Niobium-Zirconium-Oxygen Systems, Imperial Metal Industries K/RR/33/64,
(May 7, 1964),
5. D. 0. Hobson, Aging Phenomena In Columbium-Base Alloys, Oak Ridge National
Laboratory ORNL-3245 (March 1962).
6. J. M. Gerken, A Stugy of Welds in Columbium Alloy D-43, Thompson
Ramo Wooldridge, Inc. TM-3865-67 (March 1964).
A
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ORNL - AEC - Orricia
LIST OF FIGURES
· GENS - AIC - OSSICIAL
ORNI - ACC - OFFICIAL
1.
(ORNT.
:
) Variation of the Carbon-to-Oxygen Ratio in D-43
Alloy as a Function of Pressure at 1500°C.
Variation of the Carbon-to-Oxygen Ratio in
.
....
FS-80 Alloy as a function of Temperature.
3. (Y-57496, Y-57497, Y-57498) Microstructures of Alloy T-111 in the
As-Rolled Conditior and after 500 hr at 1500°C as a Function of ..
.
.
.
.
...
...
.
......
..
.
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.
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Pressure. Etchant: 60 parts H20, 20 parts H2SO4, 10 parts HF, and i
10 parts #cl. 1000x.
(Y-57504, Y-57505, Y-57487, Y-57503) Microstructures of D-43 Specimens
Tested at 1500°C as a Function of Pressure. Etchant: 60 parts H20,
20 parts H2804, 10 parts IF, and 10 parts Hci. 1000x.
5. (7-57486, Y-57506, Y-57488) Microstructures of D-43 Specimens in
the As-Rolled Condition and after 376 hr at 1300°C as a Function of
Pressure. Etchant: 60 parts H20, 20 parts H2SO4, 10 parts HF, and
10 parts ici. 1000x. ;
6. ) Replicated Carbides (Nb,Zr)c in situ. Sample over-etched.
N-10% W-1% Zr-0.1% c alloy annealed 2 hr at 3300°F. Aged 500 hr at
2200°F.
7. (7-57490) Surface Irregularity Illustrating Preferential Evaporation
from Certain Crystal Orientations in FS-80 Alloy at 1500°C and
3 x 10-9 torr. Etchant: 60 parts H20, 20 parts H2SO4, 10 parts HF,
and 10 parts HCl. 1000x.
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