U.S. patent application number 15/996438 was filed with the patent office on 2019-02-07 for feedstocks for additive manufacturing, and methods of using the same.
The applicant listed for this patent is HRL Laboratories, LLC. Invention is credited to John H. MARTIN, Brennan D. YAHATA.
Application Number | 20190040503 15/996438 |
Document ID | / |
Family ID | 65231449 |
Filed Date | 2019-02-07 |
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United States Patent
Application |
20190040503 |
Kind Code |
A1 |
MARTIN; John H. ; et
al. |
February 7, 2019 |
FEEDSTOCKS FOR ADDITIVE MANUFACTURING, AND METHODS OF USING THE
SAME
Abstract
Some variations provide a method of making an additively
manufactured metal component, comprising: providing a feedstock
that includes a high-vapor-pressure metal; exposing a first amount
of the feedstock to an energy source for melting; and solidifying
the melt layer, thereby generating a solid layer of an additively
manufactured metal component. The metal-containing feedstock is
enriched with a higher concentration of the high-vapor-pressure
metal compared to its concentration in the additively manufactured
metal component. The high-vapor-pressure metal may be selected from
Mg, Zn, Li, Al, Cd, Hg, K, Na, Rb, Cs, Mn, Be, Ca, Sr, or Ba, for
example. Additively manufactured metal components are provided.
Metal-containing feedstocks for additive manufacturing are also
disclosed, wherein concentration of at least one
high-vapor-pressure metal in the feedstock is selected based on a
desired concentration of the high-vapor-pressure metal in an
additively manufactured metal component derived from the
metal-containing feedstock. Various feedstock compositions are
disclosed.
Inventors: |
MARTIN; John H.; (Los
Angeles, CA) ; YAHATA; Brennan D.; (Los Angeles,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HRL Laboratories, LLC |
Malibu |
CA |
US |
|
|
Family ID: |
65231449 |
Appl. No.: |
15/996438 |
Filed: |
June 2, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62540615 |
Aug 3, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 35/288 20130101;
C22C 19/03 20130101; C22C 21/10 20130101; B23K 2103/15 20180801;
B23K 26/342 20151001; B23K 2103/10 20180801; C22C 9/00 20130101;
B23K 26/144 20151001; B23K 2103/08 20180801; C22C 21/06 20130101;
B23K 26/34 20130101; B23K 26/354 20151001; B23K 2103/14 20180801;
C22C 23/00 20130101; B33Y 10/00 20141201; B33Y 70/00 20141201; C22C
14/00 20130101; B32B 15/016 20130101 |
International
Class: |
C22C 21/10 20060101
C22C021/10; B33Y 10/00 20060101 B33Y010/00; B33Y 70/00 20060101
B33Y070/00; B23K 26/354 20060101 B23K026/354; B23K 26/34 20060101
B23K026/34 |
Claims
1. A method of making an additively manufactured metal component,
said method comprising: (a) providing a metal-containing feedstock
comprising a high-vapor-pressure metal and at least one other metal
species different than said high-vapor-pressure metal; (b) exposing
a first amount of said metal-containing feedstock to an energy
source for melting said first amount of said metal-containing
feedstock, thereby generating a first melt layer; and (c)
solidifying said first melt layer, thereby generating a first solid
layer of an additively manufactured metal component, wherein said
metal-containing feedstock contains a higher concentration of said
high-vapor-pressure metal compared to the concentration of said
high-vapor-pressure metal in said first solid layer.
2. The method of claim 1, wherein said high-vapor-pressure metal is
present in said metal-containing feedstock in a concentration from
about 0.1 wt % to about 20 wt %.
3. The method of claim 1, wherein an enrichment ratio of wt %
concentration of said high-vapor-pressure metal in said
metal-containing feedstock to wt % concentration of said
high-vapor-pressure metal in said first solid layer is at least
1.05.
4. The method of claim 3, wherein said enrichment ratio is at least
1.25.
5. The method of claim 4, wherein said enrichment ratio is at least
1.5.
6. The method of claim 5, wherein said enrichment ratio is at least
2.
7. The method of claim 1, wherein said high-vapor-pressure metal is
selected from the group consisting of Mg, Zn, Li, Al, Cd, Hg, K,
Na, Rb, Cs, Mn, Be, Ca, Sr, Ba, and combinations thereof.
8. The method of claim 7, wherein said high-vapor-pressure metal is
selected from the group consisting of Mg, Zn Li, Al, and
combinations thereof.
9. The method of claim 1, wherein said metal-containing feedstock
is an aluminum alloy.
10. The method of claim 1, wherein said metal-containing feedstock
is a magnesium alloy.
11. The method of claim 1, wherein said metal-containing feedstock
is a titanium alloy.
12. The method of claim 1, wherein said metal-containing feedstock
is a nickel and/or copper superalloy.
13. The method of claim 1, wherein said metal-containing feedstock
contains Al, from 0.05 wt % to 0.28 wt % Cr, from 1 wt % to 2 wt %
Cu, from 3 wt % to 10 wt % Mg, and from 6.2 wt % to 20 wt % Zn; and
wherein said first solid layer contains Al, from 0.18 wt % to 0.28
wt % Cr, from 1.2 wt % to 2 wt % Cu, from 2.1 wt % to 2.9 wt % Mg,
and from 5.1 wt % to 6.1 wt % Zn.
14. The method of claim 1, wherein said metal-containing feedstock
contains Al, from 0.01 wt % to 5 wt % Zr, from 1 wt % to 2.6 wt %
Cu, from 2.7 wt % to 10 wt % Mg, and from 6.7 wt % to 20 wt % Zn;
and wherein said first solid layer contains Al, from 0.08 wt % to 5
wt % Zr, from 2 wt % to 2.6 wt % Cu, from 1.9 wt % to 2.6 wt % Mg,
and from 5.7 wt % to 6.7 wt % Zn.
15. The method of claim 1, wherein said metal-containing feedstock
contains Al, from 0.01 wt % to 5 wt % Zr, from 1.9 wt % to 10 wt %
Mg, and from 7.1 wt % to 20 wt % Zn; and wherein said first solid
layer contains Al, from 0.07 wt % to 5 wt % Zr, from 1.3 wt % to
1.8 wt % Mg, and from 7 wt % to 8 wt % Zn.
16. The method of claim 1, wherein said metal-containing feedstock
further comprises grain-refining nanoparticles.
17. The method of claim 16, wherein said grain-refining
nanoparticles are selected from the group consisting of zirconium,
silver, lithium, manganese, iron, silicon, vanadium, scandium,
yttrium, niobium, tantalum, titanium, boron, hydrogen, carbon,
nitrogen, and combinations thereof.
18. The method of claim 16, wherein said grain-refining
nanoparticles are selected from the group consisting of zirconium,
titanium, tantalum, niobium, and oxides, nitrides, hydrides,
carbides, or borides thereof, and combinations of the
foregoing.
19. An additively manufactured metal component produced by a
process comprising: (a) providing a metal-containing feedstock
comprising a high-vapor-pressure metal and at least one other metal
species different than said high-vapor-pressure metal; (b) exposing
a first amount of said metal-containing feedstock to an energy
source for melting said first amount of said metal-containing
feedstock, thereby generating a first melt layer; (c) solidifying
said first melt layer, thereby generating a first solid layer of an
additively manufactured metal component; and (d) repeating steps
(b) and (c) a plurality of times to generate a plurality of solid
layers by sequentially solidifying a plurality of melt layers in an
additive-manufacturing build direction, wherein said
metal-containing feedstock contains a higher concentration of said
high-vapor-pressure metal compared to the concentration of said
high-vapor-pressure metal in said solid layers.
20. The additively manufactured metal component of claim 19,
wherein an enrichment ratio of wt % concentration of said
high-vapor-pressure metal in said metal-containing feedstock to wt
% concentration of said high-vapor-pressure metal in said first
solid layer is at least 1.05.
21. The additively manufactured metal component of claim 19,
wherein said high-vapor-pressure metal is selected from the group
consisting of Mg, Zn, Li, Al, Cd, Hg, K, Na, Rb, Cs, Mn, Be, Ca,
Sr, Ba, and combinations thereof.
22. The additively manufactured metal component of claim 19,
wherein said metal-containing feedstock contains Al, from 0.05 wt %
to 0.28 wt % Cr, from 1 wt % to 2 wt % Cu, from 3 wt % to 10 wt %
Mg, and from 6.2 wt % to 20 wt % Zn; and wherein said first solid
layer contains Al, from 0.18 wt % to 0.28 wt % Cr, from 1.2 wt % to
2 wt % Cu, from 2.1 wt % to 2.9 wt % Mg, and from 5.1 wt % to 6.1
wt % Zn.
23. The additively manufactured metal component of claim 19,
wherein said metal-containing feedstock contains Al, from 0.01 wt %
to 5 wt % Zr, from 1 wt % to 2.6 wt % Cu, from 2.7 wt % to 10 wt %
Mg, and from 6.7 wt % to 20 wt % Zn; and wherein said first solid
layer contains Al, from 0.08 wt % to 5 wt % Zr, from 2 wt % to 2.6
wt % Cu, from 1.9 wt % to 2.6 wt % Mg, and from 5.7 wt % to 6.7 wt
% Zn.
24. The additively manufactured metal component of claim 19,
wherein said metal-containing feedstock contains Al, from 0.01 wt %
to 5 wt % Zr, from 1.9 wt % to 10 wt % Mg, and from 7.1 wt % to 20
wt % Zn; and wherein said first solid layer contains Al, from 0.07
wt % to 5 wt % Zr, from 1.3 wt % to 1.8 wt % Mg, and from 7 wt % to
8 wt % Zn.
25. The additively manufactured metal component of claim 19,
wherein said plurality of solid layers have differing primary
growth-direction angles with respect to each other.
26. The additively manufactured metal component of claim 19,
wherein said additively manufactured metal component has a
microstructure with equiaxed grains.
27. A metal-containing feedstock for additive manufacturing,
wherein said metal-containing feedstock contains Al, from 0.05 wt %
to 0.28 wt % Cr, from 1 wt % to 2 wt % Cu, from 3 wt % to 10 wt %
Mg, and from 6.2 wt % to 20 wt % Zn.
28. A metal-containing feedstock for additive manufacturing,
wherein said metal-containing feedstock contains Al, from 0.01 wt %
to 5 wt % Zr, from 1.9 wt % to 10 wt % Mg, from 6.7 wt % to 20 wt %
Zn, and optionally from 1 wt % to 2.6 wt % Cu.
Description
PRIORITY DATA
[0001] This patent application is a non-provisional application
with priority to U.S. Provisional Patent App. No. 62/540,615, filed
on Aug. 3, 2017, which is hereby incorporated by reference
herein.
FIELD OF THE INVENTION
[0002] The present invention generally relates to processes for
additive manufacturing using optimized metal-containing precursors
(e.g., powders).
BACKGROUND OF THE INVENTION
[0003] Metal-based additive manufacturing, or three-dimensional
(3D) printing, has applications in many industries, including the
aerospace and automotive industries. Building up metal components
layer-by-layer increases design freedom and manufacturing
flexibility, thereby enabling complex geometries while eliminating
traditional economy-of-scale constraints. In metal-based additive
manufacturing, application of a direct energy source, such as a
laser or electron beam, to melt alloy powders locally results in
solidification rates between 0.1 m/s and 5 m/s, an order of
magnitude increase over conventional casting processes.
[0004] Additive manufacturing allows for one-step fabrication of
complex parts of arbitrary design. Additive manufacturing
eliminates the need for assembling multiple components or setting
up new equipment, while minimizing manufacturing time and wastage
of materials and energy. Although additive manufacturing is rapidly
growing to produce metallic, polymeric, and ceramic components,
production of metallic parts is its fastest growing sector.
[0005] In order to successfully print a metallic part, an
appropriate alloy must be selected. Successive layers need to be
adequately bonded by fusion. An understanding of printability,
including the ability of an alloy to resist distortion and fusion
defects, is important for powder bed-based additive manufacturing
processes.
[0006] Currently only a few alloys, the most relevant being
AlSi10Mg, TiAl6V4, CoCr, and Inconel 718, can be reliably
additively manufacturing. The vast majority of the more than 5,500
alloys in use today cannot be additively manufactured because the
melting and solidification dynamics during the printing process
lead to intolerable microstructures with large columnar grains and
cracks. 3D-printable metal alloys are limited to those known to be
easily weldable. The limitations of the currently printable alloys,
especially with respect to specific strength, fatigue life, and
fracture toughness, have hindered metal-based additive
manufacturing. See Martin et al., "3D printing of high-strength
aluminium alloys" Nature vol. 549, pages 365-369.
[0007] Specifically regarding aluminum alloys, for example, the
only printable aluminum alloys are based on the binary Al--Si
system and tend to converge around a yield strength of
approximately 200 MPa with a low ductility of 4%. The exception is
Scalmalloy, which relies on alloying additions of scandium, a rare
high-cost metal. In contrast, most aluminum alloys used in
automotive, aerospace, and consumer applications are wrought alloys
of the 2000, 5000, 6000, or 7000 series, which can exhibit
strengths exceeding 400 MPa and ductility of more than 10% but
cannot currently be additively manufactured. These systems have
low-cost alloying elements (Cu, Mg, Zn, and Si) carefully selected
to produce complex strengthening phases during subsequent ageing.
These same elements promote large solidification ranges, leading to
hot tearing (cracking) during solidification--a problem that has
been difficult to surmount for more than 100 years since the first
age-hardenable alloy, duralumin, was developed.
[0008] In particular, during solidification of these alloys, the
primary equilibrium phase solidifies first at a different
composition from the bulk liquid. This mechanism results in solute
enrichment in the liquid near the solidifying interface, locally
changing the equilibrium liquidus temperature and producing an
unstable, undercooled condition. As a result, there is a breakdown
of the solid-liquid interface leading to cellular or dendritic
grain growth with long channels of interdendritic liquid trapped
between solidified regions. As temperature and liquid volume
fraction decrease, volumetric solidification shrinkage and thermal
contraction in these channels produces cavities and hot tearing
cracks which may span the entire length of the columnar grain and
can propagate through additional intergranular regions. Note that
aluminum alloys Al 7075 and Al 6061 are highly susceptible to the
formation of such cracks, due to a lack of processing paths to
produce fine equiaxed grains.
[0009] Another problem associated with additive manufacturing of
metals is that producing equiaxed structures typically requires
large amounts of undercooling, which has thus far proven difficult
in additive processes where high thermal gradients arise from
rastering of a direct energy source in an arbitrary geometric
pattern. Fine equiaxed microstructures accommodate strain in the
semi-solid state by suppressing coherency that locks the
orientation of these solid dendrites and promotes tearing.
[0010] Yet another problem associated with additive manufacturing
of metals arises from the vapor pressures of some metals
themselves. Most engineering alloys contain multiple alloying
elements that vaporize rapidly at high temperatures and can be
selectively lost during additive manufacturing or welding.
Consequently, the chemical composition of the final part may be
different from that of the original material.
[0011] In particular, at high temperatures encountered during
additive manufacturing, significant vaporization of alloying
elements can happen out of the melt pool. Since some alloying
elements are more volatile than others, selective vaporization of
alloying elements often results in a significant change in the
composition of the alloy. For example, during laser welding of
aluminum alloys, losses of magnesium and zinc result in pronounced
changes to their concentrations. The composition change can cause
degradation of mechanical properties (e.g., tensile strength) and
chemical properties (e.g., corrosion resistance) in the final
structure.
[0012] A reduction in peak temperature and a smaller
surface-to-volume ratio of the melt pool may minimize pronounced
changes of chemical composition during laser processing. However,
it is not always possible to minimize temperature due to the
presence of high-melting-point metals that need to be liquefied
during additive manufacturing. Likewise, depending on the specific
additive manufacturing set-up or three-dimensional object to be
printed, it is not always possible to reduce surface-to-volume
ratio of the melt pool--or even if that can be done, it may not be
sufficient to prevent significant vaporization of
high-vapor-pressure metals.
[0013] A lack of teaching in the art with respect to processing of
alloy systems that undergo vaporization makes it very difficult to
select targeted alloy feedstock compositions. Currently, metal
powders and feedstocks are produced at the same composition as the
desired final alloy. There is a need to provide optimized
feedstocks for additive manufacturing of metals, to address this
significant problem.
SUMMARY OF THE INVENTION
[0014] The present invention addresses the aforementioned needs in
the art, as will now be summarized and then further described in
detail below.
[0015] Some variations provide a method of making an additively
manufactured metal component, the method comprising:
[0016] (a) providing a metal-containing feedstock comprising a
high-vapor-pressure metal and at least one other metal species
different than the high-vapor-pressure metal;
[0017] (b) exposing a first amount of the metal-containing
feedstock to an energy source for melting the first amount of the
metal-containing feedstock, thereby generating a first melt layer;
and
[0018] (c) solidifying the first melt layer, thereby generating a
first solid layer of an additively manufactured metal
component,
[0019] wherein the metal-containing feedstock contains a higher
concentration of the high-vapor-pressure metal compared to the
concentration of the high-vapor-pressure metal in the first solid
layer.
[0020] The high-vapor-pressure metal may be present in the
metal-containing feedstock in a concentration from about 0.1 wt %
to about 20 wt %, for example. The enrichment ratio of wt %
concentration of the high-vapor-pressure metal in the
metal-containing feedstock to wt % concentration of the
high-vapor-pressure metal in the first solid layer is typically at
least 1.05, such as at least 1.25, at least 1.5, or at least
2.0.
[0021] The high-vapor-pressure metal may be selected from the group
consisting of Mg, Zn, Li, Al, Cd, Hg, K, Na, Rb, Cs, Mn, Be, Ca,
Sr, Ba, and combinations thereof. In certain embodiments, the
high-vapor-pressure metal is selected from the group consisting of
Mg, Zn, Al, Li, and combinations thereof.
[0022] The metal-containing feedstock may be an aluminum alloy, a
magnesium alloy, a titanium alloy, a nickel superalloy, a copper
superalloy, or a combination thereof.
[0023] The metal-containing feedstock may be in the form of a
powder or a geometric object, such as a wire.
[0024] In some embodiments, the metal-containing feedstock contains
Al, from 0.05 wt % to 0.28 wt % Cr, from 1 wt % to 2 wt % Cu, from
3 wt % to 10 wt % Mg, and from 6.2 wt % to 20 wt % Zn; and wherein
the first solid layer contains Al, from 0.18 wt % to 0.28 wt % Cr,
from 1.2 wt % to 2 wt % Cu, from 2.1 wt % to 2.9 wt % Mg, and from
5.1 wt % to 6.1 wt % Zn.
[0025] In some embodiments, the metal-containing feedstock contains
Al, from 0.01 wt % to 5 wt % Zr, from 1 wt % to 2.6 wt % Cu, from
2.7 wt % to 10 wt % Mg, and from 6.7 wt % to 20 wt % Zn; and
wherein the first solid layer contains Al, from 0.08 wt % to 5 wt %
Zr, from 2 wt % to 2.6 wt % Cu, from 1.9 wt % to 2.6 wt % Mg, and
from 5.7 wt % to 6.7 wt % Zn.
[0026] In some embodiments, the metal-containing feedstock contains
Al, from 0.01 wt % to 5 wt % Zr, from 1.9 wt % to 10 wt % Mg, and
from 7.1 wt % to 20 wt % Zn; and wherein the first solid layer
contains aluminum, from 0.07 wt % to 5 wt % Zr, from 1.3 wt % to
1.8 wt % Mg, and from 7 wt % to 8 wt % Zn.
[0027] In various embodiments, steps (b) and (c) utilize a
technique selected from the group consisting of selective laser
melting, electron beam melting, laser engineered net shaping,
selective laser sintering, direct metal laser sintering, integrated
laser melting with machining, laser powder injection, laser
consolidation, direct metal deposition, wire-directed energy
deposition, plasma arc-based fabrication, ultrasonic consolidation,
and combinations thereof.
[0028] The method may further comprise repeating steps (b) and (c)
a plurality of times to generate a plurality of solid layers by
sequentially solidifying a plurality of melt layers in an
additive-manufacturing build direction. The first solid layer, and
additional solid layers, may be characterized by an average grain
size of less than 10 microns.
[0029] In some embodiments of the invention, the metal-containing
feedstock further comprises grain-refining nanoparticles. The
grain-refining nanoparticles may be present from about 0.001 wt %
to about 10 wt % of the metal-containing feedstock, for
example.
[0030] In these embodiments, the grain-refining nanoparticles are
selected from the group consisting of zirconium, silver, lithium,
manganese, iron, silicon, vanadium, scandium, yttrium, niobium,
tantalum, titanium, nitrogen, hydrogen, carbon, boron, and
combinations thereof, such as intermetallics or nitrides, hydrides,
carbides, or borides of one or more of the recited metals. In
certain embodiments, the grain-refining nanoparticles are selected
from the group consisting of zirconium, titanium, tantalum,
niobium, and oxides, nitrides, hydrides, carbides, or borides
thereof, and combinations of the foregoing.
[0031] When grain-refining nanoparticles are included in the
metal-containing feedstock, the additively manufactured first solid
layer may have a microstructure with equiaxed grains. The
additively manufactured first solid layer may also be characterized
by a crack-free microstructure, in preferred embodiments.
[0032] The present invention also provides an additively
manufactured metal component produced by a process comprising:
[0033] (a) providing a metal-containing feedstock comprising a
high-vapor-pressure metal and at least one other metal species
different than the high-vapor-pressure metal;
[0034] (b) exposing a first amount of the metal-containing
feedstock to an energy source for melting the first amount of the
metal-containing feedstock, thereby generating a first melt
layer;
[0035] (c) solidifying the first melt layer, thereby generating a
first solid layer of an additively manufactured metal component;
and
[0036] (d) repeating steps (b) and (c) a plurality of times to
generate a plurality of solid layers by sequentially solidifying a
plurality of melt layers in an additive-manufacturing build
direction,
[0037] wherein the metal-containing feedstock contains a higher
concentration of the high-vapor-pressure metal compared to the
concentration of the high-vapor-pressure metal in the solid
layers.
[0038] In some embodiments, an enrichment ratio of wt %
concentration of the high-vapor-pressure metal in the
metal-containing feedstock to wt % concentration of the
high-vapor-pressure metal in the first solid layer is at least
1.05.
[0039] In the additively manufactured metal component, the
high-vapor-pressure metal may be selected from the group consisting
of Mg, Zn, Li, Al, Cd, Hg, K, Na, Rb, Cs, Mn, Be, Ca, Sr, Ba, and
combinations thereof.
[0040] In certain additively manufactured metal components, the
metal-containing feedstock contains Al, from 0.05 wt % to 0.28 wt %
Cr, from 1 wt % to 2 wt % Cu, from 3 wt % to 10 wt % Mg, and from
6.2 wt % to 20 wt % Zn; and the first solid layer contains Al, from
0.18 wt % to 0.28 wt % Cr, from 1.2 wt % to 2 wt % Cu, from 2.1 wt
% to 2.9 wt % Mg, and from 5.1 wt % to 6.1 wt % Zn.
[0041] In certain additively manufactured metal components, the
metal-containing feedstock contains Al, from 0.01 wt % to 5 wt %
Zr, from 1 wt % to 2.6 wt % Cu, from 2.7 wt % to 10 wt % Mg, and
from 6.7 wt % to 20 wt % Zn; and the first solid layer contains Al,
from 0.08 wt % to 5 wt % Zr, from 2 wt % to 2.6 wt % Cu, from 1.9
wt % to 2.6 wt % Mg, and from 5.7 wt % to 6.7 wt % Zn.
[0042] In certain additively manufactured metal components, the
metal-containing feedstock contains Al, from 0.01 wt % to 5 wt %
Zr, from 1.9 wt % to 10 wt % Mg, and from 7.1 wt % to 20 wt % Zn;
and the first solid layer contains Al, from 0.07 wt % to 5 wt % Zr,
from 1.3 wt % to 1.8 wt % Mg, and from 7 wt % to 8 wt % Zn.
[0043] The additively manufactured metal component may be
characterized by an average grain size of less than 1 millimeter,
such as less than 10 microns.
[0044] In some embodiments, the additively manufactured metal
component has a microstructure with a crystallographic texture that
is not solely oriented in the additive-manufacturing build
direction. The plurality of solid layers may have differing primary
growth-direction angles with respect to each other.
[0045] In some embodiments, the additively manufactured metal
component has a microstructure with equiaxed grains. In certain
embodiments, the additively manufactured metal component has a
crack-free microstructure.
[0046] Variations of the present invention also provide a
metal-containing feedstock for additive manufacturing, wherein the
metal-containing feedstock contains at least one
high-vapor-pressure metal, and wherein concentration of the at
least one high-vapor-pressure metal in the metal-containing
feedstock is selected based on a desired concentration of the
high-vapor-pressure metal in an additively manufactured metal
component derived from the metal-containing feedstock. The
concentration of the high-vapor-pressure metal will be higher
(enriched) in the metal-containing feedstock, compared to the final
additively manufactured metal component.
[0047] Some embodiments provide a metal-containing feedstock for
additive manufacturing, containing Al, from 0.05 wt % to 0.28 wt %
Cr, from 1 wt % to 2 wt % Cu, from 3 wt % to 10 wt % Mg, and from
6.2 wt % to 20 wt % Zn.
[0048] Other embodiments of the invention provide a
metal-containing feedstock for additive manufacturing, wherein the
metal-containing feedstock contains Al, from 0.01 wt % to 5 wt %
Zr, from 1.9 wt % to 10 wt % Mg, and from 6.7 wt % to 20 wt % Zn.
In some embodiments, the metal-containing feedstock further
contains from 1 wt % to 2.6 wt % Cu.
BRIEF DESCRIPTION OF THE FIGURES
[0049] FIG. 1 is a schematic illustration of the vaporization of
high-vapor-pressure metals during additive manufacturing, in some
embodiments.
[0050] FIG. 2 is an exemplary method flowchart for producing an
additively manufactured metal component, in some embodiments.
[0051] FIG. 3 shows an SEM image of additively manufactured,
grain-refined aluminum alloy Al 6061 with Zr particles, revealing
fine equiaxed grains and a substantially crack-free microstructure,
in some embodiments.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0052] The compositions, structures, systems, and methods of the
present invention will be described in detail by reference to
various non-limiting embodiments.
[0053] This description will enable one skilled in the art to make
and use the invention, and it describes several embodiments,
adaptations, variations, alternatives, and uses of the invention.
These and other embodiments, features, and advantages of the
present invention will become more apparent to those skilled in the
art when taken with reference to the following detailed description
of the invention in conjunction with the accompanying drawings.
[0054] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the context clearly indicates otherwise. Unless defined otherwise,
all technical and scientific terms used herein have the same
meaning as is commonly understood by one of ordinary skill in the
art to which this invention belongs.
[0055] Unless otherwise indicated, all numbers expressing
conditions, concentrations, dimensions, and so forth used in the
specification and claims are to be understood as being modified in
all instances by the term "about." Accordingly, unless indicated to
the contrary, the numerical parameters set forth in the following
specification and attached claims are approximations that may vary
depending at least upon a specific analytical technique.
[0056] The term "comprising," which is synonymous with "including,"
"containing," or "characterized by" is inclusive or open-ended and
does not exclude additional, unrecited elements or method steps.
"Comprising" is a term of art used in claim language which means
that the named claim elements are essential, but other claim
elements may be added and still form a construct within the scope
of the claim.
[0057] As used herein, the phrase "consisting of" excludes any
element, step, or ingredient not specified in the claim. When the
phrase "consists of" (or variations thereof) appears in a clause of
the body of a claim, rather than immediately following the
preamble, it limits only the element set forth in that clause;
other elements are not excluded from the claim as a whole. As used
herein, the phrase "consisting essentially of" limits the scope of
a claim to the specified elements or method steps, plus those that
do not materially affect the basis and novel characteristic(s) of
the claimed subject matter.
[0058] With respect to the terms "comprising," "consisting of," and
"consisting essentially of," where one of these three terms is used
herein, the presently disclosed and claimed subject matter may
include the use of either of the other two terms, except when used
in Markush groups. Thus in some embodiments not otherwise
explicitly recited, any instance of "comprising" may be replaced by
"consisting of" or, alternatively, by "consisting essentially
of."
[0059] During additive manufacturing of metals, a direct energy
source locally melts metal or metal alloy feedstocks and builds up
a part, layer by layer. During this process, intense heating can
vaporize high-vapor-pressure metals, depending on temperatures and
mass-transport pathways. A simple illustration is shown in FIG. 1,
described below. Vaporization of metals from the melt pool results
in a material that, after solidification, is a different
composition compared to the starting feedstock. In many cases, this
means that the resulting structure is no longer the correct
composition. As used herein, "melt pool" refers to a volume of
molten metal that is formed during additive manufacturing or
welding.
[0060] Variations of the present invention are premised on
providing a feedstock with enriched high-vapor-pressure metals, so
that the final additively manufactured structure contains a
targeted composition. The targeted composition, which differs from
the feedstock composition, is very important to the final material
properties.
[0061] For example, during additive manufacturing of aluminum alloy
Al 7075 powders, about 30% of the magnesium and about 25% of the
zinc can be lost during the additive manufacturing process. These
elements have high vapor pressures in the melt pool, which can
reach temperatures exceeding 1000.degree. C. At these temperatures,
the vapor pressure of Mg and Zn are much higher than 1
kPa--specifically, about 40 kPa for Mg and over 100 kPa for Zn (1
kPa=0.01 bar). Other elements in the alloy, such as copper and
chromium, are relatively unchanged due to their negligible vapor
pressures at additive manufacturing temperatures. These
low-vapor-pressure metals have minor concentration enrichment from
the associated mass loss of the high-vapor-pressure elements.
[0062] Heretofore, there are no available aluminum alloy feedstocks
containing high levels of high-vapor-pressure elements such as Mg,
Zn, and Li, that will result in an additively manufactured
structure of identical composition to the original powder.
Variations of this invention enable the production of additively
manufactured high-strength metal alloys with targeted compositions
that contain high-vapor-pressure elements.
[0063] Some variations provide a method of making an additively
manufactured metal component, the method comprising:
[0064] (a) providing a metal-containing feedstock comprising a
high-vapor-pressure metal and at least one other metal species
different than the high-vapor-pressure metal;
[0065] (b) exposing a first amount of the metal-containing
feedstock to an energy source for melting the first amount of the
metal-containing feedstock, thereby generating a first melt layer;
and
[0066] (c) solidifying the first melt layer, thereby generating a
first solid layer of an additively manufactured metal
component,
[0067] wherein the metal-containing feedstock contains a higher
concentration of the high-vapor-pressure metal compared to the
concentration of the high-vapor-pressure metal in the first solid
layer.
[0068] Steps (b) and (c) may be repeated a plurality of times to
generate a plurality of solid layers by sequentially solidifying a
plurality of melt layers in an additive-manufacturing build
direction.
[0069] In this disclosure, a "metal-containing feedstock" is any
metal-containing powder, wire, sheet, or other geometric object of
any compatible size that can be utilized in additive manufacturing
or welding processes. The additive manufacturing or welding
processes may employ conventional equipment or customized apparatus
suitable for carrying out the methods taught herein to produce an
additively manufactured or welded metal component. By "component"
it is meant any object that is produced by additive manufacturing,
3D printing, or welding.
[0070] A simple illustration is shown in FIG. 1. In the schematic
of FIG. 1, a metal-containing powder feed 110 is exposed to an
energy source 120, melting the powder to form a melt pool 130.
Solidification of the melt pool results in a work piece 140, which
may contain one or more individual layers of solidified
metal-containing feedstock. High-vapor-pressure metals 150 may
vaporize from the melt pool 140, as depicted by the serpentine
arrows of FIG. 1. The energy source 120 and/or the work piece 140
may be moved in a prescribed pattern to build the desired work
piece 140. In some embodiments, a wire feed is employed, rather
than a powder feed. In other embodiments, a powder bed is employed,
in which the energy source melts metal-containing powder that is
disposed as a layer on the work piece 140. In any of these
scenarios, a melt pool 130 forms, from which high-vapor-pressure
metals 140 may be vaporized and released to a space outside of the
work area. Note that the serpentine arrows showing vaporizing
metals 150 are intended to be outside of the work piece 140, not
within it. Notwithstanding the foregoing, some vaporizing metal
atoms may penetrate through the solidifying work piece 140 or may
be temporarily contained within vapor-containing porous regions of
the work piece 140, before being released out of the system of FIG.
1.
[0071] The metal-containing feedstock includes a base metal (such
as, but not limited to, aluminum) and one or more additional
elements, to form a metal alloy. In various embodiments, at least
one additional element, or a plurality of additional elements, is
present in a concentration from about 0.01 wt % to about 20 wt %,
such as about 0.1, 0.5, 1.0, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14, or 15 wt %. In this disclosure, at least one of the
additional elements is a high-vapor-pressure metal.
[0072] In some embodiments, one or more metals are selected from
the group consisting of aluminum, iron, nickel, copper, titanium,
magnesium, zinc, silicon, lithium, silver, chromium, manganese,
vanadium, bismuth, gallium, lead, and combinations thereof. The
metal-containing feedstock may contain one or more alloying
elements selected from the group consisting of Al, Si, Fe, Cu, Ni,
Mn, Mg, Cr, Zn, V, Ti, Bi, Ga, Pb, or Zr. Other alloying elements
may be included in the metal-containing feedstock, such as (but not
limited to) H, Li, Be, B, C, N, O, F, Na, P, S, Cl, K, Ca, Sc, Co,
Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd,
In, Sn, Te, I, Cs, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Ce,
Nd, and combinations thereof. These other alloying elements may
function as grain refiners, as strength enhancers, as stability
enhancers, or a combination thereof.
[0073] The high-vapor-pressure metal, or a combination of
high-vapor-pressure metals, may be present in the metal-containing
feedstock in a concentration from about 0.1 wt % to about 20 wt %,
for example. In various embodiments, the high-vapor-pressure metal,
or a combination of high-vapor-pressure metals, may be present in
the metal-containing feedstock in a concentration of about 0.5, 1,
2, 3, 4, 5, 6, 7, 8, 9, 10 wt %, or higher. When multiple
high-vapor-pressure metals are present, the individual
high-vapor-pressure metals may each be present in the
metal-containing feedstock in a concentration of about 0.1, 0.5, 1,
2, 3, 4, 5, 6, 7, 8, 9, 10 wt %, or higher.
[0074] A "high-vapor-pressure metal" as meant herein includes a
metal that has a vapor pressure of 1 kPa or greater at a melt-pool
temperature. A "high-vapor-pressure metal" also includes a metal
for which at least 1% by mass is lost to a vapor phase or the
atmosphere from a multicomponent solution, at a melt-pool
temperature, during an additive manufacturing or welding
process.
[0075] A "melt-pool temperature" refers to a temperature that
characterizes a melt pool, which temperature may be a melt-pool
volume-average temperature, a melt-pool time-average temperature, a
melt-pool surface temperature, or a melt-pool peak temperature (the
highest temperature reached by any surface or region within the
melt pool). For a melt-pool time-average temperature, the time is
the time span for the creation and solidification of a melt pool in
an additive manufacturing or welding process. A melt-pool
temperature may also be an overall average temperature, averaged
over both space and time.
[0076] A melt-pool temperature will vary depending at least on the
specific metals to be melted, the power intensity applied to the
melt pool, and the geometry of the melt pool. A melt-pool
temperature may vary from about 800.degree. C. to about
2000.degree. C., such as about, or at least about, 900.degree. C.,
1000.degree. C., 1100.degree. C., 1200.degree. C., 1300.degree. C.,
1400.degree. C., 1500.degree. C., 1600.degree. C., 1700.degree. C.,
1800.degree. C., or 1900.degree. C., for example, noting that these
temperatures may be volume-average temperatures, time-average
temperatures, surface temperatures, and/or peak temperatures of the
melt pool. In various embodiments, a selected high-vapor-pressure
metal has a vapor pressure of 1 kPa or greater at 1000.degree. C.,
1100.degree. C., 1200.degree. C., 1300.degree. C., 1400.degree. C.,
1500.degree. C., 1600.degree. C., 1700.degree. C., or 1800.degree.
C.
[0077] In some embodiments, a selected high-vapor-pressure metal
has a vapor pressure of 5 kPa, 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50
kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa or greater at a
melt-pool temperature. In some embodiments, a selected
high-vapor-pressure metal has a vapor pressure of 1 kPa or greater
at a temperature less than a melt-pool temperature, such as about
100.degree. C., 200.degree. C., 300.degree. C., 400.degree. C., or
500.degree. C. less than the melt-pool temperature.
[0078] The high-vapor-pressure metal may be selected from the group
consisting of Mg, Zn, Li, Al, Cd, Hg, K, Na, Rb, Cs, Mn, Be, Ca,
Sr, Ba, and combinations thereof. In certain embodiments, the
high-vapor-pressure metal is selected from the group consisting of
Mg, Zn, Al, Li, and combinations thereof.
[0079] Aluminum at 1000.degree. C. has a single-component vapor
pressure of about 3.times.10.sup.-5 kPa but is experimentally
observed to be volatile during additive manufacturing. Even when
average melt-pool temperatures are around 1000.degree. C., local
hot spots are believed to reach at least 1700.degree. C., at which
the vapor pressure of Al exceeds 1 kPa. Therefore, Al is a
high-vapor-pressure metal, in some embodiments.
[0080] The other metal species different than the
high-vapor-pressure metal may be classified as a low-vapor-pressure
metal, such as (but not limited to) transition metals. Exemplary
low-vapor-pressure metals include Cu, Ni, Cr, W, and Mo. A
"low-vapor-pressure metal" as meant herein is a metal that has a
vapor pressure less than 1 kPa at a melt-pool temperature. The
vapor pressure of a selected low-vapor-pressure metal may be
significantly lower than 1 kPa, such as about 10.sup.-3 kPa,
10.sup.-4 kPa, 10.sup.-5 kPa, 10.sup.-6 kPa, 10.sup.-7 kPa,
10.sup.-8 kPa, 10.sup.-9 kPa, or 10.sup.-10 kPa, or lower, at a
melt-pool temperature.
[0081] Note that for some metals with vapor pressures below 1 kPa
at a melt-pool temperature, those metals may nevertheless be lost
to a significant extent from the solid component as it is being
formed during additive manufacturing or welding. This can occur for
several reasons. First, non-ideal multicomponent solution
thermodynamics may cause a metal to vaporize at a temperature
different than its pure (single-component) vaporization temperature
for a given pressure. Second, the specific atmosphere (e.g.,
presence of inert gases or reactive gases) above the metal solution
may alter the vaporization thermodynamics. Third, localized hot
spots can occur during additive manufacturing or welding, causing
localized regions of higher vapor pressure for a metal. Finally, in
some cases a metal may be entrained or otherwise carried into a
vapor phase despite being nominally a solid at the given
temperature and pressure. A metal that transports into a vapor
phase for any reason is considered to be vaporized, in this
disclosure.
[0082] Generally, the specific extents of metal vaporization are
dictated by the original (feedstock) composition and the associated
solvation energies keeping the alloying elements in solution. These
extents of metal vaporization can be experimentally determined
and/or predicted by calculations or simulations. With that
information, alloy systems can be optimized to accommodate the
expected mass loss of the high-vapor-pressure elements.
[0083] In some embodiments, simulations are employed to estimate
extents of metal vaporization in complex multicomponent metal
solutions. These simulations may account for variations in
temperatures, laser power intensity, pressures and pressure
gradients, time, mass-transport pathways and concentration
gradients, heat transfer (by conduction, convection, and
radiation), 3D geometry, surface tension, buoyancy forces, and/or
diluent gases, among other potential factors.
[0084] The simulations may be configured to predict both formal
vaporization of metals as well as entrainment, such as ejection of
tiny metal droplets owing to the recoil force exerted by metal
vapors. These simulations may include calculations to solve for the
temperature and velocity fields during additive manufacturing or
welding, using a transient, heat transfer and fluid flow model
based on the solution of the equations of conservation of mass,
momentum, and energy in the melt pool. Simulation software may be
utilized, such as ANSYS Fluent (Canonsburg, Pa., US), to assist in
the calculations. Fuerschbach et al., "Understanding Metal
Vaporization from Laser Welding" Sandia National Laboratories
Report No. SAND2003-3490, 2003, is hereby incorporated by reference
herein for its exemplary teachings of theoretical considerations in
simulating extents of metal vaporization in embodiments herein.
[0085] The specific extents of metal vaporization may
alternatively, or additionally, be determined experimentally. For
example, in the case of additive manufacturing of aluminum alloy Al
7075 powders, it has been experimentally found that, under certain
conditions, about 25% of zinc and about 30% of magnesium are lost
during fabrication of the 3D-printed component. This information
can be utilized in future additive manufacturing processes and
simulations for Al 7075 alloys.
[0086] The enrichment ratio of wt % concentration of the
high-vapor-pressure metal in the metal-containing feedstock to wt %
concentration of the high-vapor-pressure metal in the first solid
layer is typically at least 1.05, such as at least 1.25, at least
1.5, or at least 2.0. When multiple layers are produced, the
enrichment ratio of wt % concentration of the high-vapor-pressure
metal in the metal-containing feedstock to wt % concentration of
the high-vapor-pressure metal in each additional solid layer is
typically at least 1.05, such as at least 1.25, at least 1.5, or at
least 2.0. In various embodiments, the enrichment ratio of a
certain high-vapor-pressure metal, in one or more solid layers, is
about, or at least about, 1.01, 1.02, 1.05, 1.1, 1.15, 1.2, 1.25,
1.3, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3,
2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0. The enrichment ratios of
individual elements will generally be different due to differences
in properties of elements. Elements with higher vapor pressures
will tend to have higher enrichment ratios.
[0087] The enrichment ratios for a given element may be about the
same in all solid layers, when additive manufacturing conditions
remain constant in the build direction. In some embodiments, the
enrichment ratios for a given element may vary by build layer, such
as when local temperature, heating/cooling profile, pressure, or
gas atmosphere varies at least to some extent in the additive
manufacturing build direction.
[0088] In some embodiments, the metal-containing feedstock contains
from 0.05 wt % to 0.28 wt % Cr, from 1 wt % to 2 wt % Cu, from 3 wt
% to 10 wt % Mg, and from 6.2 wt % to 20 wt % Zn; and wherein the
first solid layer contains from 0.18 wt % to 0.28 wt % Cr, from 1.2
wt % to 2 wt % Cu, from 2.1 wt % to 2.9 wt % Mg, and from 5.1 wt %
to 6.1 wt % Zn. The enrichment ratios of Cr, Cu, Mg, and/or Zn may
vary, such as at least 1.05, at least 1.25, at least 1.5, or at
least 2.0, noting that the enrichment ratios of individual elements
will generally be different due to differences in properties of
elements.
[0089] In some embodiments, the metal-containing feedstock contains
from 0.01 wt % to 5 wt % Zr, from 1 wt % to 2.6 wt % Cu, from 2.7
wt % to 10 wt % Mg, and from 6.7 wt % to 20 wt % Zn; and wherein
the first solid layer contains from 0.08 wt % to 5 wt % Zr, from 2
wt % to 2.6 wt % Cu, from 1.9 wt % to 2.6 wt % Mg, and from 5.7 wt
% to 6.7 wt % Zn. The enrichment ratios of Zr, Cu, Mg, and/or Zn
may vary, such as at least 1.05, at least 1.25, at least 1.5, or at
least 2.0, for example.
[0090] In some embodiments, the metal-containing feedstock contains
from 0.01 wt % to 5 wt % Zr, from 1.9 wt % to 10 wt % Mg, and from
7.1 wt % to 20 wt % Zn; and wherein the first solid layer contains
from 0.07 wt % to 5 wt % Zr, from 1.3 wt % to 1.8 wt % Mg, and from
7 wt % to 8 wt % Zn. The enrichment ratios of Zr, Mg, and/or Zn may
vary, such as at least 1.05, at least 1.25, at least 1.5, or at
least 2.0, for example.
[0091] The metal-containing feedstock, the final component, or both
of these may be characterized as an aluminum alloy (e.g., from the
6000 series or 7000 series of Al alloys), a magnesium alloy, a
titanium alloy, a nickel superalloy, a copper superalloy, or a
combination thereof. FIG. 3 depicts an exemplary microstructure 300
for additively manufactured components containing aluminum alloy Al
6061, for example. FIG. 3 shows an SEM image of additively
manufactured, grain-refined aluminum alloy Al 6061 with Zr
particles (not individually visible in FIG. 3), revealing fine
equiaxed grains 310 and a substantially crack-free microstructure
300 containing a few porous voids 320, in some embodiments.
[0092] A "superalloy" is an alloy that exhibits excellent
mechanical strength, resistance to thermal creep deformation, good
surface stability, and resistance to corrosion or oxidation.
Examples of superalloys include Hastelloy, Inconel, Waspaloy, and
Incoloy. Some superalloys have a .gamma.' (gamma prime) phase,
which is an intermetallic precipitate to strengthen the superalloy.
For example, in Ni-based superalloys, a
.gamma.'-Ni.sub.3Al/Ni.sub.3Ti phase acts as a barrier to
dislocation motion. This .gamma.' intermetallic phase, when present
in high volume fractions, drastically increases the strength of
these alloys due to the ordered nature and high coherency of the
.gamma.' intermetallic phase with the continuous matrix.
[0093] In some embodiments, aluminum is present in the
metal-containing feedstock in a concentration from about 0.1 wt %
to about 90 wt %. In some embodiments, copper is present in the
metal-containing feedstock in a concentration from about 0.1 wt %
to about 90 wt %. In these or other embodiments, magnesium is
present in the metal-containing feedstock in a concentration from
about 0.1 wt % to about 90 wt %. In these or other embodiments, at
least one of zinc or silicon is present in the metal-containing
feedstock in a concentration from about 0.1 wt % to about 90 wt %.
In some embodiments, the metal-containing feedstock further
comprises chromium. In some embodiments, scandium is not present in
the metal-containing feedstock.
[0094] In general, the geometry of the metal-containing feedstock
is not limited and may be, for example, in the form of powder
particles, wires, rods, bars, plates, films, coils, spheres, cubes,
prisms, cones, irregular shapes, or combinations thereof. In
certain embodiments, the metal-containing feedstock is in the form
of a powder, a wire, or a combination thereof (e.g., a wire with
powder on the surface). When the metal-containing feedstock is in
the form of powder, the powder particles may have an average
diameter from about 1 micron to about 500 microns, such as about 10
microns to about 100 microns, for example. When the
metal-containing feedstock is in the form of a wire, the wire may
have an average diameter from about 10 microns to about 1000
microns, such as about 50 microns to about 500 microns, for
example.
[0095] The energy source in step (b) may be provided by a laser
beam, an electron beam, alternating current, direct current, plasma
energy, induction heating from an applied magnetic field,
ultrasonic energy, other sources, or a combination thereof.
Typically, the energy source is a laser beam or an electron
beam.
[0096] In various embodiments, steps (b) and (c) utilize a
technique selected from the group consisting of selective laser
melting, electron beam melting, laser engineered net shaping,
selective laser sintering, direct metal laser sintering, integrated
laser melting with machining, laser powder injection, laser
consolidation, direct metal deposition, wire-directed energy
deposition, plasma arc-based fabrication, ultrasonic consolidation,
and combinations thereof.
[0097] In certain embodiments, the additive manufacturing process
is selected from the group consisting of selective laser melting,
energy-beam melting, laser engineered net shaping, and combinations
thereof.
[0098] Selective laser melting utilizes a laser (e.g., Yb-fiber
laser) to provide energy for melting. Selective laser melting
designed to use a high power-density laser to melt and fuse
metallic powders together. The process has the ability to fully
melt the metal material into a solid 3D part. A combination of
direct drive motors and mirrors, rather than fixed optical lens,
may be employed. An inert atmosphere is usually employed. A vacuum
chamber can be fully purged between build cycles, allowing for
lower oxygen concentrations and reduced gas leakage.
[0099] Electron beam melting uses a heated powder bed of metal that
is then melted and formed layer by layer, in a vacuum, using an
electron beam energy source similar to that of an electron
microscope. Metal powder is welded together, layer by layer, under
vacuum.
[0100] Laser engineering net shaping is a powder-injected technique
operates by injecting metal powder into a molten pool of metal
using a laser as the energy source. Laser engineered net shaping is
useful for fabricating metal parts directly from a computer-aided
design solid model by using a metal powder injected into a molten
pool created by a focused, high-powered laser beam. Laser
engineered net shaping is similar to selective laser sintering, but
the metal powder is applied only where material is being added to
the part at that moment. Note that "net shaping" is meant to
encompass "near net" fabrication.
[0101] Direct metal laser sintering process works by melting fine
powders of metal in a powder bed, layer by layer. A laser supplies
the necessary energy and the system operates in a protective
atmosphere, typically of nitrogen or argon.
[0102] Another approach utilizes powder injection to provide the
material to be deposited. Instead of a bed of powder that is
reacted with an energy beam, powder is injected through a nozzle
that is then melted to deposit material. The powder may be injected
through an inert carrier gas or by gravity feed. A separate
shielding gas may be used to protect the molten metal pool from
oxidation.
[0103] Directed energy deposition utilizes focused energy (either
an electron beam or laser beam) to fuse materials by melting as the
material is being deposited. Powder or wire feedstock can be
utilized with this process. Powder-fed systems, such as laser metal
deposition and laser engineered net shaping, blow powder through a
nozzle, with the powder melted by a laser beam on the surface of
the part. Laser-based wirefeed systems, such as laser metal
deposition-wire, feed wire through a nozzle with the wire melted by
a laser, with inert gas shielding in either an open environment
(gas surrounding the laser), or in a sealed gas enclosure or
chamber.
[0104] Some embodiments utilize wire feedstock and an electron beam
heat source to produce a near-net shape part inside a vacuum
chamber. An electron beam gun deposits metal via the wire
feedstock, layer by layer, until the part reaches the desired
shape. Then the part optionally undergoes finish heat treatment and
machining. Wire can be preferred over powder for safety and cost
reasons.
[0105] Herderick, "Additive Manufacturing of Metals: A Review,"
Proceedings of Materials Science and Technology 2011, Additive
Manufacturing of Metals, Columbus, Ohio, 2011, is hereby
incorporated by reference herein for its teaching of various
additive manufacturing techniques.
[0106] FIG. 2 is a flowchart for an exemplary process 200 for
producing an additively manufactured metal component, in some
embodiments. In step 210, a metal-containing feedstock containing a
high-vapor-pressure metal is provided. In step 220, an amount of
metal-containing feedstock is exposed to an energy source for
melting, thereby generating a jth melt layer (j=1 to n; n>1). In
step 220, a fraction of high-vapor-pressure metal, or multiple
high-vapor-pressure metals, vaporizes away. In step 240, the jth
melt layer is solidified, thereby generating a jth solid layer.
Steps 220 and 240 each are repeated n times (repeat loop 230),
where n is an integer that is at least 2, to produce n individual
solid layers. Step 250 recovers the additively manufactured metal
component which contains n solid layers.
[0107] The process 200 is not limited in principle to the number of
solid layers that may be fabricated. A "plurality of solid layers"
(n in FIG. 2) means at least 2 layers, such as at least 10
individual solid layers in the additively manufactured,
nanofunctionalized metal alloy. The number of solid layers may be
much greater than 10, such as about 100, 1000, 10000, or more. The
plurality of solid layers may be characterized by an average layer
thickness of at least 10 microns, such as about 10, 20, 30, 40, 50,
75, 100, 150, or 200 microns.
[0108] The first solid layer, and additional solid layers, may be
characterized by an average grain size of less than 1 millimeter,
less than 100 microns, less than 10 microns, or less than 1 micron.
In various embodiments, the additively manufactured metal
component, or layers within it, may be characterized by an average
grain size of about, or less than about, 500 microns, 400 microns,
300 microns, 200 microns, 100 microns, 50 microns, 25 microns, 10
microns, 5 microns, 2 microns, 1 micron, 0.5 microns, 0.2 microns,
or 0.1 microns.
[0109] In any of these additive manufacturing techniques,
post-production processes such as heat treatment, light machining,
surface finishing, coloring, stamping, or other finishing
operations may be applied. Also, several additive manufactured
parts may be joined together chemically or physically to produce a
final object.
[0110] Metal alloy systems that utilize grain refiners give a
unique microstructure for the additively manufactured metal
component. The grain refiners may be designed with specific
compositions for a given metal alloy, taking into account the metal
vapor pressures according to the principles taught herein.
[0111] In some embodiments of the invention, the metal-containing
feedstock further comprises grain-refining nanoparticles. The
grain-refining nanoparticles may be present from about 0.001 wt %
to about 10 wt % of the metal-containing feedstock, for example. In
various embodiments, the grain-refining nanoparticles are present
at a concentration of about 0.01 wt %, 0.1 wt %, 1 wt %, or 5 wt %
of the metal-containing feedstock.
[0112] Nanoparticles are particles with the largest dimension
between about 1 nm and about 5000 nm. A preferred size of
nanoparticles is about 2000 nm or less, about 1500 nm or less, or
about 1000 nm or less. In some embodiments, nanoparticles are at
least 50 nm in size.
[0113] In these embodiments, the grain-refining nanoparticles are
selected from the group consisting of zirconium, silver, lithium,
manganese, iron, silicon, vanadium, scandium, yttrium, niobium,
tantalum, titanium, nitrogen, hydrogen, carbon, boron, and
combinations thereof, such as intermetallics or nitrides, hydrides,
carbides, or borides of one or more of the recited metals. In
certain embodiments, the grain-refining nanoparticles are selected
from the group consisting of zirconium, titanium, tantalum,
niobium, and oxides, nitrides, hydrides, carbides, or borides
thereof, and combinations of the foregoing.
[0114] Grain-refining nanoparticles, in certain embodiments, are
selected from the group consisting of Al.sub.3Zr, Al.sub.3Ta,
Al.sub.3Nb, Al.sub.3Ti, TiB, TiB.sub.2, WC, AlB, and combinations
thereof. These multicomponent nanoparticles may be in place of, or
in addition to, elemental forms such as zirconium, tantalum,
niobium, titanium, or oxides, nitrides, hydrides, carbides, or
borides thereof.
[0115] In some embodiments, micropowders are functionalized with
assembled nanoparticles that are lattice-matched to a primary or
secondary solidifying phase in the parent material, or that may
react with elements in the micropowder to form a lattice-matched
phase to a primary or secondary solidifying phase in the parent
material. In certain embodiments, mixtures of assembled
nanoparticles may react with each other or in some fashion with the
parent material, to form a lattice-matched material having the same
or similar function. For example, alloy powder feedstock particles
may be mixed with lattice-matched nanoparticles that
heterogeneously nucleate the primary equilibrium phases during
cooling of the melt pool. The same concept may be applied to
nanofunctionalized metal precursors besides powders (e.g.,
wires).
[0116] In some embodiments, the grain-refining nanoparticles are
lattice-matched to within .+-.5% compared to an
otherwise-equivalent metal alloy containing the one or more metals
but not the grain-refining nanoparticles. In certain embodiments,
the grain-refining nanoparticles are lattice-matched to within
.+-.2% or within .+-.0.5% compared to a metal alloy containing the
one or more metals but not the grain-refining nanoparticles.
[0117] In some embodiments, the metal-containing feedstock contains
microparticles that are surface-functionalized with grain-refining
nanoparticles, which may or may not include high-vapor-pressure
metals. Surface functionalization may be in the form of a
continuous coating or an intermittent coating. A continuous coating
covers at least 90% of the surface, such as about 95%, 99%, or 100%
of the surface (recognizing there may be defects, voids, or
impurities at the surface). An intermittent coating is
non-continuous and covers less than 90%, such as about 80%, 70%,
60%, 50%, 40%, 30%, 20%, 10%, 5%, 2%, 1%, or less of the surface.
An intermittent coating may be uniform (e.g., having a certain
repeating pattern on the surface) or non-uniform (e.g.,
random).
[0118] Various coating techniques may be employed, such as (but not
limited to) electroless deposition, immersion deposition, or
solution coating. The coating thickness is preferably less than
about 20% of the underlying particle diameter, such as less than
15%, 10%, 5%, 2%, or 1% of the underlying particle diameter.
[0119] In general, a functionalization coating may be continuous or
discontinuous. The coating may have several characteristic
features. In one embodiment, the coating may be smooth and
conformal to the underlying surface. In another embodiment, the
coating may be nodular. The nodular growth is often characteristic
of kinetic limitations of nanoparticle assembly. For example, the
coating may look like cauliflower or a small fractal growing from
the surface. These features can be affected by the underling
materials, the method of coating, reaction conditions, etc.
[0120] Nanoparticles may be attached to particles using
electrostatic forces, Van der Waals forces, chemical bonds,
physical bonds, and/or any other force. A chemical bond is the
force that holds atoms together in a molecule or compound.
Electrostatic and Van der Waals forces are examples of physical
forces that can cause bonding. A physical bond is a bond that
arises when molecular entities become entangled in space.
Typically, chemical bonds are stronger than physical bonds.
Chemical bonds may include ionic bonds, covalent bonds, or a
combination thereof.
[0121] Methods of producing nanofunctionalized metals are generally
not limited and may include immersion deposition, electroless
deposition, vapor coating, solution/suspension coating of particles
with or without organic ligands, utilizing electrostatic forces
and/or Van der Waals forces to attach particles through mixing, and
so on. U.S. patent application Ser. No. 14/720,757 (filed May 23,
2015), U.S. patent application Ser. No. 14/720,756 (filed May 23,
2015), and U.S. patent application Ser. No. 14/860,332 (filed Sep.
21, 2015), each commonly owned with the assignee of this patent
application, are hereby incorporated by reference herein. These
disclosures relate to methods of coating certain materials onto
micropowders, in some embodiments.
[0122] When grain-refining nanoparticles are included in the
metal-containing feedstock, the additively manufactured solid
layers may have a microstructure with equiaxed grains. The
additively manufactured solid layers may also be characterized by a
crack-free microstructure, in preferred embodiments (e.g., see FIG.
3B). When there are multiple solid layers, as is typical, some (but
not necessarily all) of the solid layers may be characterized by an
equiaxed-grain microstructure and/or a crack-free
microstructure.
[0123] A microstructure that has "equiaxed grains" means that at
least 90 vol %, preferably at least 95 vol %, and more preferably
at least 99 vol % of the metal alloy contains grains that are
roughly equal in length, width, and height. In preferred
embodiments, at least 99 vol % of the microstructure contains
grains that are characterized in that there is less than 25%,
preferably less than 10%, and more preferably less than 5% standard
deviation in each of average grain length, average grain width, and
average grain height. Crystals of metal alloy form grains in the
solid. Each grain is a distinct crystal with its own orientation.
The areas between grains are known as grain boundaries. Within each
grain, the individual atoms form a crystalline lattice. In this
disclosure, equiaxed grains may result when there are many
nucleation sites arising from grain-refining nanoparticles
contained initially in the metal-containing feedstock.
[0124] By providing a high density of low-energy-barrier
heterogeneous nucleation sites ahead of the solidification front,
the critical amount of undercooling needed to induce equiaxed
growth is decreased. This allows for a fine equiaxed grain
structure that accommodates strain and prevents cracking under
otherwise identical solidification conditions. Additive
manufacturing of previously unattainable high-performance alloys,
such as Al 7075 or Al 6061, is made possible with improved
properties over currently available systems.
[0125] Preferably, the microstructure of the additively
manufactured metal component is substantially crack-free. In
certain embodiments, the microstructure is also substantially free
of porous void defects.
[0126] A microstructure that is "substantially crack-free" means
that at least 99.9 vol % of the metal component or layer contains
no linear or tortuous cracks that are greater than 0.1 microns in
width and greater than 10 microns in length. In other words, to be
considered a crack, a defect must be a void space that is at least
0.1 microns in width as well as at least 10 microns in length. A
void space that has a length shorter than 10 microns but larger
than 1 micron, regardless of width, can be considered a porous void
(see below). A void space that has a length of at least 10 microns
but a width shorter than 0.1 microns is a molecular-level gap that
is not considered a defect.
[0127] Typically, a crack contains open space, which may be vacuum
or may contain a gas such as air, CO.sub.2, N.sub.2, and/or Ar. A
crack may also contain solid material different from the primary
material phase of the metal alloy. These sorts of cracks containing
material (other than gases) may be referred to as "inclusions." The
non-desirable material disposed within the inclusion may itself
contain a higher porosity than the bulk material, may contain a
different crystalline (or amorphous) phase of solid, or may be a
different material altogether, arising from impurities during
fabrication, for example. Large phase boundaries can also form
inclusions. Note that these inclusions are different than the
nanoparticle inclusions that are desirable for grain refining.
[0128] The metal component microstructure may be substantially free
of porous defects, in addition to being substantially crack-free.
"Substantially free of porous defects" means at least 99 vol % of
the additively manufactured metal component contains no porous
voids having an effective diameter of at least 1 micron.
[0129] Porous defects may be in the form of porous voids.
Typically, a porous void contains open space, which may be vacuum
or may contain a gas such as air, CO.sub.2, N.sub.2, and/or Ar.
Preferably, at least 80 vol %, more preferably at least 90 vol %,
even more preferably at least 95 vol %, and most preferably at
least 99 vol % of the additively manufactured metal component
contains no porous voids having an effective diameter of at least 1
micron. A porous void that has an effective diameter less than 1
micron is not typically considered a defect, as it is generally
difficult to detect by conventional non-destructive evaluation.
Also preferably, at least 90 vol %, more preferably at least 95 vol
%, even more preferably at least 99 vol %, and most preferably at
least 99.9 vol % of the additively manufactured metal component
contains no larger porous voids having an effective diameter of at
least 5 microns. For example, see the microstructure of FIG. 3B
which contains porous voids (but contains no cracks).
[0130] The present invention also provides an additively
manufactured metal component produced by a process comprising:
[0131] (a) providing a metal-containing feedstock comprising a
high-vapor-pressure metal and at least one other metal species
different than the high-vapor-pressure metal;
[0132] (b) exposing a first amount of the metal-containing
feedstock to an energy source for melting the first amount of the
metal-containing feedstock, thereby generating a first melt
layer;
[0133] (c) solidifying the first melt layer, thereby generating a
first solid layer of an additively manufactured metal component;
and
[0134] (d) repeating steps (b) and (c) a plurality of times to
generate a plurality of solid layers by sequentially solidifying a
plurality of melt layers in an additive-manufacturing build
direction,
[0135] wherein the metal-containing feedstock contains a higher
concentration of the high-vapor-pressure metal compared to the
concentration of the high-vapor-pressure metal in the solid
layers.
[0136] In some embodiments, an enrichment ratio of wt %
concentration of the high-vapor-pressure metal in the
metal-containing feedstock to wt % concentration of the
high-vapor-pressure metal in the first solid layer is at least
1.05, at least 1.25, at least 1.5, or at least 2.0.
[0137] In the additively manufactured metal component, the
high-vapor-pressure metal may be selected from the group consisting
of Mg, Zn, Li, Al, Cd, Hg, K, Na, Rb, Cs, Mn, Be, Ca, Sr, Ba, and
combinations thereof.
[0138] In certain additively manufactured aluminum components, the
metal-containing feedstock contained Al, from 0.05 wt % to 0.28 wt
% Cr, from 1 wt % to 2 wt % Cu, from 3 wt % to 10 wt % Mg, and from
6.2 wt % to 20 wt % Zn; and the first solid layer and/or additional
solid layers contain(s) Al, from 0.18 wt % to 0.28 wt % Cr, from
1.2 wt % to 2 wt % Cu, from 2.1 wt % to 2.9 wt % Mg, and from 5.1
wt % to 6.1 wt % Zn.
[0139] In certain additively manufactured aluminum components, the
metal-containing feedstock contained Al, from 0.01 wt % to 5 wt %
Zr, from 1 wt % to 2.6 wt % Cu, from 2.7 wt % to 10 wt % Mg, and
from 6.7 wt % to 20 wt % Zn; and the first solid layer and/or
additional solid layers contain(s) Al, from 0.08 wt % to 5 wt % Zr,
from 2 wt % to 2.6 wt % Cu, from 1.9 wt % to 2.6 wt % Mg, and from
5.7 wt % to 6.7 wt % Zn.
[0140] In certain additively manufactured aluminum components, the
metal-containing feedstock contained Al, from 0.01 wt % to 5 wt %
Zr, from 1.9 wt % to 10 wt % Mg, and from 7.1 wt % to 20 wt % Zn;
and the first solid layer and/or additional solid layers contain(s)
Al, from 0.07 wt % to 5 wt % Zr, from 1.3 wt % to 1.8 wt % Mg, and
from 7 wt % to 8 wt % Zn.
[0141] The additively manufactured metal component may be
characterized by an average grain size of less than 1 millimeter,
such as less than 100 microns, less than 10 microns, or less than 1
micron.
[0142] In some embodiments, the additively manufactured metal
component has a microstructure with a crystallographic texture that
is not solely oriented in the additive-manufacturing build
direction. The plurality of solid layers may have differing primary
growth-direction angles with respect to each other.
[0143] In some embodiments, the additively manufactured metal
component has a microstructure with equiaxed grains. In some
embodiments, the additively manufactured metal component has a
crack-free microstructure. In certain embodiments, the additively
manufactured metal component has a crack-free microstructure with
equiaxed grains.
[0144] Variations of the present invention also provide a
metal-containing feedstock for additive manufacturing or for
welding, wherein the metal-containing feedstock contains at least
one high-vapor-pressure metal, and wherein concentration of the
high-vapor-pressure metal(s) in the metal-containing feedstock is
selected based on a desired concentration of the
high-vapor-pressure metal in an additively manufactured metal
component derived from the metal-containing feedstock. The
concentration of the high-vapor-pressure metal will be higher
(enriched) in the metal-containing feedstock, compared to the final
additively manufactured or welded metal component. The enrichment
ratio of wt % concentration of the high-vapor-pressure metal in the
metal-containing feedstock to wt % concentration of the
high-vapor-pressure metal in the final additively manufactured or
welded metal component is typically at least 1.05, such as at least
1.25, at least 1.5, or at least 2.0.
[0145] Some embodiments provide a metal-containing feedstock for
additive manufacturing or welding of an aluminum component,
containing from 0.05 wt % to 0.28 wt % Cr, from 1 wt % to 2 wt %
Cu, from 3 wt % to 10 wt % Mg, and from 6.2 wt % to 20 wt % Zn,
with the balance consisting essentially of aluminum. Other elements
may be present, such as (but not limited to) Zr, Ag, Li, Mn, Fe,
Si, V, Sc, Y, Nb, Ta, Ti, B, H, C, and/or N.
[0146] Other embodiments of the invention provide a
metal-containing feedstock for additive manufacturing or welding of
an aluminum component, wherein the metal-containing feedstock
contains from 0.01 wt % to 5 wt % Zr, from 1.9 wt % to 10 wt % Mg
(such as from 2.7 wt % to 10 wt % Mg), and from 6.7 wt % to 20 wt %
Zn (such as from 7.1 wt % to 20 wt % Zn), with the balance
consisting essentially of aluminum. In some embodiments, the
metal-containing feedstock further contains from 1 wt % to 2.6 wt %
Cu. Other elements may be present, such as (but not limited to) Cr,
Cu, Ag, Li, Mn, Fe, Si, V, Sc, Y, Nb, Ta, Ti, B, H, C, and/or
N.
[0147] The materials and methods disclosed herein may be applied to
additive manufacturing as well as joining techniques, such as
welding. Certain unweldable metals, such as high-strength aluminum
alloys (e.g., aluminum alloys Al 7075, Al 7050, or Al 2199) would
be excellent candidates for additive manufacturing but normally
suffer from hot cracking. The principles disclosed herein allow
these alloys, and many others, to be processed with significantly
reduced cracking tendency.
[0148] Certain embodiments relate specifically to additive
manufacturing of aluminum alloys. Additive manufacturing has been
previously limited to weldable or castable alloys of aluminum. This
disclosure enables additive manufacturing of a variety of
high-strength and unweldable aluminum alloys by utilizing grain
refinement to induce equiaxed microstructures which can eliminate
hot cracking during processing. Potential applications include
improved tooling, replacement of steel or titanium components at
lower weight, full topological optimization of aluminum components,
low-cost replacement for out-of-production components, and
replacement of existing additively manufactured aluminum
systems.
[0149] Some embodiments of the present invention utilize materials,
methods, and principles described in commonly owned U.S. patent
application Ser. No. 15/209,903, filed Jul. 14, 2016, U.S. patent
application Ser. No. 15/808,872, filed Nov. 9, 2017, U.S. patent
application Ser. No. 15/808,877, filed Nov. 9, 2017, and/or U.S.
patent application Ser. No. 15/808,878, filed Nov. 9, 2017, each of
which is hereby incorporated by reference herein. For example,
certain embodiments utilize functionalized powder feedstocks as
described in U.S. patent application Ser. No. 15/209,903. The
present disclosure is not limited to those functionalized powders.
This specification also hereby incorporates by reference herein
Martin et al., "3D printing of high-strength aluminium alloys,"
Nature vol. 549, pages 365-369 and supplemental online content
(extended data), Sep. 21, 2017, in its entirety.
[0150] Some variations provide a method of making a welded metal
component, the method comprising:
[0151] (a) providing a metal-containing feedstock comprising a
high-vapor-pressure metal and at least one other metal species
different than the high-vapor-pressure metal;
[0152] (b) exposing an amount of the metal-containing feedstock to
an energy source for melting the amount of the metal-containing
feedstock, thereby generating a melt layer; and
[0153] (c) solidifying the melt layer, thereby generating a solid
layer of a welded metal component,
[0154] wherein the metal-containing feedstock contains a higher
concentration of the high-vapor-pressure metal compared to the
concentration of the high-vapor-pressure metal in the solid
layer.
[0155] Some variations also provide a welded metal component
produced by a process comprising:
[0156] (a) providing a metal-containing feedstock comprising a
high-vapor-pressure metal and at least one other metal species
different than the high-vapor-pressure metal;
[0157] (b) exposing an amount of the metal-containing feedstock to
an energy source for melting the amount of the metal-containing
feedstock, thereby generating a melt layer; and
[0158] (c) solidifying the melt layer, thereby generating a solid
layer of a welded metal component;
[0159] wherein the metal-containing feedstock contains a higher
concentration of the high-vapor-pressure metal compared to the
concentration of the high-vapor-pressure metal in the solid
layer.
[0160] The final additively manufactured component may have
porosity from 0% to about 75%, such as about 5%, 10%, 20%, 30%,
40%, 50%, 60%, or 70%, in various embodiments. The porosity may
derive from space both within particles (e.g., hollow shapes) as
well as space outside and between particles. The total porosity
accounts for both sources of porosity.
[0161] The final additively manufactured or welded component may be
selected from the group consisting of a structure, a coating, a
geometric object, a billet, an ingot (which may be a green body or
a finished body), a net-shape part, a near-net-shape part, a
welding filler, and combinations thereof. Essentially, the geometry
of an additive manufacturing part is unlimited.
[0162] In some embodiments, the additively manufactured or welded
component has a density from about 1 g/cm.sup.3 to about 20
g/cm.sup.3, such as about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
14, or 15 g/cm.sup.3.
[0163] Some possible powder metallurgy processing techniques that
may be applied to the additive manufactured or welded component
include hot pressing, cold pressing, low-pressure sintering,
extrusion, pressureless sintering, and metal injection molding, for
example. Melting may include induction melting, resistive melting,
skull melting, arc melting, laser melting, electron beam melting,
semi-solid melting, or other types of melting (including convention
and non-conventional melt processing techniques). Casting may
include centrifugal, pour, or gravity casting, for example.
Sintering may include spark discharge, capacitive-discharge,
resistive, or furnace sintering, for example. Mixing may include
convection, diffusion, shear mixing, or ultrasonic mixing, for
example.
[0164] Optionally, porosity may be removed or reduced in the final
component. For example, a secondary heat and/or pressure (or other
mechanical force) treatment may be done to minimize porous voids
present in an additively manufactured component. Also, pores may be
removed from the additively manufactured component by physically
removing (e.g., cutting away) a region into which porous voids have
segregated.
[0165] In addition to removal of voids, other post-working may be
carried out. For example, forging can refine defects and can
introduce additional directional strength, if desired. Preworking
(e.g., strain hardening) can be done such as to produce a grain
flow oriented in directions requiring maximum strength.
[0166] In this detailed description, reference has been made to
multiple embodiments and to the accompanying drawings in which are
shown by way of illustration specific exemplary embodiments of the
invention. These embodiments are described in sufficient detail to
enable those skilled in the art to practice the invention, and it
is to be understood that modifications to the various disclosed
embodiments may be made by a skilled artisan.
[0167] Where methods and steps described above indicate certain
events occurring in certain order, those of ordinary skill in the
art will recognize that the ordering of certain steps may be
modified and that such modifications are in accordance with the
variations of the invention. Additionally, certain steps may be
performed concurrently in a parallel process when possible, as well
as performed sequentially.
[0168] All publications, patents, and patent applications cited in
this specification are herein incorporated by reference in their
entirety as if each publication, patent, or patent application were
specifically and individually put forth herein.
[0169] The embodiments, variations, and figures described above
should provide an indication of the utility and versatility of the
present invention. Other embodiments that do not provide all of the
features and advantages set forth herein may also be utilized,
without departing from the spirit and scope of the present
invention. Such modifications and variations are considered to be
within the scope of the invention defined by the claims.
* * * * *