U.S. patent application number 17/020234 was filed with the patent office on 2021-03-25 for cosmetic aluminum alloys made from recycled aluminum scrap.
The applicant listed for this patent is Apple Inc.. Invention is credited to Brian M. Gable, Weiming Huang, Herng-Jeng Jou, Katie L. Sassaman, James A. Yurko.
Application Number | 20210087656 17/020234 |
Document ID | / |
Family ID | 1000005109269 |
Filed Date | 2021-03-25 |
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United States Patent
Application |
20210087656 |
Kind Code |
A1 |
Sassaman; Katie L. ; et
al. |
March 25, 2021 |
COSMETIC ALUMINUM ALLOYS MADE FROM RECYCLED ALUMINUM SCRAP
Abstract
The disclosure is directed to aluminum alloys made from recycled
components. The alloys have copper (Cu) from 0.051 to 0.10 wt %,
chromium (Cr) from 0.01 to 0.10 wt %, zinc (Zn) from 0.02 to 0.20
wt %, manganese (Mn) from 0.03 to 0.10 wt %, iron (Fe) in an amount
of at least 0.10 wt %, silicon (Si) in an amount of at least 0.35
wt %, magnesium (Mg) in amount of at least 0.45 wt %, and the
remaining wt % being Al and incidental impurities. In other
aspects, the disclosure is directed to aluminum alloys having
copper (Cu) from 0.010 to 0.050 wt %, chromium (Cr) from 0.01 to
0.10 wt %, zinc (Zn) from 0.01 to 0.20 wt %, manganese (Mn) from
0.03 to 0.10 wt %, iron (Fe) in an amount of at least 0.10 wt %,
silicon (Si) in an amount of at least 0.35 wt %, magnesium (Mg) in
amount of at least 0.45 wt %, and the remaining wt % being Al and
incidental impurities. The b* color of the alloys ranges from -2 to
2, and the L* color ranges from 70 to 100.
Inventors: |
Sassaman; Katie L.; (San
Jose, CA) ; Gable; Brian M.; (San Jose, CA) ;
Jou; Herng-Jeng; (San Jose, CA) ; Huang; Weiming;
(State College, PA) ; Yurko; James A.; (Saratoga,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
1000005109269 |
Appl. No.: |
17/020234 |
Filed: |
September 14, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62984054 |
Mar 2, 2020 |
|
|
|
62905896 |
Sep 25, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 21/08 20130101;
C22C 1/026 20130101 |
International
Class: |
C22C 21/08 20060101
C22C021/08; C22C 1/02 20060101 C22C001/02 |
Claims
1. An aluminum alloy comprising: copper (Cu) from 0.051 to 0.10 wt
%; chromium (Cr) from 0.01 to 0.10 wt %; zinc (Zn) from 0.02 to
0.20 wt %; manganese (Mn) from 0.03 to 0.10 wt %; iron (Fe) in an
amount of at least 0.10 wt %; silicon (Si) in an amount of at least
0.35 wt %; magnesium (Mg) in an amount of at least 0.45 wt %; and
remaining wt % being Al and incidental impurities, wherein b*
ranges from -2 to 2, and L* ranges from 70 to 100.
2. The aluminum alloy of one of claim 1, further comprising
elements selected from: titanium (Ti) from 0 to 0.10 wt %; gallium
(Ga) from 0 to 0.20 wt %; tin (Sn) from 0 to 0.20 wt %; vanadium
(V) from 0 to 0.20 wt %; calcium (Ca) from 0 to 0.01 wt %; sodium
(Na) from 0 to 0.008 wt %; boron (B) from 0 to 0.10 wt %; zirconium
(Zr) from 0 to 0.10 wt %; lithium (Li) from 0 to 0.10 wt %; cadmium
(Cd) from 0 to 0.10 wt %; lead (Pb) from 0 to 0.10 wt %; nickel
(Ni) from 0 to 0.10 wt %; phosphorous (P) from 0 to 0.10 wt %; and
combinations thereof.
3. The aluminum alloy of claim 1, wherein b* ranges from -1.5 to
1.5.
4. The aluminum alloy of claim 1, wherein b* ranges from -1.0 to
1.0.
5. The aluminum alloy of claim 1, wherein b* ranges from 0 to
1.0.
6. The aluminum alloy of claim 1, wherein b* ranges from -1.0 to
0.
7. The aluminum alloy of claim 1, wherein b* ranges from -0.7 to
0.7.
8. The aluminum alloy of claim 1, wherein b* ranges from 0 to
0.7.
9. The aluminum alloy of claim 1, wherein b* ranges from -0.7 to
0.
10. The aluminum alloy of claim 1, wherein b* ranges from -0.5 to
0.5.
11. The aluminum alloy of claim 1, wherein b* ranges from 0 to
0.5.
12. The aluminum alloy of claim 1, wherein b* ranges from -0.5 to
0.
13. The aluminum alloy of claim 1, wherein b* ranges from -1.5 to
0.
14. The aluminum alloy of claim 1, wherein b* ranges from 0 to
1.5.
15. The aluminum alloy of claim 1, wherein the aluminum alloy has
an average grain ratio from 0.7 to 1.45.
16. The aluminum alloy of claim 1, wherein the aluminum alloy has
average grain ratio from 1.0 to 1.2.
17. The aluminum alloy of claim 1, wherein the aluminum alloy is in
the form of an extruded part and has a yield strength of at least
200 MPa and a tensile strength of at least 235 MPa.
18. The aluminum alloy of claim 1, wherein the aluminum alloy is in
the form of an extruded part and has a hardness of at least 75
Vickers.
19. A process of making an aluminum alloy from an aluminum scrap,
the process comprising: (a) obtaining an aluminum scrap from one or
more sources; (b) melting the aluminum scrap to form a melted
aluminum alloy comprising: copper (Cu) from 0.051 to 0.10 wt %;
chromium (Cr) from 0.01 to 0.10 wt %; zinc (Zn) from 0.02 to 0.20
wt %; manganese (Mn) from 0.03 to 0.10 wt %; iron (Fe) in an amount
of at least 0.10 wt %; silicon (Si) in an amount of at least 0.35
wt %; magnesium (Mg) in an amount of at least 0.45 wt %; and
remaining wt % being Al and incidental impurities; (c) casting the
melted aluminum alloy to form a casted alloy; (d) rolling the
casted alloy to form a sheet, or extruding the casted alloy to form
an extrusion; and (e) fabricating the sheet or extrusion to produce
an aluminum part.
20. The process of claim 19, wherein the step of melting comprises
removing oxides from the aluminum scrap.
Description
CROSS-REFERENCES TO RELATED PATENT APPLICATIONS
[0001] This patent application claims the benefit under 35 U.S.C.
.sctn. 119(e) of U.S. Patent Application Ser. No. 62/905,896,
entitled "COSMETIC ALUMINUM ALLOYS MADE FROM RECYCLED ALUMINUM
SCRAP," filed on Sep. 25, 2019, and U.S. Patent Application Ser.
No. 62/984,054, entitled "COSMETIC ALUMINUM ALLOYS MADE FROM
RECYCLED ALUMINUM SCRAP," filed on Mar. 2, 2020, each of which is
incorporated herein by reference in its entirety.
FIELD
[0002] The disclosure is directed to recycled aluminum alloys and
processes for recycling aluminum alloy scrap with cosmetic appeal
and corrosion resistance.
BACKGROUND
[0003] Commercial aluminum alloys, such as the 6063 aluminum (Al)
alloys, have been used for fabricating enclosures for electronic
devices. Cosmetic appeal is very important for enclosures of
electronic devices.
[0004] Conventional recycling of manufacturing scrap (e.g. 6063 Al)
is generally associated with downgraded quality. Sometimes, in
order to maintain the quality of the recycled product, conventional
recycling of manufacturing scrap may be limited to a particular
source and a limited amount of scrap in the recycled material. U.S.
patent application Ser. No. 16/530,830, entitled "RECYCLED ALUMINUM
ALLOYS FROM MANUFACTURING SCRAP WITH COSMETIC APPEAL," filed on
Aug. 2, 2019, discloses recycled aluminum alloys made from
manufacturing chip scrap. However, the manufacturing chip scrap are
from a known alloy and source and are also limited in supply.
[0005] It is desirable to recycle market scrap of various alloys
and from various sources, because this enables a higher volume of
market scrap for recycling than just relying on the manufacturing
chip scrap. There remains a need for developing alloys and
processes for recycling the market scrap from various sources to
improve the cosmetic appeal of recycled aluminum alloys.
BRIEF SUMMARY
[0006] In one aspect, the disclosure is directed to an aluminum
alloy having copper (Cu) from 0.051 to 0.10 wt %, chromium (Cr)
from 0.01 to 0.10 wt %, zinc (Zn) from 0.02 to 0.20 wt %, manganese
(Mn) from 0.03 to 0.10 wt %, iron (Fe) in an amount of at least
0.10 wt %, silicon (Si) in an amount of at least 0.35 wt %,
magnesium (Mg) in amount of at least 0.45 wt %, and the remaining
wt % being Al and incidental impurities. The b* color ranges from
-2 to 2, and the L* color ranges from 70 to 100. In some
variations, the L*, a*, and b* values may be based on non-dyed
anodized aluminum or textured aluminum.
[0007] In another aspect, the disclosure is directed to an aluminum
alloy having copper (Cu) from 0.010 to 0.050 wt %, chromium (Cr)
from 0.01 to 0.10 wt %, zinc (Zn) from 0.01 to 0.20 wt %, manganese
(Mn) from 0.03 to 0.10 wt %, iron (Fe) in an amount of at least
0.10 wt %, silicon (Si) in an amount of at least 0.35 wt %,
magnesium (Mg) in amount of at least 0.45 wt %, and the remaining
wt % being Al and incidental impurities. The b* color ranges from
-2 to 2, and the L* color ranges from 70 to 100.
[0008] In various aspects, the disclosed alloys can include
titanium (Ti) from 0 to 0.10 wt %, gallium (Ga) from 0 to 0.20 wt
%, tin (Sn) from 0 to 0.20 wt %, vanadium (V) from 0 to 0.20 wt %,
calcium (Ca) from 0 to 0.01 wt %, sodium (Na) from 0 to 0.008 wt %,
boron (B) from 0 to 0.10 wt %, zirconium (Zr) from 0 to 0.10 wt %,
lithium (Li) from 0 to 0.10 wt %, cadmium (Cd) from 0 to 0.10 wt %,
lead (Pb) from 0 to 0.10 wt %, nickel (Ni) from 0 to 0.10 wt %,
phosphorous (P) from 0 to 0.10 wt %, and combinations thereof.
[0009] Additional embodiments and features are set forth in part in
the description that follows, and will become apparent to those
skilled in the art upon examination of the specification or may be
learned by the practice of the disclosed subject matter. A further
understanding of the nature and advantages of the disclosure may be
realized by reference to the remaining portions of the
specification and the drawings, which forms a part of this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The description will be more fully understood with reference
to the following figures and data graphs, which are presented as
various embodiments of the disclosure and should not be construed
as a complete recitation of the scope of the disclosure,
wherein:
[0011] FIG. 1A illustrates the yield strength for extrusion samples
formed of various 6000 series aluminum alloys in accordance with
embodiments of the disclosure;
[0012] FIG. 1B illustrates the tensile strength for extrusion
samples formed of various 6000 series aluminum alloys in accordance
with embodiments of the disclosure;
[0013] FIG. 10 illustrates the elongation for extrusion samples
formed of various 6000 series aluminum alloys in accordance with
embodiments of the disclosure;
[0014] FIG. 1D illustrates the hardness for extrusion samples
formed of various 6000 series aluminum alloys in accordance with
embodiments of the disclosure;
[0015] FIG. 2A illustrates the average grain size for extrusion
samples formed of various 6000 series aluminum alloys in accordance
with embodiments of the disclosure;
[0016] FIG. 2B illustrates the largest grain size for extrusion
samples formed of various 6000 series aluminum alloys in accordance
with embodiments of the disclosure;
[0017] FIG. 2C illustrates the grain aspect ratio for extrusion
samples formed of various 6000 series aluminum alloys in accordance
with embodiments of the disclosure;
[0018] FIG. 3 illustrates extrusion speed for various market scrap
alloys in accordance with embodiments of the disclosure;
[0019] FIG. 4A illustrates comparison of electrochemical impedance
of the aluminum samples having different total impurities and
different elemental compositions for a neutral color aluminum or
non-dyed anodized aluminum (NDA);
[0020] FIG. 4B illustrates comparison of electrochemical impedance
of the aluminum samples having different total impurities and
different elemental compositions for a grey color aluminum;
[0021] FIG. 5A illustrates comparison of corrosion rate of the
aluminum samples having different total impurities and different
elemental compositions for a non-anodized alloy;
[0022] FIG. 5B illustrates comparison of pitting potential of the
aluminum samples having different total impurities and different
elemental compositions for a non-anodized alloy;
[0023] FIG. 6A illustrates comparison of number of pits of the
aluminum samples having different total impurities and different
elemental compositions for a non-anodized alloy;
[0024] FIG. 6B illustrates comparison of pit radius of the aluminum
samples having different total impurities and different elemental
compositions for a non-anodized alloy;
[0025] FIG. 7 illustrates comparison of salt fog test pass rate of
the aluminum samples having different total impurities and
different elemental compositions for a neutral color aluminum and a
grey color aluminum; and
[0026] FIG. 8 illustrates a recycling process from materials
including manufacturing scrap in accordance with embodiments of the
disclosure.
DETAILED DESCRIPTION
[0027] The disclosure may be understood by reference to the
following detailed description, taken in conjunction with the
drawings as described below. It is noted that, for purposes of
illustrative clarity, certain elements in various drawings may not
be drawn to scale.
[0028] The disclosure provides recycled 6000 series aluminum alloys
made from scrap. The scrap can be collected from manufacturing
processes of conventional aluminum alloys (e.g. 6000 series
aluminum alloys or 6063 aluminum). The recycled 6000 series
aluminum alloys can surprisingly provide the same or similar
cosmetic appeal, mechanical properties, and/or microstructure as
aluminum alloys with lower iron, silicon, and magnesium. The
recycled 6000 series aluminum alloys can include higher Cu content,
higher Mn content, higher Zn content, and/or higher Cr content than
would be expected for alloys having cosmetic appeal.
Alloys Made from Market Scrap
[0029] In some variations, the disclosed 6000 series aluminum
alloys are designed to be tolerant to include up to 100% recycled
6000 series aluminum, such as market scraps including casting
scrap, extrusion scrap, chip scrap from various manufacturing
sources, among others. The disclosed 6000 series aluminum alloys
may also be tolerant to other series scraps, such as 1000 series
scrap. The disclosed 6000 series aluminum alloys, also referred to
as recycled 6000 series aluminum alloys, allow the use of market
scraps from various sources that can reduce use of virgin aluminum,
and result in significant reduction of emissions and related carbon
footprint. Conventional 6000 series Al alloys include small amounts
of Si and Mg, and may include small amounts of Fe, Mn, Cu, Zr, Pb,
Cr, Zn, among others.
[0030] Recycled aluminum alloys from market scrap can contain more
copper than is typically present in virgin aluminum alloys or
recycled aluminum alloys from a closed loop of manufacturing, such
as the recycled aluminum alloys disclosed in U.S. patent
application Ser. No. 16/530,830, entitled "RECYCLED ALUMINUM ALLOYS
FROM MANUFACTURING SCRAP WITH COSMETIC APPEAL," filed on Aug. 2,
2019, which is incorporated herein by reference in its entirety.
The increase in copper would be expected to have a negative effect
on the cosmetic appeal of aluminum alloys, particularly by
resulting in a more yellowish color of the anodized layer. Copper
generally cannot be removed from aluminum alloys by conventional
industrial methods, and once copper is included in the aluminum
alloy, the amount of copper in the alloy cannot be reduced. Because
of the number of copper-containing alloys in market scrap, the
amount of copper is higher in the disclosed recycled aluminum than
in other aluminum alloys, while retaining anodized layer color and
other cosmetic properties similar to alloys with lower Cu, Cr, Mn,
and/or Zn.
[0031] In some variations, the disclosed aluminum alloys include
higher amounts of Cu, Mn, Zn, Fe, and Cr than other aluminum
alloys. Various properties of the disclosed recycled aluminum
alloys from market scrap have cosmetic properties with high amounts
of copper of up to 0.10 wt %, which is significantly higher than
other aluminum alloys with cosmetic properties disclosed herein.
For example, the disclosed recycled aluminum alloys surprisingly
have a less yellow anodized layer color than would be expected for
alloys with higher quantities of copper.
[0032] The disclosed recycled 6000 series aluminum alloys allow use
of recycled materials, such as market scrap from various sources.
The disclosed recycled 6000 series aluminum alloys result in
significant reduction of the carbon footprint associated with
manufacturing.
[0033] The disclosed alloys can be described by various wt % of
elements, as well as specific properties. In all descriptions of
the alloys described herein, it will be understood that the wt %
balance of alloys is Al and incidental impurities. Impurities can
be present, for example, as a byproduct of processing and
manufacturing. In various embodiments, an incidental impurity can
be no greater than 0.05 wt % of any one additional element (i.e., a
single impurity), and no greater than 0.10 wt % total of all
additional elements (i.e., total impurities). The impurities can be
less than or equal to about 0.1 wt %, alternatively less than or
equal about 0.05 wt %, alternatively less than or equal about 0.01
wt %, alternatively less than or equal about 0.001 wt %.
[0034] In some variations, the disclosed alloys have copper (Cu)
from 0.051 to 0.10 wt %. In some variations, the disclosed alloys
have chromium (Cr) from 0.01 to 0.10 wt %. In some variations, the
disclosed alloys have zinc (Zn) from 0.02 to 0.20 wt %. In some
variations, the disclosed alloys have manganese (Mn) from 0.03 to
0.10 wt %. In some variations, the disclosed alloys have at least
0.14 wt % Fe. Further, in some variations, the disclosed alloys
have at least 0.43 wt % Si and at least 0.56 wt % Mg. In still
further variations, the disclosed alloys can have equal to or
greater than 0.20 wt % Fe. The disclosed alloys can have equal to
or less than 0.62 wt % Mg and equal to or less than 0.49 wt %
Si.
Cu Content
[0035] In some variations, the alloys can include Cu. Without
wishing to be limited to any particular mechanism, effect, or mode
of action, Cu can influence color of the anodized alloy. For
example, additional Cu may cause yellowish color to the anodized
aluminum alloy. Cu may also affect corrosion resistance.
[0036] In some variations, copper may vary from 0.051 wt % to 0.10
wt %.
[0037] In some variations, copper may be equal to or less than
0.100 wt %. In some variations, copper may be equal to or less than
0.095 wt %. In some variations, copper may be equal to or less than
0.090 wt %. In some variations, copper may be equal to or less than
0.085 wt %. In some variations, copper may be equal to or less than
0.080 wt %. In some variations, copper may be equal to or less than
0.075 wt %. In some variations, copper may be equal to or less than
0.060 wt %. In some variations, copper may be equal to or less than
0.055 wt %.
[0038] In some variations, copper may be equal to or greater than
0.051 wt %. In some variations, copper may be equal to or greater
than 0.055 wt %. In some variations, copper may be equal to or
greater than 0.060 wt %. In some variations, copper may be equal to
or greater than 0.065 wt %. In some variations, copper may be equal
to or greater than 0.070 wt %. In some variations, copper may be
equal to or greater than 0.075 wt %. In some variations, copper may
be equal to or greater than 0.080 wt %. In some variations, copper
may be equal to or greater than 0.085 wt %. In some variations,
copper may be equal to or greater than 0.090 wt %. In some
variations, copper may be equal to or greater than 0.095 wt %.
Mn Content
[0039] In some variations, the alloys can include Mn. Without
wishing to be held to a particular mechanism, effect, or mode of
action, Mn can result in breaking up coarse Al--Fe--Si particles or
AlFeSi particles. When the amount of Mn increases above a higher
value, the aspect ratio of the grains may increase such that the
grains may be elongated. The control of upper range amount of Mn
results in a surprising grain structure control at a low average
grain aspect ratio from sample-to-sample, and can have reduced
streaky lines in finished and anodized alloys. The elongated grain
structure can cause streaky lines.
[0040] In some variations, manganese may be equal to or less than
0.090 wt %. In some variations, manganese may be equal to or less
than 0.085 wt %. In some variations, manganese may be equal to or
less than 0.080 wt %. In some variations, manganese may be equal to
or less than 0.075 wt %. In some variations, manganese may be equal
to or less than 0.070 wt %. In some variations, manganese may be
equal to or less than 0.065 wt %. In some variations, manganese may
be equal to or less than 0.060 wt %. In some variations, manganese
may be equal to or less than 0.055 wt %. In some variations,
manganese may be equal to or less than 0.050 wt %. In some
variations, manganese may be equal to or less than 0.045 wt %. In
some variations, manganese may be equal to or less than 0.040 wt %.
In some variations, manganese may be equal to or less than 0.035 wt
%. In some variations, manganese may be equal to or less than 0.030
wt %. In some variations, manganese may be equal to or less than
0.025 wt %. In some variations, manganese may be equal to or less
than 0.020 wt %. In some variations, manganese may be equal to or
less than 0.015 wt %. In some variations, manganese may be equal to
or less than 0.010 wt %. In some variations, manganese may be equal
to or less than 0.005 wt %.
[0041] In some variations, manganese may be equal to or greater
than 0.005 wt %. In some variations, manganese may be equal to or
greater than 0.010 wt %. In some variations, manganese may be equal
to or greater than 0.015 wt %. In some variations, manganese may be
equal to or greater than 0.020 wt %. In some variations, manganese
may be equal to or greater than 0.025 wt %. In some variations,
manganese may be equal to or greater than 0.030 wt %. In some
variations, manganese may be equal to or greater than 0.035 wt %.
In some variations, manganese may be equal to or greater than 0.040
wt %. In some variations, manganese may be equal to or greater than
0.045 wt %. In some variations, manganese may be equal to or
greater than 0.050 wt %. In some variations, manganese may be equal
to or greater than 0.055 wt %. In some variations, manganese may be
equal to or greater than 0.060 wt %. In some variations, manganese
may be equal to or greater than 0.065 wt %.
[0042] In some variations, manganese may be equal to or greater
than 0.070 wt %. In some variations, manganese may be equal to or
greater than 0.075 wt %. In some variations, manganese may be equal
to or greater than 0.080 wt %. In some variations, manganese may be
equal to or greater than 0.085 wt %.
Cr Content
[0043] In some variations, the alloys can include Cr. Without
wishing to be held to a particular mechanism, effect, or mode of
action, Cr may affect color and corrosion resistance. When the
amount of Cr increases to a higher value, the aspect ratios of the
grains may increase such that the grains may be elongated. The
control of the upper range amount of Cr may allow surprising grain
structure control at a low average grain aspect ratio from
sample-to-sample, and can have reduced streaky lines in finished
and anodized alloys. The elongated grain structure can cause
streaky lines.
[0044] In some variations, chromium may be equal to or less than
0.10 wt %. In some variations, chromium may be equal to or less
than 0.08 wt %. In some variations, chromium may be equal to or
less than 0.06 wt %. In some variations, chromium may be equal to
or less than 0.04 wt %. In some variations, chromium may be equal
to or less than 0.03 wt %. In some variations, chromium may be
equal to or less than 0.02 wt %. In some variations, chromium may
be equal to or less than 0.01 wt %. In some variations, chromium
may be equal to or less than 0.008 wt %. In some variations,
chromium may be equal to or less than 0.006 wt %. In some
variations, chromium may be equal to or less than 0.004 wt %. In
some variations, chromium may be equal to or less than 0.002 wt
%.
Zn Content
[0045] In some variations, the alloys can include Zn. Without
wishing to be held to a particular mechanism, effect, or mode of
action, Zn may affect color and corrosion resistance. For example,
the anodized alloy may become more bluish. In some variations, zinc
may be equal to or less than 0.20 wt %. In some variations, zinc
may be equal to or less than 0.15 wt %. In some variations, zinc
may be equal to or less than 0.10 wt %. In some variations, zinc
may be equal to or less than 0.08 wt %. In some variations, zinc
may be equal to or less than 0.06 wt %. In some variations, zinc
may be equal to or less than 0.04 wt %. In some variations, zinc
may be equal to or less than 0.03 wt %. In some variations, zinc
may be equal to or greater than 0.01 wt %. In some variations, zinc
may be equal to or greater than 0.02 wt %. In some variations, zinc
may be equal to or greater than 0.03 wt %. In some variations, zinc
may be equal to or greater than 0.04 wt %. In some variations, zinc
may be equal to or greater than 0.05 wt %. In some variations, zinc
may be equal to or greater than 0.06 wt %. In some variations, zinc
may be equal to or greater than 0.07 wt %. In some variations, zinc
may be equal to or greater than 0.08 wt %. In some variations, zinc
may be equal to or greater than 0.09 wt %. In some variations, zinc
may be equal to or greater than 0.10 wt %. In some variations, zinc
may be equal to or greater than 0.15 wt %.
Fe Content
[0046] As described above, the scrap (e.g., market scrap) includes
more Fe than the conventional 6000 series aluminum alloys for
cosmetic applications. The Fe may be from sources including tooling
and fasteners, among others. The disclosed 6000 series aluminum
alloy is designed to have more Fe than conventional 6000 series
aluminum alloys or virgin aluminum alloys currently used for
cosmetic consumer electronic products.
[0047] In some variations, iron may range from 0.10 wt % to 0.50 wt
%.
[0048] In some variations, iron may be equal to or greater than
0.10 wt %. In some variations, iron may be equal to or greater than
0.14 wt %. In some variations, iron may be equal to or greater than
0.15 wt %. In some variations, iron may be equal to or greater than
0.16 wt %. In some variations, iron may be equal to or greater than
0.17 wt %. In some variations, iron may be equal to or greater than
0.18 wt %. In some variations, iron may be equal to or greater than
0.19 wt %. In some variations, iron may be equal to or greater than
0.20 wt %. In some variations, iron may be equal to or greater than
0.25 wt %. In some variations, iron may be equal to or greater than
0.30 wt %. In some variations, iron may be equal to or greater than
0.35 wt %. In some variations, iron may be equal to or greater than
0.40 wt %. In some variations, iron may be equal to or greater than
0.45 wt %.
[0049] In some variations, iron may be equal to or less than 0.50
wt %. In some variations, iron may be equal to or less than 0.45 wt
%. In some variations, iron may be equal to or less than 0.35 wt %.
In some variations, iron may be equal to or less than 0.40 wt %. In
some variations, iron may be equal to or less than 0.35 wt %. In
some variations, iron may be equal to or less than 0.30 wt %. In
some variations, iron may be equal to or less than 0.25 wt %. In
some variations, iron may be equal to or less than 0.20 wt %. In
some variations, iron may be equal to or less than 0.19 wt %. In
some variations, iron may be equal to or less than 0.18 wt %. In
some variations, iron may be equal to or less than 0.17 wt %. In
some variations, iron may be equal to or less than 0.16 wt %. In
some variations, iron may be equal to or less than 0.15 wt %.
Ti Content
[0050] Scrap can include more Ti than the conventional 6000 series
aluminum alloys. The Ti can be added as a grain refiner during the
casting process. In many instances, the 6000 series aluminum alloy
is designed to tolerate more Ti versus conventional aluminum alloys
used for cosmetic consumer electronic products.
[0051] In some variations, titanium may equal to or less than 0.10
wt %. In some variations, titanium may equal to or less than 0.09
wt %. In some variations, titanium may equal to or less than 0.08
wt %. In some variations, titanium may equal to or less than 0.07
wt %. In some variations, titanium may equal to or less than 0.06
wt %. In some variations, titanium may equal to or less than 0.05
wt %. In some variations, titanium may equal to or less than 0.04
wt %. In some variations, titanium may equal to or less than 0.03
wt %. In some variations, titanium may equal to or less than 0.025
wt %. In some variations, titanium may be equal to or less than
0.020 wt %. In some variations, titanium may be equal to or less
than 0.015 wt %. In some variations, titanium may be equal to or
less than 0.010 wt %. In some variations, titanium may be equal to
or less than 0.005 wt %.
Si Content and Mg Content
[0052] Additional Si may be added to the disclosed alloys than in
some 6000 series alloys, without a resulting loss of mechanical
strength by forming Mg--Si particles.
[0053] In some variations, silicon may vary from 0.35 wt % to 0.80
wt %.
[0054] In some variations, silicon may be equal to or less than
0.80 wt %. In some variations, silicon may be equal to or less than
0.75 wt %. In some variations, silicon may be equal to or less than
0.70 wt %. In some variations, silicon may be equal to or less than
0.65 wt %. In some variations, silicon may be equal to or less than
0.60 wt %. In some variations, silicon may be equal to or less than
0.55 wt %. In some variations, silicon may be equal to or less than
0.50 wt %. In some variations, silicon may be equal to or less than
0.49 wt %. In some variations, silicon may be equal to or less than
0.48 wt %. In some variations, silicon may be equal to or less than
0.47 wt %. In some variations, silicon may be equal to or less than
0.46 wt %. In some variations, silicon may be equal to or less than
0.45 wt %. In some variations, silicon may be equal to or less than
0.40 wt %. In some variations, silicon may be equal to or less than
0.39 wt %. In some variations, silicon may be equal to or less than
0.38 wt %. In some variations, silicon may be equal to or less than
0.37 wt %. In some variations, silicon may be equal to or less than
0.36 wt %.
[0055] In some variations, silicon may be equal to or greater than
0.35 wt %. In some variations, silicon may be equal to or greater
than 0.36 wt %. In some variations, silicon may be equal to or
greater than 0.37 wt %. In some variations, silicon may be equal to
or greater than 0.38 wt %. In some variations, silicon may be equal
to or greater than 0.39 wt %. In some variations, silicon may be
equal to or greater than 0.40 wt %. In some variations, silicon may
be equal to or greater than 0.41 wt %. In some variations, silicon
may be equal to or greater than 0.42 wt %. In some variations,
silicon may be equal to or greater than 0.43 wt %. In some
variations, silicon may be equal to or greater than 0.44 wt %. In
some variations, silicon may be equal to or greater than 0.45 wt %.
In some variations, silicon may be equal to or greater than 0.46 wt
%. In some variations, silicon may be equal to or greater than 0.47
wt %. In some variations, silicon may be equal to or greater than
0.48 wt %. In some variations, silicon may be equal to or greater
than 0.49 wt %. In some variations, silicon may be equal to or
greater than 0.50 wt %. In some variations, silicon may be equal to
or greater than 0.55 wt %. In some variations, silicon may be equal
to or greater than 0.60 wt %. In some variations, silicon may be
equal to or greater than 0.65 wt %. In some variations, silicon may
be equal to or greater than 0.70 wt %. In some variations, silicon
may be equal to or greater than 0.75 wt %.
[0056] Mg can be designed to have the proper Mg/Si ratio to form
Mg--Si precipitates for strengthening purpose. In some variations,
the ratio of Mg to Si is typically 2:1, but other variations can be
possible.
[0057] In some variations, magnesium may vary from 0.45 wt % to
0.95 wt %.
[0058] In some variations, magnesium may be equal to or less than
0.95 wt %. In some variations, magnesium may be equal to or less
than 0.90 wt %. In some variations, magnesium may be equal to or
less than 0.85 wt %. In some variations, magnesium may be equal to
or less than 0.80 wt %. In some variations, magnesium may be equal
to or less than 0.75 wt %. In some variations, magnesium may be
equal to or less than 0.70 wt %. In some variations, magnesium may
be equal to or less than 0.65 wt %. In some variations, magnesium
may be equal to or less than 0.60 wt %. In some variations,
magnesium may be equal to or less than 0.55 wt %. In some
variations, magnesium may be equal to or less than 0.50 wt
[0059] In some variations, magnesium may be equal to or greater
than 0.50 wt %. In some variations, magnesium may be equal to or
greater than 0.55 wt %. In some variations, magnesium may be equal
to or greater than 0.60 wt %. In some variations, magnesium may be
equal to or greater than 0.65 wt %. In some variations, magnesium
may be equal to or greater than 0.70 wt %. In some variations,
magnesium may be equal to or greater than 0.75 wt %. In some
variations, magnesium may be equal to or greater than 0.80 wt %. In
some variations, magnesium may be equal to or greater than 0.85 wt
%. In some variations, magnesium may be equal to or greater than
0.90 wt %.
Additional Non-Aluminum Elements
[0060] The disclosed 6000 series aluminum alloys may include other
elements as disclosed below.
[0061] In some variations, gallium may be equal to or less than
0.20 wt %. In some variations, gallium may be equal to or less than
0.15 wt %. In some variations, gallium may be equal to or less than
0.10 wt %. In some variations, gallium may be equal to or less than
0.08 wt %. In some variations, gallium may be equal to or less than
0.06 wt %. In some variations, gallium may be equal to or less than
0.04 wt %. In some variations, gallium may be equal to or less than
0.03 wt %. In some variations, gallium may be equal to or less than
0.02 wt %. In some variations, gallium may be equal to or less than
0.015 wt %. In some variations, gallium may be equal to or less
than 0.01 wt %. In some variations, gallium may be equal to or less
than 0.005 wt %. In some variations, gallium may be equal to or
less than 0.001 wt %.
[0062] In some variations, tin may be equal to or less than 0.20 wt
%. In some variations, tin may be equal to or less than 0.15 wt %.
In some variations, tin may be equal to or less than 0.10 wt %. In
some variations, tin may be equal to or less than 0.08 wt %. In
some variations, tin may be equal to or less than 0.06 wt %. In
some variations, tin may be equal to or less than 0.04 wt %. In
some variations, tin may be equal to or less than 0.01 wt %. In
some variations, tin may be equal to or less than 0.008 wt %. In
some variations, tin may be equal to or less than 0.006 wt %. In
some variations, tin may be equal to or less than 0.004 wt %. In
some variations, tin may be equal to or less than 0.002 wt %.
[0063] In some variations, vanadium may be equal to or less than
0.20 wt %. In some variations, vanadium may be equal to or less
than 0.15 wt %. In some variations, vanadium may be equal to or
less than 0.10 wt %. In some variations, vanadium may be equal to
or less than 0.08 wt %. In some variations, vanadium may be equal
to or less than 0.06 wt %. In some variations, vanadium may be
equal to or less than 0.04 wt %. In some variations, vanadium may
be equal to or less than 0.02 wt %. In some variations, vanadium
may be equal to or less than 0.01 wt %. In some variations,
vanadium may be equal to or less than 0.005 wt %. In some
variations, vanadium may be equal to or less than 0.001 wt %.
[0064] In some variations, calcium may be equal to or less than
0.01 wt %. In some variations, calcium may be equal to or less than
0.008 wt %. In some variations, calcium may be equal to or less
than 0.006 wt %. In some variations, calcium may be equal to or
less than 0.005 wt %. In some variations, calcium may be equal to
or less than 0.003 wt %. In some variations, calcium may be equal
to or less than 0.002 wt %. In some variations, calcium may be
equal to or less than 0.001 wt %.
[0065] In some variations, sodium may be equal to or less than
0.008 wt %. In some variations, sodium may be equal to or less than
0.006 wt %. In some variations, sodium may be equal to or less than
0.004 wt %. In some variations, sodium may be equal to or less than
0.002 wt %. In some variations, sodium may be equal to or less than
0.001 wt %.
[0066] One or more of other elements, including boron, zirconium,
lithium, cadmium, lead, nickel, phosphorous, among others, may be
equal to or less than 0.1 wt %. One or more of other elements,
including boron, zirconium, lithium, cadmium, lead, nickel,
phosphorous, among others, may be equal to or less than 0.08 wt %.
One or more of these other elements may be equal to or less than
0.06 wt %. One or more of these other elements may be equal to or
less than 0.04 wt %. One or more of other elements may be equal to
or less than 0.02 wt %.
[0067] In some variations, a total of other elements may not exceed
0.20 wt %. In some variations, a total of other elements may not
exceed 0.10 wt %. In some variations, a total of other elements may
not exceed 0.08 wt %. In some variations, a total of other elements
may not exceed 0.06 wt %. In some variations, a total of other
elements may not exceed 0.04 wt %.
Cosmetic Appeal
[0068] The aluminum alloys disclosed herein typically have more Fe
than in conventional aluminum alloys. Anodized aluminum alloys
having higher amounts of Fe typically have a more gray color.
Market scrap can include more Fe than the conventional 6000 series
aluminum alloys. As described above, the recycled aluminum alloys
described herein can have more Fe than that is typically present in
aluminum alloys with cosmetic appeal.
[0069] Fe has negative effects on the cosmetic appeal by creating
an unattractive gray color. In addition to having a negative effect
on cosmetics, Fe contributes to the formation of
iron-aluminum-silicon particles during processing. The acquisition
of Si by the Fe particles can reduce the amount of Si available for
strengthening. As such, more Si may be added to the alloys
disclosed herein. The presently disclosed alloys have increased Si
and increased Fe. Contrary to expectations, the properties of the
alloy are consistent or better than alloys with such undesirable
amounts of Fe.
[0070] In some embodiments, the disclosed 6000 series aluminum
alloys can be anodized. Anodizing is a surface treatment process
for metal, most commonly used to protect aluminum alloys. Anodizing
uses electrolytic passivation to increase the thickness of the
natural oxide layer on the surface of metal parts. Anodizing may
increase corrosion resistance and wear resistance, and may also
provide better adhesion for paint primers and glues than bare
metal. Anodized films may also be used for cosmetic effects, for
example, it may add interference effects to reflected light.
[0071] Surprisingly, the disclosed recycled 6000 series aluminum
alloys have the same or improved cosmetic appeal as those with
lower Fe, Si, and Mg. In particular, after anodizing they do not
have a yellowish or gray color, and do not have increased cosmetic
defects such as mottling, grain lines, black lines, discoloration,
white dots, oxidation, and line mark, among others.
[0072] In some embodiments, the disclosed 6000 series aluminum
alloys can form enclosures for electronic devices. The enclosures
may be designed to have a blasted surface finish absent of streaky
lines. Blasting is a surface finishing process, for example,
smoothing a rough surface or roughening a smooth surface. Blasting
may texture surface material by forcibly propelling a stream of
abrasive media against a surface under high pressure.
[0073] Standard methods may be used for evaluation of cosmetics
including color, gloss and haze. The color of objects may be
determined by the wavelength of light that is reflected or
transmitted without being absorbed, assuming incident light is
white light. The visual appearance of objects may vary with light
reflection or transmission. Additional appearance attributes may be
based on the directional brightness distribution of reflected light
or transmitted light, commonly referred to as glossy, shiny, dull,
clear, hazy, among others. The quantitative evaluation may be
performed based on ASTM Standards on Color & Appearance
Measurement or ASTM E-430 Standard Test Methods for Measurement of
Gloss of High-Gloss Surfaces, including ASTM D523 (Gloss), ASTM
D2457 (Gloss on plastics), ASTM E430 (Gloss on high-gloss surfaces,
haze), and ASTM D5767 (DOI), among others. The measurements of
gloss, haze, and DOI (distinctness of image) may be performed by
testing equipment, such as Rhopoint IQ.
[0074] In some embodiments, color may be quantified by parameters
L*, a*, and b*, where L* stands for light brightness, a* stands for
color between red and green, and b* stands for color between blue
and yellow. For example, high b* values suggest an unappealing
yellowish color, not a gold yellow color. Nearly zero parameters a*
and b* suggest a neutral color. Low L* values suggest dark
brightness, while high L* value suggests great brightness. For
color measurement, testing equipment, such as X-Rite ColorEye XTH,
X-Rite Coloreye 7000 may be used. These measurements are according
to CIE/ISO standards for illuminants, observers, and the L*, a*,
and b* color scale. For example, the standards include: (a) ISO
11664-1:2007(E)/CIE S 014-1/E:2006: Joint ISO/CIE Standard:
Colorimetry--Part 1: CIE Standard Colorimetric Observers; (b) ISO
11664-2:2007(E)/CIE S 014-2/E:2006: Joint ISO/CIE Standard:
Colorimetry--Part 2: CIE Standard Illuminants for Colorimetry, (c)
ISO 11664-3:2012(E)/CIE S 014-3/E:2011: Joint ISO/CIE Standard:
Colorimetry--Part 3: CIE Tristimulus Values; and (d) ISO
11664-4:2008(E)/CIE S 014-4/E:2007: Joint ISO/CIE Standard:
Colorimetry--Part 4: CIE 1976 L*, a*, and b* Color Space.
[0075] In some variations, b* is from -2 to 2. In some variations,
b* is equal to or greater than -1.9. In some variations, b* is
equal to or greater than -1.8. In some variations, b* is equal to
or greater than -1.7. In some variations, b* is equal to or greater
than -1.6. In some variations, b* is equal to or greater than -1.5.
In some variations, b* is equal to or greater than -1.4. In some
variations, b* is equal to or greater than -1.3. In some
variations, b* is equal to or greater than -1.2. In some
variations, b* is equal to or greater than -1.1. In some
variations, b* is equal to or greater than -1.0. In some
variations, b* is equal to or greater than -0.9. In some
variations, b* is equal to or greater than -0.8. In some
variations, b* is equal to or greater than -0.7. In some
variations, b* is equal to or greater than -0.6. In some
variations, b* is equal to or greater than -0.5. In some
variations, b* is equal to or greater than -0.4. In some
variations, b* is equal to or greater than -0.3. In some
variations, b* is equal to or greater than -0.2. In some
variations, b* is equal to or greater than -0.1. In some
variations, b* is equal to or greater than 0. In some variations,
b* is equal to or greater than 0.1. In some variations, b* is
greater than or equal to 0.2. In some variations, b* is greater
than or equal to 0.3. In some variations, b* is greater than or
equal to 0.4. In some variations, b* is greater than or equal to
0.5. In some variations, b* is greater than or equal to 0.6. In
some variations, b* is greater than or equal to 0.7. In some
variations, b* is greater than or equal to 0.8. In some variations,
b* is greater than or equal to 0.9. In some variations, b* is equal
to or greater than 1.0. In some variations, b* is equal to or
greater than 1.1. In some variations, b* is greater than or equal
to 1.2. In some variations, b* is greater than or equal to 1.3. In
some variations, b* is greater than or equal to 1.4. In some
variations, b* is greater than or equal to 1.5. In some variations,
b* is greater than or equal to 1.6. In some variations, b* is
greater than or equal to 1.7. In some variations, b* is greater
than or equal to 1.8. In some variations, b* is greater than or
equal to 1.9.
[0076] In some variations, b* is equal to or less than -1.9. In
some variations, b* is equal to or less than -1.8. In some
variations, b* is equal to or less than -1.7. In some variations,
b* is equal to or less than -1.6. In some variations, b* is equal
to or less than -1.5. In some variations, b* is equal to or less
than -1.4. In some variations, b* is equal to or less than -1.3. In
some variations, b* is equal to or less than -1.2. In some
variations, b* is equal to or less than -1.1. In some variations,
b* is equal to or less than -1.0. In some variations, b* is equal
to or less than -0.9. In some variations, b* is equal to or less
than -0.8. In some variations, b* is equal to or less than -0.7. In
some variations, b* is equal to or less than -0.6. In some
variations, b* is equal to or less than -0.5. In some variations,
b* is equal to or less than -0.4. In some variations, b* is equal
to or less than -0.3. In some variations, b* is equal to or less
than -0.2. In some variations, b* is equal to or less than -0.1. In
some variations, b* is equal to or less than 0. In some variations,
b* is equal to or less than 0.1. In some variations, b* is less
than or equal to 0.2. In some variations, b* is less than or equal
to 0.3. In some variations, b* is less than or equal to 0.4. In
some variations, b* is less than or equal to 0.5. In some
variations, b* is less than or equal to 0.6. In some variations, b*
is less than or equal to 0.7. In some variations, b* is less than
or equal to 0.8. In some variations, b* is less than or equal to
0.9. In some variations, b* is less than or equal to 1.0. In some
variations, b* is less than or equal to 1.1. In some variations, b*
is less than or equal to 1.2. In some variations, b* is less than
or equal to 1.3. In some variations, b* is less than or equal to
1.4. In some variations, b* is less than or equal to 1.5. In some
variations, b* is less than or equal to 1.6. In some variations, b*
is less than or equal to 1.7. In some variations, b* is less than
or equal to 1.8. In some variations, b* is less than or equal to
1.9. In some variations, b* is less than or equal to 2.0.
[0077] In some variations, L* is from 70 to 100. In some
variations, L* is equal to or greater than 70. In some variations,
L* is equal to or greater than 75. In some variations, L* is equal
to or greater than 80. In some variations, L* is equal to or
greater than 85. In some variations, L* is equal to or greater than
90. In some variations, L* is equal to or greater than 95. In some
variations, L* is less than or equal to 100. In some variations, L*
is less than or equal to 95. In some variations, L* is less than or
equal to 90. In some variations, L* is less than or equal to 85. In
some variations, L* is less than or equal to 80. In some
variations, L* is less than or equal to 75.
[0078] In some variations, a* is from -2 to 2. In some variations,
a* is equal to or greater than -2. In some variations, a* is equal
to or greater than -1.5. In some variations, a* is equal to or
greater than -1.0. In some variations, a* is equal to or greater
than -0.5. In some variations, a* is equal to or greater than 0.0.
In some variations, a* is equal to or greater than 0.5. In some
variations, a* is equal to or greater than -0.5. In some
variations, a* is equal to or greater than 1.0. In some variations,
a* is equal to or greater than 1.5. In some variations, a* is less
than or equal to 2.0. In some variations, a* is less than or equal
to 1.5. In some variations, a* is less than or equal to 1.0. In
some variations, a* is less than or equal to 0.5. In some
variations, a* is less than or equal to 0.0. In some variations, a*
is less than or equal to 2.0. In some variations, a* is less than
or equal to -0.5. In some variations, a* is less than or equal to
-1.0. In some variations, a* is less than or equal to -1.5.
Mechanical Properties
[0079] Yield strengths of the alloys may be determined via ASTM
B557, which covers the testing apparatus, test specimens, and
testing procedure for tensile testing.
[0080] The 6000 series aluminum alloys can be extruded or rolled
with the conventional process for aluminum alloys to have the
mechanical properties, including yield strength, tensile strength,
elongation, and hardness, to be the same as the aluminum alloy
without any scrap.
Grain Aspect Ratio
[0081] In some variations, the disclosed alloys have a grain aspect
ratio from 0.7 to 1.45. Assuming that the grain is in an ellipse
shape. The grain shape aspect ratio is defined as the length of the
minor axis divided by the length of the major axis of the
ellipse.
[0082] In some variations, the alloys have an average grain aspect
ratio greater than or equal to 0.7:1.0. In some variations, the
alloys have an average grain aspect ratio less than or equal to
0.8:1.0. In some variations, the alloys have an average grain
aspect ratio greater than or equal to 0.9:1.0. In some variations,
the alloys have an average grain aspect ratio greater than or equal
to 1.0:1.0.
[0083] In some variations, the alloys have an average grain aspect
ratio greater than or equal to 1:1.45. In some variations, the
alloys have an average grain aspect ratio greater than or equal to
1:1.40. In some variations, the alloys have an average grain aspect
ratio greater than or equal to 1:1.35. In some variations, the
alloys have an average grain aspect ratio greater than or equal to
1:1.30. In some variations, the alloys have an average grain aspect
ratio greater than or equal to 1:1.25. In some variations, the
alloys have an average grain aspect ratio greater than or equal to
1:1.20. In some variations, the alloys have an average grain aspect
ratio greater than or equal to 1:1.15. In some variations, the
alloys have an average grain aspect ratio greater than or equal to
1:1.10. In some variations, the alloys have an average grain aspect
ratio greater than or equal to 1:1.05.
[0084] In some variations, the alloys have an average grain aspect
ratio less than or equal to 0.8:1.0. In some variations, the alloys
have an average grain aspect ratio less than or equal to 0.9:1.0.
In some variations, the alloys have an average grain aspect ratio
less than or equal to 1.0:1.0. In some variations, the alloys have
an average grain aspect ratio less than or equal to 1:1.45. In some
variations, the alloys have an average grain aspect ratio less than
or equal to 1:1.40. In some variations, the alloys have an average
grain aspect ratio less than or equal to 1:1.35. In some
variations, the alloys have an average grain aspect ratio less than
or equal to 1:1.30. In some variations, the alloys have an average
grain aspect ratio less than or equal to 1:1.25. In some
variations, the alloys have an average grain aspect ratio less than
or equal to 1:1.20. In some variations, the alloys have an average
grain aspect ratio less than or equal to 1:1.15. In some
variations, the alloys have an average grain aspect ratio less than
or equal to 1:1.10. In some variations, the alloys have an average
grain aspect ratio less than or equal to 1:1.05.
Corrosion Resistance
[0085] The recycled alloys that include higher Fe and Zn content
than other alloys would be expected to reduce corrosion resistance.
Various corrosion tests were performed to evaluate corrosion
resistance or corrosion susceptibility of the sample alloys A0, A1,
A2, A3, and/or A4.
Cyclic Polarization Test
[0086] Cyclic polarization was performed per ASTM G5 to evaluate
the general corrosion properties of various materials. For example,
the cyclic polarization helps understand whether the material would
undergo active, passive, or localized corrosion. It also provides
measurements of corrosion rates and pitting potential.
[0087] Cyclic polarization is a short-term exposure test. It
provides information on both corrosion characteristics and
corrosion mechanisms. Cyclic polarization measurements are
typically used to characterize metals and alloys that derive their
corrosion resistance from the formation of a thin passive film.
[0088] The aluminum samples were exposed to 0.35% NaCl solution for
the duration of the test (approximately 45 minutes). The corrosion
susceptibility of the samples was evaluated by cyclic
polarization.
Metastable Pitting
[0089] Metastable pit testing was performed to gain an
understanding of susceptibility of a material to localized
corrosion, in particular, metastable pitting. This metastable
pitting test was run by placing the material at a constant
potential where metastable pitting would occur. The constant
potential used in the metastable pitting tests was determined from
the cyclic polarization test described above. The electric current
was recorded during the metastable pitting test and analyzed to
identify current transients, such as small spikes in the current.
Each current transient was associated with a metastable pitting
event. The data were analyzed for a number of metastable pitting
events, the magnitudes of these current spikes, and the time
interval for each event. The values of the number of metastable
pitting events, the magnitudes of these current spikes, and the
time interval for each event were compared to rank the
susceptibility of the material to metastable pitting. Metastable
pitting can be characterized by current fluctuations or current
transients when an alloy is held below E.sub.pit (pitting
potential). These current transients correspond to the nucleation,
growth and repassivation of metastable pits.
[0090] The aluminum samples were exposed to a 0.35% NaCl solution
for the duration of the test (approximately 15 minutes). The
corrosion susceptibility of the samples was evaluated by metastable
pitting test results.
Salt Fog Testing
[0091] Salt Fog Testing was performed per ASTM B117 to provide a
controlled corrosive environment that can be used to compare the
relative corrosion susceptibility between different materials or
coatings. In the salt spray test, a standardized solution of 5%
NaCl (sodium chloride) was aerosolized to create a highly corrosive
atmosphere. The aluminum samples were exposed to the salt fog for
24 hours.
Electrical Impedance Spectroscopy (EIS) Tests
[0092] Electrical Impedance Spectroscopy (EIS) was used to evaluate
the corrosion performance of the seal of the anodized aluminum. One
of the most useful attributes of anodizing in the cosmetic
finishing of aluminum alloys is that anodizing can generate highly
porous, optically transparent oxides which can be dyed to a
particular color, and then sealed to permanently fix this color.
This is particularly true of sulfuric acid anodizing performed in
accordance with the "Type II" category of Mil A 8625. Such anodic
aluminum oxides are mesoporous, for example, with pores of about 20
nm diameter of good wettability and very high aspect ratio.
[0093] A wide spectrum of color is achievable through organic
dyeing of anodic oxides, with organic dyes offering all colors but
white. Color can be tuned by adjusting the composition of the dye
bath (e.g. concentration of colorants, and pH), and by adjusting
the time and temperature of the dye bath. By maintaining a constant
bath composition, pH and temperature, time may be used to fine-tune
the color to any given color target during production.
[0094] The dye is locked into the pores by a subsequent "sealing"
process, which also serves to protect the porosity against staining
and any uptake of dirt in service.
[0095] Hydrothermal sealing can be used to fill the pores by
hydrating the amorphous alumina of the cell walls to a gel of
Boehmite (Al.sub.2O.sub.3.H.sub.2O) and/or Bayerite
(Al.sub.2O.sub.3.3H.sub.2O), such that the gel swells and closes
the open volume. This may be performed in steam, in hot water
(typically at or near boiling, and usually with additives to
minimize smutting), or at temperatures as low as 70.degree. C. It
is greatly enhanced (possibly catalyzed) by using chemistries such
as nickel acetate which additionally precipitate metal hydroxides
in the pores. After sealing, parts are protected against absorption
of material into their pore structure, and are thus insensitive to
staining or dirt. Indeed, one of the simpler test of seal quality
is a "dye spot test" wherein the inability of a sealed surface to
absorb dye is measured. Other tests of seal quality include the
quantitative measures of electrochemical impedance spectroscopy
(EIS), a simplified variant of EIS performed at a fixed frequency
(typically 1 kHz) called "admittance" testing, and acid dissolution
testing (ADT).
[0096] Quantitative measures of seal quality reveal a sensitivity
to time after sealing--sometimes referred to as ageing or "natural
ageing". Older parts generally show better seal quality than
freshly sealed parts and this is attributed to a continued
hydration, occurring over weeks and even months or years. It has
also been observed, however, that parts which are thoroughly dried
before sealing cannot seal naturally by this process.
[0097] A good seal (e.g. one with a 1 kHz admittance value
(measured in microSiemens in accordance with ISO 2931) of less than
400 times the reciprocal of its thickness (measured in
microns)--when measured within 48 h of sealing--a specification set
by Qualanod standard) may be achieved in production by immersion in
an aqueous solution of nickel acetate at 5-10 g/l and at
temperatures of 96 degrees C. or more, for a period of 15 minutes
or more in the case of a Type II anodic oxide film with a film
thickness of 10 to 15 microns.
[0098] The EIS tests were performed per ASTM G106. The EIS
technique can be used to evaluate materials and their coatings in
corrosive environments. The EIS measures impedance of the materials
and their coatings at different frequencies. Changes in electrical
properties determined by EIS experiments have been found to closely
relate to long-term performance of the materials and their
coatings. This EIS method can detect deterioration of the materials
and their coatings well before defects become visible and is more
quantifiable than with other accelerated corrosion testing methods
such as salt spray.
[0099] For EIS tests, a measuring cell was placed on an anodized
panel, filled with a 3.5% NaCl solution. A platinum electrode was
used as a counter electrode, and a standard Ag/AgCl cell as
reference electrode. Measurements were carried out over a broad
frequency range from 100 kHz to 10 mHz, using a 10 mV amplitude
sinusoidal voltage.
[0100] The seal quality of the anodized aluminum was determined
after 48 hours exposure to 3.5% NaCl.
Examples
[0101] The following examples are for illustration purposes only.
It will be apparent to those skilled in the art that many
modifications, both to materials and methods, may be practiced
without departing from the scope of the disclosure.
Samples
[0102] Table 1 lists the compositions for samples alloys A0, A1,
A2, A3, and A4 with different total impurities and elemental
compositions. A0, A1, and A4 were cosmetic aluminum alloys. Alloys
A2 and A3 were recycled aluminum alloys from market scrap. Alloy A0
has less than 0.02 wt % Mn, less than 0.01 wt % Cr, less than 0.01
wt % Cu, and less than 0.01 wt % Zn. Alloys A1 and A4 have less
than 0.03 wt % Mn, less than 0.01 wt % Cr, less than 0.02 wt % Cu,
and less than 0.02 wt % Zn. Alloy A0 had a low total impurity of
0.195 wt %, including Fe, Cu, Mn, Zn, Ti, and Cr. Alloy A1 had a
slightly higher total impurity of 0.3 wt %, including Fe, Cu, Mn,
Zn, Ti than alloy A0, and Cr. Alloy A3 had a higher total impurity
of 0.45 wt %, including Fe, Cu, Mn, Zn, Ti, and Cr than A0 and A1.
Alloy A2 had a higher total impurity of 0.68 wt %, including Fe,
Cu, Mn, Zn, Ti, and Cr. Alloy A4 had a total impurity of 0.35%.
[0103] Table 1 lists the composition in wt % for various alloys of
the disclosure. Surprisingly, increased amounts of one or more of
Mn, Cr, Cu, and Zn in the A1 alloys result in aluminum alloys
having a neutral color, smaller grain aspect ratio, and/or smaller
grain size as described herein.
[0104] Alloy A2 had Fe greater than 0.20, which was higher than
alloys A0, A1, and A4. Alloys A2 and A3 had Zn from 0.020 to 0.20,
which was higher than alloys A0, A1, and A4.
TABLE-US-00001 TABLE 1 Composition in wt % for Various Al Alloys
Sample A0 A1 A2 A3 A4 Total 0.20 0.30 0.69 0.45 0.35 impurity Mg at
least 0.45 at least 0.45 at least 0.45 at least 0.45 at least 0.45
Fe up to 0.20 at least 0.10 greater than 0.20 up to 0.20 up to 0.20
Si at least 0.30 at least 0.35 at least 0.35 at least 0.35 at least
0.35 Mn less than 0.05 0.03-0.10 0.03-0.10 0.03-0.10 0.03-0.10 Cr
less than 0.05 0.01-0.10 0.01-0.10 0.01-0.10 0.01-0.10 Cu less than
0.05 0.010-0.050 0.051-0.10 0.051-0.10 0.010-0.050 Ni less than
0.05 less than 0.05 less than 0.05 less than 0.05 less than 0.05 Zn
less than 0.05 0.01 to 0.020 0.020 to 0.20 0.020 to 0.20 0.01 to
0.020 Ti less than 0.05 less than 0.10 less than 0.10 less than
0.10 less than 0.10
[0105] The data corresponding to different preparations were
presented in box plots, as shown in FIGS. 1A-1D, 2A-2C, 4A-4B,
5A-5B, and 6A-6B.
[0106] FIG. 1A illustrates the yield strength for extrusion samples
formed of various 6000 series aluminum alloys in accordance with an
embodiment of the disclosure. As shown in FIG. 1A, the yield
strength was above 200 MPa for recycled alloys A2 and A3, similar
to that of alloys A0, A1, and A4.
[0107] FIG. 1B illustrates the tensile strength for extrusion
samples formed of various 6000 series aluminum alloys in accordance
with an embodiment of the disclosure. As shown in FIG. 1B, the
ultimate tensile strength was above 235 MPa for recycled alloys A2
and A3, similar to that of alloys A0, A1, and A4.
[0108] FIG. 10 illustrates the elongation for extrusion samples
formed of various 6000 series aluminum alloys in accordance with an
embodiment of the disclosure. As shown in FIG. 10, the elongation
was mostly above 5% for recycled alloys A2 and A3, similar to that
of alloys A0, A1, and A4.
[0109] FIG. 1D illustrates the hardness for extrusion samples
formed of various 6000 series aluminum alloys in accordance with an
embodiment of the disclosure. As shown in FIG. 1D, the hardness was
above 75 Hv for recycled alloys A2 and A3, similar to that of
alloys A0, A1, and A4.
[0110] Microstructure can be characterized by average grain size,
largest grain size, and grain aspect ratio.
[0111] FIG. 2A illustrates the average grain size for extrusion
samples formed of various 6000 series aluminum alloys. As shown in
FIG. 2A, the average grain size was below 240 .mu.m for recycled
alloys A2 and A3, similar to that of alloys A0, A1, and A4.
[0112] FIG. 2B illustrates the largest grain size for extrusion
samples formed of various 6000 series aluminum alloys in accordance
with an embodiment of the disclosure. As shown in FIG. 2B, the
as-large--as grain size was below 650 .mu.m for recycled alloys A2
and A3, similar to that of alloys A0, A1, and A4.
[0113] FIG. 2C illustrates the grain aspect ratio for extrusion
samples formed of various 6000 series aluminum alloys in accordance
with an embodiment of the disclosure. As shown in FIG. 2C, the
aspect ratio of the grain was between a lower limit value of 0.7
and a higher limit value of 1.45 for recycled alloys A2 and A3, and
similar to that of alloys A0, A1, and A4.
[0114] FIG. 3 illustrates extrusion speed for various 6000 series
aluminum alloys in accordance with embodiments of the disclosure.
The extrusion speeds of A2-A4 were normalized to typical extrusion
speed of A0 or A1. Product 1 includes A2, A3, and A4. Product 2
includes A2 and A3. Product 3 includes A2 and A3. Band 1 is the
typical extrusion speed. As shown in FIG. 3, recycled alloys A2,
A3, had similar extrusion speeds to Alloys A1 and A4.
[0115] Four different corrosion tests were performed on alloys A0,
A1, A2, A3, and/or A4. Surprisingly, the corrosion resistance in
each corrosion test was found to be maintained for the recycled
aluminum alloys, although the impurity contents in the recycled
aluminum alloys were increased. Four different corrosion tests were
performed.
[0116] The quality of the seal of the anodized aluminum was
determined after 48 hours exposure to 3.5% NaCl. Electrochemical
impedances were determined by using electrochemical impedance
spectroscopy per ASTM G106. FIG. 4A illustrates comparison of
electrochemical impedance of the aluminum samples having different
total impurities and different elemental compositions for a neutral
color aluminum or non-dyed anodized aluminum (NDA).
[0117] As shown in FIG. 4A, the average impedance was about 290,000
ohms-cm.sup.2 for alloy A1 and was above 290,000 ohms-cm.sup.2 for
recycled alloys A2 and A3. The recycled alloys A2 and A3 with
higher total impurities revealed that the impedance was comparable
with the alloy A1 with lower total impurities. The alloys with
higher impurities (such as Fe and/or Zn) may be expected to have
poorer corrosion resistance compared to alloys with lower
impurities because higher amounts of impurities may compromise the
anodized coating. Y. Ma et al. "Corrosion Behavior of Anodized
Al--Cu--Li Alloy: The Role of Intermetallic Particle-Introduced
Film Defects," Corrosion Science, 158 (2019) 108110, and C.
Blocking et al. "Mechanism of Adhesion Failure of Anodised Coatings
on 7075 Aluminum Alloy," disclose the anodized coatings, both of
which are herein incorporated by reference. Transactions of the
Institute of Metal Finishing, 2011, vol. 89 No. 6, pages 298-302).
As such, the results of comparable impedances of the recycled
alloys to the alloys with low impurities exceeded the
expectations.
[0118] FIG. 4B illustrates comparison of electrochemical impedance
of the aluminum samples having different total impurities and
different elemental compositions for a grey color of anodized
aluminum.
[0119] Note that raw material composition is the largest
contributor to the NDA color. The grey color of anodized aluminum
alloy can have the same alloy composition. The grey color can be
predominately affected by the dye and process and can be tuned
toward a desired color.
[0120] As shown in FIG. 4B, the average impedance was about 210,000
ohms-cm.sup.2 for alloy A1, and was above 210,000 ohms-cm.sup.2 for
recycled alloys A2 and A3. The corrosion resistance of the recycled
alloy A2 and A3 with higher total impurities revealed that the
impedance was comparable with the alloy A1 with lower total
impurities. This result suggested that the color, either neutral or
grey color, did not affect the electrochemical impedance or
corrosion resistance.
[0121] The corrosion susceptibility to 0.35% NaCl solution of the
sample alloys was determined. Corrosion rates and pitting
potentials were determined by using cyclic polarization per ASTM
G5. FIG. 5A illustrates comparison of corrosion rate of the
aluminum samples having different total impurities and different
elemental compositions for a non-anodized alloy. The non-anodized
alloy was a bare metal and was not colored with dye. As shown in
FIG. 5A, the average corrosion rate was 150 .mu.A/cm.sup.2 for
alloy A1, and was less than 150 .mu.A/cm.sup.2 for recycled alloys
A2 and A3. The recycled alloys A2 and A3 with higher total
impurities revealed that the corrosion rates were worse than the
alloy A0 with lower total impurities, but were not worse than the
alloy A1 with lower total impurities. Generally, the alloys with
higher impurities (i.e. Fe and/or Zn) may be expected to have
higher corrosion rates compared to alloys with lower impurities. As
such, the results of comparable corrosion rates of the recycled
alloys to the alloys with low impurities corrosion rates exceeded
expectations.
[0122] FIG. 5B illustrates comparison of pitting potential of the
aluminum samples having different total impurities and different
elemental compositions for a non-anodized alloy. The non-anodized
alloy was a bare metal and was not colored with dye. As shown in
FIG. 5B, the average pitting potential was below -675 mVSCE for
alloys A0 and A1, and was higher than 675 mVSCE for recycled alloys
A2 and A3. The recycled alloy A2 and A3 with higher Zn and/or Fe
impurities revealed that the pitting potential was not worse than
the alloys A0 and A1 with lower Zn and/or Fe impurities. Generally,
the alloys with higher impurities (e.g. Zn and/or Fe) may be
expected to have lower pitting potential compared to alloys with
lower impurities. As such, the results of comparable pitting
potential of the recycled alloys to the alloys with low impurities
exceeded expectations.
[0123] The metastable pitting, i.e. corrosion susceptibility to
0.35% NaCl solution, was determined. FIG. 6A illustrates comparison
of the number of pits of the aluminum samples having different
total impurities and different elemental compositions for a
non-anodized alloy. The non-anodized alloy was a bare metal and was
not colored with dye. As shown in FIG. 6A, the average number of
pits per test was about 2000 for alloy A1, and was higher than
about 1500 for recycled alloy A2. The recycled alloy A2 with higher
Zn and Fe impurities revealed that the number of pits per test was
not worse than the alloy A1 with lower Zn and Fe impurities.
Generally, the alloys with higher impurities (e.g. Fe and/or Zn)
may be expected to have higher number of pits per test compared to
alloys with lower impurities. As such, the results of comparable
number of pits per test of the recycled alloys to the alloys with
low impurities number of pits exceeded expectations.
[0124] FIG. 6B illustrates comparison of pit radius of the aluminum
samples having different total impurities and different elemental
compositions for a non-anodized alloy. The non-anodized alloy was a
bare metal and was not colored with dye. As shown in FIG. 6B, the
average pit radius was about 0.4 .mu.m for all alloys A0, A1, A2,
and A3. Surprisingly, the higher impurities in recycled alloys A2
and A3 did not seem to worsen the pit radius compared to the alloys
A0 and A1 with lower impurities.
[0125] Salt fog test pass rate was determined per ASTM B117. FIG. 7
illustrates comparison of salt fog test pass rate of the aluminum
samples having different total impurities and different elemental
compositions for a neutral color aluminum or NDA and a grey color
aluminum. As shown in FIG. 7, the recycled samples A2 and A3 having
higher total impurities revealed the same salt fog pass rates as
the alloys A0, A1, and A4 having lower total impurities. The alloys
with higher impurities (e.g. Fe and/or Zn) may be expected to have
lower pass rate compared to alloys with lower impurities. As such,
the results of comparable pass rate of the recycled alloys to the
alloys having lower impurities exceeded expectations.
Process for Cleaning and Removing Oxides from Scrap
[0126] Scrap can have a large surface area/volume ratio compared to
virgin material. The large surface area of the scrap can include a
substantial quantity of oxides, such as aluminum oxides. Scrap may
also include impurities, such as Cu, Zn, Mn, Cr, Fe, among others,
compared to conventional 6000 series aluminum alloys or 1000 series
alloys.
[0127] The cleaning process may include removing oxides by
re-melting scrap and flowing oxides and skim off the oxides. The
cleaning process may also include removing organic contaminants by
chemical solvent or solution or heating.
[0128] FIG. 8 depicts a recycling process 800 of materials
including manufacturing scrap in accordance with embodiments of the
disclosure. Aluminum scrap 802 is sourced and sent to an alloy
processor 804. Additional aluminum scrap can be obtained from
post-consumer scrap source 812 or process scrap source 814. The
alloy can be processed during aluminum manufacturing 806. The
manufactured product can proceed to final assembly 808, and then to
the customer 810. Processed scrap can be obtained from multiple
different sources in the supply chain, and the amount of different
elements can be adjusted to form the alloys of the disclosure.
[0129] The disclosed recycled 6000 series aluminum alloys can be
made from up to 100% Al scrap, and can be used to form a part by
extrusion or sheet rolling. The disclosed recycled 6000 series
aluminum alloys can also include scrap from the extrusion or sheet
fabrication process. In some variations, the disclosed methods can
include or exclude primary aluminum or virgin aluminum.
[0130] The disclosed aluminum alloys and methods of making the
alloys can be used in the fabrication of electronic devices. An
electronic device herein can refer to any electronic device known
in the art. For example, such devices can include wearable devices
such as a watch (e.g., an AppleWatch.RTM.). Devices can also be a
telephone such a mobile phone (e.g., an iPhone.RTM.) a land-line
phone, or any communication device (e.g., an electronic email
sending/receiving device). The alloys can be a part of a display,
such as a digital display, a TV monitor, an electronic-book reader,
a portable web-browser (e.g., iPad.RTM.), and a computer monitor.
The alloys can also be an entertainment device, including a
portable DVD player, conventional DVD player, Blue-Ray disk player,
video game console, music player, such as a portable music player
(e.g., iPod.RTM.), etc. The alloys can also be a part of a device
that provides control, such as controlling the streaming of images,
videos, sounds (e.g., Apple TV.RTM.), or can be a remote control
for an electronic device. The alloys can be a part of a computer or
its accessories, such as the hard drive tower housing or casing for
MacBook Air or Mac Mini.
[0131] Any ranges cited herein are inclusive. The terms
"substantially" and "about" used throughout this Specification are
used to describe and account for small fluctuations. For example,
they can refer to less than or equal to .+-.5%, such as less than
or equal to .+-.2%, such as less than or equal to .+-.1%, such as
less than or equal to .+-.0.5%, such as less than or equal to
.+-.0.2%, such as less than or equal to .+-.0.1%, such as less than
or equal to .+-.0.05%.
[0132] Having described several embodiments, it will be recognized
by those skilled in the art that various modifications, alternative
constructions, and equivalents may be used without departing from
the spirit of the invention. Additionally, a number of well-known
processes and elements have not been described in order to avoid
unnecessarily obscuring the invention. Accordingly, the above
description should not be taken as limiting the scope of the
invention.
[0133] Those skilled in the art will appreciate that the disclosed
embodiments teach by way of example and not by limitation.
Therefore, the matter contained in the above description or shown
in the accompanying drawings should be interpreted as illustrative
and not in a limiting sense. The following claims are intended to
cover all generic and specific features described herein, as well
as all statements of the scope of the method and system, which, as
a matter of language, might be said to fall there between.
* * * * *