U.S. patent application number 12/169358 was filed with the patent office on 2009-06-11 for nanophase dispersion strengthened low cte alloy.
This patent application is currently assigned to United States of America as represented by the Administrator of the National Aeronautics and. Invention is credited to Timothy A. Stephenson.
Application Number | 20090148334 12/169358 |
Document ID | / |
Family ID | 40721877 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090148334 |
Kind Code |
A1 |
Stephenson; Timothy A. |
June 11, 2009 |
NANOPHASE DISPERSION STRENGTHENED LOW CTE ALLOY
Abstract
A metal matrix composite material of a low coefficient of
thermal expansion (CTE) alloy strengthened by nanophase dispersed
particles. The low CTE alloy can be an iron-nickel alloy or an
iron-nickel-cobalt alloy. The nanophase particles can be a
refractory oxide, carbide or nitride. Also disclosed is a method of
making a metal matrix composite material in which the nanophase
particles are combined with the low CTE alloy to form a metal
matrix composite material having the nanophase particles dispersed
therein.
Inventors: |
Stephenson; Timothy A.;
(Riva, MD) |
Correspondence
Address: |
NASA GODDARD SPACE FLIGHT CENTER
8800 GREENBELT ROAD, MAIL CODE 140.1
GREENBELT
MD
20771
US
|
Assignee: |
United States of America as
represented by the Administrator of the National Aeronautics
and
Washington
DC
Space Administration
|
Family ID: |
40721877 |
Appl. No.: |
12/169358 |
Filed: |
July 8, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60992403 |
Dec 5, 2007 |
|
|
|
Current U.S.
Class: |
419/10 ; 420/581;
420/590; 420/591; 420/94; 420/95 |
Current CPC
Class: |
C22C 33/0285 20130101;
C22C 33/0228 20130101; C22C 38/08 20130101; C22C 38/105 20130101;
C22C 1/1084 20130101 |
Class at
Publication: |
419/10 ; 420/581;
420/591; 420/590; 420/94; 420/95 |
International
Class: |
B22F 3/12 20060101
B22F003/12; C22C 32/00 20060101 C22C032/00; C22C 30/00 20060101
C22C030/00; C22C 38/30 20060101 C22C038/30; C22C 38/08 20060101
C22C038/08; C22C 1/00 20060101 C22C001/00 |
Claims
1. A metal matrix composite material comprising a low coefficient
of thermal expansion (CTE) alloy strengthened by nanophase
dispersed particles.
2. The metal matrix composite material according to claim 1,
wherein said allow alloy is selected from the group consisting of
iron-nickel and iron-nickel-cobalt alloys strengthened by nanophase
dispersed particles.
3. The metal matrix composite material of claim 2 wherein the low
CTE iron-nickel alloy comprises 36 weight percent nickel, remainder
iron.
4. The metal matrix composite material of claim 2 wherein the low
CTE iron-nickel-cobalt alloys are selected from the group
consisting of a 32 weight percent nickel, 5 weight percent cobalt,
remainder iron alloy and a 26 weight percent nickel, 17 weight
percent cobalt, remainder iron alloy.
5. The metal matrix composite of claim 2 wherein the nanophase
dispersed particles comprise about 10 to 45 volume percent of the
metal matrix composite, wherein the remainder of the metal matrix
composite is the low CTE alloy.
6. The metal matrix composite of claim 2 wherein the nanophase
dispersed particles comprise about 30 volume percent of the metal
matrix composite, wherein the remainder of the metal matrix
composite is the low CTE alloy.
7. The metal matrix composite of claim 2 wherein the nanophase
dispersed particles have a grain size distribution of about 10 nm
to 200 nm with the majority of the nanophase particles having a
grain size less than about 100 nm.
8. The metal matrix composite of claim 2 wherein the nanophase
dispersed particles are selected from the group consisting of
refractory oxides, carbides and nitrides.
9. The metal matrix composite of claim 8 wherein the refractory
oxide is selected from the group consisting of Al.sub.2O.sub.3,
TiO.sub.2, Y.sub.2O.sub.3, HfO.sub.2, ZrO.sub.2, SiO.sub.2,
Ta.sub.2O.sub.5, and ZrSiO.sub.4.
10. The metal matrix composite of claim 8 wherein the nitride is
selected from the group consisting of TaN, TiN, ZrN, AlN,
Si.sub.3N.sub.4, VN, CrN, NbN, and HfN.
11. The metal matrix composite of claim 8 wherein the carbide is
devoid of free carbon and is selected from the group consisting of
TiC, ZrC, HfC, VC, NbC, TaC, Cr.sub.3C.sub.2, MO.sub.2C, WC, and
SiC.
12. A method of making a metal matrix composite material, the
method comprising the steps of: forming nanophase particles;
combining the nanophase particles with a low coefficient of thermal
expansion (CTE) alloy to form a metal matrix composite material
having the nanophase particles dispersed therein.
13. The method of claim 12 wherein the nanophase particles are
selected from the group consisting of refractory oxides, carbides
and nitrides and the low CTE alloy is selected from the group
consisting of iron-nickel and iron-nickel-cobalt alloys.
14. The method of claim 12 wherein the step of combining comprises
mixing powders of the nanophase particles with powders of the low
CTE alloy to form a compact and then heating to a temperature
sufficient to cause sintering of the low CTE alloy.
15. The method of claim 12 wherein the step of combining comprises
mechanical alloying.
16. The method of claim 12 wherein the step of combining includes
forming a porous compact of the nanophase particles and then
infiltrating the compact with a liquefied low CTE alloy.
17. The method of claim 12 wherein the nanophase particles comprise
about 10 to 45 volume percent of the metal matrix composite,
wherein the remainder of the metal matrix composite is the low CTE
alloy.
18. The method of claim 12 wherein the nanophase particles comprise
about 30 volume percent of the metal matrix composite, wherein the
remainder of the metal matrix composite is the low CTE alloy.
19. The method of claim 13 wherein the refractory oxide is selected
from the group consisting of Al.sub.2O.sub.3, TiO.sub.2,
Y.sub.2O.sub.3, HfO.sub.2, ZrO.sub.2, SiO.sub.2, Ta.sub.2O.sub.5,
and ZrSiO.sub.4.
20. The method of claim 13 wherein the nitride is selected from the
group consisting of TaN, TiN, ZrN, AlN, Si.sub.3N.sub.4, VN, CrN,
NbN, and HfN.
21. The method of claim 13 wherein the carbide is devoid of free
carbon and is selected from the group consisting of TiC, ZrC, HfC,
VC, NbC, TaC, Cr.sub.3C.sub.2, Mo.sub.2C, WC, and SiC.
22. The method of claim 12 wherein the nanophase particles have a
grain size distribution of about 10 nm to 200 nm with the majority
of nanophase particles having a grain size less than about 100
nm.
23. A method of making a metal matrix composite material of low
coefficient of thermal expansion comprising the steps of: a)
providing an iron-nickel alloy powder metal material of a low
coefficient of thermal expansion; b) providing refractory nanophase
particles having a standard molar enthalpy of formation less than
-300 kJ mol.sup.-1; c) mixing said iron nickel allow and said
refractory nanophase particles to yield a substantially uniform
mixture wherein said refractory nanophase particles amount to
10-45% of said mixture by volume; d) forming said mixture into a
compact; and e) then heating said mixture to a temperature
sufficient to cause sintering of said iron-nickel alloy.
24. The method of making a metal matrix composite material
according to claim 23, wherein said iron-nickel alloy is 36 weight
percent nickel and 64 weight percent iron.
25. The method of making a metal matrix composite material
according to claim 23, wherein said step of heating includes
sintering said mixture in one of a vacuum and a inert atmosphere
and causing densification of the mixture into said metal matrix
composite material.
26. The method of making a metal matrix composite material
according to claim 23, wherein said steps further comprising
consolidated said mixture by one of hot isostatic pressing or
extrusion.
27. The method of making a metal matrix composite material
according to claim 23, wherein said refractory nanophase particles
constitute about 30% of said mixture by volume.
28. A metal matrix composite material having of low coefficient of
thermal expansion comprising: an iron nickel alloy having a low
coefficient of thermal expansion; and refractory nanophase
particles having a standard molar enthalpy of formation less than
-300 kJ mol.sup.-1 dispersed substantially uniformly within said
iron nickel alloy, wherein said refractory nanophase particles
constitute between 10-45% by volume of said metal matrix composite
material.
29. The metal matrix composite material according to claim 28,
wherein said iron-nickel alloy is 36 weight percent nickel and 64
weight percent iron.
30. The metal matrix composite material according to claim 29,
wherein said refractory nanophase particles constitute about 30% of
said mixture by volume.
31. The metal matrix composite material according to claim 28,
wherein said refractory nanophase particles constitute about 30% of
said mixture by volume.
32. The metal matrix composite according to claim 28 wherein said
metal matrix composite has
33. The metal matrix composite according to claim 28, wherein said
nanophase particles have a grain size distribution in a range
between 10-200 nanometers (nm).
34. The metal matrix composite according to claim 30, wherein said
nanophase particles have a grain size distribution in a range
between 10-200 nanometers (nm).
36. The metal matrix composite according to claim 28, wherein said
metal matrix composite has a secant coefficient of thermal
expansion less than or equal to 1.5 ppm/K over the temperature
range between 4K to 330K.
37. The metal matrix composite according to claim 28, wherein said
metal matrix composite has a secant coefficient of thermal
expansion less than or equal to 1.5 ppm/K over the temperature
range between 4K to 330K and said nanophase particles have a grain
size distribution in a range between 10-100 nanometers (nm).
38. The metal matrix composite according to claim 34, wherein said
metal matrix composite has a secant coefficient of thermal
expansion less than or equal to 1.5 ppm/K over the temperature
range between 4K to 330K.
Description
RELATED APPLICATION
[0001] This application is based upon prior filed provisional
patent applications Ser. No. 60/992,403 filed Dec. 5, 2007, and
61/013,340 filed Dec. 13, 2007, the entire subject matter of which
are incorporated by reference herein.
ORIGIN OF INVENTION
[0002] The invention described herein was made by an employee of
the United States Government, and may be manufactured and used by
or for the Government for governmental purposes without the payment
of any royalties thereon or therefor.
BACKGROUND OF THE INVENTION
[0003] Structural materials with low coefficients of thermal
expansion (CTE) find wide application in space structures that
require high pointing accuracy and dimensional stability in the
presence of dynamic thermal disturbances. Historically, Invar 36
(36 weight percent nickel, 64 weight percent iron) has been the
material of choice, notwithstanding its low strength, low specific
stiffness and high density. These limitations of low strength, low
specific stiffness and high density were highlighted most recently
in trade studies concerning its use in the James Webb Space
Telescope Integrated Science Instrument Module (JWST ISIM) and
mirror back plane.
BRIEF SUMMARY OF THE INVENTION
[0004] The advantages of the invention have been achieved by
providing, according to a first aspect of the invention, a metal
matrix composite material comprising a low coefficient of thermal
expansion (CTE) alloy strengthened by nanophase dispersed
particles.
[0005] According to a second aspect of the invention, there is
provided a metal matrix composite material comprising a low
coefficient of thermal expansion (CTE) alloy selected from the
group consisting of iron-nickel and iron-nickel-cobalt alloys
strengthened by nanophase dispersed particles.
[0006] According to a third aspect of the invention, there is
provided a method of making a metal matrix composite material, the
method comprising the steps of:
[0007] forming nanophase particles;
[0008] combining the nanophase particles with a low coefficient of
thermal expansion (CTE) alloy to form a metal matrix composite
material having the nanophase particles dispersed therein.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The present invention relates to a metal matrix composite
material which includes a low CTE alloy strengthened by nanophase
particles dispersed within the metal matrix composite material. It
is believed that a number of suitable low CTE alloys would benefit
from
[0010] The present inventor believes that low CTE alloys,
particularly the iron--36 weight percent nickel alloy (Invar 36)
can be strengthened with a high volume fraction of small, finely
dispersed, inert, non-deformable particles and still maintain a
secant coefficient of thermal expansion (also called an average
coefficient of thermal expansion) less than or equal to 1.5 ppm/K
over the temperature range 4K to 330K.
[0011] The nanophase particles could comprise about 10 to 45 volume
percent of the metal matrix composite material but most preferably
is about 30 volume percent. The nanophase particles should be inert
meaning they do not dissolve into the metal matrix as an atomic
scale solute that would degrade thermal expansion properties.
Moreover, the nanophase particles should be refractory with a
standard molar enthalpy of formation less than -300 kJ mol.sup.-1
so that the atoms within the nanophase particles are bound tightly
together and are therefore not easily deformed or cut by a passing
dislocation.
[0012] The present invention addresses the shortcomings of the
prior art by introducing an inert nanophase dispersion into the low
CTE alloy, preferably the iron--36 weight percent nickel alloy
(Invar 36), matrix forming an ex situ composite resulting in a
lower density, higher strength metal matrix composite material with
higher specific stiffness. The ex situ composite refers to being
added to the metal matrix from outside as compared to an in situ
composite formed by adding solutes that then nucleate and grow in a
precipitation reaction within the metal matrix. The dispersion of
inert nanophase particles will reinforce the metal matrix through
Orowan strengthening which is a strengthening mechanism resulting
from dispersion hardening. Importantly, there will also be a
substantial increase in the microyield with this metal matrix
composite. A Hall-Petch effect will contribute to this as well as
the Orowan Strengthening. The Hall-Petch effect predicts that as
the grain size decreases the yield strength increases.
[0013] The nanophase particles should have a grain size
distribution of between 10 nanometers (nm) and 200 nm but generally
less than about 100 nm. Any aggregates or agglomerations of
nanophase particles should be less than about 200 nm. The thrust of
the present invention is based on the increase in shear stress
required to force a dislocation through a field of non-deformable
particles. Based on the theoretical description as described by
Orowan, the increase in shear stress is directly proportional to
the square root of the volume fraction of particles and inversely
proportional to the particle diameter. So it would be desirable to
have a high volume fraction of small particles. Regarding the size
of the nanophase particles, it should be noted that whatever
technology is used to produce the nanophase particles, there will
most likely be a size distribution of the nanophase particles.
Further, with respect to the nanophase particles in the metal
matrix, there will be a point where the nanophase particles can be
too small and the dislocations can cut through them resulting in a
reduction in strength. What is too small a size of nanophase
particle will depend on the chemistry of the nanophase particle.
However, it is believed that the size distribution above should be
sufficient for the present invention.
[0014] As noted above, the nanophase particles should be inert. The
nanophase particles, besides being inert, may be made from any
material that can be formed to a grainsize of about 100 nm or less
and that will contribute to Orowan strengthening of the metal
matrix composite. Thus, the nanophase particles may be refractory
oxides, carbides, nitrides or mixtures thereof.
[0015] Suitable oxides could include, for example, Al.sub.2O.sub.3,
TiO.sub.2, Y.sub.2O.sub.3, HfO.sub.2, ZrO.sub.2, SiO.sub.2,
Ta.sub.2O.sub.5 and ZrSiO.sub.4 while suitable nitrides could
include, for example, TaN, TiN, ZrN, AlN, Si.sub.3N.sub.4, VN, CrN,
NbN, and HfN. If carbides are to be used as the nanophase
particles, it is necessary that they contain no free carbon which
could react with the low CTE alloy matrix to adversely affect the
low expansion properties of the low CTE alloy. Suitable carbides
could include, for example, TiC, ZrC, HfC, VC, NbC, TaC,
Cr.sub.3C.sub.2, Mo.sub.2C, WC, and SiC.
[0016] The metal matrix composite material will be made by a
process in which the nanophase particles will be synthesized
separately as a powder or as a ceramic preform by conventional
processes that are then combined with (i.e., introduced into the
matrix of) the low CTE alloy, preferably the iron-36 weight percent
nickel alloy (Invar 36) during a secondary process such as powder
metallurgy, mechanical alloying or liquid metal infiltration.
[0017] The powder metallurgy process includes mixing powders of the
nanophase particles with powders of the low CTE alloy to form a
compact and then heating to a temperature sufficient to cause
sintering of the low CTE alloy. As an example, if 30 volume percent
of Al.sub.2O.sub.3 were to be added to the iron--36 weight percent
nickel alloy (Invar 36), the mixture could be solid state sintered
for about 48 hours at 1350.degree. C. in a vacuum or inert
atmosphere to cause densification of the mixture into a metal
matrix composite material.
[0018] The mechanical alloying process includes adding a mixture of
master alloy powder or pre-proportioned metal powders together with
nonmetal nanophase powder for the target composition to a
high-energy ball mill for working. The nanophase particles endure
mixing through severe plastic deformation in an inert atmosphere.
The resulting mixture is consolidated by hot isostatic pressing or
extrusion. Depending on the desired product, the billet can then be
thermomechanically processed through a descending temperature range
by press-forging to final size. A billet can also be rolled to
plate or bar, or drawn to wire.
[0019] The liquid metal infiltration process includes forming a
porous compact of the nanophase particles and then infiltrating the
compact with a liquefied low CTE alloy, preferably the iron--36
weight percent nickel alloy (Invar 36). As an example, a porous
compact of Y2O3 could be formed and then the iron--36 weight
percent nickel alloy (Invar 36) could be melted at 1500.degree. C.
and poured into the porous compact to fill the pores. Similarly,
vacuum displacement could be applied to pull the liquid alloy into
the pores of the compact. The resulting metal matrix composite
material would be approximately 30 volume percent nanophase
particles dispersed in a metal matrix of the iron--36 weight
percent nickel alloy (Invar 36).
[0020] A number of companies can provide the nanophase reinforcing
powder as well as either the high purity iron and nickel powder or
the high purity alloy powder. The nanophase reinforcement as a
ceramic preform for liquid metal infiltration is also available
commercially. In this instance, the metal for infiltration could be
produced by melting high purity iron and nickel or, for quicker
turn around, obtained commercially under conventional alloy
designated by UNS No. K93603.
[0021] The above described method differs from previous attempts to
make a low CTE alloy that has high strength, low CTE and
microstructural stability in four important ways. First, commercial
attempts to form an in situ composite by introducing solutes that
later react and precipitate through heat treatment have met with
limited success because the iron-nickel matrix always has a finite
solubility for ad-elements and because of the extreme sensitivity
of the thermal expansion properties on the presence of unreacted
elements that remain in solution. Examples include (a) the addition
of Ti and C into the low-expansion iron-nickel alloy family to
produce titanium carbide, (b) the addition of W, Cr, and C as for
example with Elinvar to precipitate tungsten and chromium carbides,
or (c) the addition of Ti and Nb as in NILO alloy 365 to
precipitate gama prime. Secondly, alloying iron and nickel with
cobalt, as with Kovar, Super Invar 32-5 and Pernifer 29-18, produce
a low CTE over limited temperature ranges but are microstructurally
unstable at cryogenic temperatures. Third, the proposed process
preferably uses high purity iron and nickel starting materials that
will ensure optimum thermal expansion properties by minimizing the
presence of tramp impurities. Fourth, the composition of the
dispersed phase will be chosen to minimize thermal expansion
mismatch between the low CTE alloy matrix, and the iron--36 weight
percent nickel alloy (Invar 36) matrix in particular, and the
individual nanophase particle thus minimizing thermal stresses in
the matrix over a wide range of temperature change.
[0022] It will be apparent to those skilled in the art having
regard to this disclosure that other modifications of this
invention beyond those embodiments specifically described here may
be made without departing from the spirit of the invention.
Accordingly, such modifications are considered within the scope of
the invention as limited solely by the appended claims.
* * * * *