Aluminum alloy components

Abstract

To provide an aluminum alloy member having high strength and capable of maintaining a wood grain pattern for a long time.SOLUTION: An aluminum alloy member 1 contains Zn: not less than 5.0 mass% and not more than 8.5 mass%, Mg: not less than 1.0 mass% and not more than 3.0 mass%, Cu: not less than 0.10 mass% and not more than 3.0 mass%, Fe: not less than 0.10 mass% and not more than 0.60 mass%, Si: not less than 0.10 mass% and not more than 0.70 mass%, and Ti: not less than 0.001 mass% and not more than 0.10 mass%, and further contains at least one elements selected from Zr: not less than 0.10 mass% and not more than 0.40 mass% and Cr: not less than 0.10 mass% and not more than 0.40 mass%, with the balance being Al and chemical components composed of inevitable impurities. The metal structure of the aluminum alloy member 1 is composed of a fibrous structure. The aluminum alloy member 1 comprises a dyed alumite film 3 on its surface, and the dyed alumite film 3 shows a stripe pattern.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy member. [Background technology]

[0002] 7000 series aluminum alloys have high strength among aluminum alloys and are therefore used in a variety of applications, such as parts for transportation equipment such as aircraft and vehicles, machine parts, and sporting goods.

[0003] On the other hand, parts used in areas that are visible to consumers, such as building materials, exterior materials for vehicles, and housings for electrical appliances, are sometimes required to have design properties in addition to strength. For example, when trying to impart a wood-grain pattern to a metal part, a method of attaching a decorative sheet printed with a wood-grain pattern to the part (e.g., Patent Document 1) or a method of cutting the surface of the part to form a wood-grain groove pattern and then painting the part (e.g., Patent Document 2) is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-80703 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-338153 Summary of the Invention [Problem to be solved by the invention]

[0005] When a pattern is applied to the surface of a part using a decorative sheet or paint, the film carrying the pattern is exposed on the surface of the part. However, the decorative sheet or paint film may peel off from the surface of the part for various reasons, such as deterioration during use, which may impair the design of the part.

[0006] The present invention has been made in view of the above background, and aims to provide an aluminum alloy member that has high strength and can maintain a wood grain pattern for a long period of time. [Means for solving the problem]

[0007] One aspect of the present invention is a composition comprising Zn (zinc): 5.0% by mass to 8.5% by mass, Mg (magnesium): 1.0% by mass to 3.0% by mass, Cu (copper): 0.10% by mass to 3.0% by mass, Fe (iron): 0.10% by mass to 0.60% by mass, Si (silicon): 0.10% by mass to 0.70% by mass, and Ti (titanium): 0.001% by mass to 0.10% by mass, and further comprising at least one element selected from Zr (zirconium): 0.10% by mass to 0.40% by mass and Cr (chromium): 0.10% by mass to 0.40% by mass, with the balance being Al (aluminum) and unavoidable impurities; The metal structure is a fibrous structure, The surface has a dyed anodized aluminum coating, The dyed anodized aluminum coating has a streaky pattern on the aluminum alloy member. [Effects of the Invention]

[0008] The aluminum alloy member has high strength because it has the specific chemical components and a metal structure consisting of a fibrous structure.

[0009] Furthermore, by forming an anodized aluminum coating on the surface of an aluminum alloy having the specific chemical composition and metallographic structure, the metallic luster of the aluminum alloy can be reduced. Furthermore, the anodized aluminum coating formed on the surface of an aluminum alloy having the specific chemical composition and metallographic structure has regions with different color tones, and these regions are arranged in a streaky pattern. Therefore, by dyeing such an anodized aluminum coating, a dyed anodized aluminum coating with less metallic luster and a streaky pattern can be formed, and a woodgrain pattern can be imparted to the surface of the aluminum alloy part.

[0010] Since dyed anodized aluminum coatings are primarily composed of aluminum oxide, they are highly durable. Furthermore, dyed anodized aluminum coatings have excellent adhesion to the aluminum alloy substrate, making them less likely to peel off from the substrate. Therefore, the aluminum alloy member can maintain its woodgrain pattern for a long period of time.

[0011] As described above, according to the above-described embodiment, an aluminum alloy member capable of maintaining a wood grain pattern for a long period of time can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a partial cross-sectional view showing a main part of an aluminum alloy member according to an embodiment of the present invention. [Figure 2] FIG. 2 is an example of a metallurgical microscope image of the dyed anodized aluminum coating in the example. [Figure 3] FIG. 3 is an explanatory diagram showing an example of the spatial frequency spectrum of the streak pattern of the dyed anodized aluminum coating in the example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The aluminum alloy member has a substrate having the specific chemical composition and metallographic structure, and a dyed anodized aluminum coating formed on the substrate. First, the chemical composition and metallographic structure of the substrate in the aluminum alloy member and the reasons for limiting these will be described.

[0014] Zn (zinc): 5.0% by mass or more and 8.5% by mass or less The aluminum alloy member contains 5.0% by mass or more and 8.5% by mass or less of Zn as an essential component. Zn exists in the aluminum alloy member as an η' phase together with Mg, and has the effect of improving the strength of the aluminum alloy member by precipitation strengthening.

[0015] By setting the Zn content in the aluminum alloy member to 5.0% by mass or more, the strength of the aluminum alloy member can be increased. If the Zn content is less than 5.0% by mass, the amount of η' phase formed in the aluminum alloy member will be small, which may lead to a decrease in the strength of the aluminum alloy member.

[0016] On the other hand, if the Zn content exceeds 8.5 mass %, there is a risk that the hot workability in the manufacturing process of the aluminum alloy member will be reduced.

[0017] Mg (Magnesium): 1.0% by mass or more and 3.0% by mass or less The aluminum alloy member contains 1.0 mass % or more and 3.0 mass % or less of Mg as an essential component. Mg exists in the aluminum alloy member together with Zn as an η' phase, and has the effect of improving the strength of the aluminum alloy member by precipitation strengthening.

[0018] Furthermore, Mg has the effect of promoting the precipitation of intermetallic compounds in aluminum alloys. Since intermetallic compounds are preferentially etched in the pretreatment for anodizing, it is presumed that fine irregularities resulting from the intermetallic compounds are formed on the surface of the aluminum alloy after etching. It is presumed that by subjecting such aluminum alloys to anodizing, it is possible to reduce the metallic luster of the surface of an aluminum alloy member on which an anodized coating is formed.

[0019] By setting the Mg content in the aluminum alloy member to 1.0 mass% or more, the strength of the aluminum alloy member can be increased and the metallic luster of the surface of the aluminum alloy member can be reduced. If the Mg content is less than 1.0 mass%, the amount of η' phase formed in the aluminum alloy member will be reduced. In addition, in this case, it may be difficult to reduce the metallic luster of the surface of the aluminum alloy member.

[0020] On the other hand, if the Mg content exceeds 3.0 mass %, there is a risk that the hot workability in the manufacturing process of the aluminum alloy member will be reduced.

[0021] ·Cu (copper): 0.10 mass% or more and 3.0 mass% or less The aluminum alloy member contains 0.10 mass % or more and 3.0 mass % or less of Cu as an essential component. Cu has the effect of improving the strength of the aluminum alloy member through solid solution strengthening. Cu also has the effect of imparting a yellowish tint to the color tone of an anodized aluminum coating formed by anodizing.

[0022] By setting the Cu content in the aluminum alloy member to 0.10% by mass or more, the strength of the aluminum alloy member can be improved. Furthermore, by setting the Cu content to 0.10% by mass or more, the color tone of the anodized aluminum coating formed on the surface of the aluminum alloy member can be imparted with a yellowish tinge, and the texture of the aluminum alloy member can be made to more closely resemble the texture of wood. If the Cu content is less than 0.10% by mass, the strength of the aluminum alloy member may be reduced.

[0023] On the other hand, if the Cu content exceeds 3.0 mass %, there is a risk that the hot workability in the manufacturing process of the aluminum alloy member will be reduced.

[0024] Fe (iron): 0.10% by mass or more and 0.60% by mass or less and Si (silicon): 0.10% by mass or more and 0.70% by mass or less The aluminum alloy member contains, as essential components, 0.10% by mass to 0.60% by mass of Fe and 0.10% by mass to 0.70% by mass of Si. Fe and Si have the effects of suppressing recrystallization during the manufacturing process of the aluminum alloy member and promoting the formation of a fibrous structure. Furthermore, Fe and Si have the effect of reducing the surface gloss of the aluminum alloy member after anodizing treatment.

[0025] By setting the Fe content and Si content in the aluminum alloy member within the above-mentioned specific ranges, the gloss of the surface of the aluminum alloy member can be appropriately reduced, and a pattern closer to a wood grain pattern can be imparted. If at least one of the Fe content and the Si content is less than 0.10 mass%, the metallic gloss of the surface of the aluminum alloy member after anodizing treatment may be excessively strong, making it difficult to obtain an aluminum alloy member with the desired texture.

[0026] On the other hand, if the Fe content exceeds 0.60 mass % or the Si content exceeds 0.70 mass %, coarse intermetallic compounds are likely to be formed in the aluminum alloy member. The presence of such coarse intermetallic compounds may cause point defects on the surface of the aluminum alloy after anodizing treatment, which may lead to deterioration of appearance characteristics.

[0027] Ti (titanium): 0.001% by mass or more and 0.10% by mass or less The aluminum alloy member contains 0.001% by mass or more and 0.10% by mass or less of Ti as an essential component. Ti has the effect of refining the crystal grains of the ingot during the manufacturing process of the aluminum alloy member. By setting the Ti content in the aluminum alloy member within the specific range, the metal structure of the aluminum alloy member before anodizing treatment can be made into a fibrous structure. Then, by anodizing treatment and dyeing the aluminum alloy member, the dyed anodized aluminum coating film can be formed on the surface of the aluminum alloy member, and a woodgrain pattern can be imparted to the surface of the aluminum alloy member.

[0028] If the Ti content in an aluminum alloy member is less than 0.001% by mass, coarse crystal grains are likely to form in the ingot during the manufacturing process of the aluminum alloy member. The formation of coarse crystal grains in the ingot makes it easier for an equiaxed structure to form in the metal structure of the aluminum alloy member before anodizing. As a result, a pattern different from woodgrain is imparted to a part of the surface of the aluminum alloy member, which may result in deterioration of appearance characteristics. On the other hand, if the Ti content exceeds 0.10% by mass, coarse Al-Ti intermetallic compounds and the like are likely to form in the aluminum alloy member. The presence of such coarse intermetallic compounds may result in point defects on the surface of the aluminum alloy after anodizing, which may result in deterioration of appearance characteristics.

[0029] Zr (zirconium): 0.10% by mass or more and 0.40% by mass or less and / or Cr (chromium): 0.10% by mass or more and 0.40% by mass or less The aluminum alloy member contains at least one element selected from the group consisting of 0.10 mass % to 0.40 mass % Zr and 0.10 mass % to 0.40 mass % Cr.

[0030] Zr forms an Al-Zr intermetallic compound in the aluminum alloy member and has the effect of suppressing recrystallization of the aluminum alloy member during the manufacturing process. By setting the Zr content in the aluminum alloy member within the above-mentioned specific range, the metal structure of the aluminum alloy member before anodizing treatment can be made into a fibrous structure. Then, by anodizing and dyeing such an aluminum alloy member, the dyed anodized aluminum coating can be formed on the surface of the aluminum alloy member, and a woodgrain pattern can be imparted to the surface of the aluminum alloy member.

[0031] If the Zr content in the aluminum alloy member is less than 0.10% by mass, the aluminum alloy member is likely to recrystallize during the manufacturing process, and an equiaxed structure is likely to form due to recrystallization in the metal structure of the aluminum alloy member before anodizing. When an aluminum alloy member having a mixture of an equiaxed structure and a fibrous structure is anodized and dyed, a pattern different from the wood grain pattern may be imparted to a portion of the surface of the aluminum alloy member, which may result in a deterioration of the appearance characteristics. On the other hand, if the Zr content exceeds 0.40% by mass, coarse intermetallic compounds and the like are likely to form in the aluminum alloy member. The presence of such coarse intermetallic compounds may result in the formation of point defects on the surface of the aluminum alloy after anodizing, which may result in a deterioration of the appearance characteristics.

[0032] Cr forms an Al-Cr intermetallic compound in the aluminum alloy member and inhibits recrystallization of the aluminum alloy member during the manufacturing process. Cr also imparts a yellowish color to the color tone of the anodized aluminum film formed by anodizing. By setting the Cr content in the aluminum alloy member within the specific range, the metal structure of the aluminum alloy member before anodizing can be made fibrous. Furthermore, by anodizing and dyeing such an aluminum alloy member, the dyed anodized aluminum film can be formed on the surface of the aluminum alloy member, and a woodgrain pattern can be imparted to the surface of the aluminum alloy member. Furthermore, because the anodized aluminum film formed on the surface of an aluminum alloy member containing Cr within the specific range has a yellowish color, the texture of the aluminum alloy member can be made more similar to that of wood.

[0033] If the Cr content in the aluminum alloy member is less than 0.10% by mass, the aluminum alloy member is likely to recrystallize during the manufacturing process, and an equiaxed structure is likely to form due to recrystallization in the metal structure of the aluminum alloy member before anodizing. When an aluminum alloy member having a mixture of an equiaxed structure and a fibrous structure is anodized and dyed, a pattern different from the wood grain pattern may be imparted to a portion of the surface of the aluminum alloy member, which may result in a deterioration of the appearance characteristics. On the other hand, if the Cr content exceeds 0.40% by mass, coarse intermetallic compounds and the like are likely to form in the aluminum alloy member. The presence of such coarse intermetallic compounds may result in the formation of point defects on the surface of the aluminum alloy after anodizing, which may result in a deterioration of the appearance characteristics.

[0034] Mn (manganese): 0.10% by mass or more and 1.0% by mass or less The aluminum alloy member may contain 0.10% by mass or more and 1.0% by mass or less of Mn as an optional component. Mn forms intermetallic compounds such as Al-Mn intermetallic compounds, Al-Mn-Fe intermetallic compounds, and Al-Mn-Fe-Si intermetallic compounds in the aluminum alloy member, and has the effect of suppressing recrystallization during the manufacturing process of the aluminum alloy member. Furthermore, like Fe and Si, Mn has the effect of reducing the surface gloss of the aluminum alloy member after anodizing treatment.

[0035] By setting the Mn content in the aluminum alloy member within the above-mentioned specific range, the pattern on the surface of the aluminum alloy member can be made to resemble a wood grain pattern more closely.

[0036] Other elements In addition to the elements described above, the aluminum alloy member contains inevitable impurities that are inevitably mixed in during the manufacturing process. The content of the elements as inevitable impurities is 0.05% by mass or less for each element, and the total content is 0.15% by mass or less.

[0037] The aluminum alloy member may contain elements other than those mentioned above, provided that the above-mentioned effects are not impaired.

[0038] ·Metal structure The aluminum alloy member has a metal structure consisting of a fibrous structure. When anodizing is performed on the surface of an aluminum alloy member having a metal structure consisting of a fibrous structure in addition to the specific chemical components, an anodized aluminum coating can be formed on the surface of the aluminum alloy member, in which regions with different color tones exist and these regions are arranged in a streaky pattern. By dyeing such an anodized aluminum coating, a dyed anodized aluminum coating with a low metallic luster and a streaky pattern can be formed. As a result, a woodgrain pattern can be imparted to the surface of the aluminum alloy member.

[0039] The reason why the above-mentioned specific anodized aluminum coating is formed when an anodizing treatment is performed on the surface of an aluminum alloy member having a metal structure consisting of a fibrous structure is thought to be, for example, as follows. Generally, when an aluminum alloy is recrystallized, the crystal orientation in the equiaxed structure formed by the recrystallization is not oriented in a specific direction, and crystal grains having various crystal orientations are arranged in a disordered manner. On the other hand, a fibrous structure has crystal grains that are elongated in the processing direction by wrought processing.

[0040] The susceptibility of crystal grains to etching varies depending on the crystal orientation, and when etching is performed, crystal faces that are easily etched are etched faster than crystal faces that are difficult to etch. As a result, etching pits are formed on the crystal faces that are easily etched. Therefore, when etching is performed on an aluminum alloy member with a fibrous structure, etching pits are formed according to the crystal orientation of the crystal grains extending in the writhing direction, resulting in streaky crystal grains with many etching pits and streaky crystal grains with few etching pits. It is believed that by anodizing and dyeing an aluminum alloy member with such a surface state, the dyeing state of the anodized aluminum coating can be changed depending on the shape of the crystal grains in the fibrous structure and the number of etching pits in each crystal grain, thereby forming an anodized aluminum coating with a streaky pattern.

[0041] The aforementioned fibrous structure refers to a structure having a large number of crystal grains that have been stretched in the processing direction by rolling, extrusion, forging, or other wrought processes. When a cross section parallel to the processing direction is observed using a metallurgical microscope at a magnification of 25 to 100 times, the fibrous structure is observed as a streaky pattern extending in the processing direction. Furthermore, the equiaxed structure refers to a structure having a large number of equiaxed crystal grains. When a cross section parallel to the processing direction is observed using a metallurgical microscope at a magnification of 25 to 100 times, the equiaxed structure is observed as a granular pattern with a relatively small difference between the major and minor axes.

[0042] The width of the crystal grains constituting the fibrous structure in the aluminum alloy member is preferably 30 μm or more. In this case, the surface pattern of the aluminum alloy member can be made to more closely resemble a wood grain pattern. The width of the crystal grains in the fibrous structure is a value calculated by the following method. First, a cross section parallel to the processing direction of the aluminum alloy member is exposed. This cross section is polished and then subjected to electrolytic etching, and then the cross section is observed using a metallurgical microscope with a magnification of 100 to 500 times. In the polarizing microscope image obtained in this way, the maximum value of the length of the crystal grains in the direction perpendicular to the processing direction is taken as the width of each crystal grain.

[0043] Dyed anodized coating The surface of the aluminum alloy member is provided with a dyed anodized aluminum coating. Specifically, the dyed anodized aluminum coating has a structure in which a dye is encapsulated in the pores of a porous anodized aluminum coating. The dye used in the dyed anodized aluminum coating is not particularly limited, and dyes having various colors, such as reddish dyes, blued dyes, greend dyes, purpled dyes, oranged dyes, brownd dyes, and yellowd dyes, can be used. Furthermore, the dyed anodized aluminum coating may contain one type of dye or two or more types of dyes.

[0044] In order to make the texture of the aluminum alloy member more similar to that of wood, the dyed anodized aluminum coating preferably contains a brown dye. Examples of brown dyes that can be used include "TAC Orange-LH," "TAC Orange-CH," "TAC Brown-GR," and "TAC Brown-RH," all manufactured by Okuno Chemical Industries Co., Ltd.

[0045] The dyed anodized aluminum coating exhibits a streaky pattern. The streaky pattern of the dyed anodized aluminum coating preferably has a characteristic that a wavelength corresponding to a spatial frequency component having a maximum amplitude is in the range of 700 μm or more and 1500 μm or less in a spatial frequency spectrum obtained by performing a Fourier transform process in a direction perpendicular to the extension direction of the aluminum alloy member on a grayscale image obtained by imaging the surface of the aluminum alloy member.

[0046] When generating the spatial frequency spectrum, any method may be used to image the aluminum alloy member as long as it can reproduce the surface pattern of the aluminum alloy member. For example, the surface of the aluminum alloy member may be imaged using a scanner or a digital camera, and the resulting color image may be converted into a grayscale image.

[0047] On the grayscale image thus obtained, a plurality of measurement areas extending in a direction perpendicular to the drawing direction of the aluminum alloy member are randomly set. The width of each measurement area may be, for example, one pixel, and the length may be set so that the length of the actual aluminum alloy member is in the range of 3 mm to 5 mm. A fast Fourier transform process is performed on each of these measurement areas in the direction perpendicular to the drawing direction of the aluminum alloy member to generate a spatial frequency spectrum for each measurement area. These spatial frequency spectra are then averaged to generate a spatial frequency spectrum of the streak pattern of the dyed anodized aluminum coating in the direction perpendicular to the drawing direction.

[0048] The distribution of gradation in the direction perpendicular to the extension direction of the aluminum alloy member in the grayscale image can be expressed as the sum of sine waves having various wavelengths. Therefore, the spatial frequency spectrum obtained by performing a fast Fourier transform on the grayscale image shows the average periodicity of gradation in the direction perpendicular to the extension direction of the aluminum alloy member in the grayscale image.

[0049] The wavelength corresponding to the spatial frequency component with the maximum amplitude in the spatial frequency spectrum is approximately equal to the period of the pattern on the surface of the aluminum alloy part. Therefore, when the wavelength corresponding to the spatial frequency component with the maximum amplitude in the spatial frequency spectrum is within the specific range, high-brightness regions and low-brightness regions are alternately arranged on the surface of the aluminum alloy part in a direction perpendicular to the extension direction of the aluminum alloy part at a period of approximately 700 μm to 1500 μm. An aluminum alloy part with such characteristics has a pattern that more closely resembles natural wood grain.

[0050] It is more preferable that the spatial frequency spectrum has a spatial frequency component with a maximum amplitude within a wavelength range of 700 μm or more and 1500 μm or less, and also has a spatial frequency component with an amplitude within a wavelength range of 300 μm or more and less than 1 time the maximum amplitude in the spatial frequency spectrum. In this case, an appropriate fluctuation is imparted to the period of the streak pattern of the dyed anodized aluminum coating in the direction perpendicular to the extension direction of the aluminum alloy member, and the pattern on the surface of the aluminum alloy member can be made to more closely resemble natural wood grain.

[0051] Furthermore, the streak pattern of the dyed anodized coating preferably has a ratio A2 / A1 of 3 or more, more preferably 4 or more, and even more preferably 5 or more, where A1 is the maximum amplitude value in a wavelength range of 700 μm or more and 1500 μm or less in a spatial frequency spectrum obtained by performing a Fourier transform process in the extension direction of the aluminum alloy member on a grayscale image obtained by imaging the surface of the aluminum alloy member, and A2 is the maximum amplitude value in a wavelength range of 700 μm or more and 1500 μm or less in a spatial frequency spectrum obtained by performing a Fourier transform process in a direction perpendicular to the extension direction of the aluminum alloy member.

[0052] In this case, the periodic color tone variation in the drawing direction at a cycle of 700 μm to 1500 μm in the pattern on the surface of the aluminum alloy part is sufficiently smaller than the periodic color tone variation in the direction perpendicular to the drawing direction at a cycle of 700 μm to 1500 μm in the pattern on the surface of the aluminum alloy part, which makes it possible to make the pattern on the surface of the aluminum alloy part more similar to natural wood grain.

[0053] The method for generating a spatial frequency spectrum in the wringing direction of an aluminum alloy member is the same as the method for generating a spatial frequency spectrum in a direction perpendicular to the wringing direction described above, except that the measurement areas are set to extend in the wringing direction and fast Fourier transform processing in the wringing direction is performed on each measurement area.

[0054] The aluminum alloy member may be produced by, for example, the following method: preparing a pre-anodized member having the chemical composition and metal structure described above; A pre-treatment including an etching treatment is performed on the surface of the pre-anodized aluminum member, Next, the pre-anodized member is subjected to an anodizing treatment to form an anodized aluminum film on the surface, The aluminum alloy member can be obtained by forming the dyed anodized aluminum film by impregnating the anodized aluminum film with a dye and then performing a sealing treatment.

[0055] The pre-anodized member used in the manufacturing method is, for example, produced by producing an ingot having the above-mentioned chemical composition, The ingot is subjected to homogenization treatment by holding it at a temperature of 400°C or higher and 600°C or lower for 2 hours or higher and 20 hours or lower, The homogenized ingot is subjected to hot extrusion to produce an extruded material. Thereafter, the extruded material is subjected to artificial aging treatment, thereby obtaining a pre-anodized member.

[0056] When producing the pre-anodized member, the method for producing the ingot is not particularly limited, and various casting methods such as DC casting and CC casting can be used.

[0057] In the homogenization treatment, the holding temperature and holding time are set within the above-mentioned specific ranges, thereby enabling the ingot to be sufficiently homogenized. The holding temperature in the homogenization treatment is preferably 450°C or higher and 580°C or lower, and more preferably 480°C or higher and 560°C or lower. The holding time in the homogenization treatment is preferably 3 hours or higher and 15 hours or lower, and more preferably 4 hours or higher and 10 hours or lower.

[0058] If the holding temperature is lower than the specific range or the holding time is shorter than the specific range, the homogenization of the ingot may be insufficient, which may result in deterioration of the appearance characteristics of the aluminum alloy structural member finally obtained. On the other hand, if the holding temperature is higher than the specific range, the aluminum alloy structural member, particularly the aluminum alloy structural member made of a 7000 series alloy, may locally melt during the homogenization treatment. Furthermore, if the holding time is longer than the specific range, it may result in deterioration of productivity.

[0059] After the homogenization treatment, the ingot is hot extruded to produce an extruded material. The larger the extrusion ratio in the hot extrusion, the more the crystals in the ingot are stretched in the direction of extension, forming a fibrous structure with elongated crystal grains. Therefore, by adjusting the extrusion ratio in the hot extrusion, the spatial frequency of the resulting streak pattern can be adjusted. The extruded material is then subjected to artificial aging treatment to produce a pre-anodized component. The extrusion conditions for the hot extrusion, and the holding time and holding temperature in the artificial aging treatment can be appropriately set depending on the chemical composition of the aluminum alloy component.

[0060] In the method for manufacturing an aluminum alloy member, the pre-anodized member obtained in this manner is subjected to a pre-treatment. The pre-treatment may include at least an etching treatment. Depending on the condition of the pre-anodized member, the pre-treatment may also include treatments other than the etching treatment, such as a degreasing treatment, buffing, or chemical polishing. The pre-treatment may also include a desmutting treatment to remove smut generated by the etching treatment.

[0061] For example, if the pre-anodized component has a metal structure consisting of a fibrous structure, the surface of the pre-anodized component can be adjusted to the desired state by performing a degreasing process as necessary and then an etching process.

[0062] Furthermore, for example, recrystallization of the surface of the extruded material during the manufacturing process of the pre-anodized component may cause the internal metal structure of the pre-anodized component to be composed of a fibrous structure, and a recrystallized structure layer containing an equiaxed structure may be formed on the outermost surface. The thickness of the recrystallized structure layer thus formed is, for example, 5 μm or more and 200 μm or less.

[0063] When pre-anodizing a component having an internal metal structure made of a fibrous structure and a recrystallized structure layer on the outermost surface is subjected to pre-treatment, the recrystallized structure layer may be removed in the pre-treatment to expose the fibrous structure, and then etching may be performed. There are no particular limitations on the method for removing the recrystallized structure layer, but for example, a method of mechanically removing the recrystallized structure layer by a method such as facing may be used.

[0064] In the etching treatment, for example, an alkaline aqueous solution such as an aqueous solution of sodium hydroxide is brought into contact with the surface of the pre-anodized member, thereby etching the surface of the pre-anodized member.

[0065] After the pretreatment is completed, the pre-anodized component is subjected to anodizing treatment to obtain an aluminum alloy component having an anodized coating formed on its surface. The specific treatment conditions for the anodizing treatment are not particularly limited as long as they are conditions that allow the formation of a porous anodized coating. For example, in the anodizing treatment, a porous anodized coating can be formed on the surface of the aluminum alloy component by performing direct current electrolysis in a mixed aqueous solution of phosphoric acid and nitric acid.

[0066] The anodized aluminum coating thus formed is impregnated with a dye, and then a sealing treatment is performed to close the pores of the anodized aluminum coating, thereby encapsulating the dye within the anodized aluminum coating and forming a dyed anodized aluminum coating. [Example]

[0067] (Example) An example of the aluminum alloy member and its manufacturing method will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the aluminum alloy member 1 of this example has a substrate 2 and a dyed anodized aluminum coating 3 formed on the substrate 2. The substrate 2 has a chemical composition containing 7.0 mass% Zn, 1.3 mass% Mg, 0.1 mass% Cu, 0.2 mass% Fe, 0.1 mass% Si, 0.1 mass% Ti, and 0.14 mass% Zr, with the balance being Al and unavoidable impurities. The metal structure of the substrate 2 is composed of a fibrous structure. The dyed anodized aluminum coating 3 exhibits a streaky pattern as shown in FIG. 2.

[0068] The aluminum alloy member of this example can be produced, for example, by the following method. First, a cylindrical ingot having the above-mentioned chemical composition and a diameter of 90 mm is produced by semi-continuous casting. Next, the ingot is held at a temperature of 500°C for 12 hours for homogenization. Thereafter, the 500°C ingot is subjected to hot extrusion to produce an extruded material. The shape of the extruded material can be, for example, a plate having a width of 150 mm and a thickness of 10 mm, but is not limited to this shape.

[0069] Thereafter, the extruded material is subjected to artificial aging treatment, thereby obtaining a pre-anodized member.

[0070] The pre-anodized component thus obtained is then subjected to pre-treatments of buffing, etching, desmutting, and chemical polishing in that order. In the etching treatment, the buffed pre-anodized component is immersed in a sodium hydroxide solution to etch the surface of the pre-anodized component. In the chemical polishing treatment, the pre-anodized component is immersed in a mixed aqueous solution of phosphoric acid and nitric acid at 90°C for 1 minute to perform chemical polishing.

[0071] Next, the pre-anodized component is anodized to produce an aluminum alloy component with an anodized film of 10 μm thickness. The electrolyte used in the anodizing process is a 15% sulfuric acid aqueous solution, and the current density is 150 mA / m. 2 The anodizing treatment is carried out using a direct current of .

[0072] The aluminum alloy member after anodizing treatment is washed with water and then dried. The anodized aluminum film is then impregnated with a brown dye. The aluminum alloy member is then immersed in boiling water for a sealing treatment, thereby obtaining an aluminum alloy member 1 having a dyed anodized aluminum film 3 on a substrate 2.

[0073] The surface pattern of the aluminum alloy member can be evaluated based on observation with a metallurgical microscope and the spatial frequency spectrum of the streak pattern of the dyed anodized aluminum coating.

[0074] When the surface pattern of the aluminum alloy part of this example is observed using a metallurgical microscope, it can be seen that the aluminum alloy part has a streaky pattern in which regions having a relatively light color tone and regions having a relatively dark color tone are alternately arranged in a direction perpendicular to the stretching direction of the aluminum alloy part, as shown in Figure 2. As a result of visual observation, the pattern of the aluminum alloy part of this example is recognized as a wood grain pattern.

[0075] In addition, after capturing an image of the surface of the aluminum alloy part to obtain a grayscale image, five evaluation areas extending in a direction perpendicular to the stretching direction of the aluminum alloy part are randomly set on the grayscale image. Each evaluation area is linear, with a length of 1024 pixels and a width of 1 pixel. The length of the evaluation area corresponds to approximately 4.45 mm when converted to the actual length on the aluminum alloy part. A fast Fourier transform is performed on each of these evaluation areas in a direction perpendicular to the stretching direction of the aluminum alloy part to generate a spatial frequency spectrum for each evaluation area. These spatial frequency spectra are then averaged to generate a spatial frequency spectrum of the streak pattern of the dyed anodized aluminum coating in a direction perpendicular to the stretching direction of the aluminum alloy part.

[0076] Furthermore, five evaluation regions extending in the wringing direction of the aluminum alloy member are randomly set on the grayscale image. Each evaluation region is linear, with a length of 1024 pixels and a width of 1 pixel. A Fourier transform process is performed on each of these evaluation regions in the wringing direction of the aluminum alloy member to generate a spatial frequency spectrum for each evaluation region. Then, by averaging these spatial frequency spectra, a spatial frequency spectrum of the streak pattern of the dyed anodized aluminum coating in the wringing direction of the aluminum alloy member can be generated.

[0077] Figure 3 shows the spatial frequency spectrum of the streak pattern of the dyed anodized aluminum coating in the direction perpendicular to the stretching direction and in the stretching direction. Note that the vertical axis of Figure 3 represents the amplitude of the spatial frequency component, and the horizontal axis represents the wavelength of the spatial frequency component.

[0078] 3, the streaky pattern of the dyed anodized aluminum coating on the aluminum alloy member of this example has a characteristic in which the wavelength of the spatial frequency component with the maximum amplitude is 1100 μm in the spatial frequency spectrum obtained by applying a Fourier transform to the grayscale image in the direction perpendicular to the drawing direction. Furthermore, the ratio A2 / A1 of the maximum amplitude A1 in the wavelength range of 700 μm to 1500 μm in the spatial frequency spectrum obtained by applying a Fourier transform to the grayscale image in the direction perpendicular to the drawing direction, to the maximum amplitude A2 in the wavelength range of 700 μm to 1500 μm in the spatial frequency spectrum obtained by applying a Fourier transform to the grayscale image in the direction perpendicular to the drawing direction, is approximately 4.3.

[0079] As described above, the aluminum alloy member 1, which has the specific chemical composition and metal structure and is provided with the dyed anodized aluminum coating 3 on its surface, has a woodgrain pattern on its surface. Furthermore, since the aluminum alloy member 1 is made of a 7000-series alloy, it has high strength. Furthermore, since the pattern on the aluminum alloy member 1 is formed by the dyed anodized aluminum coating 3, the woodgrain pattern can be maintained for a long period of time.

[0080] (Comparative Example) The aluminum alloy member of this example differs from the aluminum alloy member of the Examples in the chemical composition and metallographic structure of the substrate. Specifically, the substrate in the aluminum alloy member of this example has a chemical composition containing 0.6 mass% Mg and 0.4 mass% Si, with the remainder being Al and unavoidable impurities. The metallographic structure of the substrate is composed of an equiaxed structure. A dyed anodized aluminum coating is formed on the surface of the substrate. The method for producing the aluminum alloy member of this example is the same as the method for producing the aluminum alloy member of the Examples, except for the chemical composition of the billet.

[0081] The aluminum alloy member of this example has a chemical composition and a metal structure different from those of the specific embodiment, and therefore, no streaky patterns are observed on the surface of the aluminum alloy member of this example, and the entire surface has a uniform texture.

[0082] Specific embodiments of the aluminum alloy structural member according to the present invention have been described above based on the examples. However, the specific embodiments of the aluminum alloy structural member according to the present invention are not limited to the embodiments, and the configuration can be changed as appropriate within the scope that does not detract from the spirit of the present invention. [Explanation of symbols]

[0083] 1. Aluminum alloy components 2 Base material 3 Dyed anodized aluminum coating

Claims

1. The alloy has a chemical composition comprising Zn: 5.0% by mass or more and 8.5% by mass or less, Mg: 1.0% by mass or more and 3.0% by mass or less, Cu: 0.10% by mass or more and 3.0% by mass or less, Fe: 0.10% by mass or more and 0.60% by mass or less, Si: 0.10% by mass or more and 0.70% by mass or less, and Ti: 0.001% by mass or more and 0.10% by mass or less, and further comprises at least one element selected from Zr: 0.10% by mass or more and 0.40% by mass or less and Cr: 0.10% by mass or more and 0.40% by mass or less, with the balance being Al and unavoidable impurities; The metal structure is a fibrous structure, The surface has a dyed anodized aluminum coating, The aluminum alloy member has a dyed anodized aluminum coating that exhibits a streaky pattern.

2. The aluminum alloy structural member according to claim 1, further comprising Mn: 0.10 mass % or more and 1.0 mass % or less.

3. The aluminum alloy member according to claim 1 or 2, wherein the dyed anodized aluminum coating contains a brown dye.

4. The aluminum alloy member according to any one of claims 1 to 3, wherein the streaky pattern has a characteristic that a wavelength corresponding to a spatial frequency component having a maximum amplitude is in a range of 700 μm or more and 1500 μm or less in a spatial frequency spectrum obtained by performing Fourier transform processing in a direction perpendicular to the extension direction of the aluminum alloy member on a grayscale image obtained by imaging a surface of the aluminum alloy member.

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