One of the goals of the HOST Program is the development of electrical resistance strain gages for static strain measurements at temperatures equal to or greater than 1273 K. Strain gage materials must have a reproducible or predictable response to temperature, time and strain. It is the objective of this research to investigate criteria for the selection of materials for such applications through electrical properties studies. The results of the investigation of two groups of materials, refractory compounds and binary alloy solid solutions are presented

Brittain, J. O.

Geslin, D.

Lei, J. F.

English

NASA Technical Reports Server

N8 9 - 1288 6
ELEVATED TEMPERATURE STRAIN GAGES*
J. O. Brlttaln, D. Geslln and J. F. Lel
Northwestern Unlvers Ity
One of the goals of the Host Program is the development of electrical resist-
ance strain gages for static strain measurements at temperatures a 1273 K. Strain
gage materials must have a reproducible or predictable response to temperature, time
and strain. It is the objective of this research to investigate criteria for the
selection of materials for such applications through electrical properties studies.
The results of the investigation of two groups of materials, refractory compounds
and binary alloy solid solutions are presented in this report.
The materials selection criteria are su_mmrlzed as follows:
(I) The material should not undergo a phase transformation in the temperature
range of interest. This was ascertained by studying existing phase diagrams.
(2) The materials should not undergo any order-dlsorder transitions or the
formation of clusters. In order to satisfy this criteria interstitial refractory
compounds were selected for a study of their elevated temperature behavior. In the
case of binary alloys an effort was made to locate ideal solid solutions, i.e.,
alloys in which both elements had activity coefficients close to one (i). In the
present case based upon a recommendation of one of our colleagues (2) we set a limit
on the activity coefficients of within 15% of one. Thermodynamic data (3,4) sug-
gested that the systems Ag-Pd and AI-V have ranges of concentrations that satisfy
this criterion. However, because of the shortage of activity coefficients data2
alternative qualitative parameters have been used to select alloys that appear to
satisfy this second criterion. Based upon the Hume-Rothery's work, elements that
have similar electronegatlvltles and molar volume tend to form ideal solutions. The
systems Mo-W, Mo-Re, and Nb-V were selected based upon these qualitative parameters.
(3) Chemical and thermal stability of the materials are important in order to
reduce the tendency for oxidation and in order to insure mechanical stability. It
was deemed useful to have a high melting temperature in order to minimize recrystal-
llzatlon and grain growth. The importance of insuring elastic behavior over the
useful or desired strain range could in principle be achieved by selecting materials
for which (_E.L./E) > Cmax where _E.L. is the stress at the elastic llmlt. E is the
Young's Modulus, and Cmax is the maximum strain to be measured. This parameter will
have to be evaluated experimentally due to the lack of published data on the
materials under investigation.
(4) Finally, several materials have been selected for the experimental phase
of this work based upon published electrical reslstlvlty-temperature data. This was
true of the Cr-V alloys for which results were presented last year. Table I listed
all of the materials evaluated and the basis for their selection for this program.
*Work done under NASA Grant NAG 3-501
69
https://ntrs.nasa.gov/search.jsp?R=19890003515 2020-03-20T04:35:48+00:00Z
MATERIALSPREPARATION,PROCESSINGANDEXPERIMENTALTECHNIQUE
The alloys listed in Table I have been prepared by arc melting in the usual
mannerunder a purified Ar atmosphere. The 5 to I0 gm homogenized ingots were
sliced into thin plates via a diamond cut off disc. Specimens for electrical re-
sistance measurements were processed from the plates by electrical discharge machln-
ing. An alternative method of preparing longer and thinner specimens by means of
drawing the molten alloy into a quartz tube connected to a vacuum was tried. How-
ever, some pick up of Si occurred and we have abandoned this technique.
With two exceptions all of the refractory compounds were prepared as thin films
on AI203 substrate by the various methods listed in Table II. The two exceptions,
B4C and S-SIC, were prepared as bulk specimens by hot pressing and subsequently
thinned by slicing into electrical resistance specimens. The refractory compounds
thin films were obtained from several sources that have had considerable experience
in the various techniques utilized.
The electrical resistance (ER) of the specimens were measured via a four probe
technique using Pt or W leads and pressure contacts in conjunction with a ceramic
specimen holder. The contacts were checked and found to be ohmic at all tempera-
tures. Measurements were conducted in an evacuated quartz tube under a dynamic
vacuum of _ 10-5 torr. Thermal Emf were eliminated by alternating the direction of
the current. Initially measurements were conducted on individual specimens; cur-
rently three specimens are held in the ceramic device and readings on the three
specimens are made by rotating the contacts in the circuit.
RESULTS - REFRACTORY COMPOUND
A. Transition Metal Nitrldes
(a) TiN
The ER of two TiN films have been measured, one sample had been prepared by
HCD method and the other by CVD method. The electrical reslstance-temperature (ER-T)
curves are shown in Figs. i and 2. We can see that their electrical behaviors are
different, the resistance of TIN-I (HCD) was metallic and increased with increasing
temperature while the resistance of TIN-2 (CVD) decreased with increasing tempera-
ture llke a semiconductor. TIN-2 (CVD) was not as stable as TIN-I (HCD), however,
its TCR at the higher temperatures was much smaller (_ 143 ppm/K) and its repro-
ducibility can probably be improved by thermal cycling. An x-ray analysis indicated
that these two TiN films have different lattice parameters and compositions. TIN-I
is TiN with a - 4.174 A and TIN-2 is TIN0. 9 with a = 4.167 _, by using EDAX of SEM,
we also found that there are some chlorine (CI) in the TIN-2 films.
(%) TaN
Two TaN Rf sputtered thin films prepared with different nitrogen (N2)
partial pressures during sputtering (Table I) were tested. The ER-T data of both
films displayed metallic behavior, Fig. 3, however, the film with the lower N2
partial pressure (TaN-l) had a smaller TCR (_260 ppm/K) and the TCR of both
specimens decreased with thermal cycling. The drift rates were about 0.5%/hr for
both films.
7O
(c) ZrN
Three Rf sputtered ZrN specimenswere studied. A comparison of these three
samples during the second cycle of heating is shownin Fig. 4. The film with the
highest ratio of N2 during sputtering (i.e., ZrN-I) had the lowest TCR(_ 290 ppm/K)
but it also had the highest drift rate (DR) (_ 0.54%/hr).
(d) CrN
The ER-T data for the CrN was metallic with a very large TCR (_710 ppm/K).
The drift rate of resistance was also very large (_20%/hr). This may have been due
to the oxidation of OrN and the formation of a Cr203 layer that may not have been
protective. Figure 5 compares the reslstance-temperature data for four different
nltrldes, clearly TaN has the lowest TCR while CrN has the highest TCR.
B. Transition Metal Carbides
TiC
The results of measurements on Two TiC films are shown in Figs. 6 and 7 re-
spectively. Just llke TiN, the film prepared by CVD method (TIC-2) had the higher
drift rate at 1275 K (_-0.5%/hr) but a lower TRC (_250 ppm/K).
C. Semiconductor
(a) B4 C
Among all the specimens studied, the results obtained for the B4C specimen
are most promising: (I) the smallest TCR (_ 160 ppm/K) and (2) the smallest drift
rate (_O.l%/hr for 17 hours) as shown in Fig. 8. Additional experiments are
planned for B4C.
(b) sic
Figure 9 shows the ER-T result of a B-SIC film prepared by the EBE method
on an AI203 substrate (SiC-l), its TCR at 1273 K is _ 330 ppm/K and the drift rate
is _ 0.3%/hr. This high drift rate may be reduced by increasing the thickness of
the film in order to minimize the apparent evaporation effect. ER-T measurements
in an Argon atmosphere are planned in order to minimize any effects that may be
associated with the high vacuum utilized in the present measurements. Future plans
will also include measurements in an oxidizing euvlromnent with the R-SIC protected
by a nonconducting high temperature cement. The hot pressed high purity B-SIC was
more stable, with a drift rate of only _ O.04%/hr but a larger TCR (_ 1940 ppm/K),
Fig. I0. It may be possible to decrease the TCR in the D-SIC by doping.
SUMMARY - REFRACTORY COMPOUNDS
The results for all the specimens are summarized in Table III. Based upon the
target values for TCR of 200 ppm/K and a drift rate of _ 0.1%/hr (5) only B4C meets
the target values. However, for a total error of 10% (6), even this drift value
appears to be too large. However, TaN-I (Rf sputtered), TIN-2 (CVD), TIC-I (ARE),
TIC-2 (CVD) and R-SIC) (EBE) also warrant further investigation. Since the ratio
of the non-metal atoms to the metallic atoms play an important role in the electrical
properties of the transition metal compounds (7), future work will involve this
71
parameter in the search for strain gage materials with low TCRand high electrical
resistance stability, i.e., low drift rate at high temperatures.
RESULTS- BINARY ALLOYS
A. Silver-Palladlum System
Based upon the ideal-solld solution criteria we anticipated reproducible and
stable electrical reslstance-temperature data for alloys with Ag content of less
than 5 w/o. Experimental confirmation was reported last year but the TCR at 1273 K
of that composition was large. An increase of the Ag content from 4.1 to 15.5 w/o
reduced the TCR from 774 ppm/K to 260 ppm/K without a loss of reproducibility or
stability of the electrical resistance, Figs. II, 12, Table IV. With a further
increase in the Ag content to 35.3 w/o Ag, the composition known to produce an even
lower TCR (< 100 ppm/K) a large drift of the resistance at 1273 K occurred,
Table IV.
B. Alumlnum-Vanadlum System
As reported last year an AI-V alloy 79.3 w/o V had a very low but negative TCR
(-22 ppm/K) and a low drift (50 ppm/K0 at 1273 K. This alloy had been prepared by
drawing the molten alloy into a quartz tube. A microprobe analysis indicated the
presence of Si. Three additional specimens with higher V contents were prepared by
conventional arc melting. The results of the electrical measurements are shown in
Figs. 13, 14. The (ER-T) curves were metallic in form and the TCR for the three
alloys improved as the V content increased. A ternary alloy of AI-82.1 w/o V-2 Si
was prepared to verify the effect of Si additions, the resulting Er-T curves, Fig.
15 was of a different form from the binary alloy, the effect of Sl was quite pro-
nounced. This alloy had good TCR and drift characteristics. Further work on the
ternary system is planned.
C. Nioblum-Vanadlum System
The composition 5.2 w/o V was selected for investigation based upon the reported
good oxidation resistance (8). While the reproducibility after the first heating
cycle and the agreement in the ER-T curves for three specimens were good, Fig. 16 and
17; the TCRwas large (_ 550 ppm/K) and the drift at 1273 K of 500 ppm/Kwas larger
than desired. It may be that similar to the AI-V system a ternary addition might
result in a lower TCRand drift rate.
C. Molybdenum-Rhenlum
Based upon published data (9) the 71% Mo alloy was selected to provide an
acceptable TCR. The Er-T curve was quite reproducible after the first heating
cycle and the drift at 1273 K was quite low (< 80 ppm/hr), however, the TCR of (623
ppm/K) was higher than desired (Fig. 18). Here again there is the potential to
improve the TCRby a ternary addition.
SUMMARY - BINARY ALLOYS
With the exception of the Al-V-Si system, the alloys investigated thus far
behave as predicted in terms of reproducibility between cycles after stabilization
if the drift at 1273 K is neglected. In an effort to meet the TCR requirement of
72
< 300 ppm/K, several of the alloys show promise. These alloys are the 15.6 w/o Ag
and 35.5 w/o Ag-Pd alloys and the AI=V alloys. While the 35.5 w/o Ag-Pd alloy does
not meet our selection criterion as an ideal solution, the low TCRindicates that
further study maybe of interest. It is also possible that improvements in the
electrical behavior of the Nb-V and Mo-Realloys can be achieved by the addition
of third elements.
In order to improve the oxidation resistance of several of the alloys an effort
is underway to prepare alloys via mechanical alloying with the inclusion of Yttrium
or Cerium oxide. The oxide additions may also serve to stabilize the structure,
especially grain size, and improve the electrical behavior at elevated temperatures.
REFERENCES
I. Kubaschevskl, O., Evans, E. L. and Alcock, C. B.: Metalurglcal Thermo-
dynamics, Pergamon, N.Y., 1967, p. 76.
2. Whitmore, D.: Private conversation, March, 1985.
3. Hultgren, R., et al., "Selected Values of Thermodynamic Properties of Binary
Alloys," ASM, 1973.
4. Raychaudhuri, P. K., Ph.D. Dissertation, Northwestern University, 1971.
5. Pratt & Whitney: Thin film strain gage development program, NASA-21242.
6. Hulse, C. O., Bailey, R. S.: The Development of a High Temperature Static
Strain Gage System, NASA Conference Publication 2405, p. 45.
7. Toth, Louis E.: Transition Metal Carbides and Nitrides, Academic Press, 1971.
8. Lazarev, E. M., Eklund, G. S. (Moscos) Izv. Akad. Nauk. SSSR, Met. 1979, (4),
9. Schr8der, K.: '_ndbook of Electrical Reslstlvlties of Binary Metallic
Alloys," CRC Press, 1983.
73
TABLEI
MATERIALSELECTED FOR EVALUATION
Material Basis for Selection
Pd -Ag 1
AI-V 1
Nb-V 2
Cr-V 3
Mo-Re 2, 3
TiN 4
TiC 4
ZrN 4
TaN 4
CrN 4
B4C 4
SiC 4
i. Ideal solution, thermodynamic data.
2. Qualitative parameters, tendency to form
ideal solutions.
3. Resistance-temperature data.
4. Refractory compounds, high melting tem-
perature, structural stability,
oxidation resistance.
Specimen
TIN-1
-2
TaN- i
-2
ZrN- i
-2
-3
CrN
TIC-I
-2
B4C
_-SIC-1
C_-SIC-2
TABLE II
PREPARATION METHODS FOR REFRACTORY COMPOUNDS
Preparation Method
HCD, Hollow Cathode Discharge
CVD, Chemical Vapor Deposition
RfS Radio Frequency Sputtering
RfS, Radio Frequency Sputtering
Remarks
with N2/Ar +N 2 ~ 22 70
with N2/Ar +N 2 _ 25 %
with N2/Ar +N 2 _ 1.65%
._ O. 19%
0.16%
HCD
ARC, Activated Reactive Evaporation
CVD
Hot Pressed
EBE, Electron Beam Evaporation
Hot Pressed
Bulk Sample
Bulk Sample
74
TABLEIII
SUMMARIZEDRESULTSFORREFRACTORYCOMPOUNDS
Drift Rate
Specimen TCR _ppm/K) (ppm/hr) (DR)
TIN-I (HCD) 588 1400
TIN-2 (CVD) 143 2200
TaN- I 260 4900
-2 300 5000
ZrN- i 290 -5400
-2 330 -2600
-3 420 600
CrN 710 20%
TIC-I (ARE) 366 580
TIC-2 (CVD) 250 -5000
B4C 160 940
_-SiC-I 330 -3000
_-SIC-2 1940 380
Remarks
Reproducibility improved
by thermal cycling
TCR and DR decreased
with thermal cycling
TCR increased while
DR decreased with
cycling.
TCR increased while DR
decreased with cycling
DR decreased by
increasing thickness
TABLE IV
SUMMARIZED RESULTS FOR ALLOYS
TCR (1270 K)
Sample w/o ppm/K
AgPd 4.3 Ag 774
ii .7 460
15.5 260
35.3 30 to 165
AIV 79.3 V -22
86.65 150
88.9 134
82.1 - 2Si -20
NbV 5.2 V 550
CrN 67.4 V 556
MoRe 71 Mo 623
Drift (1270 K)
ppm/hr
1723
62
140
7000 to 38,000
50
1280
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vG TEMPERATURE _or 3 5.2 wZ V-Nb
Figure 17
®i
1300
SAMPLES
E
J_ 5.3
0
I
4.8
E 4.3
hl
U
Z
UI
01
hl
3. B
3.3
2.8
2.3
1.8
O HEATING I
-& COOLING I
+ HEATING 2
[]
250 400 550
RESISTANEE
zP
[]
[]
I I I I
700 850 I000 1150 1300
TEMPERATURE (K)
v,_ TEMPERATURE o£ 71 wX" Mo-Re
Figure 18
84


Elevated temperature strain gages

Materials were evaluated that could be used in manufacturing electrical resistance strain gages for static strain measurements at temperatures at or above 1273 K. Strain gage materials must have a characteristic response to strain, temperature and time that is reproducible or that varies in a predictable manner within specified limits. Several metallic alloys were evaluated, as well as a series of transition metal carbides, nitrides and silicides

N88-11144
ELEVATED TEMPERATURE STRAIN GAGES _
J. O. Brlttaln, D. Geslin and J. F. Lei
Northwestern University
The Host Program has as one of its goals the development of electrical re-
sistance strain gages for static strain measurements at temperatures _ 1273°K. In
order to attain this goal strain gage materials must have a characteristic response
to strain, temperature and time that is reproducible or that varies in a ptedlctable
manner within specified limits. The principal contributions to the relative change
in resistance are (i) the change in resistance with strain, (2) the change in
resistance with temperature (coefficient of thermal resistance) and (3) time de-
pendent changes in resistance due to chemical changes (e.g., oxidation) and
dimensional changes (creep) (ref. i)° These then are the principal parameters to be
considered in the selection of materials for strain gage elements. However, in
order to proceed with the development of such gages the selection of material
for the gage elements, consideration must be given to material parameters that
effect electrical resistance. The material factors are: phase, magnetic and order-
disorder transitions, short range ordering, clustering, plastic deformation and
chemical changes associated with material reactions with an elevated temperature
envlronment. These material parameters are interrelated and their effects on
elevated temperature electrical resistance are both temperature and time dependent
(refs. 2 and 3).
Prior to the selection of a llst of materials for potential strain gage
applications, we set out to establish the criteria to be used in the selection of
material for evaluation. Phase diagrams of binary alloys were utilized as the first
step in the selection of materials that have sufficiently high melting temperature,
do not undergo a phase transformation or a magnetic transition. Since phase
diagrams usually provide no information on structural changes associated with order-
disorder transitions or clustering, we made use of thermodynamic data when available
to select ideal solid solution alloys. Alloys that are ideal solutions should not
undergo transitions such as clustering, order-dlsorder, etc. The basis for classi-
fying an alloy as an ideal solution is that the activity coefficient iS equal to
one. Alloy compositions with activity coefficients of the two components within
about 15% of one were selected, see Table I. Several qualitative criteria have
evolved to aid in the selection process when quantitative activity data did not
exist° These qualitative rules suggest that alloys tend to form ideal solutions
when the molar volume of the two components are equal and when the electronegativity
of the two components are similar (refs. 4 and 5). In addltlon several alloys that
have a linear electrical reslstlvlty-temperature relation were included in the
initial llst of materials for evaluation (ref. 5). The llst of binary alloys for
the first phase of the investigation is listed in Table I.
In addition to the metallic alloys, evaluation of a series of transition metal
carbides, nitrides and silicldes, Table I, is also in progress. These materials
were selected based upon the following: (i) high melting temperature, (2) good
mechanical strength at elevated temperature, (3) low and metallic llke reslstlvl-
ties, (4) the absence of phase transitions within the 0°- 1000°C temperature range_
*Work done under NASA Grant NAG3-501.
59
https://ntrs.nasa.gov/search.jsp?R=19880001762 2020-03-20T08:35:20+00:00Z
(5) good oxidation resistance and (6) thin films can be etched for pattern geometry
(ref. 6). In addition to the six compounds(TIC, TiN, ZrC, ZrN, TaSi2 and TiSi2)
selected as most promising for evaluation, interest in SiC has evolved. This
semlconductlng compoundis of interest because of its stable physical character-
istlcs_ similar to those described above for the transition metal compounds,at
temperatures up to 1200°C, as well as the observation that efforts to develop SiC
elevated temperature gages are in progress in Russia (ref. 7).
MATERIALPREPARATIONA DPROCESSING
The alloys listed in Table I are being prepared by arc melting in the usual
manner. The homogenizedingots were processed into specimens by electric dis-
charge machining or slicing with a diamondwheel. Specimensof CrV were 25 x 2.1
x .406 ram,AI-V 12 x 1.8 x 1.5 ram. Specimenshave also been prepared by meansof
drawing the molten alloy into a quartz tube connected to a vacuum. This latter
technique produced longer wire speclmens. So far our efforts to produce specimens
of MoReand MoWby the quartz tube technique have not been successful.
Samplesof SIC, TiN, TiC in thin film form have been obtained from several
sources. These samples were prepared by sputtering or by CVDtechniques. Specimens
of SiC on a AI203 substrate were cut to 13 x 1.2 n_nand 2500 _ thick.
The electrical resistance of the specimenswas measuredvia a four probe tech-
nique using Pt leads and pressure contacts. The contacts were checked and found to
be ohmic at all temperatures. Measurementswere conducted in a quartz evacuated
tube that contained an AI203 specimen holder with a metal tube envelope surrounding
the quartz tube. The vacuumwas better than 10-5 Tort and the temperature gradient
was found to vary by about 2 - 10°C along the specimen holder, with a temperature
variation over the length of the specimen of _ 2-4°C at the elevated temperatures.
RESULTS
The reslstance-temperature data was obtained with a heating rate of
1.25°C/mln. and a cooling rate of _ 0.6°C/mln. The resistance data is an average
of approximately 8 measurementsthat were madeafter a sojourn of about 30 minutes
at the temperature of interest. Thermal EMF'swere eliminated by changing the
current direction. Figure I is a plot of resistance vs temperature for a nominal
69.1 w/o (70 a/o) V-Cr alloy. The resistance varied linearly with temperature,
with a slope of _ 2.68 x 10-3 r/_/C, there is good agreement for the two cycles
shown, furthermore the drift at 1000°Cafter 15 hrs. was relatively small. Figure
2 shows the resistance drift as a function of time, the drift after 900 minutes
was _1.7 %. Table II relates the resistance drift for short times at intermediate
temperatures. From flggre I, the thermal coefficient of'reslstance at 1000°Cwas
found to be N 5.6 x I0-4/oc,
The reslstance-temperature data for the 81.6 w/o (70 a/o) V-AI alloy is shown
in figure 3. After the first heating cycle, the resistance varied reproduclbly
with temperature. The origin of the initial high resistance from room temperature
to N 500Oc is unknown. The decrease in resistance with temperature suggests that we
repeat these measurements to insure that they are not due to a fault in the measur-
ing technique. If repeated measurements produce the same temperature dependence,
that would indicate semlconductlng electronic behavior.
6O
Figure 4 shows the reslstance-temperature data for SiC sputtered film on an
AI203 substrate. The specimenwas initially conditioned by heating and cooling
from lO00°C. The resistance drift at 1000°C during the first heating cycle was
associated with a 17 hr. sojourn at 1000°C. After the first heating cycle, there is
some indication that the reslstance-temperature relation is constant. However, as
indicated in figure 5, the resistance showeda positive drift with time at 840 and
900°C, while a negative drift was observed at 949 and 1000°C. Inasmuch as we
observed extensive contact reactions between the Pt wire and SiC, the present data
is suspect and we are in the process of examining other probe materials.
ib
•
.
.
DO
.
.
0
REFERENCES
Sharpe, W. N. Jr.: Strain Gages for Long Term High Temperature Strain
Measurements. Experimental Mechanics.
Ochial, Y. and Brlttaln, J. 0.: Anomalous Electrical Resistivity in CoGa
Intermetallic Compounds. Phys. Letters., vol. 72A, 1979, pp. 347-49.
Ochlai, Y. and Brlttaln, J.O.: Negative Temperature Coefficient of
Resistivity in _-Co52Ga48. J. Phys. F: Metal Physics, Vol. I0, 1980, pp.
1183-93.
Kubaschevskl, 0., Evans, E. L. and Alcock: Metallur_ical Thermodynamics.
Pergamon, N. Y., 1967, p. 76.
Cahn, R. W. Haasen, P.: Physlcal Metallursy. American Elsevier, N. Y., 1983,
p. 176.
Schr_der, Klaus: Handbook of Electrical Reslstlvltles of Binary Metallic
Alloys. CRC Press, 1983.
Drennen, D. C. etal.: LMFBR Instrumentatlon-Straln Gages, Phase I High
Temperature Strain Gage Development Program: Battelle Memorial Institute,
1970.
Rapatskaya, V. and Rudashevskli, G. E.: Silicon _-Garblde Strain Transducers•
Measurement Techniques 1968, pp. 771-772. Translated from Izneritel'naya
Tekhnlka, 6, 1968, pp. 117-123.
61
TABLEI
MATERIALSELECTEDFOREVALUATION
Material Basis for Selection
Pd-Ag I
AI-V i
Nb-V 2
Mo-W 2
Hf-Zr 2
Pd-Rh 2
Cr-V 3
Ta-W 3
Mo-Re 3
TiC 4
TiN 4
TiSi 2 4
ZrC 4
ZrN 4
TaSi2 4
sic 4
I. Ideal solution, thermodynamic data.
2. Qualitative parameters, tendency to form ideal
solutions.
3. Resistance-temperature data.
4. Refractory compounds,high melting temperature,
structural stability, oxidation resistance.
TABLEII
RESISTANCEDRIFT FOR CrV ALLOY, mQ
TEMPERATURE
(°c)
429.9
428.78
581.75
586
703
705.5
845
850
TIME 0 i/2 h i h
3.376
3.392
3. 749
3.743
4.179
4.084
4.481
4.484
3.283
3.755
4.081
4.486
62
5.0
4.5
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o
I 4.0E
W
u
Z3.5
<
i-
u)
u')
w 3.0
2.5
2.0
,11,
CYCLE ! HEATING
CYCLE I EOOLING
CYCLE 2 HEATING
ISOTHERMAL SOJOURNS
Y
/3-I
./z*
3-I
.I.,"
.I
j_
•* 6--15
/
../ 3.1 "I- z-t: z MEASUREMENTS
/ IN t HOURS
._3-I
0
I I I I I I I I I I
lO0 200 300 400 SOO 600 700 800 900 IOOO I
TEMPERATURE (°C)
FIGURE I RESISTANCE Vs. TEMPERATURE OF CrY
O0
5. 02
z'%
E
r-
o
I
E
L_
L3
Z
<
U3
L.d
FF
5. O0
4.98
4.92
.
4.90 x I K k I L I. I
0 100 200 300 400 500 500 700 800 900
TIME (mn)
FIGURE 2 RESISTANEE DRIFT Vs. TIME GL I[]02. 5°C OF E_V
63
5.10
5. 05
E
rS. 0o
o
E
"_ 4.95
W
U
z 4.90
tO
-- 4.85
tO
W
rY
4. 80
4.75
4.70
_$-'a o _
0
\ CYCLE I HEATING
* CYCLE 1 COOLING
CYCLE 2 HEATING
o CYCLE 2 COOLING
$ CYCLE 3 ISOTHERMAL
SOJOURNS
\
g.-
-o
I I I I I I l I I I
100 200 300 400 500 600 700 800 900 1000 1
TEMPERATURE (°C)
FIGURE 3 RESISTANCE Vs. TEMPERATURE OF AIV
OO
850
800n_
"" 750-
Ejr"
o
v 700-
Ld
U
z 650-
b-
to 600
i--i
tO
Ld
rr 550_
5O0
450
400
0
0
_0
÷
_0
0 CYCLE I HEATING
ISOTHERMAL SOJOURNS
(FOR 17 HOURS)
CYCLE 1 COOLING
+ CYCLE 2 HEATING
÷,
_0
_o
_0_ 0_0
_t
._+
0
\
0\
@
I I 1 I , I , I I I ..... I 1-
i00 200 300 400 500 600 700 800 900 I000 1 00
TEMPERATURE (°C)
F IGL]RE 4. RESISTANCE V_. TEtIFERATIJRE OF SiC
64
420_
i 415
410
z
,c
I--
to
40E
Do
ILl
rr
400
395'
39O
0
o
_0 _0_0
, 1007°C
• 949°C
÷ 900°C
o B40°C
I I I _ , l
2 4 6 8
I I I !
10 12 14 16 18
TIME (hrs.)
FIGURE 5 RESISTANCE DRIFT Vs. TIME OF SiC
65


Elevated temperature strain gages

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