Note: Descriptions are shown in the official language in which they were submitted.
WO 2018/034960 PCT/US2017/046444
ANODIZED ALUMINUM WITH DARK GRAY COLOR
CROSS-REFERENCE TO RELATED APPLICATION
[00011 This application claims the benefit of U.S. Provisional Patent
Application No.
62/375,932, filed August 17, 2016.
FIELD
[0002] Described herein are anodized aluminum alloy sheets and, in particular,
dark gray
colored anodized aluminum alloy sheets.
BACKGROUND
[0003] A dark gray color is a desirable property in certain anodized aluminum
products, such
as anodized quality ("AQ") architectural sheets. An anodization process is an
electrochemical
process that converts the aluminum alloy surface to aluminum oxide. Because
the aluminum
oxide forms in place on the surface, it is fully integrated with the
underlying aluminum substrate.
The surface oxide layer produced by an anodization process is a highly ordered
structure that,
when pure, can be clear and colorless so that the anodized sheet has a shiny,
light gray color.
The surface oxide layer is also porous and susceptible to additional
coloriz.ation by treatment
subsequent to and/or separate from the anodization process. Conventional
colored anodized
alloys are colored by additional absorptive or electrolytic coloration
processes, which increase
production costs for colored alloys relative to alloys that are not colored.
SUMMARY
[0004] Covered embodiments of the invention are defined by the claims, not
this summary.
This summary is a high-level overview of various aspects of the invention and
introduces some
of the concepts that are further described in the Detailed Description section
below. This
summary is not intended to identify key or essential features of the claimed
subject matter, nor is
it intended to be used in isolation to determine the scope of the claimed
subject matter. The
subject matter should be understood by reference to appropriate portions of
the entire
specification, any or all drawings, and each claim.
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100051 Provided herein are aluminum alloys that have a dark gray color when
anodized. The
alloys do not require any absorptive or electrolytic coloration process
separate from the
anodization process to achieve the dark gray coloration. The alloys have
economic and
environmental advantages over conventional anodized aluminum alloys that
require a separate
coloration process in order to achieve a desired color.
[0006] In one example, aluminum alloys that have a natural dark gray color
when anodized are
described herein. In some examples, the aluminum alloys include up to 0.40 wt.
% Fe, up to
0.25 wt. % Si, up to 0.2 wt. % Cr, 2.0 wt. % to 3.2 wt. % Mg, 0.8 wt. % to 1.5
wt. % Mn, up to
0.1 wt. % Cu, up to 0.05 wt% Zn, up to 0.05 wt.% Ti, and up to 0.15 wt. %
impurities, with the
remainder as Al. Throughout this application, all elements are described in
weight percentage
(wt. %) based on the total weight of the alloy. In some cases, the aluminum
alloys include up to
0.05 wt. % to 0.2 wt. % Fe, 0.03 wt. % to 0.1 wt. % Si, up to 0.05 wt. % Cr,
2.5 wt. % to 3.2 wt.
% Mg, 0.8 wt % to 1.3 wt. % Mn, up to 0.05 wt. % Cu, up to 0.05 wt. % Zn, up
to 0.05 wt. %
Ti, and up to 0.15 wt % impurities, with the remainder as Al.
100071 In another example, methods of preparing an aluminum sheet comprising
dispersoids
are described herein. In some examples, the method comprises casting an
aluminum alloy to
form an ingot; homogenizing the ingot to form a homogenized ingot; hot rolling
the
homogenized ingot to produce a hot rolled intermediate product; cold rolling
the hot rolled
intermediate product to produce a cold rolled intermediate product;
interannealing the cold rolled
intermediate product to produce an interannealed product; cold rolling the
interannealed product
to produce a cold rolled sheet; and annealing the cold rolled sheet to form an
annealed sheet
comprising dispersoids, wherein the alloy is a 2xxx, 3x.xx, 5xxx, or 7xxx
series alloy.
[0008] Other objects and advantages will be apparent from the following
detailed description
of non-limiting examples.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1A is a scanning transmission electron microscopy (STEM) image of
dispersoids
in a comparative aluminum alloy.
[0010] FIG. 1B is a STEM image of dispersoids in a comparative aluminum alloy.
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100111 FIG. 1C is a STEM image of dispersoids in an aluminum alloy with a dark
anodized
color, as described herein.
[0012] FIG. 2A is a high-resolution scanning electron microscopy (SEM) image
of dispersoids
in a comparative anodized aluminum alloy.
[0013] FIG. 2B is a high-resolution SEM image of dispersoids in a comparative
anodized
aluminum alloy.
[0014] FIG. 2C is a high-resolution SEM image of dispersoids in an anodized
aluminum alloy
with natural dark anodized color, as described herein.
[0015] FIG. 3A is a phase diagram of phases in a comparative alloy.
[0016] FIG. 3B is a phase diagram of phases in a comparative alloy.
[0017] FIG. 3C is a phase diagram of phases in an anodized aluminum alloy with
natural dark
anodized color.
DETAILED DESCRIPTION
[0018] Described herein are alloys and processes providing colorized anodized
substrates
designed based on in-depth microstructure and metallurgical analysis.
Generally, an anodized
layer on a conventional aluminum alloy substrate is almost transparent and the
anodized
substrate shows a deep and shiny light gray metallic color due to light
reflectance from both the
surface of the anodized layer and the surface of the base metal. In the alloy
products prepared
according to the present methods, fine intermetallic particle dispersoids
(alternately called
precipitates) inside the normally-transparent anodized oxide layers of the
anodized alloys
described herein affect the color of the anodized material by interrupting
light as it passes
through the anodized layer before it can reach the surface of the base metal.
By controlling alloy
composition and process parameters, the number density of certain dispersoids
inside the
anodized layer is maximized. Those dispersoids give the anodized substrate a
dark gray color
without an additional coloring process.
[0019] The alloys and methods disclosed herein provide dark anodized sheets
that can be
prepared with significantly reduced processing and cost as compared to known
dark anodized
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sheets. The methods described herein eliminate conventional adsorptive or
electrolytic
coloration steps which are required in current production of dark colored
anodized materials.
The methods described herein result in fewer byproducts and are more
environmentally friendly
than conventional methods of producing similarly colored products.
[0020] In some examples, an anodized aluminum sheet as described herein has a
dark gray
color. The color of the anodized aluminum sheet can be quantified by
colorimetry measurement
by CIE lab 1931 standard and/or ASTM E313-15 (2015). In some examples, the
anodized
aluminum sheet has an L* value lower than 60, lower than 55, or lower than 50,
as measured by
CIE lab 1931 standard. In some examples, the anodized sheet has a white
balance of lower than
35, lower than 30, or lower than 25, as measured by ASTM E313-15 (2015).
Definitions and Derottions
[0021] The terms "invention," "the invention," "this invention" and "the
present invention"
used herein are intended to refer broadly to all of the subject matter of this
patent application and
the claims below. Statements containing these terms should be understood not
to limit the
subject matter described herein or to limit the meaning or scope of the patent
claims below.
[0022] In this description, reference is made to alloys identified by AA
numbers and other
related designations, such as "series" or "5xxx." For an understanding of the
number designation
system most commonly used in naming and identifying aluminum and its alloys,
see
"International Alloy Designations and Chemical Composition Limits for Wrought
Aluminum
and Wrought Aluminum Alloys" or "Registration Record of Aluminum Association
Alloy
Designations and Chemical Compositions Limits for Aluminum Alloys in the Form
of Castings
and Ingot," both published by The Aluminum Association.
[0023] Aluminum alloys are described herein in terms of their elemental
composition in
weight percentage (wt. %) based on the total weight of the alloy. In certain
examples of each
alloy, the remainder is aluminum, with a maximum wt. % of 0.15 % for the sum
of the
impurities.
[0024] As used herein, the meaning of "a," "an," and "the" includes singular
and plural
references unless the context clearly dictates otherwise.
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100251 As used herein, the meaning of "room temperature" can include a
temperature of from
about 15 C to about 30 C, for example about 15 C, about 16 C, about 17 C,
about 18 C,
about 19 C, about 20 C, about 21 C, about 22 C, about 23 C, about 24 C,
about 25 CC,
about 26 C, about 27 C, about 28 C, about 29 C, or about 30 C.
100261 All ranges disclosed herein are to be understood to encompass any and
all subranges
subsumed therein. For example, a stated range of "1 to 10" should be
considered to include any
and all subranges between (and inclusive of) the minimum value of 1 and the
maximum value of
10; that is, all subranges beginning with a minimum value of 1 or more, e.g.,
1 to 6.1, and ending
with a maximum value of 10 or less, e.g., 5.5 to 10.
Alloys.
10027] The dark anodized aluminum alloy sheets described herein can be
prepared from any
suitable aluminum alloy. The final anodized quality and color will vary
depending on the alloy
composition. In some examples, the aluminum alloy used in the methods
described herein is a
2xxx, 3voc, 5xxx, or 7xxx series alloy.
[0028] Non-limiting exemplary AA2xxx series alloys include AA2001, A2002,
AA2004,
AA2005, AA2006, AA2007, AA2007A, AA2007B, AA2008, AA2009, AA2010, AA2011,
AA2011A, 4,42111, AA2111A, AA2111B, AA2012, AA2013, AA2014, AA2014A, AA2214,
AA2015, AA2016, AA2017, AA2017A, AA2117, AA2018, AA2218, AA2618, AA2618A,
AA2219, AA2319, AA2419, AA2519, AA2021, AA2022, AA2023, AA2024, AA2024A,
AA2124, AA2224, AA2224A, AA2324, AA2424, AA2524, AA2624, AA2724, AA2824,
AA2025, AA2026, AA2027, AA2028, AA2028A, AA2028B, AA2028C, AA2029, AA2030,
AA2031, AA2032, AA2034, AA2036, AA2037, AA2038, AA2039, AA2139, AA2040,
AA2041, AA.2044, AA..2045, AA2050, .AA2055, A.A2056, A A2060, AA..2065,
AA.2070,
AA2076, AA2090, AA2091., AA2094, AA2095, AA2195, AA2295, AA21.96, AA2296,
AA2097, AA2197, AA2297, AA2397, AA2098, AA2198, AA2099, and AA2199.
[0029] Non-limiting exemplary AA3xxx series alloys for use as the aluminum
alloy product
can include AA3002, AA3102, AA3003, AA3103, AA3103A, AA3103B, AA3203, AA3403,
AA3004, AA3004A, AA31G4, AA3204, AA3304, AA3005, AA3005A, AA.3105, AA3105A,
AA3105B, AA3007, AA3107, AA3207, AA3207A., AA3307, AA3009, AA3010, AA3110,
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AA3011, AA3012, AA3012A, AA3013, AA3014, AA3015, AA3016, AA3017, AA3019,
AA3020, AA3021, AA3025, AA3026, AA3030, AA3130, and AA3065.
[0030] Non-limiting exemplary AA5xxx series alloys include AA5182, AA5183,
AA5005,
A.A5005A, AA5205, AA5305, AA5505, A.A5605, AA5006, AA5106, AA5010, AA5110,
AA5110A, AA5210, AA5310, AA5016, AA5017, AA5018, AA5018A, AA5019, AA5019A,
AA5119, AA5119A, AA5021, AA5022, AA5023, AA5024, AA5026, AA5027, AA5028,
AA5040, AA5140, AA5041, AA5042, AA5043, AA5049, AA5149, AA5249, AA5349,
AA5449, AA5449A, AA5050, AA5050A, AA5050C, AA5150, AA5051, AA5051A, AA5151,
AA5251, AA5251A, AA5351, AA5451, AA5052, AA5252, AA5352, AA5154, AA5154A,
AA5154B, AA5154C, AA5254, AA5354, AA5454, AA5554, AA5654, AA5654A, AA5754,
AA5854, AA5954, AA5056, AA5356, AA5356A, AA5456, AA5456A, AA5456B, AA5556,
AA5556A, AA5556B, AA5556C, AA5257, AA5457, AA5557, AA5657, AA5058, AA5059,
AA5070, AA5180, AA5180A, AA5082, AA5182, AA5083, AA5183, AA5183A, AA5283,
AA5283A, AA5283B, A A5383, AA5483, A.A5086, AA.5186, A.A5087, AA.5187, and A
A5088.
[0031] Non-limiting exemplary AA7xxx series alloys include AA7011, AA7019,
AA7020,
AA7021, AA7039, AA7072, AA7075, AA7085õkA7108, AA7108A, AA7015, AA7017,
AA7018, AA7019A, AA7024, AA7025, AA7028, AA7030, AA7031, AA7033, AA7035,
AA7035A, AA7046, AA7046A, AA7003, AA7004, AA7005, AA7009, AA7010, AA7011,
AA7012, AA7014, AA7016, AA7116, AA7122, AA7023, AA7026, AA7029, AA7129,
AA7229, AA7032, AA7033, AA7034, AA7036, AA7136, AA7037, AA7040, AA7140,
AA7041, AA7049, AA7049A, AA7149, AA7249, AA7349, AA7449, AA7050, AA7050A,
AA7150, AA7250, AA7055, AA7155, AA7255, AA.7056, AA7060, AA7064, AA7065,
AA7068, AA7168, AA7175, AA7475, A.A7076, AA71.78, AA.7278, A.A7278A, AA7081,
AA7181, AA7185, AA7090, AA7093, AA7095, and AA7099.
[0032] In some non-limiting examples, the aluminum alloys useful for providing
dark
anodized aluminum alloy sheets as described herein include those having
compositions with up
to about 0.40 wt. % Fe, up to about 0.25 wt. % Si, up to about 0.2 wt. % Cr,
about 2.0 wt % to
about 3.2 wt. % Mg, about 0.8 wt. % to about 1.5 wt. % Mn, up to about 0.1 wt.
% Cu, up to
about 0.05 wt. % Zn, up to about 0.05 wt. % Ti, and up to about 0.15 wt. %
total impurities, with
the remainder as Al. For example, the aluminum alloy for use as anodized
aluminum having a
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dark gray color includes up to about 0.05 wt. % to about 0.20 wt. A Fe, about
0.03 wt. % to
about 0.1 wt. % Si, up to about 0.05 wt. % Cr, about 2.5 wt. % to about 3.2
wt. % Mg, about 0.8
wt.% to about 1.3 wt. % Mn, up to about 0.05 wt. % Cu, up to about 0.05 wt.%
Zn, up to about
0.05 wt.% Ti, and up to about 0.15 wt. % total impurities, with the remainder
as Al. In some
examples, the aluminum alloy includes up to about 0.30 wt. % Fe, up to about
0.13 wt. % Si, up
to about 0.07 wt. % Cr, from about 2.0 wt. % to about 2.75 wt. % Mg, from
about 0.80 wt. % to
about 1.5 wt. % Mn, up to about 0.05 wt. % Cu, up to about 0.05 wt.% Zn, up to
about 0.05 wt.%
Ti, and up to 0.15 wt. % impurities, with the remainder as Al. Optionally, the
aluminum alloy
includes about 0.1 wt. % Fe, about 0.06 wt. % Si, about 0.005 wt. % Cr, about
2.74 wt. % Mg,
about 1.13 wt. % Mn, about 0.024 wt. % Cu, about 0.005 wt.% Zn, about 0.005
wt.% Ti, and up
to about 0.15 wt. % total impurities, with the remainder as Al. In some
examples, an aluminum
sheet includes any one of the aluminum alloys described herein.
[0033] In some non-limiting examples, the aluminum alloy includes iron (Fe) in
an amount of
from 0% to 0 4 % (e.g., from about to 0.05 wt % to about 0.20 wt %) based on
the total weight
of the alloy. For example, the alloy can include about 0.001 %, about 0.002 %,
about 0.003 %,
about 0.004%, about 0.005 %, about 0.006%, about 0.007 %, about 0.008 %, about
0.009 %,
about 0.01 %, about 0.02 %, about 0.03 %, about 0.04 %, about 0.05 %, about
0.06 %, about
0.07%, about 0.08%, about 0.09%, about 0.1 %, about 0.11 %, about 0.12%, about
0.13 %,
about 0.14 %, about 0.15 %, about 0.16 %, about 0.17 %, about 0.18 %, about
0.19 %, about 0.2
%, about 0.21 %, about 0.22 %, about 0.23 %, about 0.24 %, about 0.25 %, about
0.26 %, about
0.27%, about 0.28%, about 0.29%, about 0.3 %, about 0.31 %, about 0.32%, about
0.33 %,
about 0.34 %, about 0.35 %, about 0.36 %, about 0.37 %, about 0.38 %, about
0.39 %, or about
0.4 % Fe. In some cases, Fe is not present in the alloy (i.e., 0 %). All
expressed in wt. %.
[0034] In some non-limiting examples, the aluminum alloy includes silicon (Si)
in an amount
of from 0 % to about 0.25% (e.g., from about 0.03 % to about 0.1 %) based on
the total weight of
the alloy. For example, the alloy can include about 0.001 %, about 0.002 %,
about 0.003 %,
about 0.004 %, about 0.005 %, about 0.006 %, about 0.007 %, about 0.008 %,
about 0.009 %,
about 0.01 %, about 0.02 %, about 0.03 %, about 0.04 %, about 0.05 %, about
0.06 %, about
0.07 %, about 0.08 %, about 0.09 %, about 0.1 %, about 0.11 %, about 0.12 %,
about 0.13 %,
about 0.14%, about 0.15 %, about 0.16%. about 0.17%, about 0.18 %, about
0.19%, about 0.2
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%, about 0.21 %, about 0.22 %, about 0.23 %, about 0.24 %, or about 0.25 % Si.
In some cases,
Si is not present in the alloy (i.e., 0 %). All expressed in wt. %.
[0035] In some non-limiting examples, the aluminum alloy includes chromium
(Cr) in an
amount of from 0 % to about 0.2% (e.g., from about 0.001 % to about 0.15 %)
based on the total
weight of the alloy. For example, the alloy can include about 0.001 %, about
0.002 %, about
0.003 %, about 0.004 %, about 0.005 %, about 0.006 %, about 0.007 %, about
0.008 %, about
0.009 %, about 0.01 %, about 0.02 %, about 0.03 %, about 0.04 %, about 0.05 %,
about 0.06 %,
about 0.07 %, about 0.08 %, about 0.09 %, about 0.1 %, about 0.11 %, about
0.12 0/0, about 0.13
%, about 0.14 %, about 0.15 %, about 0.16 %, about 0.17 %, about 0.18 %, about
0.19 %, or
about 0.24% Cr. In some cases, Cr is not present in the alloy (i.e., 0 %). All
expressed in wt. %.
[0036] In some non-limiting examples, the aluminum alloy includes magnesium
(Mg) in an
amount of from about 2.0% to about 3.2% (e.g., from about 2.5% to about 3.2 %)
based on the
total weight of the alloy. In some examples, the alloy can include about 2.0
%, about 2.1 %,
about 2.2 %, about 2.3 %, about 2.4 %, about 2.5 %, about 2.6 %, about 2.7 %,
about 2.75 %,
about 2.8 %, about 2.9 %, about 3.0 %, about 3.1 %, or about 3.2 % Mg. All
expressed in wt. %.
[0037] In some non-limiting examples, the aluminum alloy includes manganese
(Mn) in an
amount of from about 0.8% to about 1.5 % (e.g., from about 0.8 % to about 1.3
%) based on the
total weight of the alloy. In some examples, the alloy can include about 0.1
%, about 0.2 %,
about 0.3 %, about 0.4 %, about 0.5 %, about 0.6 %, about 0.7 %, about 0.8 %,
about 0.9 %,
about 1.0%, about 1.1 %, about 1.2%, or about 1.3 % Mn. All expressed in wt.
%.
[0038] In some non-limiting examples, the aluminum alloy includes copper (Cu)
in an amount
of from 0 % to about 0.1 % (e.g., from 0 % to about 0.05 /0) based on the
total weight of the
alloy. For example, the alloy can include about 0.001 %, about 0.002 %, about
0.003 %, about
0.004 %, about 0.005 %, about 0.006 %, about 0.007 %, about 0.008 %, about
0.009 %, about
0.01 %, about 0.02 %, about 0.03 %, about 0.04 %, about 0.05 %, about 0.06 %,
about 0.07 %,
about 0.08 %, about 0.09 %, or about 0.1 % Cu. In some cases, Cu is not
present in the alloy
(i.e., 0%). All expressed in wt. %.
[0039] In some non-limiting examples, the aluminum alloy includes zinc (Zn) in
an amount of
from 0 % to about 0.05 % based on the total weight of the alloy. For example,
the alloy can
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include about 0.001 %, about 0.002 %, about 0.003 %, about 0.004 %, about
0.005 %, about
0.006 %, about 0.007 %, about 0.008 %, about 0.009 %, about 0.01 %, about 0.02
%, about 0.03
%, about 0.04 %, or about 0.05 % Zn. In some cases, Zn is not present in the
alloy (i.e., 0 %).
All expressed in wt. %.
[0040] In some non-limiting examples, the aluminum alloy includes titanium
(Ti) in an amount
of from 0 % to about 0.05 % based on the total weight of the alloy. For
example, the alloy can
include about 0.001 %, about 0.002 (?/0, about 0.003 %, about 0.004 %, about
0.005 %, about
0.006 %, about 0.007 %, about 0.008 %, about 0.009 %, about 0.01 %, about 0.02
0/0, about 0.03
%, about 0.04 %, or about 0.05 % Ti. In some cases, Ti is not present in the
alloy (i.e., 0 %). All
expressed in wt. %.
[0041] Optionally, the alloy compositions described herein can further include
other minor
elements, sometimes referred to as impurities, in amounts of 0.05 % or below,
0.04 % or below,
0.03 % or below, 0.02 % or below, or 0.01 % or below each. These impurities
may include, but
are not limited to, V, Zr, Ni, Sn, Ga, Ca, or combinations thereof.
Accordingly, V, Zr, Ni, Sn,
Ga, or Ca may be present in alloys in amounts of 0.05 % or below, 0.04 % or
below, 0.03 % or
below, 0.02 % or below, or 0.01 % or below. In some cases, the sum of all
impurities does not
exceed 0.15% (e.g., 0.10%). All expressed in wt. %. The remaining percentage
of the alloy is
aluminum.
[0042] As further described below, the alloys described herein can be prepared
as sheets and
can be anodized. The surface oxide layer produced by an anodization process of
a conventional
alloy is a highly ordered structure that, when pure, can be clear and
colorless. The alloys
described herein, in contrast, are designed to form fine intermetallic
particles (e.g., dispersoids or
precipitates) in the substrate that are maintained inside the oxide layer
formed during the
anodization process.
[0043] The intermetallic particles include two or more elements, for example,
two or more of
Al, Fe, Mn. Si, Cu, Ti, Zr, Cr, and/or Mg. The intermetallic particles
include, but are not limited
to, Alx(Fe,Mn), Al3Fe, Ali2(Fe,Mn)3Si, Al7Cu2Fe, A120Cu2Mn3, Al3Ti, Al2Cu,
Al(Fe,Mn)2Si3,
Al3Zr, Al7Cr, Alx(Mn,Fe), A112(Mn,Fe)3Si, A13,Ni, Mg2Si, MgZn3, Mg2A13,
A.132Zn49, Al2CuMg,
and Al6Mn. While many intermetallic particles contain aluminum, there also
exist intermetallic
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particles that do not contain aluminum, such as Mg2Si. The composition and
properties of
intermetallic particles are described further below.
1100441 In some examples, the alloys described herein include various weight
percent of phases
Alx(Fe,Mn), A112(Fe,Mn)3Si, and Al6Mn, Mg2Si. When an element in an
intermetallic particle
designation is italicized, that element is the dominantly present element in
the particle. The
notation (Fe,Mn) indicates that the element can be Fe or Mn, or a mixture of
the two. The
notation (Fe,Mn) indicates that the particle contains more of the element Fe
than the element
Mn, while the notation (Fe,Mn) indicates that the particle contains more of
the element Mn than
the element Fe.
[0045] The weight percent of each phase differs at different annealing
temperatures used in the
methods for preparing the aluminum alloy sheets, as detailed below. An alloy
having a higher
weight percent of Alx(Fe,Mn) and/or A112(Fe,Mn)3Si particles will have a
darker natural
anodized color. In some examples, the aluminum alloy includes at least 1.5
weight %
Alõ(Fe,Mn) and/or A112(Fe,Mn)351 at 400 C (e.g., at least 1.0 %, at least
1.25 %, at least 1.5 %,
or at least 1.75 %, all weight %). In some examples, the aluminum alloy
includes at least 2.0
weight % Alx(Fe,111n) and/or A112(Fe,Mn)3Si at 500 C (e.g., at least 2.0 %,
at least 2.2 %, or at
least 2.4 %, all weight %).
[00461 In some examples, the aluminum sheet having a dark gray color includes
dispersoids at
a density of at least 1 dispersoid per 25 square micrometers (e.g., at least 1
dispersoid per 25
square micrometers, at least 2 dispersoids per 25 square micrometers, at least
4 dispersoids per
25 square micrometers, at least 10 dispersoids per 25 square micrometers, or
at least 20
dispersoids per 25 square micrometers).
10047] In some examples, the dispersoids have an average dimension of greater
than 50
nanometers in any direction. For purposes herein, "any direction" means
height, width, or depth.
For example, the dispersoids can have an average particle dimension of greater
than 50
nanometers, greater than 100 nanometers, greater than 200 nanometers, or
greater than 300
nanometers. In some examples, the dispersoids include one or more of Al, Fe,
Mn, Si, Cu, Ti,
Zr, Cr, Ni, Zn, and/or Mg. In some examples, the dispersoids include Al-Mn-Fe-
Si dispersoids.
In some examples, the dispersoids include one or more of Al3Fe,
A112(Fe,Mn)3Si, Al20Cu2Mn3,
Al(Fe,Mn)2Si3, Al3Zr, Al7Cr, Al12(Mn,Fe)3Si, Mg2Si, Al2CuMg, and Al6Mn. In
some examples,
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the dispersoids include one or more of Al3Fe, Alx(Ile,Mn), Al3Fe,
A112(F'e,Mn)3Si, Al7Cu2Fe,
A120Cu2Mn3, Al3Ti, Al2Cu, Al(Fe,Mn)2Si3, Al3Zr, Al7Cr, Alx(Mn,Fe),
Ali2(Mn,Fe)3Si, A13,Ni,
Mg2Si, MgZn3, Mg2A13, Ai32Zn49, Al2Cu.Mg, and Al6Mn.
[0048] In some examples, the aluminum sheet has a grain size of from 10
microns to 50
microns. For example, the aluminum sheet can have a grain size of from 15
microns to 45
microns, from 15 microns to 40 microns, or from 20 microns to 40 microns.
Methods of Preparing
[0049] Methods of producing an aluminum sheet are also described herein. In
some examples,
the method includes casting the aluminum; homogenizing the aluminum; hot
rolling the
homogenized aluminum to produce a hot rolled intermediate product; cold
rolling the hot rolled
intermediate product to produce a cold rolled intermediate product;
interannealing the cold rolled
intermediate product to produce an interannealed product; cold rolling the
interannealed product
to produce a cold rolled sheet; and annealing the cold rolled sheet to form an
annealed sheet. In
some examples, the method further includes etching the annealed aluminum
sheets (e.g., in an
acid or base bath) and anodizing the annealed aluminum sheets.
[00501 In some examples, the alloys described herein can be cast into ingots
using a direct chill
(DC) process. The resulting ingots can optionally be scalped. In some
examples, the alloys
described herein can be cast in a continuous casting (CC) process. The cast
product can then be
subjected to further processing steps. In some examples, the processing steps
further include a
homogenization step, a hot rolling step, a cold rolling step, an optional
interannealing step, a cold
rolling step, and a final annealing step. The processing steps described below
exemplify
processing steps used for an ingot as prepared from a DC process.
[0051] The homogenization step described herein can be a single homogenization
step or a
two-step homogenization process. The first homogenization step dissolves
metastable phases
into the matrix and minimizes microstructural inhomogeneity. An ingot is
heated to attain a peak
metal temperature of 500-550 C for about 2-24 hours. In some examples, the
ingot is heated to
attain a peak metal temperature ranging from about 510 C to about 540 C,
from about 515 C
to about 535 C, or from about 520 C to about 530 C. The heating rate to
reach the peak metal
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temperature can be from about 30 C per hour to about 100 C per hour. The
ingot is then
allowed to soak (i.e., maintained at the indicated temperature) for a period
of time during the first
homogenization stage. In some examples, the ingot is allowed to soak for up to
5 hours (e.g., up
to 1 hour, up to 2 hours, up to 3 hours, up to 4 hours, inclusively) For
example, the ingot can be
soaked at a temperature of about 515 C, about 525 C, about 540 C, or about
550 C for 1 hour
to 5 hours (e.g., 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours).
[0052] In the second homogenization step, if present, the ingot temperature is
decreased to a
temperature of from about 480 C to 550 C prior to subsequent processing. In
some examples,
the ingot temperature is decreased to a temperature of from about 450 C to
480 C prior to
subsequent processing. For example, in the second stage the ingot can be
cooled to a
temperature of about 450 C, about 460 C, about 470 C, or about 480 C and
allowed to soak
for a period of time. In some examples, the ingot is allowed to soak at the
indicated temperature
for up to eight hours (e.g., from 30 minutes to eight hours, inclusively). For
example, the ingot
can be soaked at a temperature of about 450 C, of about 460 C, of about 470
C, or of about
480 C for 30 minutes to 8 hours.
[0053] Following the second homogenization step, a hot rolling step can be
performed. The
hot rolling step can include a hot reversing mill operation and/or a hot
tandem mill operation.
The hot rolling step can be performed at a temperature ranging from about 250
C to about 450
C (e.g., from about 300 C to about 400 C or from about 350 C to about 400
C). In the hot
rolling step, the ingots can be hot rolled to a thickness of 10 mm gauge or
less (e.g., from 3 mm
to 8 mm gauge). For example, the ingots can be hot rolled to a 8 mm gauge or
less, 7 mm gauge
or less, 6 mm gauge or less, 5 mm gauge or less, 4 mm gauge or less, or 3 mm
gauge or less.
Optionally, the hot rolling step can be performed for a period of up to one
hour. Optionally, at
the end of the hot rolling step (e.g., upon exit from the tandem mill), the
aluminum sheet is
coiled to produce a hot rolled coil.
[0054] The hot rolled coil can be uncoiled into a hot rolled sheet which can
then undergo a
cold rolling step. The hot rolled sheet temperature can be reduced to a
temperature ranging from
about 20 C to about 200 C (e.g., from about 120 C to about 200 C). The
cold rolling step can
be performed for a period of time to result in a final gauge thickness of from
about 1.0 mm to
about 3 mm, or about 2.3 mm. Optionally, the cold rolling step can be
performed for a period of
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up to about 1 hour (e.g., from about 10 minutes to about 30 minutes) and the
sheet can be coiled
to produce a cold rolled coil.
10055] Optionally, the cold rolled coil can then undergo an interannealing
step. The
interannealing step can include heating the coil to a peak metal temperature
of from about 300 C
to about 400 C (e.g., about 300 C, 305 C, 310 C, 315 C, 320 C, 325 C,
330 C, 335 C,
340 C, 345 C, 350 C, 355 C, 360 C, 365 C, 370 C, 375 C, 380 C, 385
C, 390 C, 395
C, or 400 C). The heating rate for the interannealing step can be from about
20 C per minute
to about 100 C per minute (e.g., about 40 C per minute, about 50 C per
minute, about 60 C
per minute, or about 80 C per minute). The interannealing step can be
performed for a period of
about 2 hours or less (e.g., about 1 hour or less). For example, the
interannealing step can be
performed for a period of from about 30 minutes to about 50 minutes.
[0056] The interannealing step can optionally be followed by another cold
rolling step. The
cold rolling step can be performed for a period of time to result in a final
gauge thickness
between about 0.5 mm and about 2 mm, between about 0.75 and about 1.75 mm,
between about
1 and about 1.5 mm, or about 1.27 mm. Optionally, the cold rolling step can be
performed for a
period of up to about 1 hour (e.g., from about 10 minutes to about 30
minutes).
10057] The cold rolled coil can then undergo an annealing step. The annealing
step can
include heating the cold rolled coil to a peak metal temperature of from about
180 C to about
350 C. The heating rate for the annealing step can be from about 10 C per
hour to about 100
C per hour. The annealing step can be performed for a period of up to 48 hours
or less (e.g., 1
hour or less). For example, the annealing step can be performed for a period
of from 30 minutes
to 50 minutes.
10058] Following the annealing step and before the anodizing step, the
aluminum sheets can be
etched. Any known etching process may be used, including alkaline etching or
acidic etching.
As an example, an alkaline etching process can be performed with sodium
hydroxide (e.g., a
10% aqueous sodium hydroxide solution) followed by a desmutting process. As
another
example, an acidic etching process can be performed with phosphoric acid,
sulfuric acid, or a
combination of these. For example, the acidic etching process can be performed
using 75%
phosphoric acid and 25% sulfuric acid at an elevated temperature. As used
herein, an elevated
temperature refers to a temperature higher than room temperature (e.g.,
greater than 40 C,
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greater than 50 C, greater than 60 C, greater than 70 C, greater than 80
C, or greater than 90
C, such as 99 C). During the etching process, the bulk aluminum matrix and
intermetallic
particlesidispersoids are dissolved. Depending on the etching process, the
degree and uniformity
of etched surface can be varied.
100591 After the etching step, the aluminum sheets described herein are
anodized. In some
examples, the aluminum sheets described herein are anodized by placing the
aluminum in an
electrolytic solution and passing a direct current through the solution. In
some examples, the
electrolytic solution is an acidic solution, such as, but not limited to, a
solution including
hydrochloric acid, sulfuric acid, chromic acid, phosphoric acid, and/or an
organic acid.
Anodization creates an oxide surface layer on the aluminum alloy. In some
examples, the
aluminum sheet includes an oxide surface layer.
Methods of Using
[0060] The materials described herein are particularly useful in architectural
quality
applications as well as other decorative applications, such as decorative
panels, street signs,
appliances, furniture, jewelry, artwork, boating and automotive components,
and even consumer
electronics where high quality dark gray color in anodized sheets are required
by customers.
[00611 The following examples will serve to further illustrate the present
invention without, at
the same time, however, constituting any limitation thereof. On the contrary,
it is to be clearly
understood that resort may be had to various embodiments, modifications, and
equivalents
thereof which, after reading the description herein, may suggest themselves to
those skilled in the
art without departing from the spirit of the invention. During the studies
described in the
following examples, conventional procedures were followed, unless otherwise
stated. Some of
the procedures are described below for illustrative purposes.
EXAMPLE 1
[0062] An inventive alloy sheet and three comparative alloy sheets having the
compositions
detailed in Table 1 were prepared. The sheets were prepared by casting an
ingot at
approximately 650 C, homogenizing the ingot at 525 C for less than 1 hour
soaking time, hot
rolling the homogenized ingot for 10 minutes at 250-450 C to produce a hot
rolled intermediate
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product, and cold rolling the hot rolled intermediate product for 10 minutes
at 150-180 C to
produce a cold rolled intermediate product.
Table 1. Alloy elemental compositions, with up to 0.15 weight % total
impurities, the
balance Aluminum.
Si = Fe Cu Mn Mg Cr Zn Ti
Comparative 0.14 0.32 0.050 0.77 2.88 0.071 0.013 0.013
Alloy 1
Comparative 0.20 0.37 0.050 0.30 2.76 0.092 0.048 0.025
Alloy 2
Comparative 0.18 0.31 0.019 0.23 2.87 0.008 0.01 0.01
Alloy 3
Alloy 4 0.06 0.10 0.024 1.13 2.74 0.005 0.005 1 0.005
EXAMPLE 2
[0063] The aluminum sheets of Alloy 4 and Comparative Alloys 1 and 2 described
in Example
1 were imaged with scanning transmission electron microscopy (STEM). FIG. IA
and FIG. 1B
are STEM images of Comparative Alloy 1 and Comparative Alloy 2, respectively.
FIG. 1C is a
STEM image of Alloy 4. Alloy 4 showed a much higher density of dispersoids
than the
comparative alloys. Alloy 3 had a lower density of dispersoids than Alloys 1
and 2, and thus is
not pictured.
EXAMPLE 3
[0064] Sheets of Comparative Alloys 1 and 2 and Alloy 4 prepared as described
in Example 1
were alkaline etched with 10% sodium hydroxide solution and anodized to a 10
micrometer (gm)
anodized layer thickness. The resulting anodized layer cross section was
imaged with high-
resolution scanning electron microscopy (SEM). The SEM images of Comparative
Alloys 1 and
2 and Alloy 4 are shown in FIGs. 2A-2C, respectively. As identified in Figure
2A, fine particles
were Al6Fe and Mg2Si in these example alloys. The anodized aluminum sheet from
Alloy 4 has
a significantly darker gray color, with many dispersoids visible (see FIG.
2C), whereas the two
comparative anodized aluminum alloy sheets have a light gray color and fewer
dispersoids (see
F1Gs. 2A-2B).
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EXAMPLE 4
[0065] Thermodynamic modelling by Thermo-Calc software (Thermo-Calc Software,
Inc.,
McMurray, PA) was used to calculate the equilibrium phase transformation
behavior of
Comparative Alloys 1-2 (see FIGs. 3A and 3B, respectively) and Alloy 4 (see
FIG. 3C).
Equilibrium phases at each temperature of given alloy composition was
calculated by
CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) technique.
Each
line represents specific phase. Line 1: liquid; line 2: Al matrix; line 3:
Al6Mn; line 4:
Al(Fe,Mn)2S13; line 5: Mg2Si; line 6: AlCuMn; line 7: AlCuMg; line 8: Al8Mg.5;
line 9: All2Mn.
Modeling results indicate that the amount of Al6Mn dispersoids (line 3) is the
most in alloy 4
(Figure 3C). Not intending to be bound by theory, the inventive alloy's higher
Mn content
relative to the comparative alloys results in a greater concentration of Al6Mn
dispersoids in the
inventive alloy oxide layer, which provides scattering of incoming light.
[0066] All patents, publications and abstracts cited above are incorporated
herein by reference
in their entirety. Various embodiments of the invention have been described in
fulfillment of the
various objectives of the invention. It should be recognized that these
embodiments are merely
illustrative of the principles of the present invention. Numerous
modifications and adaptations
thereof will be readily apparent to those skilled in the art without departing
from the spirit and
scope of the present invention as defined in the following claims.
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