CN111051557A

CN111051557A - Aluminum alloy with visible grains and aluminum alloy colored by double anodization

Info

Publication number: CN111051557A
Application number: CN201880056566.2A
Authority: CN
Inventors: 拉杰什·普拉森纳文卡特森; 理查德·希利; 迈克尔·比德尔
Original assignee: Facebook Inc
Current assignee: Meta Platforms Inc
Priority date: 2017-08-29
Filing date: 2018-08-23
Publication date: 2020-04-21
Also published as: US20190062885A1; WO2019046107A1

Abstract

Embodiments relate to an aluminum alloy having grains visible to the naked eye. The aluminum alloy may have an average grain size of at least 100 μm. Aluminum alloys can be produced by processes such as casting, extrusion, solutionizing, aging, and etching. Solutionizing causes recrystallization of aluminum and causes grain growth of aluminum. Aging is carried out at a lower temperature than solutionizing, but enhances the strength of the aluminum alloy. Etching makes the grain boundaries of the aluminum alloy more prominent, making the grains of the aluminum alloy visible to the naked human eye.

Description

Aluminum alloy with visible grains and aluminum alloy colored by double anodization

Background

The present disclosure relates generally to aluminum alloys, and in particular to aluminum alloys having visible grains and aluminum alloys colored by double anodization (double anodization).

Aluminum alloys are widely used. However, most of the metallurgical characteristics of currently available aluminum alloys are not visible to the human eye. For example, the grain boundaries (grain boundaries) of currently available aluminum alloys are microscopic in size, and they cannot be seen or analyzed without optical magnification. Furthermore, the currently available aluminium alloys themselves have hardly any decorative appearance (cosmetic appearance), which limits their use in products.

SUMMARY

Embodiments relate to processing aluminum alloys to make grain boundaries visible to the human eye. The iron concentration in the aluminum alloy is reduced to obtain an iron concentration below a threshold value. The aluminum alloy is then heated at a first temperature for a period of time to cause recrystallization of the aluminum. Aging the aluminum alloy at a second temperature for another period of time to enhance the strength of the aluminum alloy. The second temperature is lower than the first temperature.

In one or more embodiments, the aluminum alloy is grown to an average grain size (average grain size) of at least 100 μm.

In one or more embodiments, the growth of the average grain size occurs during a solutionizing process.

In one or more embodiments, the solutionizing temperature is greater than 480 ℃.

In one or more embodiments, the aging is performed at a temperature lower than the temperature at which the solutionizing process is performed.

In one or more embodiments, the iron concentration is reduced during the casting process.

In one or more embodiments, the method can include reducing one or more of zirconium, scandium, titanium, and carbides.

In one or more embodiments, making the grain boundaries visible includes etching the grain boundaries of the aluminum alloy.

In one or more embodiments, the etching uses a material selected from the group consisting of caustic soda (NaOH), hydrofluoric acid (HF), and ferric chloride (FeCl)₃) Or one of the group of any combination thereof.

In one or more embodiments, making the grain boundaries visible includes precipitating an anodic phase (anodic phase) on the grain boundaries.

In one or more embodiments, the method can include:

casting aluminum alloys using a direct chill casting process; and

the cast aluminum alloy is extruded into a predetermined shape.

In one or more embodiments, a method for anodizing (anodizing) an aluminum alloy can comprise:

etching the grain boundaries of the aluminum alloy;

anodizing the aluminum alloy to have a first color, wherein the anodizing coats the grain boundaries and grains of the aluminum alloy with an anodic oxide layer (anodic oxide layer) of the first color;

removing the anodic oxide layer of the first color from the grains of the aluminum alloy; and

anodizing the aluminum alloy to have the second color, wherein the anodizing coats the grains of the aluminum alloy with an anodic oxide layer of the second color.

In one or more embodiments, the method may include sandblasting (sanding) after etching the grain boundaries.

In one or more embodiments, the removal of the anodic oxide layer is performed by lapping.

In one or more embodiments, the aluminum alloy may be produced by a process that may include:

reducing the iron concentration in the aluminum alloy to obtain an iron concentration below a threshold;

heating an aluminum alloy at a first temperature for a first period of time, wherein the heating causes recrystallization of the aluminum;

aging the aluminum alloy at a second temperature for a second period of time, the second temperature being lower than the first temperature, wherein the aging enhances the strength of the aluminum alloy; and

the grain boundaries of the aluminum alloy are visible to the human eye.

In one or more embodiments, the aluminum alloy may include:

the average grain size of the aluminum alloy is grown to at least 100 μm.

In one or more embodiments, the growth of the average grain size occurs during the solutionizing process.

In one or more embodiments, the aluminum alloy may be anodized by a process comprising:

etching the grain boundaries of the aluminum alloy;

anodizing the aluminum alloy to have a first color, wherein the anodizing coats the grain boundaries and grains of the aluminum alloy with an anodic oxide layer of the first color;

Embodiments are also directed to anodizing aluminum alloys. The grain boundaries of the aluminum alloy are etched. The aluminum alloy is then etched to have a first color. The anodization coats the grain boundaries and grains of the aluminum alloy with an anodic oxide layer of a first color. The anodic oxide layer of the first color is removed from the grains of the aluminum alloy. The aluminum alloy anode is oxidized to have a second color. The anodizing coats the grains of the aluminum alloy with an anodized oxide layer of a second color.

Embodiments according to the invention are disclosed in particular in the appended claims relating to a method for processing an aluminium alloy, a method for anodizing an aluminium alloy, a process for processing an aluminium alloy and a process for anodizing an aluminium alloy, wherein any feature mentioned in one claim category, such as the method, may also be claimed in another claim category, such as the process, the aluminium alloy, the system, the storage medium and the computer program product. The dependencies or back-references in the appended claims are chosen for formal reasons only. However, any subject matter resulting from an intentional back-reference (especially multiple references) to any preceding claim may also be claimed, such that any combination of a claim and its features is disclosed and may be claimed, irrespective of the dependencies chosen in the appended claims. The subject matter which can be claimed comprises not only the combination of features as set forth in the appended claims, but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any embodiments and features described or depicted herein may be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or in any combination with any feature of the appended claims.

Brief Description of Drawings

Fig. 1 is a diagram illustrating a process for producing an aluminum alloy having visible grains by heat treatment according to an embodiment.

Fig. 2 graphically illustrates the effect of iron concentration on average grain size of a solutionized aluminum alloy (solutionized aluminum alloy), according to an embodiment.

FIG. 3 graphically illustrates the effect of solutionizing temperature on the average grain size of a solutionized aluminum alloy, according to an embodiment.

Fig. 4A and 4B illustrate etched grain boundaries of an aluminum alloy according to an embodiment.

Fig. 5 illustrates differences in appearance between aluminum alloys etched by three different types of etchants according to an embodiment.

Fig. 6 graphically illustrates the effect of etch time on the groove depth of grain boundaries, according to an embodiment.

Fig. 7 illustrates precipitation of an anode phase on a grain boundary of an aluminum alloy, according to an embodiment.

Fig. 8 is a flow chart illustrating a process of double anodization of an aluminum alloy sample according to an embodiment.

Fig. 9 is a diagram illustrating double anodization of an aluminum alloy according to an embodiment.

Fig. 10 is an image of an aluminum alloy colored by double anodization according to an embodiment.

The figures depict embodiments of the present disclosure for purposes of illustration only.

Detailed Description

Embodiments are also directed to an aluminum alloy colored by dual anodization. The grain boundaries of the aluminum alloy are etched such that there are grooves at the grain boundaries. The double anodization includes a first anodization and a second anodization. The first anodization produces a first anodized layer that coats (coating) the grain boundaries and grains. The first anodized layer is then removed from the grains, but remains in the grooves. The second anodization produces a second anodized layer that covers the grains but does not cover the grain boundaries because the grain boundaries are still covered by the first anodized layer. The first anodized layer and the second anodized layer have different colors, and thus the grain boundaries are distinguished from the grains.

Visible crystal grain

Fig. 1 is a diagram illustrating a process 100 for producing an aluminum alloy with visible grains by heat treatment according to an embodiment. The process 110 includes casting 110, extruding 120, solutionizing 130, aging 140, and etching 150. In some embodiments, process 100 may include different or additional steps than those described below in connection with fig. 1. For example, the process 100 may also include polishing prior to etching 150. Additionally, the steps of process 100 may be performed in a different order than the order described in connection with fig. 1.

The casting 110 solidifies the liquid aluminum alloy in the mold. In some embodiments, the casting 110 is direct chill casting, which produces a solid ingot of aluminum alloy that is cylindrical or rectangular. The cooling process of direct chill casting involves two cooling cycles of the aluminum alloy. The first cooling cycle is by thermal expansion through the mold and the second cooling cycle is by applying a coolant (e.g., water) on the ingot. The second cooling cycle accounts for most of the cooling process.

During casting 110, the iron (Fe) concentration in the aluminum alloy is reduced. Iron is a grain inhibitor, meaning that it inhibits grain growth. Thus, high concentrations of iron may result in small grain sizes. FIG. 2 graphically illustrates the effect of iron concentration on average grain size of a solutionized aluminum alloy, according to an embodiment. Fig. 2 includes two

images

210 and 220 showing grains of solutionized aluminum alloys having different iron concentrations. Image 210 shows grains of a solutionized aluminum alloy having an iron concentration of about 0.2 wt.%, and image 210 shows grains of a solutionized aluminum alloy having an iron concentration of about 0.05 wt.%.

The grains in image 220 have a larger average grain size than the grains in image 210. The average grain size in image 210 is about 20 μm, while the average grain size in image 220 is about 60 to 80 μm. Thus, fig. 2 graphically illustrates that the average grain size of a solutionized aluminum alloy increases with decreasing iron concentration.

In some embodiments, the iron concentration in the aluminum alloy is reduced to less than 0.12 wt.%. For example, the iron concentration in the aluminum alloy after casting 110 is about 0.01 wt.% or 0.03 wt.%. Iron may be removed from the aluminum alloy by a variety of methods including reducing the amount of recovered aluminum carrying a significant amount of iron, adding a filter procedure (filter) to the aluminum alloy during casting 110 to remove phases containing iron, cleaning the furnace/mold made of iron-based materials to reduce iron contamination, melting aluminum in graphite-based or molybdenum-based crucibles to reduce iron contamination, adding alloying elements that react with iron during casting 110, other similar methods of removing iron, or any combination thereof. Other suitable methods for removing iron from aluminum alloys may be used. For example, iron is removed from aluminum alloys by precipitating and separating intermetallic phases (e.g., iron-rich phases) from the liquid aluminum alloy. This separation can be performed by several techniques, such as filtration, centrifugation, and electromagnetic separation, or any combination thereof. As another example, iron may be removed by electroslag refining (ESR). In addition to iron, other types of grain inhibitors, such as zirconium, scandium, titanium, carbides, etc., may also be removed from the aluminum alloy.

Returning to FIG. 1, extrusion 120 forces the solid aluminum alloy through a die (die) to form a predetermined shape, such as a predetermined cross-section. In some embodiments, the extrusion 120 forms the final shape of the aluminum alloy. Optionally, the extrusion 120 forms an intermediate shape of the aluminum alloy, and the aluminum alloy is reformed after the process 100. In some embodiments, process 100 includes different steps to form the aluminum alloy into a predetermined shape in addition to extrusion 120 or in place of extrusion 120. For example, examples of different steps include three-dimensional printing, stamping, cold rolling, cold forging, or any combination thereof. In some embodiments, such as in the case of large scale manufacturing, the aluminum alloy is preheated prior to solutionizing 130. For example, the aluminum alloy may be preheated at about 400 ℃.

Solutionizing 130 is a thermal treatment process that results in grain growth. In some embodiments, solutionizing 130 is performed at a temperature that is at least as high as the recrystallization temperature of the aluminum alloy (i.e., the solutionizing temperature). Therefore, the solutionizing 130 is accompanied by recrystallization. Recrystallization is a process in which the original grains are replaced by a new set of grains, and the new grains grow until the original grains have been completely consumed. Further, because iron and other types of grain inhibitors are reduced from the aluminum alloy during casting 110, new grains of the aluminum alloy may grow to a larger size than aluminum alloys having higher concentrations of iron or other types of grain inhibitors. Thus, after solutionizing 130, the average grain size of the aluminum alloy increases.

In some embodiments, grain growth of the aluminum alloy occurs in a different heat treatment process than solutionizing 130. For example, grain growth of aluminum alloys (e.g., AA5XXX alloys, AA3XXX alloys, and AA1XXX alloys) occurs during annealing processes that result in recrystallization. The annealing treatment may be a full anneal or a partial anneal. As another example, grain growth may occur during preheating prior to a process such as hot stamping or hot forging.

In some embodiments, the average grain size after solutionizing 130 is greater than 100 μm, such that new grains are visible to the naked human eye. In one embodiment, the average grain size may fall in the millimeter range, e.g., 1-2 mm. The average grain size is at least partially dependent on the solutionizing temperature. Different solutionizing temperatures can result in different grain sizes. FIG. 3 graphically illustrates the effect of solutionizing temperature on the average grain size of a solutionized aluminum alloy, according to an embodiment. Fig. 3 includes 6 images 310 through 360 showing grains of an aluminum alloy solutionized at three different temperatures: 500 ℃, 530 ℃ and 545 ℃. In some embodiments, the duration of solutionizing is two hours. Alternatively, the solutionizing duration may be shorter or longer. Each temperature corresponds to two images: one image shows coarse grains on the surface of the solutionized aluminum alloy, i.e., Peripheral Coarse Grains (PCG), and the other image shows grains in a cross section of the solutionized aluminum alloy, i.e., cross-sectional grains.

As shown by image 310, the PCG and cross-sectional grains of the aluminum alloy solutionized at 500 ℃ have different grain sizes. The grain size of the PCG was about 200. mu.m. But the cross-sectional grain as shown in image 340 is significantly larger than the PCG. As shown by image 330, the PCG grain size of the aluminum alloy solutionized at higher temperatures is larger compared to image 310. In addition, for aluminum alloys that solutionize at higher temperatures, the difference between PCG and cross-sectional grain is smaller. The grain size in image 320 is similar to the grain size in image 350. The difference between the grain sizes in image 330 and image 360 is not significant. In some embodiments, 545 ℃ is selected as the solutionizing temperature of the aluminum alloy because it corresponds to larger grains and a uniform distribution of grain sizes. A solutionizing temperature above 545 ℃ may be selected for producing even larger grains. However, because larger grains result in lower strength, in some other embodiments, a solutionizing temperature of less than 545 ℃ may be selected in view of strength. In some embodiments, the PCG layer is removed via machining to achieve a consistent grain structure.

In one embodiment, the solutionizing temperature is greater than 480 ℃. For example, for a 6000 series aluminum alloy, solutionizing 130 may be performed at 530 ℃ for 1 hour. Increased grain size can result in lower aluminum alloy strength. The lower strength may be improved by aging 140.

Returning to FIG. 1, aging 140 is another heat treatment process that increases the strength of the solutionized aluminum alloy. For example, aging 140 allows alloying elements (e.g., Fe, Mg, Si, etc.) in the aluminum alloy to diffuse through the microstructure and form intermetallic particles. The intermetallic particles formed act as a reinforcing phase and thereby increase the strength of the solutionized aluminum alloy. The aging temperature is lower than the solutionizing temperature. The duration of aging 140 may be longer than the duration of solutionizing 130. In some embodiments, aging 140 of the 6000 series aluminum alloy is performed at about 180 ℃ for about 6 hours. In other embodiments, the temperature and duration of aging 140 may be different.

In some embodiments, the aged aluminum alloy is subjected to a hardness test to determine whether the aluminum alloy has sufficient strength. Further, the grain size of the surface coarse grains (i.e., the peripheral coarse grains) can be measured for estimating the strength of the aluminum alloy. If the tests indicate that the strength of the aluminum alloy is lower than the required strength or the preferred strength, the aluminum alloy is subjected to one or more additional aging processes to improve the strength. In some embodiments, after aging 140, the aluminum alloy is machined and/or polished for obtaining a smooth surface, such as a mirror-like finish (mirror-like finish), to facilitate etching 150.

The etch 150 enhances the contrast between the grain boundaries and the grains by creating grooves at the grain boundaries such that the grain boundaries are distinct from the grains. For example, the etchant is applied to the aged aluminum alloy for a predetermined amount of time (i.e., an etch time). Atoms located on the grain boundaries dissolve in the etchant, resulting in grooves. The grain boundaries look like black lines and the grains become more visible.

Fig. 4A illustrates etched grain boundaries of an aluminum alloy according to an embodiment, and fig. 4B is a height map 450 of an aluminum alloy according to an embodiment. Fig. 4A includes two

graphs

400 and 430. Graph 400 in fig. 4A includes a plurality of grains 410, and each grain is surrounded by a plurality of grain boundaries 420. Grain boundaries 420 in image 400 are darker than grains 410. By enlarging a portion of image 400, diagram 430 shows a groove 440 of grain boundary 420. In one embodiment, the grooves have a depth of about 10-50 μm. In alternative embodiments, the grooves may have different depths. Image 450 shows the decorative appearance of the aluminum alloy. Height map 450 shows the height of grains 410 and grain boundaries 420. For most aluminum alloys, grain boundaries 420 are at least about 10 μm lower than grains 410. The difference in height enhances the differentiation of grain boundaries 420 from grains 410.

Different etchants or different etching times can result in grooves having different depths or different surface finishes, resulting in different appearances of the aged aluminum alloy. In some embodiments, the etchant is selected from the group consisting of caustic soda (NaOH), hydrofluoric acid (HF), and ferric chloride (FeCl)₃) Or any combination thereof. Other types of etchants may also be used for etching 150. Fig. 5 illustrates differences in appearance between aluminum alloys etched by three different types of etchants according to an embodiment. Image 510 corresponds to NaOH and image 520 corresponds to FeCl₃And image 530 corresponds to HF. The three images show the advantages and disadvantages of three types of etchants. NaOH gives an improved appearance overall. However, in some cases, significant pitting (pitting) is observed after etching at high concentrations or longer time intervals. The pitting may be hidden or removed by sandblasting or polishing. Using FeC1₃Etching produces a distinctive grain color, but also produces excessive pitting that leads to spalling and etches the grain line direction. No pitting was observed in image 530. Furthermore, etching by HF produces a surface with a good appearance.

Different appearances can also be produced by varying the etching time. Turning now to fig. 6, fig. 6 illustrates the effect of etch time on the groove depth of grain boundaries, according to an embodiment. Fig. 6 includes three

images

610, 620, and 630 showing grain boundaries of an aluminum alloy that was etched for three different etching times. The aluminum alloys of the three images were etched with the same type of etchant (e.g., NaOH) having the same solution concentration (e.g., 40 g/L). Image 610 corresponds to an etch time of 5 minutes, while image 620 corresponds to an etch time of 10 minutes, and image 630 corresponds to an etch time of 20 minutes. As shown in fig. 6, grain boundaries in image 630 are more visible than grain boundaries in image 620, and grain boundaries in image 620 are more visible than grain boundaries in image 610. In other words, longer etch times make grain boundaries more visible in the aluminum alloy. Therefore, different grain boundary differences can be produced by changing the etching time, and an appropriate etching time can be determined based on the requirement of the grain boundary difference (or the requirement of the groove depth).

Instead of etching 150, the grain boundaries may be highlighted by precipitating an anode phase on the grain boundaries. In some embodiments, the grain boundaries are cathodic and the grains are anodic. Precipitation of the cathode phase in the grain boundaries and subsequent exposure to a corrosive environment (e.g., 3.5 wt% NaCl solution) can result in preferential corrosion of the grains and result in grain boundaries higher than the grains. The time of exposure to the corrosive environment and the corrosivity of the corrosive environment may be adjusted to achieve the desired height differential. Taking the Al-Cu-Li system as an example, the cathode phase deposited at the grain boundaries may be a non-Li-containing phase. Therefore, the crystal grains have more Li. Li is highly reactive and can make the grains more anodic. In some other embodiments, the grain boundaries are anodic and the grains are cathodic, resulting in grains above the grain boundaries.

Fig. 7 illustrates precipitation of an anode phase on a grain boundary 720 of an aluminum alloy, according to an embodiment. In some embodiments, a salt solution is used to anodize the grain boundaries 710. Grains 710 serve as the cathode, while grain boundaries 720 serve as the anode. The anodic oxidation causes the anodic grain boundaries to grow and have a different height from the cathodic grains 710, and thus causes a difference in texture (texture) between the grains 710 and the grain boundaries 720. Thus, grain boundaries 720 are distinct from grains 710.

The etched aluminum alloy may be further processed. For example, etched aluminum alloys can be colored by double anodization, which coats one color anode layer over the grains and coats another anode layer of a different color over the grain boundaries. More details regarding the dual anodization are provided below in connection with fig. 8-10.

Double anodic oxidation

Fig. 8 is a flow diagram illustrating a process 800 for dual anodization of an aluminum alloy sample, according to an embodiment. Process 800 produces different colors for the grains and grain boundaries of the aluminum alloy samples, such that the grain boundaries are distinct from the grains. Process 800 includes grinding 810, etching 820, first anodization 830, removing anodization 840, and second anodization 850. In some embodiments, process 800 may include different or additional steps than those described below in connection with fig. 8. For example, alternatively or additionally, step 810 includes polishing. Further, the steps of process 800 may be performed in a different order than described in connection with fig. 8.

The grinding 810 produces a smooth surface of the aluminum alloy sample. The etch 820 may be similar to the etch 160 described in connection with fig. 1. The etching removes 10-50 μm between the grains, i.e. creates a 10-50 μm deep groove at the grain boundaries. In some embodiments, the depth of the grooves may be different. The grains of the aluminum alloy sample may be visible to the unaided human eye. For example, the grains have an average grain size of at least 100 μm. Alternatively, the grains of the aluminum alloy sample are smaller and may not be visible to the human eye. In some embodiments, process 800 includes sandblasting after etching 820. The grit blasting smoothes the surface of the etched aluminum alloy samples.

The first anodization 830 coats the aluminum alloy sample (both grains and grain boundaries) with a first anodization layer. The first anodized layer has a first color. Thus, both the grains and the grain boundaries have the first color. In some embodiments, the first anodized layer is an anodized layer.

The first anodized layer is removed 840, such as by grinding. For example, a layer having a depth of 10-50 μm is removed. After removal 840, the first anodized layer covering the grains is removed. But the grain boundaries are still coated with the first anodized layer due to the grooves at the grain boundaries.

The second anodization 850 coats the grains of the aluminum alloy sample with another anodization layer, such as another anodization layer. The further anodic oxide layer has a second color. The second color may be different from the first color. Since the grain boundaries are coated with the first anodized layer, the grain boundaries are not coated with the second anodized layer by the second anodization 850. Thus, the grains are coated with the second color, while the grain boundaries are coated with the first color. The color difference enhances the contrast between the grains and the grain boundaries.

The steps in process 100 and process 800 may be combined, reordered, or selected to produce a predetermined decorative appearance of the aluminum alloy article. Furthermore, different parts of the aluminium alloy piece may be differently machined for creating a unique decorative appearance between these parts. For example, a predetermined pattern may be made on the aluminum alloy member.

Fig. 9 is a diagram illustrating double anodization of an aluminum alloy according to an embodiment. In the embodiment shown in fig. 9,

graphs

900, 950, and 960 each have three grains 910 and four grain boundaries 920. In other embodiments, however, the aluminum alloy samples include different numbers of grains or grain boundaries. Graph 900 illustrates an aluminum alloy sample after first anodization 830. As shown in diagram 900, there are recesses 930 at the grain boundaries 920. The recess 930 and the die 910 are covered by a first anodized layer 940. Fig. 950 shows an aluminum alloy sample after the first anodized layer 940 is removed 840. As shown in fig. 950, the first anodized layer 940 covering the grains 910 is removed. However, some of the first anodized layer 940 covering the recesses 930 is retained in the recesses 930.

Fig. 950 shows an aluminum alloy sample after the second anodization 850. Die 910 is coated with a second anodized layer 970, which may be, for example, an anodized layer. But there is no second anodization layer 970 on top of the recess 930 because the recess 930 is coated with the first anodization layer 940 prior to the second anodization 850. Thus, grains 910 and grain boundaries 920 are coated with two different anodized layers. In embodiments where first anodized layer 940 has a different color than second anodized layer 970, grain boundaries 920 are distinct from grains 910.

Fig. 10 is an image of an aluminum alloy colored by double anodization according to an embodiment. The grain boundaries of the aluminum alloy are pink, while the grains are dark blue. In one embodiment, the grains have an average grain size of at least 100 μm. The grain boundaries and/or grains may have different colors. In addition, a portion of the aluminum alloy may have one color and a different portion of the aluminum alloy may have another color, for example, for creating a pattern on the aluminum alloy.

The language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the patent rights be limited not by this detailed description, but rather by any claims issued from this application. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the patent, which is set forth in the following claims.

Claims

1. A method for processing an aluminum alloy, the method comprising:

heating the aluminum alloy at a first temperature for a first period of time, wherein the heating results in recrystallization of the aluminum;

the grain boundaries of the aluminum alloy are made visible to the human eye.

2. The method of claim 1, further comprising:

growing the average grain size of the aluminum alloy to at least 100 μm.

3. The method of claim 2, wherein the growth of the average grain size occurs during a solutionizing process.

4. A process as claimed in claim 3, wherein the solutionisation temperature is higher than 480 ℃.

5. The method of claim 3, wherein the aging is performed at a temperature lower than the temperature at which the solutionizing process is performed.

6. The method of claim 1, wherein the iron concentration is reduced during a casting process.

7. The method of claim 1, further comprising reducing one or more of zirconium, scandium, titanium, and carbides.

8. The method of claim 1, wherein making the grain boundaries visible comprises etching the grain boundaries of the aluminum alloy.

9. The method of claim 9, wherein the etching uses a material selected from the group consisting of caustic soda (NaOH), hydrofluoric acid (HF), and ferric chloride (FeCl)₃) Or one of the group of any combination thereof.

10. The method of claim 1, wherein said making the grain boundaries visible comprises precipitating an anode phase on the grain boundaries.

11. The method of claim 1, further comprising:

casting the aluminum alloy using a direct chill casting process; and

the cast aluminum alloy is extruded into a predetermined shape.

12. A method for anodizing an aluminum alloy, the method comprising:

etching the grain boundaries of the aluminum alloy;

anodizing the aluminum alloy to have a first color, wherein the anodizing coats the grain boundaries and grains of the aluminum alloy with an anodized oxide layer of the first color;

anodizing the aluminum alloy to have a second color, wherein the anodizing coats the grains of the aluminum alloy with an anodic oxide layer of the second color.

13. The method of claim 12, further comprising sandblasting after etching the grain boundaries.

14. The method of claim 12, wherein said removing of said anodic oxide layer is performed by grinding.

15. An aluminum alloy produced by a process comprising:

the grain boundaries of the aluminum alloy are made visible to the human eye.

16. The aluminum alloy of claim 15, further comprising:

growing the average grain size of the aluminum alloy to at least 100 μm.

17. The aluminum alloy of claim 16, wherein the growth of the average grain size occurs during a solutionizing process.

18. The aluminum alloy of claim 17, wherein the solutionizing temperature is greater than 480 ℃.

19. The aluminum alloy of claim 15, wherein the aging is performed at a temperature lower than a temperature at which the solutionizing process is performed.

20. An aluminum alloy anodized by a process comprising:

etching the grain boundaries of the aluminum alloy;

21. A method for processing an aluminum alloy, the method comprising:

the grain boundaries of the aluminum alloy are made visible to the human eye.

22. The method of claim 21, further comprising:

growing the average grain size of the aluminum alloy to at least 100 μm.

23. The method of claim 22, wherein said growth of said average grain size occurs during a solutionizing process;

optionally, wherein the solutionizing temperature is greater than 480 ℃; and/or

Optionally, wherein the aging is performed at a temperature lower than the temperature at which the solutionizing process is performed.

24. The method of any one of claims 21 to 23, wherein the iron concentration is reduced during a casting process.

25. The method of any one of claims 21 to 24, further comprising reducing one or more of zirconium, scandium, titanium, and carbides.

26. The method of any of claims 21-25, wherein making the grain boundaries visible comprises etching the grain boundaries of the aluminum alloy;

optionally, wherein the etching uses a material selected from the group consisting of caustic soda (NaOH), hydrofluoric acid (HF), and ferric chloride (FeCl)₃) Or one of the group of any combination thereof.

27. The method of any of claims 21-26, wherein the making the grain boundaries visible comprises precipitating an anode phase on the grain boundaries.

28. The method of any of claims 21 to 27, further comprising:

casting the aluminum alloy using a direct chill casting process; and

the cast aluminum alloy is extruded into a predetermined shape.

29. A method for anodizing an aluminum alloy, in particular an aluminum alloy processed according to the method of any one of claims 20 to 28, comprising:

etching the grain boundaries of the aluminum alloy;

30. The method of claim 29, further comprising sandblasting after etching the grain boundaries.

31. The method of claim 29 or 30, wherein the removing of the anodic oxide layer is performed by grinding.

32. An aluminum alloy produced by a process comprising:

the grain boundaries of the aluminum alloy are made visible to the human eye.

33. The aluminum alloy of claim 32, further comprising:

growing the average grain size of the aluminum alloy to at least 100 μm;

optionally, wherein said growth of said average grain size occurs during a solutionizing process;

optionally, wherein the solutionizing temperature is greater than 480 ℃.

34. The aluminum alloy of claim 32 or 33, wherein the aging is performed at a temperature lower than a temperature at which the solutionizing process is performed.

35. An aluminium alloy, in particular an aluminium alloy produced by the process according to any one of claims 32 to 34, anodised by a process comprising:

etching the grain boundaries of the aluminum alloy;