U.S. patent application number 15/674680 was filed with the patent office on 2018-02-22 for anodized aluminum with dark gray color.
This patent application is currently assigned to Novelis Inc.. The applicant listed for this patent is Novelis Inc.. Invention is credited to Simon Barker, Martin Frank, Daehoon Kang, Devesh Mathur.
Application Number | 20180051387 15/674680 |
Document ID | / |
Family ID | 59738425 |
Filed Date | 2018-02-22 |
United States Patent
Application |
20180051387 |
Kind Code |
A1 |
Kang; Daehoon ; et
al. |
February 22, 2018 |
ANODIZED ALUMINUM WITH DARK GRAY COLOR
Abstract
Provided herein are aluminum alloys and aluminum sheets
including alloys that have a natural 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. Also provided herein are methods for making such
aluminum alloys.
Inventors: |
Kang; Daehoon; (Kennesaw,
GA) ; Frank; Martin; (Ulrichstein-Bobenhausen,
DE) ; Barker; Simon; (Woodstock, GA) ; Mathur;
Devesh; (Marietta, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Novelis Inc. |
Atlanta |
GA |
US |
|
|
Assignee: |
Novelis Inc.
Atlanta
GA
|
Family ID: |
59738425 |
Appl. No.: |
15/674680 |
Filed: |
August 11, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62375932 |
Aug 17, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 21/08 20130101;
C22F 1/047 20130101; C22C 21/06 20130101; C22F 1/04 20130101; C25D
15/00 20130101; C25D 11/16 20130101; C25D 11/04 20130101 |
International
Class: |
C25D 11/04 20060101
C25D011/04; C22F 1/047 20060101 C22F001/047; C22C 21/08 20060101
C22C021/08; C25D 15/00 20060101 C25D015/00 |
Claims
1. An aluminum alloy comprising about 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.
2. The aluminum alloy of claim 1, wherein the aluminum alloy
comprises 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.
3. The aluminum alloy of claim 1, comprising at least 1.5 weight
percent Al.sub.6Mn and/or Al.sub.12(Fe,Mn).sub.3Si.
4. An aluminum sheet comprising the aluminum alloy of claim 1.
5. The aluminum sheet of claim 4, wherein the aluminum alloy sheet
comprises an oxide surface layer.
6. The aluminum sheet of claim 4, wherein the aluminum alloy sheet
has a white balance of lower than 35 as measured by ASTM E313-15
(2015).
7. The aluminum sheet of claim 4, further comprising dispersoids at
a density of at least 2 disperoids per 25 square micrometer.
8. The aluminum sheet of claim 7, wherein the dispersoids have an
average dimension of greater than 50 nanometers in any
direction.
9. The aluminum sheet of claim 8, wherein the dispersoids comprise
one or more of Al.sub.3Fe, Al.sub.x(Fe,Mn), Al.sub.3Fe,
Al.sub.12(Fe,Mn).sub.3Si, Al.sub.7Cu.sub.2Fe,
Al.sub.20Cu.sub.2Mn.sub.3, Al.sub.3Ti, Al.sub.2Cu,
Al(Fe,Mn).sub.2Si.sub.3, Al.sub.3Zr, Al.sub.7Cr, Al.sub.x(Mn,Fe),
Al.sub.12(Mn,Fe).sub.3Si, Al.sub.3,Ni, Mg.sub.2Si, MgZn.sub.3,
Mg.sub.2Al.sub.3, Al.sub.32Zn.sub.49, Al.sub.2CuMg, and
Al.sub.6Mn.
10. The aluminum sheet of claim 8, wherein the dispersoids comprise
Al--Mn--Fe--Si.
11. The aluminum sheet of claim 8, wherein the dispersoids comprise
one or more of Al.sub.3Fe, Al.sub.12(Fe,Mn).sub.3Si,
Al.sub.20Cu.sub.2Mn.sub.3, Al(Fe,Mn).sub.2Si.sub.3, Al.sub.3Zr,
Al.sub.7Cr, Al.sub.12(Mn,Fe).sub.3Si, Mg.sub.2Si, and Al.sub.2CuMg,
and Al.sub.6Mn.
12. The aluminum sheet of claim 4, comprising a grain size of from
10 microns to 50 microns.
13. A method of preparing an aluminum sheet comprising dispersoids,
the method comprising: 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 aluminum sheet
comprising dispersoids, wherein the aluminum alloy comprises a
2xxx, 3xxx, 5xxx, or 7xxx series alloy.
14. The method of claim 13, further comprising anodizing the
aluminum sheet.
15. The method of claim 13, wherein the aluminum alloy comprises
about 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.
16. The method of claim 13, wherein the dispersoids comprise one or
more of Al.sub.3Fe, Al.sub.x(Fe,Mn), Al.sub.3Fe,
Al.sub.12(Fe,Mn).sub.3Si, Al.sub.7Cu.sub.2Fe,
Al.sub.20Cu.sub.2Mn.sub.3, Al.sub.3Ti, Al.sub.2Cu,
Al(Fe,Mn).sub.2Si.sub.3, Al.sub.3Zr, Al.sub.7Cr, Al.sub.x(Mn,Fe),
Al.sub.12(Mn,Fe).sub.3Si, Al.sub.3,Ni, Mg.sub.2Si, MgZn.sub.3,
Mg.sub.2Al.sub.3, Al.sub.32Zn.sub.49, Al.sub.2CuMg, and
Al.sub.6Mn.
17. The method of claim 13, wherein the aluminum sheet has a white
balance of lower than 35 as measured by ASTM E313-15 (2015).
18. The method of claim 13, wherein the dispersoids are present in
the aluminum sheet at a density of at least 2 disperoids per 25
square micrometers.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/375,932, filed Aug. 17, 2016, which is
incorporated by reference herein in its entirety.
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
colorization 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.
[0005] 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.
[0007] 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, 3xxx, 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.
[0011] 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 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 Descriptions
[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.
[0025] As used herein, the meaning of "room temperature" can
include a temperature of from about 15.degree. C. to about
30.degree. C., for example about 15.degree. C., about 16.degree.
C., about 17.degree. C., about 18.degree. C., about 19.degree. C.,
about 20.degree. C., about 21.degree. C., about 22.degree. C.,
about 23.degree. C., about 24.degree. C., about 25.degree. C.,
about 26.degree. C., about 27.degree. C., about 28.degree. C.,
about 29.degree. C., or about 30.degree. C.
[0026] 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
[0027] 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, 3xxx, 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, AA2111, 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, AA2044, AA2045, AA2050, AA2055, AA2056, AA2060,
AA2065, AA2070, AA2076, AA2090, AA2091, AA2094, AA2095, AA2195,
AA2295, AA2196, 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, AA3104, AA3204,
AA3304, AA3005, AA3005A, AA3105, AA3105A, AA3105B, AA3007, AA3107,
AA3207, AA3207A, AA3307, AA3009, AA3010, AA3110, 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, AA5005A, AA5205, AA5305, AA5505, AA5605, 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, AA5383, AA5483,
AA5086, AA5186, AA5087, AA5187, and AA5088.
[0031] Non-limiting exemplary AA7xxx series alloys include AA7011,
AA7019, AA7020, AA7021, AA7039, AA7072, AA7075, AA7085, AA7108,
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, AA7056, AA7060, AA7064,
AA7065, AA7068, AA7168, AA7175, AA7475, AA7076, AA7178, AA7278,
AA7278A, 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 dark gray color includes up to about
0.05 wt. % to about 0.20 wt. % 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%, 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%,
about 0.13%, about 0.14%, about 0.15%, about 0.16%, about 0.17%,
about 0.18%, about 0.19%, or about 0.2% 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%) 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 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%, 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% 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,
Al.sub.x(Fe,Mn), Al.sub.3Fe, Al.sub.12(Fe,Mn).sub.3Si,
Al.sub.7Cu.sub.2Fe, Al.sub.20Cu.sub.2Mn.sub.3, Al.sub.3Ti,
Al.sub.2Cu, Al(Fe,Mn).sub.2Si.sub.3, Al.sub.3Zr, Al.sub.7Cr,
Al.sub.x(Mn,Fe), Al.sub.12(Mn,Fe).sub.3Si, Al.sub.3,Ni, Mg.sub.2Si,
MgZn.sub.3, Mg.sub.2Al.sub.3, Al.sub.32Zn.sub.49, Al.sub.2CuMg, and
Al.sub.6Mn. While many intermetallic particles contain aluminum,
there also exist intermetallic particles that do not contain
aluminum, such as Mg.sub.2Si. The composition and properties of
intermetallic particles are described further below.
[0044] In some examples, the alloys described herein include
various weight percent of phases Al.sub.x(Fe,Mn),
Al.sub.12(Fe,Mn).sub.3Si, and Al.sub.6Mn, Mg.sub.2Si. 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 Al.sub.x(Fe,Mn) and/or Al.sub.12(Fe,Mn).sub.3Si
particles will have a darker natural anodized color. In some
examples, the aluminum alloy includes at least 1.5 weight %
Al.sub.x(Fe,Mn) and/or Al.sub.12(Fe,Mn).sub.3Si at 400.degree. 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 % Al.sub.x(Fe,Mn) and/or
Al.sub.12(Fe,Mn).sub.3Si at 500.degree. C. (e.g., at least 2.0%, at
least 2.2%, or at least 2.4%, all weight %).
[0046] 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).
[0047] 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 Al.sub.3Fe, Al.sub.12(Fe,Mn).sub.3Si,
Al.sub.20Cu.sub.2Mn.sub.3, Al(Fe,Mn).sub.2Si.sub.3, Al.sub.3Zr,
Al.sub.7Cr, Al.sub.12(Mn,Fe).sub.3Si, Mg.sub.2Si, Al.sub.2CuMg, and
Al.sub.6Mn. In some examples, the dispersoids include one or more
of Al.sub.3Fe, Al.sub.x(Fe,Mn), Al.sub.3Fe,
Al.sub.12(Fe,Mn).sub.3Si, Al.sub.7Cu.sub.2Fe,
Al.sub.20Cu.sub.2Mn.sub.3, Al.sub.3Ti, Al.sub.2Cu,
Al(Fe,Mn).sub.2Si.sub.3, Al.sub.3Zr, Al.sub.7Cr, Al.sub.x(Mn,Fe),
Al.sub.12(Mn,Fe).sub.3Si, Al.sub.3,Ni, Mg.sub.2Si, MgZn.sub.3,
Mg.sub.2Al.sub.3, Al.sub.32Zn.sub.49, Al.sub.2CuMg, and
Al.sub.6Mn.
[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.
[0050] 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.degree. C. for about
2-24 hours. In some examples, the ingot is heated to attain a peak
metal temperature ranging from about 510.degree. C. to about
540.degree. C., from about 515.degree. C. to about 535.degree. C.,
or from about 520.degree. C. to about 530.degree. C. The heating
rate to reach the peak metal temperature can be from about
30.degree. C. per hour to about 100.degree. 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.degree. C., about 525.degree. C., about
540.degree. C., or about 550.degree. 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.degree.
C. to 550.degree. C. prior to subsequent processing. In some
examples, the ingot temperature is decreased to a temperature of
from about 450.degree. C. to 480.degree. C. prior to subsequent
processing. For example, in the second stage the ingot can be
cooled to a temperature of about 450.degree. C., about 460.degree.
C., about 470.degree. C., or about 480.degree. 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.degree. C., of
about 460.degree. C., of about 470.degree. C., or of about
480.degree. 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.degree. C. to about 450 .degree. C. (e.g., from about
300.degree. C. to about 400.degree. C. or from about 350.degree. C.
to about 400.degree. 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.degree. C. to about 200.degree. C. (e.g., from about 120.degree.
C. to about 200.degree. 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 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.
[0055] 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.degree. C.
to about 400.degree. C. (e.g., about 300.degree. C., 305.degree.
C., 310.degree. C., 315.degree. C., 320.degree. C., 325.degree. C.,
330.degree. C., 335.degree. C., 340.degree. C., 345.degree. C.,
350.degree. C., 355.degree. C., 360.degree. C., 365.degree. C.,
370.degree. C., 375.degree. C., 380.degree. C., 385.degree. C.,
390.degree. C., 395.degree. C., or 400.degree. C.). The heating
rate for the interannealing step can be from about 20.degree. C.
per minute to about 100.degree. C. per minute (e.g., about
40.degree. C. per minute, about 50.degree. C. per minute, about
60.degree. C. per minute, or about 80.degree. 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).
[0057] 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.degree. C. to about 350.degree.
C. The heating rate for the annealing step can be from about
10.degree. C. per hour to about 100 .degree. 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.
[0058] 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.degree. C., greater than 50.degree. C., greater than
60.degree. C., greater than 70.degree. C., greater than 80.degree.
C., or greater than 90 .degree. C., such as 99.degree. C.). During
the etching process, the bulk aluminum matrix and intermetallic
particles/dispersoids are dissolved. Depending on the etching
process, the degree and uniformity of etched surface can be
varied.
[0059] 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.
[0061] 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.degree. C., homogenizing the ingot at 525.degree. C. for less
than 1 hour soaking time, hot rolling the homogenized ingot for 10
minutes at 250-450.degree. C. to produce a hot rolled intermediate
product, and cold rolling the hot rolled intermediate product for
10 minutes at 150-180.degree. C. to produce a cold rolled
intermediate product.
TABLE-US-00001 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 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. 1A 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 (.mu.m) 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 FIG. 2A, fine particles
were Al.sub.6Fe and Mg.sub.2Si 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 FIGS. 2A-2B).
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: Al.sub.6Mn; line 4:
Al(Fe,Mn).sub.2Si.sub.3; line 5: Mg.sub.2Si; line 6: AlCuMn; line
7: AlCuMg; line 8: Al.sub.8Mg.sub.5; line 9: Al.sub.12Mn. Modeling
results indicate that the amount of Al.sub.6Mn dispersoids (line 3)
is the most in alloy 4 (FIG. 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 Al.sub.6Mn
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.
* * * * *