U.S. patent application number 11/833281 was filed with the patent office on 2008-06-12 for high-temperature high-strength aluminum alloys processed through the amorphous state.
This patent application is currently assigned to QuesTek Innovatioans LLC. Invention is credited to Herng-Jeng Jou, Gregory B. Olson, Caian Qiu, Weijia Tang.
Application Number | 20080138239 11/833281 |
Document ID | / |
Family ID | 31999122 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080138239 |
Kind Code |
A1 |
Olson; Gregory B. ; et
al. |
June 12, 2008 |
HIGH-TEMPERATURE HIGH-STRENGTH ALUMINUM ALLOYS PROCESSED THROUGH
THE AMORPHOUS STATE
Abstract
Aluminum alloys having improved strength at 300.degree. C.
characterized by formation from an intermediate amorphous state to
a final fcc matrix hardened by optimal 25 nm-diameter Ll.sub.2
precipitates with an interphase misfit less than about 4% in all
three dimensions and Al.sub.23Ni.sub.6M.sub.4 precipitates where M
is one or more elements selected from the group consisting of Y and
Yb. An appropriate melt of aluminum with selected transition metals
(Co, Cu, Fe, Ni, Ti, Y) and Ll.sub.2 stabilizers (Sc, Yb) in
amounts of about 2 to 12 and 2 to 15 atomic percent, respectively,
is processed to achieve an intermediate amorphous state to dissolve
Ll.sub.2-forming components. The amorphous alloys are then
thermo-mechanically devitrified to a final crystalline
microstructure. The alloys have good ductility and a short-term
tensile strength exceeding about 275 MPa (40 ksi) at 300.degree.
C., and are useful for applications such as high-temperature
turbine engine components or aircraft structural components.
Inventors: |
Olson; Gregory B.;
(Riverwoods, IL) ; Tang; Weijia; (Wilmette,
IL) ; Qiu; Caian; (Wilmette, IL) ; Jou;
Herng-Jeng; (Wilmette, IL) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
TEN SOUTH WACKER DRIVE, SUITE 3000
CHICAGO
IL
60606
US
|
Assignee: |
QuesTek Innovatioans LLC
Evanston
IL
|
Family ID: |
31999122 |
Appl. No.: |
11/833281 |
Filed: |
August 3, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10422234 |
Apr 24, 2003 |
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11833281 |
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60375940 |
Apr 24, 2002 |
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60450114 |
Feb 25, 2003 |
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Current U.S.
Class: |
420/531 ;
420/528; 420/529; 420/550; 420/551; 420/552; 420/553 |
Current CPC
Class: |
C22C 45/08 20130101;
C22C 21/00 20130101; C22F 1/04 20130101 |
Class at
Publication: |
420/531 ;
420/550; 420/551; 420/529; 420/552; 420/553; 420/528 |
International
Class: |
C22C 21/00 20060101
C22C021/00 |
Goverment Interests
GOVERNMENT INTERESTS
[0002] Activities relating to the development of the subject matter
of this invention were funded at least in part by United States
Government, U.S. Army Aviation & Missile Command Contract No.
DAAH01-02-C-R125, and thus may be subject to license rights and
other rights in the United States.
Claims
1. An aluminum alloy characterized by high strength iii the
temperature range greater than about 300.degree. C. comprising, in
combination: an alloy mixture in primarily crystalline form having
at least about 70% by volume fcc phase, at least about 110% by
volume Ll.sub.2 precipitate phase, and at least about 10% by volume
Al.sub.23Ni.sub.6M.sub.4 precipitate phase where M is one or more
elements selected from the group consisting of Y and Yb, said alloy
consisting essentially of one or more transition metals selected
from the group consisting of about 2 to 12 atomic percent Co, Cu,
Fe, Ni, Ti, and Y; and one or more elements comprising said
Ll.sub.2 phase selected from the group consisting of about 2 to 15
atomic percent Sc and Yb; optionally of transition metals selected
from the group consisting of Cr, Li, Mn, V, and Zn, and the balance
Al and incidental elements and impurities; said Ll.sub.2 phase in
the form of a precipitate particle dispersion having a particle
diameter of less than about 80 nm.
2. The alloy of claim 1 having a tensile yield strength of at least
about 275 MPa at 300.degree. C.
3. An aluminum alloy characterized by high strength at a
temperature greater than about 300.degree. C. made by a process
comprising the steps of: (a) formulating a melt comprised of Al; at
least one transition metal selected from the group consisting of
Co, Cu, Fe, Ni, Ti and Y; at least one element selected from the
Ll.sub.2-stabilizing element group consisting of Sc and Yb;
optionally of transition metals selected from the group consisting
of Cr, Li, Mn, V, and Zn; (b) converting the melt to at least about
70% by volume amorphous material; and (c) devitrifying, at least in
part, the amorphous material to a mixture of Ll.sub.2 crystalline
rare earth precipitate phase material in a particle dispersion
wherein the particle size is less than about 80 nm,
Al.sub.23Ni.sub.6M.sub.4 precipitate phase where M is one or more
elements selected from the group consisting of Y and Yb, and fcc
phase material.
4. The alloy product by the process of claim 3 wherein the
transition metal is provided in an amount of about 2 to 12 atomic
percent.
5. The alloy product by the process of claim 3 wherein the
Ll.sub.2-stabilizing element is provided in an amount of about 2 to
10 atomic percent.
6. The alloy product by the process of claim 3 wherein devitrifying
the amorphous material comprises forming at least about 70% by
volume fcc phase.
7. The alloy product by the process of claim 3 wherein devitrifying
the amorphous material comprises forming at least 10% by volume
Ll.sub.2 phase in partial form.
8. The alloy product by the process of claim 3 wherein devitrifying
the amorphous material comprises forming at least 10% by volume
Al.sub.23Ni.sub.6M.sub.4 phase in partial form, where M is one or
more elements selected; from the group consisting of Y and Yb.
9. The alloy product by the process of claim 3 wherein converting
the melt to amorphous material comprises at least one step selected
from the group consisting of gas powder atomization, water powder
atomization and melt spinning.
10. The alloy product by the process of claim 3 wherein,
devitrification comprises at least one step selected from the group
consisting of hot isostatic pressing, thermal aging, and
extrusion.
11. The product by the process of claim 3 wherein converting the
melt comprises rapid solidification processing.
12. An aluminum alloy consisting essentially of about 2-12 atomic
percent of at least one transition element selected from the group
consisting of Co, Cu, Fe, Ni, Ti, and Y; about 2-15 atomic percent
of at least one element selected from the group consisting, of Yb
and Sc; optionally of transition metals selected from the group
consisting of Cr, Li, Mn, V, and Zn; and the balance Al and
incidental elements and impurities characterized by greater than
about 70% crystalline microstructure with a dispersion of Ll.sub.2
phase particles greater than 10% by volume and
Al.sub.23Ni.sub.6M.sub.4 phase particles greater than 10% by
volume, where M is one or more elements selected from the group
consisting of Y and Yb, in a matrix of greater than 70% by volume
fcc phase generated by a rapid solidification process from a
substantially amorphous vitrified phase, said particle diameter of
said Ll.sub.2 particles in the range of about 1.0 to 80 nm.
13. The alloy of claim 12 wherein the nominal particle diameter of
the Ll.sub.2 particles is about 25 nm.
14. The alloy of claim 12, consisting essentially of about 0.7
atomic % Co, 3.5 atomic % Ni, and at least one element selected
from the group consisting of Sc and Yb.
15. The alloy of claim 12 consisting essentially of about 0.7
atomic % Co, about 3.5 atomic % Ni, and Sc, Ti, Y, Yb, and Zr,
cumulatively in the range of about 4 to 8 atomic %.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part utility
application of application Ser. No. 10/422,234 filed Apr. 24, 2003
entitled Nanophase Precipitation-Strengthened Al Alloys Processed
Through the Amorphous State, which is based upon previously filed
provisional applications: Ser. No. 60/375,940 filed Apr. 24, 2002
entitled "Amorphous metal alloy compositions" and Ser. No.
60/450,114 filed Feb. 25, 2003 entitled "Amorphous metal alloy
compositions", all of which are incorporated by reference and for
which priority is claimed.
BACKGROUND OF THE INVENTION
[0003] In a principal aspect, the present invention relates to
Al-based alloys processed through an amorphous state, preferably by
means of a Rapid Solidification Process (RSP) from molten alloy,
and then devitrified to a primarily crystalline microscale fine
grain structure by thermo-mechanical processing. To promote
glass-forming ability, the Al alloys comprise selected transition
metal (TM) and lanthanide rare earth (RE) elements. The final
crystalline microstructure has a combination of stable strength at
or above about 300.degree. C. and good ductility, characterized by
optimal 25 nm-diameter Ll.sub.2 precipitates in an fcc matrix with
an interphase misfit typically less than about 4% in all three
dimensions, and rod-shaped Al.sub.23Ni.sub.6M.sub.4
precipitates.
[0004] Improved strength at elevated temperatures has been a
continuing goal in Al alloy development for more than three
decades. Currently available commercial Al alloys, either
manufactured with ingot or powder processing, are not capable of
simultaneously achieving high strength and high-temperature
stability near 300.degree. C.; such characteristics being
particularly important in applications such as fan components in
turbine engines. Precipitation hardening introduced by aging is a
known method to strengthen Al alloys. Conventional high-strength Al
alloys in commercial applications employ Guinier-Preston zones and
subsequent precipitation at or below 250.degree. C. Examples of Al
alloys processed with relatively high aging temperatures in
commercial practice include alloy 2618 (200.degree. C. for 20
hours), 4032 (170-175.degree. C. for 8-12 hours), and 2218
(240.degree. C. for 6 hours) [Metals Handbook-Properties and
Selection: Nonferrous Alloys and Special-Purpose Materials, Volume
2, 10.sup.th Edition, ASM International]. At the noted aging
temperatures, these alloys have an improved microstructure
stability relative to other commercial Al alloys. These Al alloys,
when precipitation-hardened, usually possess a room temperature
yield strength of about 600 MPa. (85 ksi). However, at temperatures
approaching 300.degree. C., the precipitation hardening efficiency
in these alloys quickly and significantly degrades as a result of
precipitate coarsening and/or dissolution. Due to the unstable
strengthening precipitate size distribution at such high
temperatures, the yield strength of currently available aluminum
alloys at 300.degree. C. is often only 10% of the yield strength at
room temperature, and thus renders such alloys unsuitable for
high-temperature applications above 150.degree. C. For
high-temperature turbine engine components or aircraft structural
components, a short-term tensile strength exceeding about 275 MPa
(40 ksi) at 300.degree. C. is desired.
[0005] In order to achieve a combination of high strength and
usable high-temperature properties in Al alloys, researchers have
investigated a variety of intermetallic precipitation dispersions.
The Al-based Ll.sub.2 phase is one of the best-known precipitates
to achieve a good combination of high strength and high toughness
of ambient temperatures. There are reportedly only seven elements
stabilizing the Ll.sub.2 phase: Er, Lu, Np, Sc, Tm, U, and Yb
[Knipling, K. E. et al. Z. Metallkd 97:246-265]. Since crystalline
Al has very limited solubility for these Ll.sub.2 stabilizers, it
is difficult to produce a fine dispersion through crystalline
solid-state heat treatments. Alternatively, with RSP from the
liquid state, it is possible to either (1) directly produce a fine
crystalline structure, or (2) produce partially amorphous Al
alloys. Nonetheless, crystalline RSP Al alloys have not been able
to meet the high-temperature strength requirements due to the
difficulty of producing small, stable particles at adequate volume
fraction. The focus on amorphous RSP Al alloys has been primarily
on face centered cubic (fcc)-Al nanocrystals to enhance the ambient
strength [Kim, Inoue, Masumoto, Mater Trans JIM 1990; 31: 747].
Upon devitrification, Al nanocrystals of up to 30% volume fraction
can be dispersed within the amorphous matrix. However, this
nanoscale ultra-fine grain stricture is undesirable because at high
temperatures, typically .gtoreq.0.4-0.5 T.sub.m where T.sub.m is
the material's absolute melting temperature, the contribution of
grain boundary strengthening is minimal and the refined grain
structures promote rapid diffusional creep. In addition, it has
been reported that ultra-fine grain sizes may be undesirable when,
considering formability and fracture toughness [Hornbogen, Starke,
Acta metall. mater. 1993; 41: 1].
[0006] In sum, previous development on Al-based materials with high
strength at elevated temperatures failed to meet the property
objective of 275 MPa at 300.degree. C.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a new class of Al
alloys characterized by formation from an intermediate amorphous
state to a final fcc-Al matrix hardened by a combination of
Ll.sub.2 precipitates and Al.sub.23Ni.sub.6M.sub.4 precipitates in
order to establish the Al-based analogue of Ni-base superalloys and
achieve high-temperature strength with usable ductility.
[0008] An appropriate melt of Al with selected TM and RE is first
processed to achieve an intermediate amorphous state to dissolve
Ll.sub.2-forming components. The preferred method to achieve a
primarily (above 70% in volume) amorphous state is RSP from the
molten alloy by process techniques such as powder atomization, melt
spinning, and spray casting. The RSP process should have a cooling
rate of at least about 10.sup.3.degree. C./sec, preferably at least
10.sup.4.degree. C./sec. Other methods to achieve amorphous
microstructure through a solid-state process, such as mechanical
milling, may also be used. The intermediate amorphous alloys are
then thermo-mechanically devitrified to a final primarily (above
70% in volume) fcc/Ll.sub.2/Al.sub.23Ni.sub.6M.sub.4 crystalline
microstructure with at least about 70% fcc phase in volume, at
least about 0.10% Ll.sub.2 phase, and at least about 10%
Al.sub.23Ni.sub.6M.sub.4 phase in volume.
[0009] The selection of alloying elements is based on (1) good
glass-forming ability with RSP, (2) long-term strength at or above
300.degree. C., and (3) composition tolerance for a robust design.
For glass-forming ability, elements with strong short-range
ordering effects, and slow long-range diffusing kinetics in molten
Al are employed. For long-term strength at or above 300.degree. C.,
the alloy of the present invention employs 25 nm-diameter Ll.sub.2
particles which are reported to provide optimal creep resistance
[E. A. Marquis, Microstructural Evolution and Strengthening
Mechanisms in Al--Sc and Al--Mg--Sc Alloys, Ph.D. thesis,
Northwestern University, 2002.]. For a robust design, the present
invention employs Al.sub.23Ni.sub.6M.sub.4, where M is one or more
elements selected from the group consisting of Y and Yb. When there
is deficiency of the Ll.sub.2-formers, the incoherent
D0.sub.11-Al.sub.3Ni phase is expected to precipitate, leading to
low ductility. Al.sub.23Ni.sub.6M.sub.4 is more solute-rich that
the Al.sub.3X phase and will consume less Al for a given amount of
solute, giving rise to a higher amount of fcc matrix which in turn
increases the ductility.
[0010] Thus, it is an object of the invention to provide a new
class of high-temperature high-strength Ll.sub.2-phase strengthened
Al alloys processed through the amorphous state, preferably with
RSP, and then subsequently devitrified with thermo-mechanical,
processes.
[0011] A further object of the invention is to combine selected TM
and RE to provide good glass forming ability during RSP such as
powder atomization or melt spinning to form an amorphous Al alloy,
dissolving the Ll.sub.2-stabilizers before the devitrification
process.
[0012] Another object of the invention is to provide aluminum
alloys with usable strength at or above about 300.degree. C. by
selecting Ll.sub.2-stabilizers which reduce the interphase lattice
misfit in all three dimensions to promote a finer dispersion.
[0013] Another object of the invention is to employ
Al.sub.23Ni.sub.6M.sub.4 precipitates to provide composition
tolerance and maintain reasonable alloy ductility.
[0014] These and a other objects, advantages and features will be
set forth in the detailed description which follows.
BRIEF DESCRIPTION OF THE DRAWING
[0015] In the detailed description which follows, reference will be
made to the drawing comprised of the following figures:
[0016] FIG. 1 is an X-ray diffractogram of the alloy of Example 1
as melt-spun with positions of fcc pure aluminum reflections
indicating a fully amorphous state;
[0017] FIG. 2 is an X-ray diffractogram of the alloy of Example 1
after devitrification at 550.degree. C. for 24 hours, with
positions of reflections of pure fcc Al, Al.sub.3Yb, and
Al.sub.23Ni.sub.6Yb.sub.4 phases, indicating the desired phases:
fcc+Ll.sub.2;
[0018] FIG. 3 is a Scanning Electron Microscope (SEM) secondary
electron image of devitrified alloy of Example 1 indicating phase
constituents fcc+Ll.sub.2Al.sub.23Ni.sub.6Yb.sub.4; and
[0019] FIG. 4 is an SEM secondary electron image of devitrified
alloy of Example 2 indicating phase constituents
fcc+Ll.sub.2+Al.sub.23Ni.sub.6Yb.sub.4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] General Summary
[0021] In general, the subject matter of the invention comprises an
Al alloy in crystalline form having higher or greater strength
particularly at elevated temperatures, i.e. greater than about
300.degree. C. The Al alloy is; made by compounding a mixture of Al
with selected TM and RE in amorphous state followed by
devitrification to a mixed crystalline state comprising fcc,
Ll.sub.2, and Al.sub.23Ni.sub.6M.sub.4 phases wherein the ratios of
the crystalline states are within certain preferred ranges.
Preferably the resultant alloy has at least about 70% by volume fcc
phase, at least about 10% by volume Ll.sub.2 phase, and at least
about 10% by volume Al.sub.23Ni.sub.6M.sub.4 phase where M is
selected from the group consisting of Y, Yb and a combination of Y
and Yb with limited residual amorphous or quasi-crystalline phase
material.
[0022] The choice of starting materials may vary, as may the
compounding processes, the glass formation processes and the
devitrification processes. In the amorphous state, there may be
some crystalline material contained therein, but preferably no more
than about 30% by volume. The particle size of alloys passing
through a fully or almost fully glassy state is much finer than
that of alloys without passing through the glassy state or only
passing through a partially glassy state with Ll.sub.2 already
present in the as-spun condition. Thus forming the mixture in the
amorphous intermediate state constitutes a very important aspect of
the invention.
[0023] The alloy materials, in addition to Al, include one or more
TM taken or selected from the group of Cu, Ni, Co, Ti, Fe, Y, and
Sc, and one or more RE selected or taken from the group of Er, Tm,
Yb, and Lu. TM metals are utilized in the range of about 2 to 12 at
%, and RE materials are utilized in the range of about 2 to 15 at
%.
[0024] The processes for mixing or forming the starting materials
in the amorphous state are not necessarily limiting. Thus, it is
contemplated that solid state processing, liquid or melt processing
as well as gas phase processing may be utilized, though liquid
phase processing is preferred. The completeness of the amorphous
state is at least about 70% by volume and preferably greater.
[0025] Development Technique
[0026] Precipitation-hardened Al alloys are difficult to develop
for high strength due to limited solubility of alloying elements.
Al alloys with high fractions of precipitate that cannot be
completely solution-treated have very coarse particles that tend to
limit strength, corrosion resistance and toughness. In contrast,
the Al alloys of the present invention exhibit high strength, good
ductility, and high-temperature stability at or above 300.degree.
C.
[0027] By carefully selecting an appropriate Al alloy composition,
processing techniques can achieve a fully amorphous state after
rapid cooling. Furthermore, this glass can then be
thermo-mechanically processed such that the glass devitrifies into
a crystalline fcc matrix with nanophase precipitates. By passing
through the glass state, the equilibrium solidification that would
produce coarse precipitates is avoided. Certain TM such as Fe, Co,
Ni and Cu promote short-range ordering in liquid Al, which leads to
low partial molar volume, low thermal expansion, and high viscosity
that are beneficial to glass-forming ability. RE elements such as
Ce, Gd, Yb, and Er with large atomic size exhibit low diffusivity
in Al and thus retard crystal nucleation. Therefore, Al-TM-RE
comprise a class of glass-forming system for Al alloys of the
present invention.
[0028] The elements Er, Lu, Tm and Yb are reported as the only RE
Ll.sub.2-stabilizers. Among these four RE elements, Yb has the
smallest lattice parameter and relatively low-cost. Er has the
lowest cost. To evaluate the effect on glass-forming ability of
these alloying additions, a reduced glass transition temperature
(T.sub.rg) model was developed. In the Al-TM-RE system, this model
predicts that Er has no beneficial effect to T.sub.rg. As a
consequence, alloys of the invention utilize Yb as the preferred
Ll.sub.2-stabilizer rather than Er, Tm, and Lu.
[0029] Sc is the oily TM element that can form a stable Ll.sub.2
with Al. Compared to RE Ll.sub.2 formers, Sc can form Ll.sub.2 with
a smaller lattice parameter, reducing the misfit between Ll.sub.2
and Al matrix. However, Sc is by far the most expensive of the
Ll.sub.2-stabilizers and therefore embodiments of the invention
seek to limit. Sc as much as possible. Efforts have been made to
search for other TM to substitute for Sc. A preliminary requirement
for such substitution is solubility. Ti has a substantial
solubility in Al.sub.3Sc. In addition, Ti has the lowest diffusion
coefficient in solid Al among TMs. Adding Ti to Al.sub.3Sc thus
reduces the coarsening rate of Ll.sub.2 precipitates. Moreover,
addition of Ti decreases the lattice parameter of Al.sub.3(Sc,Ti)
and hence minimizes the lattice misfit with Al. Thus, alloys of the
invention incorporate Yb and Sc as base Ll.sub.2 formers but are
not limited to these elements. TM such as Ti, V, Zr, etc., which
will result in low misfit and thus retard coarsening are considered
useful.
[0030] For a robust design, the present invention employs
Al.sub.23Ni.sub.6M.sub.4, where M is one or more elements selected
from the group consisting of Y and Yb. To introduce both
Al.sub.23Ni.sub.6M.sub.4 and Ll.sub.2 in the design, thermodynamic
equilibrium calculations were performed using the thermodynamic
database and calculation package Thermo-Calc.RTM. [Sundman, B. B.
Jansson, and J. O. Andersson. 1985. Calphad 9: 153-190].
Thermodynamic calculations predict that Y has certain solubility in
Ll.sub.2, which expands the Ll.sub.2 lattice spacing, increasing
the misfit. Therefore, a design criterion should be set to limit
the partitioning of Y in Ll.sub.2. In addition, other phases such
as Al.sub.3Ni, Al.sub.3Y and Al.sub.9CO.sub.2 should be
avoided.
[0031] Al-base alloys will have good ductility when the amount of
fcc is equal to or over about 70%. Thus, the total amount of
Al.sub.23Ni.sub.6M.sub.4 and Ll.sub.2 is fixed to less than about
30%. At the desired phase constitution, Co content is set by
[x.sub.Ni+x.sub.Co]/x.sub.Y=6/4 because Co has a small solubility
in Al.sub.23Ni.sub.6M.sub.4 by substituting for Ni. After examining
the effect of Co addition based on thermodynamic calculations, an
optimum was found around 0.6 at % Co, at which partitioning of Y in
Ll.sub.2 is almost zero. If Co addition is significantly more than
0.6 at %, Al.sub.9CO.sub.2 and Al.sub.3Y may precipitate.
[0032] Experimental Results
[0033] The present invention alloys, through, computational design
of multi-component Al-TM-RE systems incorporate, desired processing
properties-glass forming ability and the desired microstructure--a
fine dispersion of Ll.sub.2 after devitrification in the Al
matrix.
Example 1
[0034] Prototypes of preferred embodiments can be made by
arc-melting, melt spinning or wedge casting. Through melt spinning,
ribbons of Al-3.46Ni-2.78Y-0.72Co-0.42Yb-0.63Sc-0.42Zr-0.21Ti (at
%) were made. Melt-spun ribbons are approximately 3-4 mm wide and
30-40.mu. in thickness. The ribbons were characterized using
micro-hardness) x-ray diffraction, and SEM analysis. The x-ray
diffraction pattern (FIG. 1) of the as-spun ribbon indicates a
partial amorphous microstructure without intermetallic
precipitates. After devitrification at 550.degree. C. for 24 hours,
x-ray diffraction (FIG. 2) shows precipitation of
Al.sub.23Ni.sub.6Yb.sub.4 and peaks of Ll.sub.2. It is noted that
the peaks of Ll.sub.2 are shifted compared to Ll.sub.2-Al.sub.3Yb,
indicating; decrease of lattice parameters due to dissolution of
Sc, Ti, and Zr in Al.sub.3Yb. Such decrease of the Ll.sub.2 lattice
parameter will reduce the misfit. FIG. 3 shows an SEM image of the
devitrified specimens confirming the phase constituents
fcc+Ll.sub.2+Al.sub.23Ni.sub.6Yb.sub.4. The matrix is fcc-Al, the
large sized grey phase material is Al.sub.23Ni.sub.6Yb.sub.4, and
the small white particles are Ll.sub.2 phase particles. The
Ll.sub.2 particles remain smaller than .about.50 nm in diameter,
while the rod-shaped Al.sub.23Ni.sub.6Yb.sub.4 phase material is
less than 1.mu. in length. The small Ll.sub.2 particles will
provide optimal creep resistance at or above 300.degree. C. and the
Al.sub.23Ni.sub.6Yb.sub.4 material is present to avoid detrimental
compounds and improve the ductility at the high temperature.
Example 2
[0035] Ribbons of Al-3Ni-2.42Y-0.62Co-0.6Yb-0.6Sc-0.6Zr-0.6Ti (at
%) were made using the protocol of Example 1. The ribbons were
characterized using micro-hardness, x-ray diffraction, and SEM
analysis. FIG. 4 shows an SEM image of the devitrified specimens
confirming the phase constituents
fcc+Ll.sub.2+Al.sub.23Ni.sub.6Yb.sub.4. The matrix is fcc-Al, the
large sized grey phase material is Al.sub.23Ni.sub.6Yb.sub.4, and
the small white particles are Ll.sub.2 phase material. The Ll.sub.2
particles remain smaller than .about.50 nm in diameter, while the
rod-shaped Al.sub.23Ni.sub.6Yb.sub.4 phase material is less than
1.mu. in length. The small Ll.sub.2 particles will provide optimal
creep resistance at or above 300.degree. C. and the
Al.sub.23Ni.sub.6Yb.sub.4 material is present to avoid detrimental
compounds and improve the ductility.
Example 3
[0036] Scale-up processing of the alloy in Example 1 was
engineered. Amorphous powder produced by high-pressure He
atomization can be used as a raw material to produce an amorphous
bulk by consolidation at high temperatures. The amorphous alloy
powder is produced by gas atomization, followed by sieving,
precompaction, canning and sealing into a Cu tube, carried out in a
well-controlled atmosphere with an oxide or moisture concentration
below 1 ppm. Powder of the alloy in Example 1 was successfully
atomized and extruded. The extrusion is a thermo-mechanical process
where the glass devitrifies into a crystalline fcc matrix with
nanophase precipitates.
Example 4
[0037] Powder of the alloy in Example 2 was successfully atomized
and extruded using the protocol of Example 3. The extrusion is a
thermo-mechanical process where the glass devitrifies into a
crystalline fcc matrix with nanophase precipitates.
[0038] Variations of the described aluminum alloy as well as the
process for manufacture thereof and the product created by the
process arc available to provide the expected functionality of high
short-term and long-term strength at temperatures above about
300.degree. C. Thus the invention is to be limited only by the
following claims and equivalents thereof.
* * * * *