U.S. patent application number 11/108865 was filed with the patent office on 2005-12-08 for titanium tungsten alloys produced by additions of tungsten nanopowder.
Invention is credited to Abkowitz, Stanley, Abkowitz, Susan M., Fisher, Harvey, Schwartz, Patricia J..
Application Number | 20050268746 11/108865 |
Document ID | / |
Family ID | 36591414 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050268746 |
Kind Code |
A1 |
Abkowitz, Stanley ; et
al. |
December 8, 2005 |
Titanium tungsten alloys produced by additions of tungsten
nanopowder
Abstract
Disclosed herein are titanium-tungsten alloys and composites
wherein the tungsten comprises 0.5% to 40% by weight of the alloy.
Also disclosed is a method of making such alloys and composites
using powders of tungsten less then 3 .mu.m in size, such as 1
.mu.m or less. Also disclosed is a method of making the titanium
alloy by powder metallurgy, and products made from such alloys or
billets that may be cast, forged, or extruded. These methods of
production can be used to make titanium alloys comprising other
slow-diffusing beta stabilizers, such as but not limited to V, Nb,
Mo, and Ta.
Inventors: |
Abkowitz, Stanley;
(Lexington, MA) ; Abkowitz, Susan M.; (Burlington,
MA) ; Fisher, Harvey; (Lexington, MA) ;
Schwartz, Patricia J.; (Andover, MA) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
901 New York Avenue, NW
Washington
DC
20001-4413
US
|
Family ID: |
36591414 |
Appl. No.: |
11/108865 |
Filed: |
April 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60563009 |
Apr 19, 2004 |
|
|
|
Current U.S.
Class: |
75/248 ; 148/421;
419/28 |
Current CPC
Class: |
B22F 2998/00 20130101;
B22F 2998/10 20130101; B22F 2998/00 20130101; B22F 3/15 20130101;
B22F 3/15 20130101; B22F 5/007 20130101; B22F 3/17 20130101; B22F
3/10 20130101; B22F 3/10 20130101; B22F 3/20 20130101; B22F 3/02
20130101; B22F 3/22 20130101; B22F 3/02 20130101; A61L 31/022
20130101; B22F 1/0003 20130101; C22C 32/0047 20130101; B22F 2998/10
20130101; C22C 1/0458 20130101; C22C 27/04 20130101; B22F 3/12
20130101; C22C 14/00 20130101; B22F 2998/10 20130101; B22F 1/0003
20130101; B22F 2998/00 20130101; A61L 27/06 20130101 |
Class at
Publication: |
075/248 ;
148/421; 419/028 |
International
Class: |
C22C 014/00; B22F
003/24 |
Claims
What is claimed is:
1. A composition comprising a titanium alloy, said alloy comprising
tungsten in an amount ranging from 0.5% to 40% by weight of said
alloy, wherein the tungsten has an average diameter less then 3
.mu.m in size.
2. The composition of claim 1, wherein the tungsten powder has an
average diameter ranging from 8 angstroms to 1 .mu.m or less.
3. The composition of claim 2, wherein the tungsten powder has an
average diameter ranging from 10 nm to 500 nm.
4. The composition of claim 1, comprising at least one beta
stabilizer chosen from V, Nb, Mo, and Ta.
5. The composition of claim 1, wherein said alloy comprises
dispersions of beta phase islands.
6. The composition of claim 5, wherein said beta phase islands
comprise undiffused particulate beta stabilizer at the core of said
islands.
7. The composition of claim 1, wherein said titanium material
comprises a material chosen from Ti powder and Ti alloy.
8. The composition of claim 1, wherein said alloy has a
microstructure that comprises alpha/beta phases, all beta phases,
or alpha/beta phases comprising a dispersion of beta phase
islands.
9. The composition of claim 8, wherein said beta phase islands
include partially diffused beta stabilizer within the beta phase
islands.
10. The composition of claim 1, further comprising at least one
particulate material chosen from titanium carbide (TiC), titanium
boride (TiB), titanium diboride (TiB.sub.2) or combinations
thereof.
11. A powder metallurgy method of producing a tungsten comprising
titanium alloy, said method comprising: blending a titanium
containing powder with a tungsten containing powder to form a
blended powder, said blended powder comprising tungsten powder in
an amount ranging from 0.5% to 40% by weight of said alloy, wherein
said tungsten powder has an average diameter less then 3 .mu.m in
size; compacting the blended powder; sintering the compacted and
blended powder to form a tungsten containing titanium alloy; and
optionally subjecting the sintered tungsten containing titanium
alloy to hot isostatic pressing.
12. The method of claim 11, further comprising subjecting the
sintered tungsten containing titanium alloy to a process chosen
from casting, forging, and extrusion.
13. The method of claim 11, wherein the tungsten containing powder
has an average diameter ranging from 8 angstroms to 1 .mu.m or
less.
14. The method of claim 13, wherein the tungsten containing powder
has an average diameter ranging from 10 to 500 nm.
15. The method of claim 11, wherein the blended powder further
comprises at least one beta stabilizer chosen from V, Nb, Mo, and
Ta.
16. The method of claim 11, wherein the blended powder further
comprises at least one particulate material chosen from titanium
carbide (TiC), titanium boride (TiB), titanium diboride (TiB.sub.2)
or combinations thereof.
17. The method of claim 11, wherein said tungsten containing
titanium alloy contains dispersions of beta phase islands.
18. The method of claim 17, wherein said beta phase islands contain
residual beta stabilizer at the core.
19. The method of claim 11, wherein said titanium containing powder
comprises a Ti powder or a Ti alloy.
20. The method of claim 19, wherein said Ti alloy comprises
Ti-6Al-4V.
21. The method of claim 11, wherein the tungsten containing
titanium alloy has a microstructure that comprises all-alpha phase,
alpha/beta phases, or all-beta phase, or all-alpha phase or
alpha/beta phases comprising a dispersion of beta phase
islands.
22. The method of claim 21, wherein said beta phase islands include
partially diffused beta stabilizer within the beta phase
islands.
23. A product comprising the composition of claim 1.
24. The product of claim 23, wherein said product is an orthopedic
device chosen from knee, hip, spinal, and dental implants.
25. The product of claim 23, wherein said product is an automotive
component chosen from valves, connecting rods, piston pins and
spring retainers.
26. The product of claim 23, wherein said product is an military
vehicle component chosen from tank track, suspension, and
undercarriage parts.
27. The product of claim 23, wherein said product is a tool or die
material for metal forming chosen from shot sleeves, plungers and
dies.
28. The product of claim 23, wherein said product is an aircraft
component chosen from a turbine rotor, and a leading edge of a
helicopter rotor blade, tubing, valves and fittings.
29. The product of claim 23, wherein said product is a billet for
subsequent casting, forging or extrusion.
30. A powder metallurgy method of producing a titanium containing
product, said method comprising: blending a titanium containing
powder with a tungsten containing powder to form a blended powder,
said blended powder comprising tungsten powder in an amount ranging
from 0.5% to 40% by weight of said alloy, wherein said tungsten
powder has an average diameter less then 3 .mu.m in size;
compacting the blended powder; and sintering the compacted and
blended powder, said method optionally comprising a post-sintering
process chosen from hot isostatically pressing, casting, forging
and extrusion.
31. The method of claim 30, wherein said product is an orthopedic
or dental implant.
32. The method of claim 30, wherein said product is a billet that
is subjected to at least one post-sintering process chosen from
casting, forging, and extrusion.
Description
[0001] This application claims the benefit of domestic priority to
U.S. Provisional Patent Application Ser. No. 60/563,009, filed Apr.
19, 2004, which is herein incorporated by reference in its
entirety.
[0002] Disclosed herein are titanium-tungsten alloys and
composites. Also disclosed is a method of making such alloys and
composites using nanopowders of tungsten and optionally comprising
slow-diffusing beta stabilizers, such as but not limited to V, Nb,
Mo, and Ta.
[0003] While Ti alloys strengthened by W are generally desirable
because they are strong wear resistant alloys, such alloys are
difficult, if not impossible, to prepare by typical techniques. For
example, in a casting process, W generally completely dissolves in
the molten Ti during the melting step. As the resulting ingot
solidifies beta-rich large, elongated islands form between the
dendrites of the solidified casting. These resulting defects lead
to poor mechanical properties in the final product.
[0004] Until the present disclosure, the preparation of Ti--W by
powder metallurgy (P/M), was not commercially viable because of the
high melting point and slow diffusivity associated with W that
causes it to remain segregated as discrete or undissolved
particles. Ti--W alloys are mentioned in the literature for use as
sputtering targets and in thin film applications; however, these
alloys are tungsten (W) based with typically 10% or less Ti.
[0005] Literature that does describe Ti based alloys comprising W
describes W being added to form a particulate dispersion. For
example, M. Frary, S. M. Abkowitz, and D. C. Dunand,
"Microstructure and Mechanical Properties of Ti/W and Ti-6Al-4V/W
Composites Fabricated by Powder-Metallurgy," Materials Science and
Engineering A344 (2003) 103-112, which is herein incorporated by
reference, shows that partially diffused W dispersions in Ti powder
(Commercially Pure "CP" Ti) and Ti-based alloys (Ti-6Al-4V)
increases strength with an acceptable loss in ductility. The alloys
described in Frary et al. comprise 3 .mu.m to 10 .mu.m tungsten
powders that are too large to completely diffuse.
SUMMARY OF THE INVENTION
[0006] The present disclosure avoids the aforementioned problems by
using tungsten nanopowder. As used herein, nanopowder is defined as
powders less than 1 micron, such as powders ranging from about 8
angstroms (the detection limit of electron microscopy) to less than
1 micron. The Inventors have discovered that the use of W
nanopowder in the preparation of Ti--W alloys allows the W to
completely diffuse into the Ti matrix during a typical P/M
sintering cycle.
[0007] In one embodiment, completely diffused W nanopowder forms an
alpha/beta or all beta microstructure, or as alpha/beta or all beta
microstructure containing a dispersion described as "beta phase
islands." Beta phase islands are a microscopic beta rich structure
dispersed throughout an alpha, alpha/beta or all-beta
microstructure. These dispersions result in Ti/W alloys with
properties that are superior to a dispersion of partially diffused
W particulates produced using Ti powder 3 .mu.m or larger. In fact,
the commercially pure (CP) Ti with 10% W containing dispersions of
beta phase islands can have properties superior to Ti-6Al4V. In
addition, the Ti-6Al-4V with 10% W can have annealed properties
equivalent to the highly alloyed all-beta alloys that require
solution treatment and aging to fully develop their properties
(e.g. Ti-13V-11 Cr-3Al).
[0008] In accordance with the present disclosure, W nanopowder can
be blended with CP (commercially pure) Ti powder and, in the case
of an alloy, blended with Ti powder, other elemental powders or
with master alloy powders, which is defined as the mixture of
starting metal powders used to form the resulting alloy by powder
metallurgy processing. The powder blend is compacted, sintered and
may or may not be hot isostatic pressed. The product may be
subjected to additional processing, such as, forging, casting, or
extrusion.
[0009] A casting billet may also be prepared in the manner
described above and then cast to shape. Ti--W master alloy
additions can also be prepared by the methods disclosed in this
invention. These master alloy additions can be used in casting of
Ti--W or may be made into master alloy powder by attrition for use
in P/M processing.
[0010] The total diffusion of W, as disclosed herein, results in an
alpha/beta phase microstructure in CP titanium typical of
commercial alpha/beta alloys. In alpha/beta alloys the total
diffusion of W results in a near beta or all beta microstructure.
The Ti--W alloys also have properties that are superior to
conventional Ti-6Al-4V. Further the Ti--W alpha/beta and all-beta
alloys can be solution treated and aged in much the same way as
conventional heat treatable Ti alloys.
[0011] Disclosed herein is a method of making an alloy having a
uniform dispersion of beta phase islands within a Ti matrix.
According to this aspect, this uniform dispersion of beta phase
islands can be controlled within the Ti matrix by adjusting the P/M
sintering time and/or by manipulating the W powder size to a range
from 8 angstroms to less then 3 .mu.m, such as less than 1 .mu.m.
The beta phase island dispersion results in improved room and
elevated temperature properties.
[0012] In another aspect of the disclosure, the above-described
method based on tungsten (W) can be used with other beta
stabilizers, such as but not limited to V, Nb, Mo, and Ta. In this
embodiment, the powder size of the particular beta stabilizer is
related to the beta stabilizer's diffusivity at the sintering
temperature of Ti.
[0013] The creation of a uniform dispersion of beta phase is
dependent on, among other things, the size of the beta stabilizer
powder. In one embodiment, the beta stabilizer powder is less then
3 .mu.m, such as less than 1 .mu.m. The powder size used according
to the present disclosure is also related to the beta stabilizer's
diffusivity at the sintering temperature. In addition, the powder
size range can depend on the desired matrix microstructure (i.e.
alpha/beta or all beta), the size and number of beta phase islands
and the desired amount of partially diffused beta stabilizer
(residual undiffused particulate) with the beta phase islands, such
as at the center of the beta phase islands.
[0014] Partially dissolved particles of the beta-stabilizing
addition, such as partially dissolved particles of W, V, Nb, Mo, or
Ta, may be present within, such as at the center of, the beta phase
islands and may contribute to the strengthening mechanism.
[0015] The properties of Ti metal matrix composites containing
particulate reinforcement of titanium carbide (TiC), titanium
boride (TiB) or titanium diboride (TiB.sub.2) can also be enhanced
by W nanopowder additions or the addition of sub-sieve sized powder
of other beta stabilizers.
[0016] The accompanying micrograph that is incorporated in and
constitutes a part of this specification, illustrates one
embodiment of the invention and together with the description,
serve to explain the principles of the disclosure.
BRIEF DESCRIPTION OF THE DRAWING
[0017] FIG. 1 is a scanning electron micrograph of a
titanium-tungsten alloy according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] One aspect of the present disclosure is directed to a
composition of a titanium based alloy comprising a titanium
material and tungsten in an amount ranging from 0.5% to 40% by
weight. In one embodiment, the W powder addition used to make the
alloy has an average diameter of less then 3 .mu.m in size, such as
less than 1 .mu.m, and ranging from 8 angstroms to less then 1
.mu.m as measured by the Fisher sub-screen size method, electron
microscopy and/or photon correlation spectroscopy.
[0019] The titanium in the Ti/W alloy described herein may comprise
CP Ti powder or a Ti alloy, such as Ti-6Al-4V.
[0020] The composition may comprise an alternative or additional
slow diffusing beta stabilizer chosen from but not limited to V,
Nb, Mo, and Ta. Such stabilizers will lead to an alloy containing
dispersions of beta phase islands or an all beta structure with
dispersions of partially dissolved beta stabilizer. In one
embodiment, the beta phase islands contain undiffused particulate
beta stabilizer at the core of the islands.
[0021] As described in the prior art, "beta flecks", are generally
a form of beta phase islands that are well-known as a defect. See,
for example, "Powder Metallurgy of Titanium Alloys," by Froes and
Smugeresky, The Metallurgical Society of AIME, Warrendale, Pa.
1980; ASM Online Handbook, "Wrought Titanium and Titanium
Alloys--Wrought Titanium Processing,"; "Processing of Titanium and
Titanium Alloys--Secondary Fabrication," Y. G. Zhou, J. L. Tang, H.
Q. Yu, and W. D. Zeng, "Effects of Beta Fleck on the Properties of
Ti-10V-2Fe-3Al Alloy," Titanium 1992 Science and Technology, The
Minerals, Metals and Materials Society, Warrendale, Pa. 1992, Vol
1, pp 513-521; and http://mse-p012.eng.ohio-state.edu/fraser/ms-
e663/AlphaBeta JCW.pdf, "Properties and Applications of
.alpha.+.beta. Ti Alloys, which are all incorporated herein by
reference.
[0022] The occurrence of beta fleck defects is generally
unpredictable, and usually results in poor properties, and thus may
lead to the premature failure of a component. Contrary to the
teachings of the prior art, the present disclosure provides for the
creation of uniform dispersions of beta phase islands that can
improve the mechanical properties of Ti and its alloys. The beta
fleck defect occurs in alpha-beta and near beta alloys where
segregation of alloying elements results in localized regions
depleted in alpha stabilizers (e.g. aluminum) or with an excess of
beta stabilizers (e.g. molybdenum). These regions then transform to
the beta phase resulting in beta flecks. Contamination of powder or
castings by tramp particles of a beta stabilizer, such as W, can
also result in beta flecks.
[0023] The present disclosure teaches that controlled dispersions
of the so-called "beta fleck", herein termed "beta phase islands",
can be beneficial and improve the properties of titanium and its
alloys.
[0024] In another embodiment, the alloy has a microstructure that
comprises all-alpha phase, alpha/beta phases and all beta phase, or
all-alpha phase and alpha/beta phases comprising a dispersion of
beta phase islands. The beta phase islands optionally include
partially diffused beta stabilizer within the beta phase islands,
such as at the center of the beta phase islands.
[0025] Also described herein is a powder metallurgical method of
making the above-described composition. This method comprises:
[0026] blending a titanium material powder with a tungsten powder
to form a blended powder that comprises from 0.5% to 40% by weight
of tungsten powder having an average diameter less then 3 .mu.m in
size, such as ranging from 8 angstroms to less than 1 .mu.m, such
as ranging from 10 nm to 500 nm;
[0027] compacting the blended powder; and
[0028] sintering the compacted and blended powder, wherein
[0029] the sintered compact can then be hot isostatically pressed
if necessary.
[0030] After powder metallurgical processing as described above the
part may be further processed by techniques including, but not
limited to casting, forging, and extrusion.
[0031] In one embodiment, the alloy described herein may be used in
implantable medical devices, such as orthopedic implants, including
spinal implants, disc prostheses, nucleus prostheses, bone fixation
devices, bone plates, spinal rods, rod connectors, knees, and hip
prostheses, dental implants, implantable tubes, wires, and
electrical leads. In other embodiments, the alloy may be used in
drug delivery devices, including stents.
[0032] The alloy disclosed herein may also be formed into a
product, such as a billet for further processing. In other
embodiment, the product may be an automotive component such as
valves, conrods, and piston pins.
[0033] The product may also comprise an armored vehicle component
such as tank track center guides and undercarriage parts.
[0034] In another embodiment, the product may comprise a tool or
die material for metal casting.
[0035] The product may also be an aircraft component such as a
turbine rotor, and a leading edge of a helicopter rotor blade.
[0036] All amounts, percentages, and ranges expressed herein are
approximate.
[0037] The present invention is further illuminated by the
following non-limiting example, which is intended to be purely
exemplary of the invention.
EXAMPLE
[0038] A powder metallurgy technique was used to produce a tungsten
containing titanium alloy. Using this method, beta phase island
dispersions were created in CP Ti and in Ti-6Al-4V with 10% by
weight W. In this example, nanopowder 30 to 45 nanometers (0.003 to
0.004 .mu.m) in size with a specific surface area of between 7 to
10 m.sup.2/g was blended with CP Ti powder and processed as
described above. These W nanopowders were also blended with CP Ti
and master alloy powders to form the Ti-6Al-4V composition shown in
Table 1.
[0039] The W nanopowder was taken into solution in the Ti matrix on
sintering the compacted blend, forming an alpha/beta structure with
a uniform beta phase island dispersion.
[0040] FIG. 1 shows that the W nanopowder completely diffused to
form a beta phase island dispersion in the alpha/beta matrix. The
diffusion of the W nanopowder transformed the all alpha
microstructure typical of CP Ti to alpha/beta containing a
dispersion of beta phase islands. In this case there was no
evidence of any undissolved W.
[0041] Table 1 shows that 10% W nano-sized powder addition
substantially improved the strength of CP Ti resulting in twice the
strength of CP Ti, as well as a higher strength then Ti-6Al-4V with
roughly equivalent ductility. In the Ti-6Al-4V containing
composition, the W nanopowder addition resulted in a 30%
improvement in strength while maintaining satisfactory
ductility.
1TABLE 1 The Effect of 10% W Nano-sized Powder Addition on the
Mechanical Properties of CP Ti and Ti-6Al-4V Ultimate Tensile Yield
Reduction Material Strength Strength in Area Composition (psi)
(psi) Elongation (%) (%) Ti 75,110 59,595 24 46 Ti + 10% W 147,320
131,515 15 37 Ti-6Al-4V 137,605 124,700 14 28 Ti-6Al-4V + 10% W
178,350 171,100 9 20
[0042] Unless otherwise indicated, all numbers expressing
quantities of ingredients, reaction conditions, and so forth used
in the specification and claims are to be understood as being
modified in all instances by the term "about." Accordingly, unless
indicated to the contrary, the numerical parameters set forth in
the following specification and attached claims are approximations
that may vary depending upon the desired properties sought to be
obtained by the present invention.
[0043] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *
References