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MICROCOPY RESOLUTION TEST CHART.
NATIONAL BUREAU OF STANDAROS -1963
2
,
9
ORN-P1634
0 0% 6S/6S - -
4
COMPARATIVE CREEP-PRIPTURE PROPERTIES OF D-43 AND B-66 ALLOYS*
NOV 1 105
1...:..
..
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R. L. Stephenson
Metals and Ceramics Division
Oak Ridge Hational Laboratory
Oak Ridge, Tennessee
INTRODUCTION
A large mmber of refractory-metal alloys are currently under consideration
for high-temperature structural applications. In most cases, the only mechani-
cal property data available on these materials are tensile test data and very
chort-time crrop data. Since long-time creep properties are a critical criterion
for many high-temperature applications, an evaluation of several promising
refractory-inetal alloys we undertaken. This evaluation included the dateraina-
tion of creep properties to 1000 hr, so that a valid comparison of their suitability
for high-temperature structural applications could be made. This report describes
such an evaluation of D-43 (16-10% 51% 2% 0.1%C) and B-66 (N6-58 59-59% M-1% Zr).
MATERIALS
The D-43 sheet, designated as heat No. 284-02, was obtained from
E. I. du Pont de Nemours Company. A typical analysis of the finished sheet 16
as follovat
Dement
Tungsten
Zirconium
Weight
Percent
9.4
0.95
0.0970
0.0032
0.0008
0.0032
balance

RELEASED FOR ANNOUNCEMENT
IN NUCILAR SCIENCE ABSTRACTS
Oxygen
Hydrogen
Mitrogen
Hiobium
*Research Ansored by the vis. Atomic Energy Congiasion under contract
with the Union Carbido Corporation.
-
-
-
-
..
.
- IO.
Io preparing this sheet, an 8-in.-dian, arc-ited angot was extrudied
(from 1093°c) to . 2-10.-thick sheet bar. The material wc thun hot rolled
(fron 1093°C) to an 0.25-1n, thi akness with appropriate crose rolling to
control the width. The material was then cold rolled to 0.065 in. with inter-
ediete streas-relieving treatments of approximtaly 10 min at 1.2040 and
conditioned by abot blasting. The material was atruse rollend (12044C) after
the final rolling. At no tipse during the fabrication was the material hented
abo e 1204*C.
The B-66 alloy, heat Mo. DX-569, wau procured from Westinghouse Mectric
Company, and the analygio of this heat is shown below:
.
Weight
Element Percent
Molybdeno 4.88
Vanadium
4,61
Zirconiram 1.02
Carbon 0.0045
Oxygen 0.0190
Mitrogen 0.0011
Hydrogen 0.0003
Mobium Balonce
This material was cold rolled 50% (to 0.068 in.) After the final recryatallixing
annes) and was teated in the no-rolled condition. The detailed processing
history of this material le not known.
AJ l material used was even a fluorescent-penetrant Inupection which showed
1t free of surface flana greater than 0.0005 in. Gep, a transitional trusonic
inspection which abwed it to be froe of laminations ernatur tchise 0.125 in. in
diamotor, and a sheax-wave ultrasondo Ioapection which showed it to be free of
tranaverso atacontimuities in excess of 3% of the material thakness.
APPARATUS
The tøsting was done in a cold-wall vanw-creep apparatus in which the
specimen was heated by a tantalum wre turnace. This apparatus le capable of
preasures in the range of 10~7 to 10-torr, and the testing described here
was generally donc at pressures 32 x 10-7 torr. These pressures were obtained
with a sola-trapped 011 diffusion pussp. The apparatus was baked out for about
20 br et approximately 150°C by circulating 50-pei steam through the water
Jacket botore the specimen kø allowed to exceed 200°C at the beginning of
cach tost. Analyota of the specimens after testing showed no change in the
nitrogen ir cerbou contents and a 50- do 300-ppm Increase in oxygen content.
The strain was measured at the pull rod with a dial Indicator. The creep
valves reported reflect plastic deformation only.
RESULTS
D-43 Alloy
man asbep-stature properties of stress-relleved Dw43 alloy at Care
even in Fig. la. Curves are shown that edive the timea to 1, 2, 5, and
10% elongation and to rupture. Similar data are given at 1090 and 1204°C in
P188. Id and do, sospectively. In Fig. 14, the secondary croop rate la sbown
no a function of atrees at 980, 109, and 1204C.
The microstructure of the us-received D-43 16 shown in Fig. 2. The
med crostructures of apecineno tested for substantial times at 980, 1090, and
1204C are shown in Fig. 20, 20, and 2d, respectively.
B-66 Alloy
The creep-rupture properties of B-66 alloy at 900 C are shown in Fig. 3a.
Curves are included that give the times to 1, 2, 5, and 10% crow and tire.
Similar curves at 1090 and 1204°C are shown in Figa. D and 30, respectively.
7lgurt 3d shows the secondary creep rate as a function et stress at 40, 1090,
and 1204C.
The aa-received microstructure of the B-66 alloy lo shown in M8. hm.
In M8. 40 the red crostructure of a specimen tested at $0 18 show. : :
Figure 5 compares the microstructures of specie tented Sche, 212, and
1238 br, respectively, at 1090°С. Figure 6 cameras the red crostiratures of
specimens tested for various times at 1204°C.
DISCUSSION
The D-43 alloy mic structures shown in Figi 2 appuar no different from
those of specimens annealed for 1 lr at the same temperaturaa. Henon, 1t is
concluded that tha miorcetructures shown are stable for at least 1000 br.
Upon comparison of the as-racel.ver. B-66 alloy microstructure with the
mi crostructure of a specimen tested at $0°C (Fig. 4), the presence of small .
strain-fres graino is noted, in adilltion to evidence of frther deformation.
It is apparent that a small amount of recryotallization 18 taking place under
these conditions of atrein rate and tenxrature.
From Fig. Sa, it can be seen that the material has fully recrystallized
and attained a substantial grain size while being testad 54 hr at 1090. At
an intermediate test duration (Fig. 5b), Baller grain size 1. cbservand,
while a larger grain size 16 again observed in a test lasting 1138 br:
(Fig. 5c). Each of these photonicrographa was taken in the region of the spool-
meno having essentially unifom elongation. It is conceivable that the rapid
strain rate supplied energy for acnelurated suuda growth in the short-time
specimens, while simple time-dependent grain growth accounts for the larger grain
bine in the long-time specimaa. Aaditional evidence of strain annealing 18 found
in the microstmictures of spacinens tarted at 1204°С. Figure 6 compares
specimene tasted various times at this temperature. In the shortest test
(9.9 hr), there apparently inaa not sufficient time for excessive grain growth,
although nocrystallization soona complate. In 718, 6b, the critical strain
rato to produce large grains was apparently present. In the longer time tests,
the grains are not nearly as equiaxed and perhaps not as lerge. However, the
microstructure of the 926.5-box specimen (Fig. 6e) nour its fracture is much like
that of the speedmens teated 16.8 hr; 1t 18 hypothesised that the critical
strain rate was duplicated in this region of the specimens immediately prior to
fractura. The grains immediately adjacent to the fracture are equiaxed but
omaller, indicating that recrystalliestion was taking place but that the high
strain rate provided an increased mucleation rate and did not allow time for
the growth of large grains.
In all of the microstructures shown in Fig. 6 (with the exception of 6e),
raint lines can be seen which give the appearance of grain boundaries. Some
of these are similar in shape and immediately adjacent to distinct grain bound-
arie10 a s er rond niscent of the traces 07 previoue locations of grain
boundaries delineated by thermal *tching. One wonders, however, why such former
positions should be doiineated by chemical etching. If alloying elements or
laparities negregate to train boundaries that, under these test conditions,
mova to new locations faster than these compcoitional variatione homogeniza,
tibeyin dolinations of these areas by chemical etching would be expected. It
this is the case, then it surnishes additional evidence of the rapid motion of
Krala boundaries during test.
A comparison of F188. ln, 10, and lc with Tiga. 30, 90, and 3c reveals
that the creep-rupture properties of B-66 alloy are olgnificantly inferior to
those of D-43 alloy for material haring the particular thermomechanial histories
examined hore. In particular, the slopes of the atroci-rupture curves for
B-66 alloy are steeper than those for D-43 alloy. the alluring of atobium
with vanadium produces a substantial increase in room-temperature tensile
properties (1), which 18 Indicative of good short-time proportier. On the
other hand, the addition of vanadium to niobium produasi a aparicant decrease
la melting point.(2). This fact, together with the microntructural considera-
tions previously discussed, indicates that diffusion-controlled proocanes
proceed rapidly 10 this alloy. Therefore, poor long-time, high-temperature
properties (and hence the steep alope of the stress-rupturo plot) art to be
expected.
The fracture ductility of B-66 alloy 18 mich greater than that of D-43
alloy. In addition, the secondary creep rate at a given temperature and
streas 18 faster żor B-66 alloy than for D- alloy. As a result, the Bw. 36
alloy compares even 1088 favorably on the basis of st7Oases to produce a
specific strain in a specified time than on the basis of strese to produce
rupture (Fig. 7).
In summary, D-43 alloy 10 characterized by a stable microstructure at
temperatures up to 1204°C. In contrast, B-66 alloy 16 characterized by rapid
diffusion-controlled processes (6.8., rapid grain-boundary motion and low
recrystallization temperature) and as a result exhibits interior long-time
high-temperature creer properties.
ACKROWIADCHETS
The author wishes to acknowledge the contributions made to this work by
others. Those who nerit specific nection are J. A. Weir, Jr., R. A. Vandardner,
And W. C. Thurber for valuable suggestions on the proventation of this material,
H. R. Tłach for metallograputo preparation, C. K. Thorams for performance of
experimental details, and the Metals and Carance Diviston Reports Office
for the preparation of this paper.
BIMLIOGRAPHY
2. Rajala, B. R., Holtz, F. C., and Van 'llyne, R. J., Armour Rescarch
Foundation A.RF-2212-2 (April 24, 1961).
2. Wilhelm, 8. m., Corlson, 0. N., ond Dicklason, J. M., Trans. Ang &(8),
915 (1994).
FIGURE CAPTIONS
Ms. 1. Creep-Rupture Properties of Dada] Alloy (n) at 9.0°C, (b) at
10904, and (e) at 1204°C: (a) Secondary Croep Rate ve stress for D-63 Alloy.
Fig. 2. Photomicrographs of D-63 Alloy (a) As Peceived, (b) Tested
563.5 bar at 90 °C (Test No. 296?), (c) Testod 1121.1 hr at 1090°C (Tost
10g, , 12804. 250%.
Fig. 3. Croep-Rupture Properties of B-66 Alloy (@) at 8800, (b) at 2090,
and (c) at 1204C3 ! Secondary Creep Rato ve stxsea for B-66 Allsy.
118. 4. Photomicrographs of B-66 Alloy (a) As Received, and (o) Testod at
980°C. Itabant: 820, 8, Mids, HÖSCH. 100%.
718. 5. Photomicrographs of Specimene Tested Various Mimos at 1090*C.
Itchant: 830, #, HIO), 1280* Original magnifications 100% , reducad 16%.
Pig, 6. Photoni cruxgraphs (a,b,c,d, net Spbad was Testad Various TL1628.
at 12040. Btchant: 120, #, 103, 12804. Original magnification: 100%,
reduced. 16%. (e) Pantomi argaraphs Showing Practure Area of Specimens Testad
916.5 kr at 1204°C. Btchant: RO, B, ora: 144. 200%.
118. 7. Comparative Croop-itupture Properties və Temperature for Dek3
and Bhed Alloys.
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20,000
40,000
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STRESS (psi)
6000
4000
RUPTURE IN 1000 hr
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% CREEP IN 1000 nr
O 0-43
• 8-66
2000
• 8-66
20,000
1% CREEP IN 1000 hr
O 0-43
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10,000
8000
STRESS (psi)
2000
2% CREEP IN 1000 nr
to 0-43
• 8-66
4000 1100 1200
TEMPERATURE (°C)
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TEMPERATURE (°C)
Fig. 2. Comparative Creep-Rupture Properties vs Temperature
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END
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DATE FILMED
12/ 3 /65







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