U.S. patent application number 14/744774 was filed with the patent office on 2015-12-24 for aluminum alloys with anodization mirror quality.
The applicant listed for this patent is Apple Inc.. Invention is credited to Herng-Jeng Jou, Abhijeet Misra.
Application Number | 20150368772 14/744774 |
Document ID | / |
Family ID | 54869118 |
Filed Date | 2015-12-24 |
United States Patent
Application |
20150368772 |
Kind Code |
A1 |
Jou; Herng-Jeng ; et
al. |
December 24, 2015 |
Aluminum Alloys with Anodization Mirror Quality
Abstract
The disclosure provides an aluminum alloy comprising second
phase particles having an Al(FeMn)Si phase with an (Fe+Mn):Si ratio
of 0.5 to 2.5 and a mean particle diameter of 0.5 .mu.m to 10
.mu.m. The disclosure also provides an aluminum alloy comprising
0.02 to 0.11 wt % Fe, 0 to 0.16 wt % Mn, 0 to 0.08 wt. % Cr, 0.40
to 0.90 wt % Mg, and 0.20 to 0.60 wt % Si, wherein the aluminum
alloy is homogenized at a temperature from 550 to 590.degree.
C.
Inventors: |
Jou; Herng-Jeng; (San Jose,
CA) ; Misra; Abhijeet; (Mountain View, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
54869118 |
Appl. No.: |
14/744774 |
Filed: |
June 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62014546 |
Jun 19, 2014 |
|
|
|
Current U.S.
Class: |
148/688 ;
148/439 |
Current CPC
Class: |
C22F 1/05 20130101; C22C
21/08 20130101 |
International
Class: |
C22F 1/047 20060101
C22F001/047; C22C 21/08 20060101 C22C021/08 |
Claims
1. An aluminum alloy comprising less than 16% area fraction of
Fe-containing particles.
2. The aluminum alloy according to claim 1, wherein said alloy is a
6000 series aluminum alloy.
3. The aluminum alloy according to claim 1, wherein the alloy is a
6063 aluminum alloy.
4. The aluminum alloy according to claim 1, wherein said alloy
comprises from 0.2 wt % to 0.16 wt % Fe.
5. The aluminum alloy according to claim 4, wherein the alloy is a
6063 aluminum alloy.
6. The aluminum alloy according to claim 1, wherein said alloy
comprises from 0.10 wt % to 0.12 wt % Fe.
7. The aluminum alloy according to claim 1, wherein said alloy
comprises from 0 to 0.16 wt % Mn.
8. The aluminum alloy according to claim 1, wherein said alloy
comprises from 0.02 to 0.06 wt % Mn.
9. The aluminum alloy according to claim 1, wherein said alloy
comprises from 0-0.08 wt % Cr.
10. The aluminum alloy according to claim 1, wherein said alloy
comprises more than 0.02 wt % Cr.
11. The aluminum alloy according to claim 1, wherein said alloy
comprises iron-containing particles.
12. The aluminum alloy according to claim 11, wherein the mean
diameter of the iron-containing particles is less than 9
microns.
13. The aluminum alloy according to claim 12, wherein the area
fraction of the iron-containing particles is less than 16%.
14. The alloy of claim 1, wherein the gloss (20.degree.) of the
alloy is greater than 160.
15. The alloy of claim 1, wherein the gloss (60.degree.) of the
alloy is greater than 135.
16. The alloy of claim 1, wherein the DOI of the anodized aluminum
alloy is greater than 80.
17. The alloy of claim 1, wherein the LogHaze of the anodized
aluminum alloy is less than 600.
18. A method of processing a 6000 series aluminum alloy having less
than 16% area fraction of Fe-containing particles, said method
comprising homogenizing the alloy at a temperature from 550.degree.
C. to 590.degree. C.
19. The method of claim 18, wherein said homogenizing occurs for
between 1 hour and 6 hours.
20. A 6000 series aluminum alloy having less than 16% area fraction
of Fe-containing particles, the alloy prepared by homogenizing the
alloy at a temperature from 550.degree. C. to 590.degree. C. for
from between 1 hour and 6 hours.
Description
[0001] This patent application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application No. 62/014,546,
entitled "Aluminum Alloys with Anodized Mirror Quality," filed on
Jun. 19, 2014, which is incorporated herein by reference in its
entirety.
FIELD
[0002] Embodiments described herein generally relate to aluminum
alloys. More specifically, the embodiments relate to aluminum
alloys with anodization mirror quality for applications including
enclosures for electronic devices.
BACKGROUND
[0003] Commercial aluminum alloys, such as the 6063 aluminum (Al)
alloy, are used for fabricating enclosures for electronic devices.
The 6063 Al alloys and other 6000 series Al alloys contain iron and
other alloying elements. During alloy casting processing, primary
iron(Fe)-containing second phase particles, such as
Al.sub.8Fe.sub.2Si (.alpha.-AlFeSi phase) and Al.sub.5FeSi
(.beta.-AlFeSi) particles, precipitate from the alloy.
Iron-containing particles conventionally have a mean diameter of
several microns, and provide grain-pinning for the polycrystalline
bulk Al of the alloy. In the absence of grain pinning, the grain
boundaries between the different crystals would be highly mobile
during high-temperature processing steps, resulting in rapid grain
growth. This manifests in undesired cosmetic defects such as
mottling and orange peel.
[0004] These Fe-containing second phase particles also do not
anodize. The Fe-containing second phase particles thereby reduce
the quality of the polished anodized surface of the Al alloy, and
reduce mirror quality. There is a need to develop aluminum alloys
having an improved mirror quality when the surface is anodized to
achieve a balance of sufficient grain pinning and reduced
anodization defects.
SUMMARY
[0005] The disclosure is directed to aluminum alloy compositions
having reduced amounts of iron, optionally coupled with the
addition of manganese and/or chromium. Both manganese and chromium
promote the formation of .alpha.-AlFiSi particles. However, use of
manganese and chromium can lead to compositional micro-segregation,
so the amount of them can be limited. The amounts of these elements
can be in specific compositional ranges. The alloys can have
smaller area fraction and/or mean particle size of the
Fe-containing particles. This can result in improved mirror
quality. Processing temperatures and methods are also
disclosed.
[0006] In various aspects, the disclosed aluminum alloys have
reduced Fe content of 0.02 wt % to 0.16 wt % Fe. In some
embodiments, the disclosed aluminum alloys have from 0.02 wt % to
0.12 wt % Fe.
[0007] In various additional aspects, the disclosed aluminum alloys
include manganese. In some embodiments, the alloy comprises 0-0.16
wt % Mn. In some embodiments, the alloy comprises 0.02-0.06 wt %
Mn. In some embodiments, the alloy comprises 0.04 wt % Mn.
[0008] In various additional aspects, the disclosed aluminum alloys
include chromium. In some embodiments, the alloy comprises 0-0.08
wt % Cr.
[0009] In various additional aspects, Fe-containing particles in
the aluminum alloys have an area fraction of less than 0.4%, and in
some cases less than 0.25%. In further aspects, the mean diameter
of iron containing particles is less than 8 microns, and in some
cases less than 4 microns.
[0010] In various embodiments, the alloy is a 6063 aluminum
alloy.
[0011] In some embodiments, an aluminum alloy comprises 0.02 to
0.16 wt % Fe, 0 to 0.16 wt % Mn, 0 to 0.08 wt % Cr, 0.40 to 0.90 wt
% Mg, and 0.20 to 0.60 wt % Si.
[0012] In some embodiments, a 6063 aluminum alloy comprises 0.10 to
0.12 wt % Fe, 0.02-0.06 wt % Mn, 0.40 to 0.90 wt % Mg, and 0.20 to
0.60 wt % Si.
[0013] Additional embodiments and features are set forth in part in
the description that follows, and in part will become apparent to
those skilled in the art upon examination of the specification, or
may be learned by the practice of the embodiments discussed herein.
A further understanding of the nature and advantages of certain
embodiments 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
[0014] The disclosure will be readily understood by the following
detailed description in conjunction with the accompanying drawings,
wherein like reference numerals designate like structural elements.
The drawings provide exemplary embodiments or aspects of the
disclosure and do not limit the scope of the disclosure.
[0015] FIG. 1 depicts the reduction of constituent Fe-containing
particles between the baseline alloy (6063 Al alloy with 0.10-0.12
wt % Fe) and Sample A (6063 Al alloy with 0.08 wt % Fe and 0.04 wt
% Mn) disclosed herein, both in size and area fraction.
[0016] FIG. 2A depicts a bright field optical micrograph of
anodization defects for the baseline aluminum alloy.
[0017] FIG. 2B depicts a bright field optical micrograph of
anodization defects for Sample A.
[0018] FIG. 3 depicts the reduction of anodization defects between
the baseline alloy and Sample A, both in size and area
fraction.
[0019] FIG. 4 depicts the increases of gloss (20.degree.), gloss
(60.degree.), and distinctness of image (DOI) and the decrease in
haze of anodized Sample A compared to the baseline alloy.
DETAILED DESCRIPTION
[0020] 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, may be represented schematically or
conceptually, or otherwise may not correspond exactly to certain
physical configurations of embodiments.
[0021] The disclosure provides aluminum alloys that have improved
mirror quality after anodization than conventional aluminum alloys.
In various embodiments, the disclosed alloys comprise aluminum as
the primary metal and iron, silicon, and magnesium as alloying
elements. Optionally, the disclosed alloys can further comprise
manganese and chromium. The alloys can also include copper, zinc,
titanium, or other alloying elements to impart various
characteristics to the alloy. Exemplary aluminum alloys include,
but are not limited to, 6000 series aluminum alloys, such as 6063
aluminum alloys.
[0022] Without wishing to be limited to any theory or mechanism of
action, .beta.-AlFeSi particles can be converted to .alpha.-AlFeSi
particles during the solid-state homogenization treatment. This
conversion can improve anodized surface quality. First, the shapes
of .alpha.-AlFeSi particles can have a lower aspect ratio than the
often elongated shape of .beta.-AlFeSi particles. The sizes of
round cosmetic defects, for example due to the disruption of
anodization process around the Fe-containing particles, can be set
by the longest dimension of the particles. Hence, .alpha.-AlFeSi
particles with lower aspect ratio are more favorable than
.beta.-AlFeSi. Second, with lower ratio of Fe over Al chemical
composition, .alpha.-AlFeSi particles have lower phase fraction
than .beta.-AlFeSi particles, resulting in lower amount of
anodization defects with .alpha.-AlFeSi particles. The resulting
surfaces achieve a balance of sufficient grain pinning and reduced
anodization defects.
[0023] The aluminum alloy can be a casting alloy or a wrought
alloy, either of which can be heat-treatable or non-heat-treatable.
Aluminum alloys are widely used in engineering structure and
components having light weight or corrosion resistance, such as the
casings for consumer electronics.
[0024] The disclosed aluminum alloys include iron-containing
(Fe-containing) second phase particles. Several Fe-containing
intermetallic phases have been identified in second phase
Fe-containing particles, depending on the solidification conditions
and alloy composition. The Fe-containing second phase particles can
restrict grain growth during high temperature processing, a process
known as grain pinning. However, when anodized, the bulk aluminum
in the alloy is oxidized while the micron-sized Fe-containing
second phase particles are not, resulting in non-anodized cosmetic
defects that reduce the mirror quality of the anodized alloy.
[0025] The disclosed alloys reduce the area fraction and/or mean
diameter of the Fe-containing particles while maintaining grain
pinning capability. By reducing the area fraction of the
Fe-containing particles, the unanodized surface area lacking mirror
quality can be reduced, resulting in a promotion of visual gloss.
Similarly, by reducing the mean diameter of Fe-containing
particles, the unanodized surface area lacking mirror quality can
be reduced.
[0026] In various aspects, the disclosed aluminum alloys reduce the
iron content below that of a conventional alloy. In further
aspects, the aluminum alloys add a quantity of manganese and/or
chromium to promote .alpha.-AlFeSi Fe-containing particles, which
are less detrimental to anodized mirror quality than .beta.-AlFeSi
particles. In certain embodiments, the aluminum alloys can be
homogenized at a temperature or temperatures within a specific
range. Such alloys, when anodized, have improved mirror qualities
due to effective conversion to the more favorable Fe-containing
particles.
[0027] In certain embodiments, the aluminum alloy is a 6063 Al
alloy. Conventional 6063 aluminum alloys can include Si from 0.2 to
0.6 wt %, Fe from 0.2 to 0.4 wt %, Cu of not more than 0.1 wt %, Mg
from 0.45 to 0.9 wt %, Cr of not more than 0.1 wt %, Zn of not more
than 0.10 wt %, and Ti of not more than 0.10 wt %. Other alloying
elements may each be present in not more than 0.05 wt %, and
typically total no more than 0.15 wt %. The balance of the alloy is
aluminum.
[0028] In various aspects, the disclosure is directed to a modified
6063 aluminum alloy having reduced Fe wt %. By reducing Fe content,
the area fraction of Fe-containing particles is reduced, and the
area fraction of anodizable bulk aluminum is increased. In some
variations, the aluminum alloys have reduced iron content to 0.2 wt
% to 0.16 wt % Fe. In some embodiments, the disclosed aluminum
alloys have from 0.10 wt % Fe to 0.12 wt % Fe.
[0029] In certain variations, the modified alloy is a modified 6063
alloy includes Fe from 0.02 to 0.16 wt %, Si from 0.2 to 0.6 wt %,
Cu of not more than 0.1 wt %, Mg from 0.40 to 0.90 wt %, Cr of
0-0.08 wt %, Zn of not more than 0.10 wt %, and Ti of not more than
0.10 wt %, with the balance as aluminum.
[0030] In some embodiments, the disclosed alloys include less than
or equal to 0.3 wt % Fe. In some embodiments, the disclosed alloys
include less than or equal to 0.4 wt % Fe. In some embodiments, the
disclosed alloys include less than or equal to 0.06 wt % Fe. In
some embodiments, the disclosed alloys include less than or equal
to 0.08 wt % Fe. In some embodiments, the disclosed alloys include
less than or equal to 0.10 wt % Fe. In some embodiments, the
disclosed alloys include less than or equal to 0.12 wt % Fe. In
some embodiments, the disclosed alloys include less than or equal
to 0.14 wt % Fe. In some embodiments, the disclosed alloys include
less than or equal to 0.16 wt % Fe.
[0031] In some embodiments, the disclosed alloy has greater than or
equal to 0.02 wt % Fe. In some embodiments, the disclosed alloys
include greater than or equal to 0.04 wt % Fe. In some embodiments,
the disclosed alloys include greater than or equal to 0.06 wt % Fe.
In some embodiments, the disclosed alloys include greater than or
equal to 0.08 wt % Fe. In some embodiments, the disclosed alloys
include greater than or equal to 0.10 wt % Fe. In some embodiments,
the disclosed alloys include greater than or equal to 0.12 wt % Fe.
In some embodiments, the disclosed alloys include greater than or
equal to 0.14 wt % Fe.
[0032] In some variations, Mn can be added to the alloy. The
presence of Mn reduces the size of Fe-containing particles, thereby
increasing the anodizable surface area of the alloy.
[0033] In some embodiments, the disclosed alloys include from 0 to
0.16 wt % Mn. In some embodiments, the disclosed alloys include
from 0.02 to 0.06 wt % Mn. In some embodiments, the disclosed
alloys include less than or equal to or equal to 0.2 wt % Mn. In
some embodiments, the disclosed alloys include less than or equal
to or equal to 0.4 wt % Mn. In some embodiments, the disclosed
alloys include less than or equal to or equal to 0.6 wt % Mn. In
some embodiments, the disclosed alloys include less than or equal
to or equal to 0.8 wt % Mn. In some embodiments, the disclosed
alloys include less than or equal to 0.10 wt % Mn. In some
embodiments, the disclosed alloys include less than or equal to
0.12 wt % Mn. In some embodiments, the disclosed alloys include
less than or equal to 0.14 wt % Mn. In some embodiments, the
disclosed alloys include less than or equal to 0.16 wt % Mn.
[0034] In some embodiments, the disclosed alloys include greater
than or equal to 0.02 wt % Mn. In some embodiments, the disclosed
alloys include greater than or equal to 0.04 wt % Mn. In some
embodiments, the disclosed alloys include greater than or equal to
0.06 wt % Mn. In some embodiments, the disclosed alloys include
greater than or equal to 0.08 wt % Mn. In some embodiments, the
disclosed alloys include greater than or equal to 0.10 wt % Mn. In
some embodiments, the disclosed alloys include greater than or
equal to 0.12 wt % Mn. In some embodiments, the disclosed alloys
include greater than or equal to 0.14 wt % Mn.
[0035] In various additional aspects, the disclosed aluminum alloys
include chromium. In some embodiments, the disclosed alloys include
from 0 to 0.1 wt % Cr. In some embodiments, the disclosed alloys
include less than or equal to 0.01 wt % Cr. In some embodiments,
the disclosed alloys include less than or equal to 0.02 wt % Cr. In
some embodiments, the disclosed alloys include less than or equal
to 0.03 wt % Cr. In some embodiments, the disclosed alloys include
less than or equal to 0.4 wt % Cr. In some embodiments, the
disclosed alloys include less than or equal to 0.05 wt % Cr. In
some embodiments, the disclosed alloys include less than or equal
to 0.06 wt % Cr. In some embodiments, the disclosed alloys include
less than or equal to 0.07 wt % Cr. In some embodiments, the
disclosed alloys include less than or equal to 0.08 wt % Cr.
[0036] In some embodiments, the disclosed alloys include greater
than or equal to 0.0 wt % Cr. In some embodiments, the disclosed
alloys include greater than or equal to 0.02 wt % Cr. In some
embodiments, the disclosed alloys include greater than or equal to
0.03 wt % Cr. In some embodiments, the disclosed alloys include
greater than or equal to 0.04 wt % Cr. In some embodiments, the
disclosed alloys include greater than or equal to 0.05 wt % Cr. In
some embodiments, the disclosed alloys include greater than or
equal to 0.06 wt % Cr. In some embodiments, the disclosed alloys
include greater than or equal to 0.07 wt % Cr.
[0037] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, and 0.10 to 0.12 wt % Fe.
[0038] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, and 0.08 wt % Fe.
[0039] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.08 wt % Fe, and 0.10 wt % Mn.
[0040] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.08 wt % Fe, and 0.04 wt % Mn.
[0041] In one embodiment, the aluminum alloy comprises 53 wt % Mg,
0.41 wt % Si, 0.02 wt % Fe, and 0.16 wt % Mn.
[0042] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.05 wt % Fe, and 0.12 wt % Mn.
[0043] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.08 wt % Fe, and 0.06 wt % Mn.
[0044] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.08 wt % Fe, 0.02 wt % Mn, and 0.04 wt % Cr.
[0045] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.08 wt % Fe, 0.04 wt % Mn, and 0.06 wt % Cr.
[0046] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.08 wt % Fe, 0.02 wt % Mn, and 0.08 wt % Cr.
[0047] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, 0.11 wt % Fe, and 0.02 wt % Mn.
[0048] In one embodiment, the aluminum alloy comprises 0.53 wt %
Mg, 0.41 wt % Si, and 0.11 to 0.12 wt % Fe.
[0049] The concentrations of Fe, Mn, and Cr can be selected to
provide smaller average particle sizes and/or fewer second phase
particles while still providing grain pinning during
high-temperature processing of the Al alloy. The fine grain
structure can be maintained to provide an anodized mirror
quality.
[0050] In some embodiments, the mean diameter of the Fe-containing
particles is less than 9 microns. In some embodiments, the mean
diameter of the Fe-containing particles is less than 8 microns. In
some embodiments, the mean diameter of the Fe-containing particles
is less than 7 microns. In some embodiments, the mean diameter of
the Fe-containing particles is less than 6 microns. In some
embodiments, the mean diameter of the Fe-containing particles is
less than 5 microns. In some embodiments, the mean diameter of the
Fe-containing particles is less than 4 microns.
[0051] In some embodiments, the area fraction of the Fe-containing
particles is less than 16%. In some embodiments, the area fraction
of the Fe-containing particles is less than 15%. In some
embodiments, the area fraction of the Fe-containing particles is
less than 14%. In some embodiments, the area fraction of the
Fe-containing particles is less than 13%. In some embodiments, the
area fraction of the Fe-containing particles is less than 12%. In
some embodiments, the area fraction of the Fe-containing particles
is less than 11%. In some embodiments, the area fraction of the
Fe-containing particles is less than 10%. In some embodiments, the
area fraction of the Fe-containing particles is less than 9%. In
some embodiments, the area fraction of the Fe-containing particles
is less than 8%.
[0052] It will be appreciated by those of skill in the art that the
amount of other elements in the 6063 alloy can vary.
[0053] In some embodiments, the disclosed alloys include Mg from
0.45 to 0.9 wt %. In some embodiments, the disclosed alloys include
Mg less than 0.9 wt %. In some embodiments, the disclosed alloys
include Mg less than 0.5 wt %. In some embodiments, the disclosed
alloys include Mg more than 0.45 wt %.
[0054] In some embodiments, the disclosed alloys include Si from
0.2 to 0.6 wt %. In some embodiments, the disclosed alloys include
Si less than 0.6 wt %. In some embodiments, the disclosed alloys
include Si less than 0.4 wt %. In some embodiments, the disclosed
alloys include Si more than 0.2 wt %. In some embodiments, the
disclosed alloys include Si more than 0.4 wt %.
[0055] In some embodiments, the disclosed alloys include Cu from 0
to 0.1 wt %. In some embodiments, the disclosed alloys include Cu
less than 0.1 wt %. In some embodiments, the disclosed alloys
include Cu more than 0 wt %.
[0056] In some embodiments, the disclosed alloys include Zn from 0
to 0.1 wt % Zn. In some embodiments, the disclosed alloys include
Zn less than 0.1 wt %. In some embodiments, the disclosed alloys
include Zn more than 0 wt %.
[0057] In some embodiments, the disclosed alloys include Ti from 0
to 0.1 wt %. In some embodiments, the disclosed alloys include Ti
less than 0.1 wt %. In some embodiments, the disclosed alloys
include Ti more than 0 wt %.
[0058] In some embodiments, the aluminum alloys comprises 0.02 to
0.11 wt % Fe, 0 to 0.16 wt % Mn, 0 to 0.08 wt. % Cr, 0.40 to 0.90
wt % Mg, and 0.20 to 0.60 wt % Si.
[0059] In some embodiments, the aluminum alloy comprises 0.06 to
0.11 wt % Fe, 0.02 to 0.06 wt % Mn, 0.40 to 0.60 wt % Mg, and 0.30
to 0.50 wt % Si.
[0060] It will be appreciated by those skilled in the art that
other aluminum alloys besides 6063 aluminum alloys can be
modified.
[0061] In some embodiments, the aluminum alloy is a 6000 series Al
alloy, which is defined by the presence of Mg and Si in the
aluminum bulk material. In some embodiments, the aluminum alloy is
a 6005 Al alloy. In some embodiments, the aluminum alloy is a 6005A
Al alloy. In some embodiments, the aluminum alloy is a 6060 Al
alloy. In some embodiments, the aluminum alloy is a 6063 Al alloy.
In some embodiments, the aluminum alloy is a 6066 Al alloy. In some
embodiments, the aluminum alloy is a 6070 Al alloy. In some
embodiments, the aluminum alloy is a 6083 Al alloy. In some
embodiments, the aluminum alloy is a 6105 Al alloy. In some
embodiments, the aluminum alloy is a 6162 Al alloy. In some
embodiments, the aluminum alloy is a 6262 Al alloy. In some
embodiments, the aluminum alloy is a 6351 Al alloy. In some
embodiments, the aluminum alloy is a 6463 Al alloy.
[0062] In other embodiments, the disclosed alloy can be a 6000
series Al alloy. 6000 series Al alloys are alloyed with magnesium
and silicon. Alloys of the 6000 series can be relatively easy to
machine compared to other Al alloys, and they can also be
precipitation hardened. In some embodiments, 6000 series Al alloys
can include Si from 0.2 to 1.8 wt %, Fe from 0.1 to 0.7 wt %, Cu
from 0.1 to 1.2 wt %, Mn from 0.05 to 1.1 wt %, Mg from 0.40 to 1.4
wt %, Cr of not more than 0.4 wt %, Zn from 0.05 to 0.25 wt %, Ti
of not more than 0.20 wt %, Bi of not more than 0.7 wt %, and Pb of
not more than 0.7 wt %. In other embodiments,
[0063] In some embodiments, a melt for an alloy can be prepared by
heating the alloy, including the composition, as described herein.
After the melt is cooled to room temperature, the alloy can go
through various heat treatments, such homogenization, extruding,
forging, aging, and/or other forming or solution heat treatment
techniques as are known in the art.
[0064] In some embodiments, the cooled alloy can be homogenized by
heating to an elevated temperature and holding at the elevated
temperature for a period of time. Homogenization refers to a
process in which high-temperature soaking is used at an elevated
temperature for a period of time. It will be appreciated by those
skilled in the art that the heat treatment condition (e.g.
temperature and time) may vary. In various embodiments, the
homogenization temperature for the aluminum alloys disclosed herein
can range from about 550.degree. C. to about 590.degree. C. In
other embodiments, the homogenization temperature can range from
about 570.degree. C. to about 580.degree. C. In some embodiments,
the homogenization temperature is above 550.degree. C. In some
embodiments, the homogenization temperature is below 590.degree. C.
The iron-containing particles are not homogenized in solution.
[0065] Homogenation can occur from about 1 hour to about 6 hours,
such as from about 2 hours to about 4 hours. In some embodiments,
homogenization can occur for less than 6 hours. In some
embodiments, homogenization can occur for less than 4 hours. In
some embodiments, homogenization can occur for more than 2
hours.
[0066] In some embodiments, the homogenized alloy can be
hot-worked, e.g., extruded. Extrusion is a process for converting a
metal ingot or billet into lengths of uniform cross section by
forcing the metal to flow plastically through a die orifice.
[0067] In various aspects, the disclosed alloys can be anodized.
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.
[0068] Any of the Al alloys disclosed herein can be anodized. In
particular embodiments, the Al alloy can be anodized to a depth of
about 5 to about 10 .mu.m. In some embodiments, the disclosed alloy
is anodized to a depth less than 10 .mu.m. In some embodiments, the
disclosed alloy is anodized to a depth greater than 5 .mu.m.
Aluminum is microscopically transparent, so the non-anodized second
phase particles can be seen through the aluminum, permitting an
observer to see all particles in the volume of the anodized layer,
not just the first surface.
[0069] In some embodiments, the disclosed alloys can form
enclosures for the electronic devices. The enclosures may be
designed to have a blasted surface finish, or absence of streaky
lines. Blasting is a surface finishing process, for example,
smoothing a rough surface or roughening a smooth surface. Blasting
may remove surface materials by forcibly propelling a stream of
abrasive material against a surface under high pressure.
[0070] Standard methods may be used for evaluation of cosmetics
including color, gloss and haze. Gloss describes the perception of
a surface appearing "shiny" when light is reflected. The Gloss Unit
(GU) is defined in international standards including ISO 2813 and
ASTM D523. It is determined by the amount of reflected light from a
highly polished black glass standard of known refractive index of
1.567. The standard is assigned with a specular gloss value of 100.
Haze describes the milky halo or bloom seen on the surface of high
gloss surfaces. Haze is calculated using the angular tolerances
described in ASTM E430. The instrument can display the natural haze
value (HU) or Log Haze Value (HU.sub.LOG). A high gloss surface
with zero haze has a deep reflection image with high contrast. DOI
(Distinctness Of Image) is, as the name implies a function of the
sharpness of a reflected image in a coating surface, based on ASTM
D5767. Orange peel, texture, flow out and other parameters can be
assessed in coating applications where high gloss quality is
becoming increasingly important. The measurements of gloss, haze,
and DOI may be performed by testing equipment, such as Rhopoint
IQ.
[0071] By using the aluminum alloys of the disclosure, defects
viewed through the anodized layer were reduced, providing a high
gloss and high distinctness of image with surprisingly low
haze.
[0072] In some embodiments, the gloss (20.degree.) of the anodized
aluminum alloy is greater than 160. In some embodiments, the gloss
(20.degree.) of the anodized aluminum alloy is greater than 170. In
some embodiments, the gloss (20.degree.) of the anodized aluminum
alloy is greater than 180. In some embodiments, the gloss
(20.degree.) of the anodized aluminum alloy is greater than 190. In
some embodiments, the gloss (20.degree.) of the anodized aluminum
alloy is greater than 200. In some embodiments, the gloss
(20.degree.) of the anodized aluminum alloy is greater than 210. In
some embodiments, the gloss (20.degree.) of the anodized aluminum
alloy is greater than 220.
[0073] In some embodiments, the gloss (60.degree.) of the anodized
aluminum alloy is greater than 135. In some embodiments, the gloss
(60.degree.) of the anodized aluminum alloy is greater than 140. In
some embodiments, the gloss (60.degree.) of the anodized aluminum
alloy is greater than 145.
[0074] In some embodiments, the DOI of the anodized aluminum alloy
is greater than 80. In some embodiments, the DOI of the anodized
aluminum alloy is greater than 85. In some embodiments, the DOI of
the anodized aluminum alloy is greater than 87.5. In some
embodiments, the DOI of the anodized aluminum alloy is greater than
90.
[0075] In some embodiments, the LogHaze of the anodized aluminum
alloy is less than 600. In some embodiments, the LogHaze of the
anodized aluminum alloy is less than 550. In some embodiments, the
LogHaze of the anodized aluminum alloy is less than 500. In some
embodiments, the LogHaze of the anodized aluminum alloy is less
than 450. In some embodiments, the LogHaze of the anodized aluminum
alloy is less than 400. In some embodiments, the LogHaze of the
anodized aluminum alloy is less than 350. In some embodiments, the
LogHaze of the anodized aluminum alloy is less than 300. In some
embodiments, the LogHaze of the anodized aluminum alloy is less
than 250. In some embodiments, the LogHaze of the anodized aluminum
alloy is less than 200.
EXAMPLES
[0076] The following examples describe in detail preparation and
characterization of alloys and methods disclosed herein. It will be
apparent to those of ordinary skill in the art that many
modifications, to both materials and methods, may be practiced.
Example 1
[0077] A baseline alloy (6063 Al alloy with 0.10-0.12 wt % Fe) and
Sample A alloy (6063 Al alloy with 0.08 wt % Fe and 0.04 wt % Mn)
were produced by vertical direct chill casting and extrusion into a
thin profile. The baseline alloy was homogenized at a temperature
between 560.degree. C. and 580.degree. C. Sample A was homogenized
at a temperature of 580.degree. C. FIG. 1 depicts the data
collected from backscattered secondary electron micrographs (SEMs)
of ten images quantifying Fe-containing particles and
microstructures in each alloy sample. The baseline alloy displayed
an average particle Feret diameter of 2.4.+-.0.2 .mu.m and an
average area fraction of 0.21.+-.0.05%. Sample A displayed an
average particle Feret diameter of 2.25.+-.0.15 .mu.m and an
average area fraction of 0.18.+-.0.02%. Thus, the size and area
fraction of constituent Fe-containing particles were decreased
between the baseline alloy and Sample A.
[0078] The baseline and Sample A alloys were also examined using
bright field optical microscopy, as depicted at FIGS. 2A & B.
Using these photomicrographs, the anodization defects and dyed
anodization were quantified. Specifically, the anodized layer is
optically transparent. Thus viewing the sample from the top down
through the anodization layer permits one to quantify the defects
through the entire thickness of the anodization layer. As shown at
FIG. 3, the baseline alloy displayed second phase particles with a
mean diameter of 9.5 .mu.m and an area fraction of 16.5%, and
Sample A displayed second phase particles with a mean diameter of
5.5 .mu.m and an area fraction of 8%. Thus, the size of the
particles between the baseline alloy and Sample A decreased by
nearly half, as did the area fraction.
[0079] The baseline and Sample A alloys were also examined for
gloss (20.degree.), gloss (60.degree.), distinctness of image
(DOI), and haze using a gloss/DOI/haze meter based on the ASTM
standards described herein. As shown at FIG. 4, the baseline alloy
had an average high gloss measurement (gloss (20.degree.)) of 150
GU, a medium gloss measurement (gloss (60.degree.)) of 133 GU, a
DOI of 76, and a haze of 650. In comparison, Sample A had an
average gloss (20.degree.) of 215 GU, a gloss (60.degree.) of 143
GU, a DOI of 87, and a haze of 200. Thus gloss (20.degree.), gloss
(60.degree.), and DOI increased between Sample A and the baseline
alloy. Surprisingly, the haze of Sample A decreased relative to the
baseline alloy.
Example 2
[0080] A series of sample alloys were prepared, and are depicted in
Table 2.
TABLE-US-00001 TABLE 2 Modified 6063 Alloys containing 0.53 wt % Mg
and 0.41 wt % Si Iron wt % Manganese wt % Chromium wt % 0.10-0.12
wt % Fe 0.08 wt % Fe 0.08 wt % Fe 0.10 wt % Mn 0.08 wt % Fe 0.04 wt
% Mn 0.02 wt % Fe 0.16 wt % Mn 0.05 wt % Fe 0.12 wt % Mn 0.08 wt %
Fe 0.06 wt % Mn 0.11 wt % Fe 0.02 wt % Mn 0.08 wt % Fe 0.02 wt % Mn
0.04 wt % Cr 0.08 wt % Fe 0.04 wt % Mn 0.06 wt % Cr 0.08 wt % Fe
0.02 wt % Mn 0.08 wt % Cr
[0081] 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 disclosure. Additionally, a number of well-known
processes and elements have not been described in order to avoid
unnecessarily obscuring the embodiments disclosed herein.
Accordingly, the above description should not be taken as limiting
the scope of the document.
[0082] 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 various generic and specific features described herein, as
well as statements of the scope of the present method and system,
which, as a matter of language, might be said to fall there
between. Certain subject matter lying outside the scope of the
claims can be claimed in future patent applications.
* * * * *