U.S. patent application number 10/909061 was filed with the patent office on 2005-04-21 for titanium group powder metallurgy.
Invention is credited to Myrick, James J..
Application Number | 20050084407 10/909061 |
Document ID | / |
Family ID | 34526267 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050084407 |
Kind Code |
A1 |
Myrick, James J. |
April 21, 2005 |
Titanium group powder metallurgy
Abstract
Methods and compositions relating to powder metallurgy in which
an amorphous-titanium-based metal glass alloy is compressed above
its glass transition temperature Tg with a titanium alloy powder
which is a solid at the compression temperature, to produce a
compact with a relative density of at least 98%.
Inventors: |
Myrick, James J.; (Glencoe,
IL) |
Correspondence
Address: |
James J. Myrick
748 Greenwood Avenue
Glencoe
IL
60022
US
|
Family ID: |
34526267 |
Appl. No.: |
10/909061 |
Filed: |
July 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60493176 |
Aug 7, 2003 |
|
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Current U.S.
Class: |
419/66 |
Current CPC
Class: |
B22F 1/0003 20130101;
B22F 2999/00 20130101; B22F 2999/00 20130101; B22F 1/0003 20130101;
B22F 9/002 20130101 |
Class at
Publication: |
419/066 |
International
Class: |
B22F 003/02 |
Claims
What is claimed:
1. A powder manufacturing method for manufacturing an titanium
group alloy product comprising the steps of blending from about 1
to about 25 volume percent of an amorphous metal powder having a
glass transition temperature Tg, with from about 75 to about 99
volume percent of an titanium group metal powder, and compressing
the blend at a temperature of at least Tg to produce a metal
component having a density of at least 98% with about 2 percent or
less porosity.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of the filing date of
U.S. Provisional Application No. 60/493,176 filed Aug. 7, 2003.
FIELD OF THE INVENTION
[0002] The present invention is directed to powder metallurgy, and
more particularly, to high performance powder metallurgy for
titanium group metal alloys.
BACKGROUND OF THE INVENTION
[0003] Titanium, zirconium and hafnium (Titanium Group) alloys have
high utility, but are relatively difficult to fabricate because of
their susceptibility to oxidation and reaction with other materials
at their high melting and forging temperatures.
[0004] Because of its relatively high temperature capability and
high strength to weight ratio, titanium and its alloys are
desirable for a variety of aerospace, industrial, marine, military
and commercial applications where weight and/or high temperature
performance are important, such as fan blades, compressor blades,
discs, hubs and other components of turbine engines, automotive
vehicle components such as engine valves, rocker arms, connecting
rods and frames and sporting equipment. Because of its
biocompatibility, corrosion resistance, titanium and its alloys are
also used for chemical processing, desalination, power generation
equipment, valve and pump parts, marine hardware, and prosthetic
devices, implants, surgical devices and pacemaker cases. Because of
its corrosion resistance, titanium is used for marine ball valves,
fire pumps, heat exchangers, castings, hulks, water jet propulsion
systems, shipboard cooling and piping systems. Titanium valve train
components can substantially improve fuel efficiency because of
their lightweight and high temperature operation.
[0005] Titanium alloys continue to be widely used in military and
NASA space applications. In addition to manned space craft,
titanium alloys are extensively employed in solid missile and
rocket cases, and guidance control pressure vessels. Zirconium
alloys are used in medical, chemical and nuclear reactor
applications, while hafnium alloys find use in nuclear absorber
components and rocket motors.
[0006] Titanium alloys which are reinforced with fibers or
filaments such as high strength SiC filaments, are important
materials. These fiber reinforced materials, such as titanium metal
matrix composites, are conventionally produced by powder metallurgy
and related technology in which the high strength, high modulus
filaments are aligned and compacted at elevated temperatures with
titanium alloy powders to form a dense metal matrix surrounding the
SiC filaments. The preparation of titanium alloy base foils and
sheets and of reinforced structures in which silicon carbide fibers
are embedded in a titanium base alloy are described for example, in
U.S. Pat. Nos. 4,775,547; 4,782,884; 4,786,566; 4,805,294;
4,805,833; 4,838,337; 5,939,313; 6,190,133 and 6,122,884.
[0007] Powder metallurgy is an important technology in which metal
powders are formed and sintered to produce consolidated articles of
manufacture. Powder metallurgy techniques include relatively simple
procedures such as uniaxial powder compression in a mold followed
by sintering at an elevated temperature somewhat below the melting
point of the metal powder, as well as more complicated and
expensive techniques such as hot isostatic pressing (HIPing) and
metal injection molding (MIM). Titanium group metals are typically
sintered under vacuum, or in inert or reducing gas atmosphere such
as argon or hydrogen. Benefits of powder metallurgy fabrication can
include near net shape manufacture, and control of crystal
morphology. However, it is difficult to economically eliminate
porosity and achieve full density using strong titanium group
metals, because their relatively high temperature performance and
high yield strength, which are desirable in the final products,
make compaction difficult during manufacture. The relative density
(D, in percent of full density) of a metal powder compacted during
hot isostatic pressing by plastic yielding may be approximated by
D=100[1-e.sup.(-3P/2Y)] where P is the consolidation pressure (in
MPa) and Y is the yield strength (in MPa) of the alloy at the
compression temperature [A. S. Helle, et al, Acta Metall. 33, 2163
(1985)]. For example, a titanium alloy powder having a nominal
yield strength of just 300 MPa at the compacting temperature, and a
practical maximum compression pressure of 750 MPa, the density of
the compact is only about 98 percent, with about 2 percent
remaining porosity in the finished product. Similarly, in metal
injection molding (MIM) processes, powdered steel alloy powders may
be mixed with a flowable thermoplastic organopolymer or other
viscous binder to form a homogeneous, highly loaded mixture having,
for example, approximately 60% volume metal powder and 40% volume
of the flowable binder. The highly-solids-loaded mixture may be
injection molded using conventional plastic injection molding
systems, to produce molded "green" parts of considerable geometric
complexity, which are highly filled with the titanium group metal
alloy powder. The thermoplastic resin or other binder is
subsequently thermally vaporized from the molded green parts in a
debinding step, to leave a shaped metal part having high porosity.
The porous, formed part may be subsequently sintered in an inert
gas atmosphere, which densifies the part isotropically, while
retaining the complex shape of the original molded part to
relatively close tolerances. However, the finished, sintered parts
retain considerable porosity, and carbide components from the
thermoplastic binder.
[0008] Titanium forms a variety of refractory ceramic materials
such as TiB.sub.2 and TiC and TiSi with small metalloid elements C,
B and Si, and also forms relatively stable intermetallic compounds
with metals including aluminum, nickel, cobalt and iron.
Intermetallic compounds have a variety of attractive properties for
high-temperature use, but have limited room-temperature ductility.
Significant effort has been directed to the improvement of the
ductility of titanium-aluminum intermetallic compounds. One
approach which may provide increased ductility is reduction of
grain size through compaction of controlled crystalline powder
structures. Unfortunately, properties of consolidated powders may
be affected by the conventional compaction methods such as
hot-pressing because the prolonged heating can lead to coarsening
of the microstructure. Efforts to avoid prolonged heating include
explosive compaction in which a high-amplitude explosive stress
wave compacts the titanium alloy powder. [E. Szewczak et al,
"explosive consolidation of mechanically alloyed Ti--Al alloys",
materials science and engineering A226-228, pp 115-118 (1997)].
[0009] PM product density can be increased by use of high
compression and sintering temperatures. However, properties of
consolidated metal alloy powders may also be adversely affected
because prolonged and/or high-temperature heating may lead to
coarsening of the microstructure, and/or undesired reaction with
reinforcing fibers or filaments.
DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic cross sectional illustration of a
low-temperature, low-pressure titanium alloy process in accordance
with the present invention, utilizing a blend of a major amount of
a crystalline titanium group metal powder, with a minor amount of a
BMG alloy powder, prior to consolidation; and
[0011] FIG. 2 is schematic view of a process for forming a
net-shape or net net-shape titanium alloy article of manufacture
such as a gear, in accordance with an embodiment of the present
invention.
SUMMARY OF THE INVENTION
[0012] The present invention is directed to methods for
manufacturing titanium group powder metallurgy (PM) products, and
to new titanium group PM products.
[0013] In accordance with such methods, a relatively small amount
of an amorphous metal alloy powder having a glass transition
temperature at a temperature Tg and supercooled liquid state at a
temperature at or above its glass transition temperature, is
blended with or coated on a major amount of a titanium group metal
alloy powder. The powder blend is compressed at a temperature
substantially below the melting point and within the supercooled
liquid range of the amorphous alloy, to decrease the porosity of
the blend and increase the total surface area of the amorphous
powder. In this regard, the porosity of the mixture is preferably
decreased to less than about 3 volume percent by compaction or
other compression. When using an independent BMG amorphous metal
powder (e.g., not a uniform amorphous metal glass coating on
crystalline metal particles, the surface area of the amorphous
metal alloy is preferably increased by at least 50 percent, and
more preferably at least 100 percent during the compression step.
The blend may also contain reinforcing powders or fibers such as B,
C, Al.sub.2O.sub.3, SiC, SiCN, TiC powders, filaments or fibers,
which will be incorporated in the finished PM products. Desirably,
the titanium group powders and amorphous metal powders should have
a particle size of less than about 300 microns, preferably with a
range of particle sizes to facilitate packing. For some blends, it
is desirable that the mean particle size of the amorphous metal
component be less than half that of the titanium group metal
particles, to facilitate more uniform dispersion in the interstices
of the titanium group particles. The titanium group and amorphous
powder components may, respectively, be produced in any suitable
manner, such as by inert gas atomization, or centrifugal
atomization of a molten metal stream, mechanical grinding or
milling, chemical reaction, precipitation from the vapor phase,
and/or electrolytic or electrodes deposition aqueous from or
non-aqueous electrolytes.
[0014] Various preferred production methods of the present
disclosure comprise blending from about 2 to about 30 volume
percent, and more preferably from about 5 to about 25 volume
percent, of amorphous metal alloy powder having a glass transition
temperature below its crystallization temperature such that it has
a supercooled liquid region, with from about 70 volume percent to
about 98 volume percent, and more preferably from about 25 to about
95 volume percent, of a titanium group metal powder which does not
have a supercooled liquid region (e.g., a conventional crystalline
titanium or titanium group allow powder), based on the total volume
(excluding voids) of the titanium group metal powder and the
amorphous metal powder. The metal powder mixture is preferably
blended to form a substantially homogenous mixture. The resulting
blended metal powder mixture is formed and preferably compacted at
a temperature in the supercooled liquid temperature range of
amorphous metal powder, to produce a metal compact having a
relative density of at least 98 percent, more desirably at least 99
percent, and most preferably substantially 100 percent
(substantially fully dense). The powder mixture may be first
compacted or otherwise compressed at a temperature below the glass
transition temperature of the amorphous metal alloy component(s),
which may also provide shear deformation at particle interfaces.
This deformation produces new material surfaces, without surface
oxidation or other passivation, which more readily bond to adjacent
particles. Below Tg, the amorphous alloy may be typically stronger
than the crystalline titanium group alloy powder, in which case
shear deformation below Tg will largely occur at the crystalline
titanium group powder surfaces, and even the reinforcement fiber
surfaces.
[0015] The blend is subsequently compressed to high relative
density at a temperature in the supercooled liquid temperature
range at which the amorphous metal alloy powder is a viscous
liquid, rather than a metal melt. This compression produces viscous
flow of the amorphous metal glass, forcing it into the interstices
of the titanium group metal particles, substantially increasing the
total surface area of the amorphous metal component and desirably
forming it into an at least partially interconnected matrix at
least partially enclosing the titanium group metal particles.
[0016] This substantial increase in surface area, and decrease in
the median thickness of the amorphous metal component facilitates
reactive diffusion with the titanium group metal component at
elevated temperature, if desired, to form new alloy(s) having
higher melting points than the amorphous metal component, which has
a relatively low melting point.
[0017] As indicated, the powder mixture comprises a major volume
fraction V of titanium group metal powder and any filler or
reinforcing agent powders, fibers or filaments, and a minor volume
fraction v of the BMG amorphous metal powder or coating component.
The compressive pressure applied to compact the mixed powder will
desirably be at least that necessary to compact the titanium group
metal powder and the filler or reinforcing component(s) (if any) to
a relative density R of at least 97-100 v, and more preferably at
least 98-100 v. This compression pressure Pc may be approximated by
Pc=-2Y{ln(1-R)/3} where Pc is the minimum compression pressure at
the supercooled liquid temperature, Y is the yield strength of the
titanium group metal powder at the compression temperature, and R
is the relative density of the titanium group metal powder (in the
absence of the BMG amorphous alloy component).
[0018] For example, an titanium group metal powder having a yield
strength of 400 MPa at 700.degree. K. would itself (without the
presence of a BMG amorphous metal component) be compressed to a
relative density R, of 0.9 of full density, by a compression
pressure Pc of approximately -2.times.400 (ln(1-0.9)/3 or
approximately Pc=615 MPa. To compress the titanium group metal
powder itself (without a BMG amorphous metal component) to a
relative density of 0.98, leaving 2 percent porosity, would require
over 1 Gpa (over 100,000 psi) which is difficult and expensive to
provide in an economical production process under vacuum or inert
atmosphere.
[0019] A mixture of 87 volume percent of this titanium group metal
powder, and 13 volume percent of a BMG amorphous metal powder (or a
BMG coating on a crystalline titanium alloy powder) with a glass
transition at a temperature of 650.degree. K. and a supercooled
viscous glass liquid region of 100.degree. (Tx=750.degree. K.)
could accordingly be compressed at 700.degree. C using a
compression pressure Pc of about 615 MPa, to produce a compact
product having a relative density of 0.97 or higher.
[0020] The compacted PM product may be cooled to provide a dense
metal compact in which the crystalline titanium group metal
particles are embedded in an amorphous metal matrix which has
substantially increased in total surface area to fill zones between
the titanium group powders. The compacted PM product may also be
heated to a temperature above the crystallization temperature of
the amorphous metal continuous phase. In this manner, the iron
metal group particles are embedded in a fully or partially
crystalline continuous phase which is still substantially distinct
from the titanium group metal particles. This can be advantageous
for certain BMG alloys which form a strong, partially or fully
crystalline alloy upon heating to an initial crystallization
temperature Tx or above. The compact may then be heated to a
temperature above the crystallization temperature of the amorphous
metal, to nanocrystallize the amorphous component. There is very
little shrinkage, if any, because the metal glass is already close
to crystal density. The crystallization can also initiate from the
crystalline metal particles, to get a good boundary.
[0021] Such PM products with discrete titanium group powder zones
(even though compressed or distorted) and BMG alloy composition
zones, may not have optimum heat resistance under stress, however,
because the at least partially discrete continuous amorphous phase
may remain as a eutectic or near-eutectic material with a
relatively low melting point, Tm. In order to provide a finished PM
product with increased heat resistance, the compacted product may
also be further heated to a sintering temperature at which the
titanium group alloy particles and the relatively continuous matrix
phase diffuse together to form a new composition having a higher
melt temperature than the original SLM amorphous alloy.
[0022] After diffusion of the original crystalline metal powder
components with the original amorphous metal components, the
composite does not "remelt" at the relatively low melting
temperature Tm of the bulk metal glass component, because the
different effective composition of the reacted compact has a higher
melting point than the original BMG.
[0023] While some amorphous metals fully or partially crystallize
over a limited period of time at temperatures coextensive with or
only slightly above their effective glass transition temperature, a
wide variety of amorphous metal compositions are relatively stable
at temperatures at or slightly above their glass transition
temperature, Tg, and do not initiate substantial crystallization
unless raised to a crystallization temperature, Tx, which may be 10
to 100 or more degrees Celsius higher than Tg. By "bulk metal
glass" (BMG) is meant an amorphous metal alloy composition having a
glass transition temperature, Tg, at which it exhibits a
supercooled liquid phase for at least one second, and preferably at
least 30 seconds.
[0024] The glass transition temperature Tg (if any) and the
crystallization temperature(s) Tx of an amorphous alloy are
typically determined by differential scanning calorimetry, in which
the temperature of a sample is slowly raised, and correlated, as a
function of temperature, with the amount of energy necessary to
raise the temperature. The glass transition phase change is
typically an endothermic process, while crystallization is
typically an exothermic process involving slight volume increase.
Many, if not most, amorphous metal compositions do not have a glass
transition temperature, but instead crystallize at one or more
elevated temperatures without going through a distinct viscous
glass transition phase. An amorphous metal composition may have a
number of distinct crystallization temperatures Tx(1), Tx(2) . . .
at which various components crystallize or recrystallize from
components crystallized in a less stable or metastable crystalline
phase at a lower crystallization temperature. As will be discussed,
a variety of amorphous metal alloys have a distinct glass
transition Tg, at which they undergo a slight volume expansion upon
phase transition to a viscous glass state, and undergo partial
crystallization, typically forming nanoscale crystallites in an
amorphous matrix which remains in a viscous glassy state. These
partially-nano-crystalline bulk metal glasses retain a viscous
glassy matrix above Tg, and are useful in the present methods and
are considered to have a supercooled liquid temperature region in
which they form a viscous glass, albeit one with nanoscale
crystallites at high temperatures, still below their metal
temperature Tm, they will fully crystallize and lose their viscous,
supercooled glass condition.
[0025] The determination of glass transition temperature and
crystalline temperature(s) is typically a function of the rate at
which the temperature of the metal glass foam is increased. For
purposes of this disclosure, a rate of temperature increase of 0.25
degrees Celsius per second may be used to determine Tg, although
other rates are used in determining reported Tg and Tx values
herein.
[0026] Bulk metal glasses (BMGs) used herein preferably have a
crystallization temperature, Tx, which is at least 20.degree. C.
and more preferably at least 40.degree. C. higher than the glass
transition temperature, Tg, of the bulk metal glass.
[0027] Amorphous metal alloys may be produced by rapidly cooling
appropriate alloy compositions from their homogeneous melts. The
temperature Tm at which an amorphous metal alloy fully melts, is
generally significantly higher than the crystallization
temperature(s) Tx, which in turn is higher than the glass
transition temperature Tg (if any), of the alloy. Accordingly, a
"typical" BMG may be heated from ambient temperature to its glass
transition Tg (e.g., about 300.degree. C.) at which is undergoes a
phase change to a viscous supercooled liquid phase and undergoes a
small volume expansion. Further heating produces a reduction of
viscosity in the supercooled liquid until the crystallization
temperature(s) Tx is (are) reached (e.g., 400.degree. C.) at which
crystalline phases nucleate and grow. There may be a number of
crystallization temperatures Tx, at which different crystal phases
and compositions are formed. If the BMG is heated above its Tg but
below Tx, it may be cooled below its Tg and retain its glassy
state. However, if such a BMG is raised to its crystallization
temperature(s), Tx (Tx.sub.1, Tx.sub.2, etc.) it remains partially
or fully crystallized when cooled, unless it is fully remelted at a
much higher temperature (e.g., 1500.degree. C.) and then rapidly
cooled below its Tg. As indicated, some BMG alloys initially
partially crystallize while retaining their viscous glass
properties in their supercooled liquid region, and accordingly are
useful as BMG powders and coatings in the present methods and
products.
[0028] Amorphous metal alloys may have exceptionally high impact
resistance and strength, which are important qualities for various
metal products and components. For example, Bulk Metal Glasses
(BMGs) based on Fe, Zr, Ti, Cu, Mg and/or Al metal systems can
exhibit unique combinations of high hardness, strength, toughness
and corrosion resistance, which are ideal for cellular foam
materials. BMG alloys such as Fe--(Zr,Ti,Ni,Co,Mo)--(B,C,Si,P);
Zr--Ni--Al--Cu; and Zr--Ti--Cu--Ni--(Si,Be) exhibit very good bulk
glass-forming ability with high thermal stability in the
supercooled glass state, and low critical cooling rates. [See,
e.g., A. Inoue, et al., Mater. Trans. JIM, 31 (1991), p. 425; T.
Zhang, et al., Mater. Trans. JIM, 32 (1991), p. 1005; A. Inoue et
al., Mater. Trans. JIM, 32 (1991), p. 609; A. Peker, et al., Appl.
Phys. Lett., 63 (1993), p. 2342.
[0029] The toughness of amorphous metals, including bulk metal
glasses (BMGs) can increase with increasing impact or shear rates,
to relatively high levels, which would be an important
characteristic for metal foams designed for energy absorption. The
more stable BMG alloys typically form dense, deep eutectic liquids
with relatively small free volume, and relatively high melt
viscosity, above their glass transition temperature, Tg. They
typically comprise three, and preferably four or more components
having negative heats of mixing and at least 12% difference in
atomic size, in proportions which permit high packing density and
short-range order. Being energetically close to the crystalline
state in this manner, can provide slow crystallization kinetics,
with high viscosity and high glass forming ability. R. Busch, "The
Thermophysical Properties of Bulk Metallic Glass-Forming Liquids",
JOM, 52:7 (2000), pp. 39-42. However, the thickness of amorphous
metal alloys which can be formed directly by casting from the melt
is generally limited by the cooling rate and thermal conductivity.
Reducing the thermal conductivity of a high temperature amorphous
metal alloy melt by introducing gas bubbles prior to rapid cooling
is possible, but does not facilitate the rapid cooling necessary
for thick section casting.
[0030] A wide variety of high-strength glassy metal alloys may be
used in the present methods. Amorphous Al.sub.94V.sub.4Fe.sub.2,
with Al nanocrystals in an amorphous matrix, has relatively high
tensile strength (1390 MPa) for a very light alloy. [Inoue, A., et
al., "Deformation and fracture behavior of high-strength
Al.sub.94(V, Ti).sub.4Fe.sub.2 and Al.sub.93Ti.sub.5Fe.sub.2
Chemistry and Physics of Nanostructures and Related Non-Equilibrium
Materials, TMS Annual Meeting, p 201-209 (1997); "Alloys consisting
of nanogranular amorphous and Al phases", TMS Annual Meeting, p
201-209 (1997)] Lightweight Ti-based bulk amorphous alloys such as
Ti.sub.50Ni.sub.20Cu.sub.23Sn.sub.7 and Ti.sub.50Cu.sub.20Ni.sub.-
25Si.sub.4B.sub.2 can have very high tensile strength (2200 MPa)
resulting in high strength-to-weight ratio, and a wide supercooled
liquid region of viscous flow. [See, e.g., Louzguine, D. V., et
al., "Nanocrystallization of Ti--Ni--Cu--Sn Amorphous Alloy",
Scripta mater., 43:371-376 (2000); Zhang, T., et al., Mater. Trans.
JIM, 39:1001 (1998)]
[0031] Fe75CoNiSi8B 17 glassy alloys have a Young's modulus of 110
GPa, compressive fracture strength of 2800 MPa and fracture
elongation of 1.9%. The glassy iron-based alloys exhibit a distinct
glass transition, followed by a supercooled liquid region of over
50.degree. C. before crystallization in a wide composition range of
7.5 to 45 at % Co and 7.5 to 60 at % Ni. Zhang, T.; et al., "Bulk
glassy alloys in (Fe, Co, Ni)--Si--B system", Materials
Transactions, Vol. 42, pp. 1015-1018 (2001).
[0032] As indicated previously, these amorphous alloys can be used
as a minor component of a powder blend with a relatively large
amount of titanium group metal powder. The compacted composite may
be formed with the titanium group metal powder component in a
distinct matrix of the BMG amorphous metal alloy, or the compacted
composite may be further heated to diffuse and react the components
to form new alloys having a higher melt temperature than the
original BMG. Desirably, the final composition after reaction above
Tx of the BMG alloy, will have a melting temperature, Tm at least
100.degree. C. higher than the BMG composition melting temperature
Tm, and more preferably at least 250.degree. higher.
[0033] Having described the BMG component, the titanium group alloy
component will now be described. As indicated, the major component
of the PM mixture is a titanium group alloy powder. By "titanium
group alloy" is meant an alloy comprising at least 35 weight
percent of the Group 4 periodic table elements titanium, zirconium
and hafnium. Preferably, the titanium group alloy will comprise at
least about 45 weight percent Ti, Zr and/or Hf, and more preferably
at least about 60 weight percent of one or more of these elements,
based on the weight percent total of the alloy powder. The titanium
group alloy powder, as used herein, may also include substantially
pure Ti, Zr and/or Hf powders, although titanium group alloys also
containing other elements are preferred. Examples of other elements
and their weight percent range in the alloy, are as follows:
1 Element Weight Percent B 0-20 Be 0-5 C 0-2.5 Co 0-100 Cr 0-25 Fe
0-60 Mn 0-10 Mo 0-15 Nb 0-15 Ni 0-60 Re 0-10 Si 0-10 Sn 0-5 Ta 0-5
W 0-20 Bi 0-5 Ga 0-5
[0034] Other elements may be present as well, and total Ti, Zr, Hf
should best be at least weight percent, based on the total titanium
group alloy weight.
[0035] Examples of preferred titanium group metal powders include
titanium alloys, such as alpha, near alpha, alpha-beta and beta
titanium alloys:
2 TITANIUM ALLOYS (weight percent) Alpha Near Alpha Alpha Beta Beta
Ti--5Al--2.5Sn Ti--2.25--Al--11Sn--5Zr--1M- o--0.2Si
Ti--10V--2Fe--3Al Ti--11.5Mo--6Zr--4.5Sn
Ti--5Al--5Sn--2Zr--2Mo--0.25Si Ti--3Al--2.5V Ti--13V--11Cr--3Al
Ti--6Al--2Nb--1Ta--1Mo Ti--6Al--2Sn--2Zr--2Mo--2Cr--0.25Si
Ti--3Al--8V--6Cr--4Mo--4Zr Ti--6Al--2Sn--4Zr--2Mo
Ti--6Al--2Sn--4Zr--6Mo Ti--5Al--2Sn--2Zr--4Mo--4Cr
Ti--6Al--2Sn--1.5Zr--1Mo--0.35Bi--0.1Si Ti--6Al--4V
Ti--8Mo--8V--2Fe--3Al Ti--6Al--6V--2Sn--0.75Cu Ti--7Al--4Mo
Ti--8Mn
[0036] Examples of commercial alloys with practical total weight
percent ranges are exemplified as follows:
[0037] Ti-10V-2Fe-3Al Ti=83-86.8%
[0038] Ti-15V-3Cr-3Sn-3Al Ti=72.6-78.5%
[0039] Ti-2.5Cu.dbd.Ti=96.1-98% (high strength)
[0040] Ti-3Al-2.5V-0.05Pd Ti=92.5-95.5%
[0041] Ti-6Al-7Nb Ti=84.5-88% (high strength)
[0042] Ti-5Al-1Sn-1Zr-1V-0.8Mo Ti=88.5-93%
[0043] Ti-4Al-4Mo-2Sn Ti=85.9-92.2%
[0044] Ti-4Al-4Mo-4Sn-0.5Si Ti=83.2-90.7%
[0045] Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti=83.6-87.2%
[0046] Ti-6Al-2Sn-4Zr-6Mo Ti=79.4-83.7% (high temperature)
[0047] Ti-6Al-2Fe-0.1Si Ti=90.7-93%
[0048] Ti-11Sn-5Zr-2.25Al-1Mo-0.2Si Ti=77.9-82.6% (high
temperature)
[0049] Ti-6Al-5Zr-0.5Mo-0.25Si Ti=85.8-89.5%
[0050] Ti-5.5Al-3.5Sn-3Zr-1Nb-0.25Mo-0.3Si Ti=84.2-88.1% (high
temperature)
[0051] Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si-0.06C Ti=81-87.4%
(high temperature)
[0052] The alpha phase is typically fostered and strengthened by
aluminum and/or tin. Zr may also be present in alpha alloys.
[0053] Beta phase stabilizers (e.g., Mo, V, Fe, Cr, Ni, Nb, Hf, Ta,
Mn, Co, Cu, W) promote the relatively ductile beta phase and thus
enhance heat treatability and fabricability. Beta eutectoid
stabilizers (e.g., Fe, Ni and Cr) may be used in combination with
beta isomorphous stabilizers (e.g., Mo and V) provide definite
advantages over additions of beta isomorphous stabilizers
alone.
[0054] Alpha-beta titanium alloys may contain alpha-forming
strengthening elements (aluminum, tin and zirconium) together with
beta phase solid solution elements such as molybdenum, chromium,
vanadium, iron and nickel to promote strength and ductility.
[0055] Examples of titanium group based alloy compositions suitable
as crystalline major component powders, or as final composition
alloys after diffusion-reaction of the BMG amorphous metal matrix
with an titanium group alloy in the compacted part, include:
[0056] Titanium alpha alloys typically contain aluminum and tin, as
well as molybdenum, zirconium, nitrogen, vanadium, columbium,
tantalum, and silicon. Alpha alloys are not generally designed for
heat treatment, but are weldable and are commonly used for
cryogenic applications, aircraft parts, and chemical processing
equipment.
[0057] Alpha-beta alloys can be strengthened by heat treatment and
aging, and therefore can undergo processing and fabrication while
the material is still ductile, then undergo heat treatment to
strengthen the material for use in aircraft and aircraft turbine
parts, chemical processing equipment, marine hardware, and
prosthetic devices.
[0058] Beta titanium alloys have good hardenability, and cold
formability when they are solution-treated, and high strength when
they are aged. Beta alloys tend to be denser than other titanium
alloys but have high yield strengths.
[0059] Zirconium alloys such as 99Zr, 1Nb and Zircaloy-2
98.5Zr0.1Cr0.1Fe and 0.05 Ni-1.4Sn have high temperature
performance and are used for chemical and nuclear applications. Hf
alloys have high reaction absorption for nuclear applications.
[0060] As indicated, titanium and its alloys are used as the matrix
component in high performance metal-matrix composites (MMCs) for
gas turbine engine components, including fan blades, fan frames,
actuators, rotors, vanes, cases, ducting, shafts, and liners.
Titanium-based metal matrix composites are important structural
materials which are strong, temperature resistant, and relatively
stiff for their relatively light weight.
[0061] Substantial research effort has been directed to developing
Ti MMC materials, but despite this effort, current Ti MMC
manufacturing capabilities are still relatively limited and
material costs are relatively high. It would be desirable to reduce
the cost of Ti MMC parts to affordable levels, to facilitate use of
such parts in gas turbine engine and other aerospace
applications.
DETAILED DESCRIPTION OF THE INVENTION
[0062] Bulk Metallic Glasses (BMGs) having a broad supercooled
liquid range (preferably at least about 25.degree. C., and
desirably at least 50 K or more) can be fabricated from their
low-temperature glassy melts in a bulk form at slow cooling rates
of the order of 1-100K/s. The metallic glasses can have very high
strength at ambient temperature. They can be heated to form a
relatively viscous, "soft" glass without crystallizing, typically
at temperatures below 500.degree. C., e.g., 200-450.degree. C. Bulk
metallic glasses with the same or similar tensile strength as the
cast bulk glassy alloy and melt-spun metallic glass ribbon can also
be shaped by extrusion of gas-atomized glass powders. Kawamura, Y.
et al., "Development and industrialization of powder-consolidation
and forging technologies in metallic glasses" Funtai Oyobi Fummatsu
Yakin/Journal of the Japan Society of Powder and Powder Metallurgy,
Vol. 48, p 845-853 (2001).
[0063] BMGs such as Zr--Al Ni--Cu glasses and La--Al--Ni glasses
can be easily forged into complex shapes above their glass
transition temperatures, Tg. See, A. Inoue at al, "Novel
Superplasticity of Supercooled Liquid for Bulk Amorphous Alloys",
Materials Science Forum, Vol. 243-245, pp. 197-206 (1997). The
stress-strain rate curves for such supercooled ZrAl--Ni--Cu glass
liquid shows the decreasingly viscous nature of the supercooled
metal glass liquid as the temperature is increased above Tg, but
below Tx. For example, the bulk metal glass
Zr.sub.65Al.sub.10Cu.sub.15Ni.sub.10 has a glass transition
temperature of about 652.degree. K. (.about.379.degree. C.). At
temperatures slightly above Tg (379 to 440.degree. C.), this metal
forms a viscous, easily shapable glass which is easily deformed or
extruded. Such viscous metal glasses can be readily shaped, formed
and/or extruded as desired. In accordance with the present
disclosure, they may be used to manufacture cellular metal foams
with a wide variety of high performance characteristics.
[0064] Mg--Cu--Y based bulk amorphous alloys such as
Mg.sub.60Cu.sub.30Y.sub.10 have a high strength to weight ratio,
and good flow behavior in the supercooled liquid region, which
provides excellent formability at relatively low temperatures.
Mg.sub.60Cu.sub.30Y.sub.10 has a Tg of about 400.degree. K.
(125.degree. C.) and a Tx of about 450.degree. K. (175.degree.
C.).
[0065] A variety of amorphous metals with their Tg, Tx and
supercooled liquid region are listed in the following Table (with
compositions given at atomic %):
3 Major element Alloy Composition Tg (K) Tx (K) Tx - Tg Ref. Mg--
Mg80Ni10Nd10 454 471 17 k Mg75Ni15Nd10 450 470 20 k Mg60Cu30Y10 419
466 47 c (Mg99Al1)60Cu30Y10 419 459 40 c (Mg98Al2)60Cu30Y10 421 454
33 c (Mg96Al4)60Cu30Y10 411 455 44 c (Mg95Al5)60Cu30Y10 415 453 38
c (Mg93Al7)60Cu30Y10 411 445 34 c Mg70Ni15Nd15 467 489 22 k
Mg65Ni20Nd15 459 501 42 k Mg65Cu25Y10 425 479 54 k Mg60Cu30Y10 400
450 50 Zr-- Zr66Al8Ni26 672 708 36 k Zr66Al8Cu7Ni19 662 721 59 k
Zr66Al8Cu12Ni14 655 733 78 k Zr66Al9Cu16Ni9 657 736 79 k
Zr65Al7.5Cu17.5Ni10 657 736 79 k Zr57Ti5Al10Cu20Ni8 677 720 43 k
Zr41.2Ti13.8Cu12.5Ni10Be22.5 623 672 49 k
Zr38.5Ti16.5Ni9.75Cu15.25Be20 630 678 48 k
Zr39.88Ti15.12Ni9.98Cu13.77Be21.25 629 686 57
Zr42.63Ti12.37Cu11.25Ni10 Be23.75 623 712 89 k Zr44Ti11Cu10Ni10Be25
625 739 114 k Zr55Al10N15Cu30 683 748 65 d
Zr45.38Ti9.62Cu8.75Ni10Be26.25 623 740 117 Zr65Al10Ni10Cu15 652 757
105 e Zr65Al7.5Cu17.5Ni10 633 749 116 i (Zr65Al7.5Cu17.5Ni10)95Fe5
650 725 75 i (Zr65Al7.5Cu17.5Ni10)90Fe- 10 670 730 60 i
(Zr65Al7.5Cu17.5Ni10)85Fe15 675 735 60 i
(Zr65Al7.5Cu17.5Ni10)80Fe20 680 740 60 i Zr52.5Cu17.9Ni14.6Al10Ti-
5 686 725 39 j (Zr67Hf33)52.5Cu117.9Ni14.6Al10Ti5 708 753 45 j
(Zr50Hf50)52.5Cu17.9Ni14.6Al10Ti5 722 767 45 j
(Zr33Hf67)52.5Cu17.9Ni14.6Al10Ti5 737 786 49 j
Zr52.5Cu17.9Ni14.6Al10Ti5 767 820 53 j Zr52.2Ti16.7Cu17.7Ni8.7B4.-
7 564 668 104 l Zr50.2Ti16.7Cu17.7Ni8.7B6.7 646 719 73 l
Zr48.2Ti16.7Cu17.7Ni8.7B8.7 682 720 38 l Zr54.9Ti16.7Cu17.7Ni8.7P-
2.0 578 686 108 l Zr53.9Ti16.7Cu17.7Ni8.7P3.0 636 722 86 l
Zr52.9Ti16.7Cu17.7Ni8.7P4.0 698 734 36 l Zr54.9Ti16.7Cu17.7Ni8.7S-
i2.0 562 681 119 l Zr53.9Ti16.7Cu17.7Ni8.7Si3.0 563 681 118 l
Zr52.9Ti16.7Cu17.7Ni8.7Si4.0 639 742 103 l
Zr41.2Ti13.8Cu12.5Ni10Be22.5 633 741 108 l Zr70Fe20Ni10 646 673 27
o Zr60Al10Cu30 680 750 70 p La-- La55Al25Ni10Cu10 467 547 80 k
La55Al25Ni5Cu15 459 520 61 k La55Al25Cu20 456 495 39 k
La55Al25Ni5Cu10Co5 465 542 77 k La66Al14Cu20 395 449 54 k
La60Al20Ni10Co5Cu5 451 523 72 g Pd-- Pd40Cu30Ni10P20 577 656 79 k
Pd81.5Cu2Si16.5 633 670 37 k Pd79.5Cu4Si16.5 635 675 40 k
Pd77.5Cu6Si16.5 637 678 41 k Pd77Cu6Si17 642 686 44 k
Pd73.5Cu10Si16.5 645 685 40 k Pd71.5Cu12Si16.5 652 680 28 k
Pd40Ni40P20 590 671 80 k Nd-- Nd60Al15Ni10Cu10Fe5 430 475 45 k
Nd61Al11Ni8Co5Cu15 445 469 24 k Cu-- Cu60Zr30Ti10 713 763 50 k
Cu54Zr27Ti9Be10 720 762 42 k Cu48Ti34Zr10Ni8 -- -- -- Ti--
Ti34Zr11Cu47Ni8 698 727 29 k Ti50Ni24Cu20B1Si2Sn3 726 800 74 k
Ti50Ni24Cu20B1Si2Sn3 726 800 74 h Ti45Ni20Cu25Sn5Zr5 Ti50Cu25Ni25
713 753 40 m Ti50Ni22Cu25Sn3 715 765 50 m Ti50Ni20Cu25Sn5 710 770
60 m Ti50 Ni20Cu23Sn7 710 759 49 m Ti50Ni24Cu25Sb1 707 740 33 m
Ti50Ni22Cu25Sb3 763 718 45 m Ti50Cu35Ni12Sn3 -- -- --
Ti50Cu40Ni4Si4B2 740 786 46 m Ti50Cu20 Ni24Si4B2 745 810 65 m Fe--
Fe63Ni7Zr10B20 553 579 26 b and/or Fe56Ni14Zr10B20 579 601 22 b
Co-- Fe49Ni21Zr10B20 589 611 22 b Fe42Ni28Zr10B20 602 619 18 b
Fe42Co7Ni21Zr10B20 580 611 30 b Fe72Hf8Nb2B18 856 932 76 f (Fe,
Co)85 Zr7B6(Nb, Nd)2 Fe 74.5Si13.5B9Nb3 Fe58Co7Ni7Zr8B20 821 899 78
n Fe52Co10Nb8B30 907 994 87 n Fe62Co9.5RE3.5B25 (RE = Pr, Nd,
>50 Sm, Gd, Tb, Dy, Er) (22.5-30 at % B, 0-30 at % Co and 2.5-6
at % RE) Co63Fe7Zr6Ta4B20 858 895 37 n Co40Fe22Nb8B30 895 976 81 n
Co43Fe20Ta5.5B31.5 910 980 Fe75-x-yCoxNiySi8B17 (7.5 to 45 Up to 54
s at % Co and 7.5 to 60 at % Ni) Fe90-xNb10Bx -- -- -- t
Fe85.5Zr2Nb4B8.5 -- -- -- Fe70B20Zr8Nb2 91 u Al-- Al85Ni5Y8Co2 538
570 32 a Al87(La,Nd,Pr)8Ni5 500 553 53 r Al92(La,Nd,Pr)4Ni4 525 608
83 r Al--Ti--M (M = V, Fe, Co and/or Ni) v alloys, such as
Al94V4Fe2, Al93Ti4Fe3, Al93Ti4V3 Al94V2Ti2Fe2 Al93Ti5Fe2 a.
Kawamura, Y., et al., "Nanocrystalline Aluminum Bulk Alloys with a
High Strength of 1420 MPa Produced by the Consolidation of
Amorphous Powders", Scripta mater., 44; 1599-1604 (2001) b. Liu, Y.
J., et al., "The correlation of microstructural development and
thermal stability of mechanically alloyed multicomponent
Fe--Co--Ni--Zr--B alloys", Acta Materialia, 50, 2747-2760 (2002) c.
Linderoth, S., et al., "On the stability and crystallization of
bulk amorphous Mg--Cu--Y--Al Alloys", Materials Science and
Engineering A304-306, 656-659 (2001) d. deOliveira, M. F., et al.,
"Effect of oxide particles on the crystallization behaviour of
Zr.sub.55Al.sub.10Ni.sub.5Cu3.sub.0 Alloy", Materials Science &
Engineering A304-306, 665-6659 (2001) e. Kawamura, Y., et al.,
"Newtonian and non-Newtonian viscosity of supercooled liquid in
metallic glasses", Materials Science & Engineering, A304-306,
674-678 (2001) f. Kawamura, Y., et al., "Superplasticity in
Fe-based metallic glass with wide supercooled liquid region",
Materials Science & Engineering, A304-306, 674-678 (2001) g.
Saotome, Y., et al., "Superplastic micro/nano formability of
La.sub.60Al.sub.20Ni.sub.10Co.sub.5Cu5 amorphous alloy in
supercooled liquid state", Materials Science & Engineering,
A304-306, 716-720 (2001) h. Zhang, T., et al., "Ti-based amorphous
alloys with a large supercooled liquid region", Materials Science
& Engineering, A304-306, 771-774 (2001) i. Mattern, N., et al.,
"Influence of iron additions on structure and properties of
amorphous Zr.sub.65Al.sub.7.5Cu.sub.17.5Ni.sub.10", Materials
Science and Engineering A304-306, 311-314 (2001) j. Glass-forming
ability and crystallization of bulk metallic glass
(HfxZr1-x)52.5Cu17.9Ni14.6Al10Ti5", Journal of Non-Crystalline
Solids", 311 77-82 (2002) k. Lu, Z. P., et al., "A new
glass-forming ability criterion for bulk metallic glasses", Acta
Materialia, 50, 3501-3512 (2002) l. Choi, et al., "Effect of
Additive Elements on the Glass Forming Ability and Crystallization
of Zr--Ti--Cu--Ni Metallic Glasses", Journal of Metastable and
Nanocrystalline Materials, Vols. 343-346, pp. 109-115 (2000) m.
Inoue, A., "Synthesis and Properties of Ti-Based Bulk Amorphous
Alloys with a Large Supercooled Liquid Region", Journal of
Metastable and Nanocrystalline Materials, Vols. 2-6 (1999), pp.
307-314 n. Inoue, et al., "Ferromagnetic Bulk Glassy Alloys with
Useful Engineering Properties", Journal of Metastable and
Nanocrystalline Materials, Vols. 343-346, pp. 81-90 (2000) o.
Saida, et al., "Nano-Icosahedral Quasicrystalline Phase Formation
from a Supercooled Liquid State in Zr--Fe Ternary Metallic Glass",
Applied Physics Letters, Vol. 76, No. 21, pp. 3037-3039 (May 22,
2000) p. Inoue, et al., "Synthesis of High Strength Bulk
Nanocrystalline Alloys Containing Remaining Amorphous Phase",
Journal of Metastable and Nanocrystalline Materials, Vol. 1, pp.
1-8 (1999) q. Eckert, J., "Mechanical Alloying of Highly
Processable Glassy Alloys", Materials Science and Engineering,
A226-228, pp. 364-373 (1997) r. Tong, et al., "Microstructure and
Thermal Analysis of Amorphous Al87RE8Ni5 and AL92RE4Ni4 Alloys",
Materials Letters, Vol. 28, pp. 133-136 (1996) s. Zhang, et al,
"Bulk glassy alloys in (Fe, Co, Ni)--Si--B system", Materials
Transactions, v 42, (2001) t. Imafuku, et al, "Structural variation
of Fe--Nb--B metallic glasses during crystallization process",
Scripta Materialia, v 44 (2001) u. Ma, et al, "Fe-based metallic
glass with significant supercooled liquid region of over 90 K",
Journal of Materials Science Letters, v 17 (1998) v. Kimura, et al,
"Formation of nanogranular amorphous phase in rapidly solidified
Al--Ti--M (M = V, Fe, Co or Ni) alloys and their mechanical
strength", Nanostructured Materials, v 8, p 833-844 (1997)
[0066] S. J. Poon, et al. in "Glass formability of ferrous- and
aluminum-based structural metallic alloys." Journal of
Non-Crystalline Solids v317, pp1-9(2003) describe and refer to a
variety of ferrous- and aluminum-based amorphous metals which are
also incorporated herein by reference.
[0067] However, while BMGs are superb structural materials due to a
unique combination of properties such as a large elastic strain
limit, high strength and good fracture toughness, they also may be
characterized by high concentration of shear deformation under
intense loading conditions.
[0068] Bulk metallic glasses (BMGs) may have a reasonably large
elastic strain limit (e.g., about 2%), high strength (e.g., up to
3.8 GPa or more) and a good fracture toughness (up to 55 MPa m
1/2). Shear deformation concentration in an amorphous metal matrix
may be reduced through the use of nonamorphous reinforcements, such
as in situ precipitates or composite reinforcements. [see, Clausen,
B., et al., "Deformation of In-Situ-Reinforced Bulk Metallic Glass
Matrix Composites", Mater. Sci. Forum (2002)], and through the use
of BMG composites, as described hereinafter.
[0069] Particulate reinforcements may be used, or nanoscale
precipitates may be formed in the glass directly from the amorphous
metal composition by partial crystallization which retains a
supercooled liquid matrix. Bulk nanocrystalline amorphous metal
alloys such as aluminum-based amorphous alloys of Al--Ni--Y--Co,
Al--Si--Ni--Ce and Al--Fe--Ti-TM (TM=Cr,Mo,V,Zr) systems, such as
A189 (Ni0.33Y0.54Co0.13) 11 may be produced by arc-melting the pure
metals in the appropriate composition ratios, in an argon
atmosphere. Rapidly solidified BMG alloy powders may be produced by
high pressure He gas atomization at a dynamic pressure of about 10
MPa with powder below 25 micron particle size being rapidly cooled
to retain the amorphous condition.
[0070] As shown in FIG. 1, upon heating and compressing (e.g.,
under vacuum), the mixture of BMG powder and a crystalline Ti or Ti
alloy powder to a temperature above the glass transition Tg of the
BMG powder but below its Tx, a substantially fully dense composite
is formed in which the titanium particles are embedded in a BMG
alloy matrix. Upon heating, the matrix substantially above the
crystallization temperature(s) Tx of the BMG matrix, the matrix
crystallizes. In addition, at higher temperatures still below the
full melt temperature Tm, the crystallized matrix and the
reinforcing powders will react to form new crystalline phases and
crystal structures which would not form from the BMG composition
itself. In this way, stronger crystalline alloys can be fabricated
in desired shape in a supercooled liquid matrix state, followed by
conversion to new, higher performance alloys by heating to a
temperature below the finished alloy melt temperature, which is
higher than the BMG melting temperature Tm. Preferably, the final
composite alloy composition will have a melting temperature Tm at
least 100.degree. C., and more preferably at least 250.degree. C.
higher than the melt temperature Tm of the original amorphous metal
(BMG) component of the powder blend.
[0071] Even upon fully melting the newly formed composition, it
will not form the same eutectic BMG alloy on cooling when the BMG
and the particulate reinforcement are of different compositions.
For example, a high aluminum BMG mixed with a titanium-group powder
can form high-melting titanium-aluminide compositions.
[0072] It should also be noted that amorphous metal composites of a
plurality of two or more different amorphous metal compositions may
be provided which have advantageous properties, and which can
provide an increased range of final alloy compositions when blended
with the major titanium-group alloy component of the powder
mixture.
[0073] As indicated, embodiments of the present disclosure is
directed to processing of relatively small amounts of amorphous
metal with relatively large amounts of crystalline (including
quasicrystalline) metal and/or ceramic powders. Relatively small
amounts of amorphous metals may be used in powder metallurgy
processes and formulations to produce high performance parts and
components. In conventional powder metallizing processes, metal
powders and blends of metal powders with reinforcing or hardening
components, are formed, compressed and sintered (in various orders
and combinations of these steps by MIM, HIPing, compressive
sintering, etc.), to produce finished or semi-finished products.
One disadvantage of powder conventional metal sintering processes
is that it is difficult to achieve full density by compression and
sintering, even under vacuum hot isostatic pressing or expensive
compression wave techniques. While amorphous metal powders with a
sufficiently wide supercooled region can be compressed to full
density and formed into complex shapes, they generally have low
crystallization temperatures, and low melting points, which limit
their use. In this regard, a relatively small amount of from about
1 to about 25 volume percent of an appropriate amorphous metal
powder (or BMG coating) may be blended with from about 60 to about
99 volume percent of a conventional crystalline (including
quasicrystalline) or non glass-transitioning amorphous titanium
group metal powder, based on the total volume of the blend
(excluding voids). From about 0 to about 15 volume percent of
additional reinforcing powders, fibers, filaments, lubricating,
molding and/or blending agents may also be incorporated in the
blend. The amorphous metal powder should desirably exhibit a
supercooled liquid temperature range above its Tg of at least about
20.degree. C., and more preferably at least about 35.degree. C. for
at least 5 minutes before fully crystallizing to a point that it
loses its gear-like viscosity and under shear. In addition, the
amorphous metal powder and the conventional metal powder
component(s) should form an alloy which both has a higher melting
temperature than the liquid melting temperature of the amorphous
metal itself, and which has a tensile strength which is larger than
the tensile strength of the fully crystallized amorphous alloy
composition. For example, 5 volume percent of a Zr-based, Al-based
or Ti-based amorphous metal powder having a particle size smaller
than 10 microns may be blended with titanium power, a titanium
alloy powder, such as TiAl6V4, or a titanium intermetallic powder
such as Ti.sub.3Al or TiAl. The powders are mixed to produce a
homogeneous blend of ingredients. The powder mixture may be
pressure or gravity-fed into a die, and compacted at a temperature
in the superfluid temperature range of the Fe-based amorphous metal
powder, between Tg and Tx. Compacting pressures may be increased,
for example, from an initial 100 KPa to a final pressure in the
30-50 tons per square inch range in conventional PM presses. The
compacted parts may subsequently be heated to at least partially
crystallize the metallic glass composition or matrix. During
sintering the pressed parts may be conveyed through a
controlled-atmosphere furnace. The pressed powder particles may
crystallize and/or react together, to form a dense steel product
when using a strong iron or steel crystalline powder with a small
amount of an amorphous BMG alloy such as a Ti, Zr and/or Fe-based
BMG in this manner.
[0074] Conventional P/M presses operate with a vertical stroke to
compact metal powders in a single cavity die to form the desired
parts or components, such as gears such as pinion gears, bevel
gears (straight and spiral), face gears and sprockets, cams,
counterweights, armatures, pole pieces, bearings, and bushings. A
wide variety of parts for automotive, computer, medical, dental,
musical, electronic, tool, and aerospace uses may be produced in
this manner.
[0075] For example, as indicated above, suitable metal powders
include titanium and titanium alloy powders (in weight percent)
such as:
[0076] Ti-3Al-8V-6Cr-4Zr-4Mo (Beta C)
[0077] Ti-15Mo-3Nb-3Al-0.2Si
[0078] High strength
[0079] Ti-6Al-4V
[0080] Ti-5Al-2.5Sn
[0081] Ti-4Al-4Mo-2Sn
[0082] Ti-6Al-6V-2Sn
[0083] Ti-10V-2Fe-3Al
[0084] Ti-15V-3Cr-3Sn-3Al
[0085] Ti-5.5Al-3Sn-3Zr-0.5Nb
[0086] Ti-5Al-2Sn-4Mo-2Zr-4Cr
[0087] Ti-8Al-1Mo-1V
[0088] High Temperature
[0089] Alpha--Two Aluminide (Ti-24Al-11Nb, intermetallic compound
based on Ti3Al)
[0090] Alpha--Two Aluminide (25/10/3/1)
[0091] Ti-6Al-2Sn-4Zr-2Mo
[0092] Ti-6Al-7Nb
[0093] Ti-6Al-2Sn-4Zr-6Mo
[0094] Ti-5.5Al-3.5Sn-3Zr-1Nb
[0095] Ti-5.8Al-4Sn-3.5Zr-0.7Nb
[0096] Ti-6Al-2Sn-4Zr-6Mo
[0097] Powder formation for both the titanium alloy compositions,
and the powdered amorphous metal component (which is desirably
cooled) at a rate, for example, of at least 1.times.10.sup.4
degrees K. per second for some less-stable alloys, can be
accomplished by a number of different processes, including, for
example, melt-spinning, gas atomization, centrifugal atomization,
and splat quenching. The powder can be consolidated by, for
example, hipping, hot pressing, hot extrusion, powder rolling,
powder forging and dynamic compaction. In centrifugal atomization,
for example, the melt stream is discharged from a rapidly spinning
centrifugal cup, and is contacted by high pressure cold helium gas
to facilitate fast cooling (e.g., greater than 1.times.10.sup.5
K/s). The helium gas can be collected, purified and reused. The
speed of the rotating centrifugal cup may, for example, be about
20,000-45,000 (e.g., 40,000) RPM, the speed and other processing
conditions can be adjusted to produce a fine powder with about a 25
micrometer mean particle size.
[0098] As indicated, it may be desirable to provide conventional
(crystalline/nanocrystalline) metal surfaces, fibers, wires, sheets
and powders with a thin BMG surface which facilitates metallurgical
joining of these materials with the BMG. The surface layers may be
provided in a variety of ways, including PVD. One way to deposit an
amorphous metal layer on a substrate is to fully vaporize an
amorphous metal composition, such as by E-beam or plasma jet, and
subsequently rapidly condense and cool it on the powder, fiber or
sheet surface of the crystalline metal or ceramic to be coated, and
cool the condensed deposit within the amorphous metal cooling time
required to prevent crystallization. For example, when utilizing a
plasma gun, as a suitable BMG powder with a particle size of less
than 5 microns, and preferably less than 3 microns, is fully
vaporized in a plasma jet in an argon atmosphere. The plasma jet
will typically reach a temperature of at least 8,000-15,000 K, and
small particle size of the BMG facilitates its vaporization. The
vaporized metal and the plasma jet stream may be expanded to cool
it and substantially simultaneously mix it with a cooled (e.g, room
temperature) crystallized titanium group metal powder, at a mass
ratio of 1-100 times the mass of the vaporized metal. Vaporized BMG
rapidly condenses on the crystalline powder, and can cool rapidly
to form an amorphous, preferably metallurgically-bonded thin
amorphous metal surface layer. An amorphous metal coating may also
be electroplated or electrolessly deposited on the titanium group
powder, or fibers.
[0099] The use of filament reinforcements is also an important
option. The amorphous metal powder blend may also include other
components such as reinforcing and/or alloying fibers or powders.
Such fibers or powders may be densely consolidated within the metal
glass matrix. The additional particulate component may also provide
alloying constituents to modify the composition of the alloy(s)
crystallized from the amorphous alloy upon heating above the
crystallization temperature(s) Tx.
[0100] As illustrated in FIG. 1 a blend of a BMG amorphous alloy
powder with a crystalline metal which, may be, for example, a Ti,
Zr or Al-based powder or an Fe-based powder having a mean particle
size from 0.5 to 25 microns. For Al, Zr and/or Ti-based BMG
amorphous metal matrices, the crystalline metal powder may be, for
example, a titanium powder, a titanium aluminide powder such as
Ti.sub.3Al or TiAl, or a crystallized titanium group alloy powder,
having a particle size of from about 0.5 to about 50 microns. Bulk
Metallic Glasses having a broad supercooled liquid range (e.g.,
preferably 50 K or more) can be shaped and fabricated from their
viscous, low-temperature glassy melts. When heated above Tg, they
can form a "soft" viscous glass without crystallizing, typically at
relatively low temperatures of 200-400.degree. C. Bulk metallic
glasses can be shaped by die forging and extrusion of amorphous
metal powders [e.g., Kawamura, Y. et al., "Development and
industrialization of powder-consolidation and forging technologies
in metallic glasses" Funtai Oyobi Fummatsu Yakin/Journal of the
Japan Society of Powder and Powder Metallurgy, v 48, p 845-853
(2001)].
[0101] Net-shape, low-temperature, low pressure powder metallurgy
fabrication processes for rapidly producing full density
high-performance Titanium alloys and lighter-weight Titanium alloy
metal matrix composites with lightweight, high-stiffness filaments
or fibers such as SiC or SiBCN are a significant advance for rapid
prototyping and rapid manufacture of a very wide variety of
high-performance Titanium-based components, which conventionally
require much more expensive tooling, forging and shaping. As shown
in FIG. 2, virtually any Titanium product shape can be produced
using relatively inexpensive, low-pressure, low-temperature molds
or dies, which themselves can be made quickly and inexpensively
because of the relatively low temperature and strength requirements
involved.
[0102] The disclosed process technology permits inexpensive
fabrication of advanced Titanium-based materials, rapid prototyping
of new components and structures, and rapid manufacturing of
high-performance Titanium and Titanium composite components for new
and current components and subcomponents.
[0103] The powder blend can be compacted at relatively low
temperature, which is above the Tg of the Bulk Metal Glass (e.g.,
300.degree. C.) but well below the sintering temperature of
titanium powders (e.g., 1200.degree. C.). Compacting pressures are
also relatively low, because it is primarily the viscous Bulk Metal
Glass which is consolidated, not the hard titanium powders. The
compacted parts may be used with a BMG matrix, or can subsequently
be heated to at least partially crystallize the metallic glass
composition or matrix. The particles may crystallize and/or react
together, to form a dense product. The powder blend is compressed
at a relatively low temperature (well below the melting point)
within the supercooled liquid range of the amorphous alloy, to
eliminate the porosity of the blend, and increase the total surface
area of the amorphous metal powder. The blend may also contain
reinforcing filaments or fibers such as strong, lightweight B, SiC,
or SiCN fibers, which will be incorporated in the finished
products. Desirably, the titanium group powders and amorphous metal
powders should have a particle size of less than about 200 microns,
preferably with a range of particle sizes to facilitate packing.
The mean particle size of the BMG amorphous metal component should
probably be less than half that of the titanium group metal
particles, to facilitate more uniform dispersion in the interstices
of the titanium group particles.
[0104] As shown in FIG. 2, the blend is subsequently compacted
above the Tg of the BMG component, where it is a viscous liquid.
This compression produces viscous flow of the amorphous metal
glass, forcing it into the interstices of the titanium group metal
particles, substantially increasing the total surface area of the
amorphous metal component and desirably forming it into an at least
partially interconnected matrix enclosing the titanium group metal
particles. This decreases the median thickness of the amorphous
metal component. This facilitates reactive diffusion with the
titanium group metal component at elevated temperatures to form new
high performance alloy(s) having much higher melt temperatures than
the amorphous metal component.
[0105] As indicated, the powder mixture comprises a major volume
fraction V of titanium group metal powder and any reinforcing
filaments, and a minor volume fraction v of the BMG amorphous metal
powder or coating component. The compressive pressure Pc applied to
compact the mixed powder is much less than that necessary to
compact the titanium group metal powder. This compression pressure
Pc may be approximated by:
Pc=-2Y{ln(1-R)/3}
[0106] where Pc is the minimum compression pressure at the
supercooled liquid temperature, Y is the yield strength of the
titanium group metal powder at the compression temperature, and R
is the relative density of the titanium group metal powder (in the
absence of the BMG amorphous alloy component).
[0107] For example, a titanium group metal powder having a yield
strength of 300 MPa at 700.degree. K. would itself (without the
presence of a BMG amorphous metal component) be compressed to a
relative density R of 0.85 (85% of full density), by a compression
pressure Pc of approximately -2.times.300 (ln(1-0.85)/3 or
approximately Pc=-380 MPa. To compress the titanium group metal
powder itself (without a BMG amorphous metal component) to a
relative full density of 0.999, could require over 1.3 Gpa, which
is difficult and expensive to provide in an economical production
process under vacuum or inert atmosphere.
[0108] The compacted PM product may be cooled to provide a dense
metal compact in which the crystalline titanium group metal
particles are embedded in an ultrastrong amorphous metal
matrix.
[0109] Importantly, the fully compacted titanium alloy product may
also be heated to a temperature above the crystallization
temperature of the amorphous metal continuous phase. In this
manner, the titanium metal group particles are embedded in a fully
or partially crystalline continuous phase which is still
substantially distinct from the titanium group metal particles.
This can be advantageous for certain BMG alloys which form a
strong, partially or fully crystalline alloy upon heating to an
initial crystallization temperature Tx or above.
[0110] Such titanium alloy products with discrete titanium group
powder zones (even though compressed or distorted) and BMG alloy
composition zones, will not have optimum heat resistance under
stress for high temperature operation, because the partially
discrete continuous amorphous phase may remain as a eutectic
material with a relatively low melting point, Tm. In order to
provide a finished product with increased heat resistance, the
compact product may be further heated to a sintering temperature at
which the titanium group alloy particles and the relatively
continuous matrix phase diffuse together to form a new composition
of high performance titanium. The Bulk Metal Glass, and the
titanium alloy components may be selected to provide
high-performance titanium alloys upon diffusion-reaction. This
reaction may form selected Ti-alloys, with formation of nano- or
micron-scale ceramic reinforcing particles such as TiB.sub.2, TiNi,
etc., which improve the high-temperature strength of the alloy.
[0111] After diffusion of the original crystalline metal powder
components with the original amorphous metal components, the
composite does not "remelt" at the relatively low melting
temperature of the bulk metal glass component, because of the
different composition of the reacted compact. The new, high
performance titanium alloy may include highly refractory ceramic
(e.g., TiB.sub.2) and intermetallic (e.g., TiCu, NiAl.sub.3, TiAl)
reinforcements produced in situ, as previously indicated.
EXAMPLE 1
[0112] Al85Ni5Y8Co2 fully amorphous alloy has a glass transition
temperature Tg of 538.degree. K., a relatively high strength of
1250 MPa at room temperature and a relatively wide and a 38.degree.
K. supercooled liquid region [Y. Kawamura, et al, "Nanocrystalline
Aluminum Bulk Alloys With A High Strength Of 1420 Mpa Produced By
The Consolidation Of Amorphous Powders", Scripta mater. 44 (2001)
1599-1604; A. Inoue, et al., Mater. Trans. JIM. 31, 493 (1990).].
Its initial crystallization occurs through the precipitation of
fcc-Al particles while retaining viscous flow in the supercooled
liquid region [Y. Kawamura, et al, Int. J. Powder Metall. 33, 50
(1997); Y. Kawamura, et al, J. Jpn. Soc. Powder Powder Metall. 38,
948 (1991); Y. Kawamura, et al, Mater. Trans. JIM. 40, 749 (1999)],
and accordingly is used as a minor BMG component with a large
volume of crystalline titanium powder.
[0113] A one Kg ingot of an Al85Ni5Y8Co2 (at %) alloy is prepared
by arc melting a mixture of the pure elements. The ingot is
re-melted at a temperature of 1573 K and then gas atomized through
a melt stream with a diameter of 2.0 mm, using helium gas with a
dynamic pressure of 10 MPa for atomization. The powder is sieved to
below 25 microns. 200 grams of this amorphous alloy powder is
uniformly mixed with 800 grams of CP titanium powder having a
particle size of less than about 75 microns. The CP titanium has a
tensile strength of about 220 MPa at ambient temperature. The
entire blend (100 g) is flushed with argon, and heated in a steel
die under vacuum to a temperature of 560.degree. K., under a
compaction pressure of 240 MPa, which upon cooling to 25.degree. C.
produces a fully dense composite cylinder of CP titanium powder
embedded in a somewhat discontinuous matrix of the amorphous metal
composition.
[0114] The composite cylinder is subsequently heated to a
temperature of 1100.degree. C., in an inert atmosphere. As the
temperature increases over Tx of the amorphous material, it
crystallizes. Upon additional heating, the CP titanium powder and
the amorphous matrix reactively diffuses to "consume" the amorphous
matrix to form a high-aluminum, unitary titanium alloy having a
melting temperature much higher than the amorphous matrix. Similar
runs using Fe, Zr, Al and Cu-based amorphous alloys as described
above (compressed in their supercooled liquid region) produce
similar results, with different final alloy compositions.
EXAMPLE 2
[0115] 200 grams of SiBNC fibers having a tensile strength of 2-4
GPa, a density of 1.8/cm.sup.3, a diameter of 8-14 microns [See
e.g., H. P. Balddus, et al., "Properties of Amorphous SiBNC-Ceramic
Fibers", Key Engineering Materials, Vol. 127-131, pp. 177-184
(1977)] are aligned in a blend of 900 grams of CP titanium powder
and 100 grams of a BMG alloy powder, by weight, based on the total
powder weight. The BMG alloy powder is Ti50Cu20Ni24Si4B2 (atomic
percent), having a Tg of about 745.degree. K. and a supercooled
liquid region of about 65.degree. K. The aligned fibers and powder
blend are compressed between sheet platens under vacuum at a
temperature of 8000 K, at a compression pressure of 465 MPa to
produce a fully dense sheet "tape" with a monolayer of aligned
fibers. The sheet is removed from the platen press and subsequently
heated in an inert temperature to a temperature of about
1200.degree. C. to form a fiber-reinforced, high-temperature
composite, in which the fibers are embedded in a matrix having an
overall alloy composition of Ti94.18, Cu2.63, Ni2.92, Si0.23 and
B0.04 percent by weight.
EXAMPLE 3
[0116] 89 grams of a titanium alloy powder which is 96.4 atomic
percent titanium and 3.6 atomic percent vanadium is blended with 11
grams of a bulk metal glass powder having a composition of
A194V4Fe2 atomic percent. The 100 grams of the powder blend is
compressed in a gear-shaped mold under vacuum at a compression
pressure of 25 kSI, at a temperature 25.degree. above the glass
transition temperature Tg of the amorphous alloy to form a
substantially fully dense gear component. The gear is removed from
the mold, and heated in a vacuum furnace to a temperature of
1000.degree. C. to first crystallize the BMG and then reactively
diffuse it with the Ti alloy powder, to form an alloy with a
nominal composition in weight percent of 89.6Ti, 6.09Al, 4.04V and
0.27Fe.
EXAMPLE 4
[0117] Silicon carbide fibers (SCS-6 fibers of Textron Specialty
Materials Company) are sputter coated with a layer of Nb about one
micron in thickness. Alternatively, an amorphous metal alloy
composition having predominantly beta-stabilizing elements, such as
Zr70Fe20Ni10 may be sputter-coated on the filaments, while coating
the filaments below 500.degree. K. to maintain the coating in an
amorphous condition.
[0118] 900 grams of titanium alloy powder (particle size 50-100
microns) having a composition of 95 weight percent Ti, a5 weight
percent V, 2 weight percent Mo, is blended with 10 weight percent
of an amorphous Zr alloy powder (particle size 20-50 microns)
having a composition of Zr66Al18Cu7Ni19 (atomic %). 200 grams of
the coated SiC fibers are aligned and embedded in the powder blend,
and compressed under vacuum at a temperature of 715.degree. K. and
a pressure of 45 ksi to form a substantially dense foil with SiC
monofilaments embedded therein. The reinforced foil is subsequently
cut and stacked with other like foils to form finished component
shaped, and compressed and heated to 1100.degree. C. in an inert
atmosphere to reaction-diffuse the amorphous alloy with the
titanium alloy powder, and to unify the sheets to form a
high-strength, fiber reinforced composite article suitable for high
temperature use.
* * * * *