US20150368772A1

US20150368772A1 - Aluminum Alloys with Anodization Mirror Quality

Info

Publication number: US20150368772A1
Application number: US14/744,774
Authority: US
Inventors: Herng-Jeng Jou; Abhijeet Misra
Original assignee: Apple Inc
Current assignee: Apple Inc
Priority date: 2014-06-19
Filing date: 2015-06-19
Publication date: 2015-12-24

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 μm to 10 μm. 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° C.

Description

This patent application claims the benefit under 35 U.S.C. §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

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

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 Al₈Fe₂Si (α-AlFeSi phase) and Al₅FeSi (β-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.
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

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 α-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.
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.
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.
In various additional aspects, the disclosed aluminum alloys include chromium. In some embodiments, the alloy comprises 0-0.08 wt % Cr.
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.
In various embodiments, the alloy is a 6063 aluminum alloy.
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.
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.
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

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.

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.

FIG. 2A depicts a bright field optical micrograph of anodization defects for the baseline aluminum alloy.

FIG. 2B depicts a bright field optical micrograph of anodization defects for Sample A.

FIG. 3 depicts the reduction of anodization defects between the baseline alloy and Sample A, both in size and area fraction.

FIG. 4 depicts the increases of gloss (20°), gloss (60°), and distinctness of image (DOI) and the decrease in haze of anodized Sample A compared to the baseline alloy.

DETAILED DESCRIPTION

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.
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.
Without wishing to be limited to any theory or mechanism of action, β-AlFeSi particles can be converted to α-AlFeSi particles during the solid-state homogenization treatment. This conversion can improve anodized surface quality. First, the shapes of α-AlFeSi particles can have a lower aspect ratio than the often elongated shape of β-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, α-AlFeSi particles with lower aspect ratio are more favorable than β-AlFeSi. Second, with lower ratio of Fe over Al chemical composition, α-AlFeSi particles have lower phase fraction than β-AlFeSi particles, resulting in lower amount of anodization defects with α-AlFeSi particles. The resulting surfaces achieve a balance of sufficient grain pinning and reduced anodization defects.
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.
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.
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.
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 α-AlFeSi Fe-containing particles, which are less detrimental to anodized mirror quality than β-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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, and 0.10 to 0.12 wt % Fe.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, and 0.08 wt % Fe.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, 0.08 wt % Fe, and 0.10 wt % Mn.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, 0.08 wt % Fe, and 0.04 wt % Mn.
In one embodiment, the aluminum alloy comprises 53 wt % Mg, 0.41 wt % Si, 0.02 wt % Fe, and 0.16 wt % Mn.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, 0.05 wt % Fe, and 0.12 wt % Mn.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, 0.08 wt % Fe, and 0.06 wt % Mn.
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.
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.
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.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, 0.11 wt % Fe, and 0.02 wt % Mn.
In one embodiment, the aluminum alloy comprises 0.53 wt % Mg, 0.41 wt % Si, and 0.11 to 0.12 wt % Fe.
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.
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.
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%.
It will be appreciated by those of skill in the art that the amount of other elements in the 6063 alloy can vary.
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 %.
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 %.
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 %.
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 %.
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 %.
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.
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.
It will be appreciated by those skilled in the art that other aluminum alloys besides 6063 aluminum alloys can be modified.
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.
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,
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.
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° C. to about 590° C. In other embodiments, the homogenization temperature can range from about 570° C. to about 580° C. In some embodiments, the homogenization temperature is above 550° C. In some embodiments, the homogenization temperature is below 590° C. The iron-containing particles are not homogenized in solution.
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.
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.
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.
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 μm. In some embodiments, the disclosed alloy is anodized to a depth less than 10 μm. In some embodiments, the disclosed alloy is anodized to a depth greater than 5 μm. 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.
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.
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_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.
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.
In some embodiments, the gloss (20°) of the anodized aluminum alloy is greater than 160. In some embodiments, the gloss (20°) of the anodized aluminum alloy is greater than 170. In some embodiments, the gloss (20°) of the anodized aluminum alloy is greater than 180. In some embodiments, the gloss (20°) of the anodized aluminum alloy is greater than 190. In some embodiments, the gloss (20°) of the anodized aluminum alloy is greater than 200. In some embodiments, the gloss (20°) of the anodized aluminum alloy is greater than 210. In some embodiments, the gloss (20°) of the anodized aluminum alloy is greater than 220.
In some embodiments, the gloss (60°) of the anodized aluminum alloy is greater than 135. In some embodiments, the gloss (60°) of the anodized aluminum alloy is greater than 140. In some embodiments, the gloss (60°) of the anodized aluminum alloy is greater than 145.
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.
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

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

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° C. and 580° C. Sample A was homogenized at a temperature of 580° 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 μm and an average area fraction of 0.21±0.05%. Sample A displayed an average particle Feret diameter of 2.25±0.15 μm 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.
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 μm and an area fraction of 16.5%, and Sample A displayed second phase particles with a mean diameter of 5.5 μm 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.
The baseline and Sample A alloys were also examined for gloss (20°), gloss (60°), 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°)) of 150 GU, a medium gloss measurement (gloss (60°)) of 133 GU, a DOI of 76, and a haze of 650. In comparison, Sample A had an average gloss (20°) of 215 GU, a gloss (60°) of 143 GU, a DOI of 87, and a haze of 200. Thus gloss (20°), gloss (60°), and DOI increased between Sample A and the baseline alloy. Surprisingly, the haze of Sample A decreased relative to the baseline alloy.

Example 2

A series of sample alloys were prepared, and are depicted in Table 2.

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

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.
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.

Claims

What is claimed is:

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°) of the alloy is greater than 160.

15. The alloy of claim 1, wherein the gloss (60°) 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° C. to 590° 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° C. to 590° C. for from between 1 hour and 6 hours.