Method for processing aluminum alloy material and aluminum alloy material

Abstract

To provide a processing method of an aluminum alloy material capable of forming a groove on a surface of the aluminum alloy material containing copper and magnesium by using laser irradiation.SOLUTION: A method for processing an aluminum alloy raw material 10 includes an oxide film removing step of removing a surface-oxide-film 10a portion from the aluminum alloy raw material 10 containing 1.2 mass% to 4.9 mass% of copper, 0.4 mass% to 2.9 mass% of magnesium, and 87.0 mass% to 94.0 mass% of aluminum to expose a surface-to-be-processed 10b portion, a laser irradiating step of irradiating a groove forming region of the surface-to-be-processed 10b portion with a laser, and an etching step of removing the groove forming region irradiated with the laser using a hydrochloric acid-containing etchant.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for processing an aluminum alloy material and an aluminum alloy material. [Background technology]

[0002] Aluminum alloys include those containing Cu (copper) and Mg (magnesium), such as duralumin. Aluminum alloys containing copper and magnesium are lightweight and strong, so they are widely used in aircraft components, automobile parts, and other applications.

[0003] Conventional methods for processing the surface of metal materials include thermal processing and laser processing such as ablation processing. When forming grooves using laser processing, the shape of the groove, such as its width and depth, can be adjusted by changing the laser irradiation conditions, such as the beam diameter and output. For this reason, laser processing can form a wide range of groove widths, and can also form fine grooves less than 1 mm wide.

[0004] Non-Patent Document 1 describes a method of processing grooves by irradiating a passive film of stainless steel with a laser in a corrosive solution, and destroying and corroding the film by heating. Furthermore, Non-Patent Document 2 describes a technique for micromachining an aluminum surface using laser irradiation and electrolytic etching. Non-Patent Document 2 describes irradiating pure aluminum with a laser to destroy and remove an oxide film, thereby exposing the aluminum substrate on the surface. Non-Patent Document 2 further describes that immersing the aluminum substrate in an NaCl solution and performing anodic polarization locally dissolves only the aluminum substrate metal in the laser irradiated area, forming grooves. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Kazuki Aoshima, Hiroyuki Saito, Motoaki Osawa Materials and Environment, Vol. 67, No. 1 p. 33-36 (2018) [Non-patent document 2] Tatsuya Kikuchi, Hideaki Takahashi, Tomohiro Maruko, Surface Technology, Vol. 56, No. 7, 2005 pp. 409-404 Summary of the Invention [Problem to be solved by the invention]

[0006] In products such as aircraft components and automobile parts made of aluminum alloy materials containing Cu (copper) and Mg (magnesium), such as duralumin, it is required to form grooves on the surface to improve sliding properties and wear resistance, improve bonding with other components such as carbon fiber reinforced plastics, and add the function of storing oil in sealed areas.

[0007] However, laser processing, which is used as a surface processing method for metal materials, is difficult to use as a surface processing method for aluminum alloys. The reason for this is the presence of a surface oxide film on the surface of aluminum alloys. More specifically, the surface oxide film formed on the surface of aluminum alloys has poor thermal conductivity, so heat generated by laser irradiation is difficult to diffuse from the surface in the depth direction.

[0008] As a surface processing method for metal materials other than laser processing, there is a mechanical processing method using tools such as milling. However, compared to laser processing, the range of groove widths that can be formed with mechanical processing is narrower, and it is not suitable for forming fine grooves with widths of less than a few millimeters. Furthermore, although mechanical processing is suitable for forming grooves with wall surfaces perpendicular to the surface in cross-sectional view, it has been difficult to use it when forming grooves in which part of the inner surface is formed outside the opening in cross-sectional view. For this reason, mechanical processing has sometimes been unable to form grooves with the desired shape on the surface of aluminum alloys containing copper.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a method for processing an aluminum alloy material, which can form grooves on the surface of an aluminum alloy material containing copper and magnesium by irradiating it with a laser. Another object of the present invention is to provide an aluminum alloy material made of an aluminum alloy material containing copper and magnesium, having on its surface a groove of a fine width that is difficult to form by machining, and / or a groove in which a portion of the inner surface is formed at a position outside the opening in a cross-sectional view. [Means for solving the problem]

[0010] The present inventors have focused on combining a laser processing method with an etching method and have conducted extensive research in order to solve the above problems and realize a method for processing an aluminum alloy material that can form grooves on the surface of a high-strength aluminum alloy material containing copper and magnesium, such as duralumin, by irradiating it with a laser.

[0011] As a result, the inventors discovered that grooves can be formed by using a method in which a surface oxide film is removed from an aluminum alloy material containing a predetermined amount of copper, a predetermined amount of magnesium, and a predetermined amount of aluminum to expose the surface to be processed, a laser is irradiated onto the groove formation area of ​​the surface to be processed, and the groove formation area after laser irradiation is removed using an etching solution containing hydrochloric acid, thereby arriving at the present invention.

[0012] Here, the mechanism of the method for processing an aluminum alloy material of the present invention will be described with reference to the drawings. Figure 1 is a cross-sectional view illustrating the state after a laser is irradiated onto a processing surface (base material) exposed by removing a surface oxide film from an aluminum alloy material containing 1.2 mass % to 4.9 mass % copper, 0.4 mass % to 2.9 mass % magnesium, and 87.0 mass % to 94.0 mass % aluminum.

[0013] As shown in FIG. 1 , after the laser irradiation, a dendrite layer 1 having a generally arc-shaped cross section is formed in the aluminum alloy material 10, projecting from the surface 11 in the depth direction. Furthermore, a high-concentration aluminum layer 2 is formed in contact with the outer surface of the dendrite layer 1 and has a generally uniform thickness. The dendrite layer 1 contains additive elements such as copper and magnesium at higher concentrations than the aluminum alloy material 10, which is the base material. The high-concentration aluminum layer 2 contains aluminum at a higher concentration than the aluminum alloy material 10. It is presumed that the dendrite layer 1 and the high-concentration aluminum layer 2 are formed by atomic diffusion of additive elements other than aluminum contained in the aluminum alloy material 10 into the dendrite layer 1 due to heat caused by the laser irradiation.

[0014] The dendritic structure layer 1 has dendrite crystals that grow in a dendritic shape. Therefore, even if the dendritic structure layer 1 contains higher concentrations of copper and magnesium than the high-concentration aluminum layer 2, it can be removed using an etching solution containing hydrochloric acid.

[0015] Furthermore, the high-concentration aluminum layer 2 arranged in contact with the outer surface (the surface on the aluminum alloy material 10 side) of the dendritic structure layer 1 is easily dissolved in hydrochloric acid because of its low copper content. In contrast, the aluminum alloy material 10, which is the base material arranged in contact with the high-concentration aluminum layer 2, contains a large amount of copper and is therefore less likely to dissolve in hydrochloric acid than the high-concentration aluminum layer 2. Therefore, the aluminum alloy material 10, which is the base material, can function as an etching stopper layer when the region of the aluminum alloy material 10 irradiated with a laser is removed using an etching solution containing hydrochloric acid.

[0016] For these reasons, when the laser-irradiated region of the aluminum alloy material 10 is etched using an etching solution containing hydrochloric acid, the dendrite structure layer 1 is removed by the etching solution, and the high-concentration aluminum layer 2 is removed together with the dendrite structure layer 1 by the etching solution that reaches the high-concentration aluminum layer 2 through the dendrite structure layer 1. Then, when the high-concentration aluminum layer 2 is removed and the etching solution reaches the aluminum alloy material 10, the etching rate decreases.

[0017] As a result, after etching, grooves are obtained that have an inner surface shape derived from the outer surface shape of the high-concentration aluminum layer 2 and a cross-sectional shape that corresponds to the laser irradiation conditions. More specifically, by appropriately adjusting the angle, output, scanning speed, number of scans, trajectory, etc., at which the laser is irradiated onto the surface of the aluminum alloy material 10, grooves with various shapes, such as grooves with fine widths that are difficult to form by mechanical processing methods and grooves where part of the inner surface is formed at a position outside the opening in cross-section, can be easily formed on the surface of the aluminum alloy material 10.

[0018] [1] An oxide film removing step of removing a surface oxide film from an aluminum alloy material containing 1.2 mass% to 4.9 mass% copper, 0.4 mass% to 2.9 mass% magnesium, and 87.0 mass% to 94.0 mass% aluminum to expose a workpiece surface; a laser irradiation step of irradiating a laser onto a groove formation region of the workpiece surface; an etching step of removing the groove formation region after the laser irradiation using an etching solution containing hydrochloric acid.

[0019] [2] The method for processing an aluminum alloy material according to [1], wherein the etching solution is 2 vol % to 8 vol % hydrochloric acid. [3] The method for processing an aluminum alloy material according to [1], wherein the aluminum alloy material contains 3.4 mass % to 5.3 mass % of copper and magnesium in total. [4] The method for processing an aluminum alloy material according to [1], wherein the aluminum alloy material further contains 5.1 mass % to 6.1 mass % zinc.

[0020] [5] The method for processing an aluminum alloy material according to [1], wherein a pretreatment step of providing a heat absorption layer on the surface to be processed is carried out before the laser irradiation step. [6] The method for processing an aluminum alloy material according to [5], wherein a post-treatment step of removing the heat absorption layer is carried out after the laser irradiation step and before the etching step. [7] The method for processing an aluminum alloy material according to [1], wherein the laser is a YAG laser.

[0021] [8] An aluminum alloy material containing 1.2 mass% to 4.9 mass% copper, 0.4 mass% to 2.9 mass% magnesium, and 87.0 mass% to 94.0 mass% aluminum; An aluminum alloy material with grooves 5μm to 1mm wide on the surface.

[0022] [9] An aluminum alloy material containing 1.2 mass% to 4.9 mass% copper, 0.4 mass% to 2.9 mass% magnesium, and 87.0 mass% to 94.0 mass% aluminum; An aluminum alloy material having a groove on its surface, with a portion of the inner surface of the groove being formed at a position outside an opening in a cross-sectional view.

[0023]

[10] The aluminum alloy material according to [8] or [9], wherein the aluminum alloy material contains copper and magnesium in a total amount of 3.4 mass% to 5.3 mass%.

[11] The aluminum alloy material according to [8] or [9], further containing 5.1 mass % to 6.1 mass % of zinc. [Effects of the Invention]

[0024] In the method for processing an aluminum alloy material of the present invention, a surface oxide film is removed from an aluminum alloy material containing 1.2 to 4.9 mass% copper, 0.4 to 2.9 mass% magnesium, and 87.0 to 94.0 mass% aluminum to expose the workpiece surface, a laser is irradiated onto the groove formation region of the workpiece surface, and the groove formation region after laser irradiation is removed using an etching solution containing hydrochloric acid. Therefore, according to the processing method of the present invention, grooves can be formed on the surface of an aluminum alloy material containing copper by irradiating it with a laser. Therefore, by using the processing method of the present invention, grooves of various shapes can be formed on the surface of an aluminum alloy material, including grooves with fine widths that are difficult to form by mechanical processing methods and grooves in which a portion of the inner surface is located outside the opening in cross-sectional view.

[0025] The aluminum alloy material of the present invention is made of an aluminum alloy material containing 1.2 to 4.9 mass% copper, 0.4 to 2.9 mass% magnesium, and 87.0 to 94.0 mass% aluminum, and has grooves of a specific shape formed on its surface. The grooves in the aluminum alloy material of the present invention can be suitably used for applications such as improving the sliding properties and wear resistance of the aluminum alloy material, improving the bondability with other members such as carbon fiber reinforced plastics, and adding the function of storing oil at sealed locations. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view illustrating the state after a laser is irradiated onto a work surface (base material) exposed by removing a surface oxide film from an aluminum alloy material. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of an aluminum alloy material produced using the method for processing an aluminum alloy material of this embodiment, as viewed from a direction perpendicular to the extending direction of the grooves. [Figure 3] FIG. 3 is a flowchart illustrating an example of the method for processing an aluminum alloy material according to this embodiment. [Figure 4]4(a) to 4(e) are process diagrams illustrating an example of a method for processing an aluminum alloy material according to this embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing another example of the aluminum alloy material of the present invention, as viewed from a direction perpendicular to the extending direction of the grooves. [Figure 6] 6(a) and 6(b) are schematic cross-sectional views showing other examples of the aluminum alloy material of the present invention, as viewed from a direction perpendicular to the extending direction of the grooves. [Figure 7] Figure 7(a) is a laser microscope photograph of the top surface of the aluminum alloy material of Experimental Example 1 after laser irradiation. The vertical center in Figure 7(a) is the area irradiated with the laser. Figure 7(b) is a laser microscope photograph of the cross section of the aluminum alloy material of Experimental Example 1 after laser irradiation. The horizontal center in Figure 7(b) is the center of the area irradiated with the laser. [Figure 8] FIG. 8(a) is a scanning electron microscope photograph of the cross section of the aluminum alloy material of Experimental Example 1 after laser irradiation, and is a photograph of the cross section taken at approximately the center in the width direction of the laser-irradiated area. FIGS. 8(b) to 8(e) are photographs showing the results of elemental mapping by energy dispersive X-ray spectroscopy (EDS) of the same cross section as the photograph of FIG. 8(a). FIG. 8(b) shows the results of aluminum mapping. FIG. 8(c) shows the results of copper mapping. FIG. 8(d) shows the results of magnesium mapping. FIG. 8(e) shows the results of zinc mapping. [Figure 9] 9(a) to 9(d) are graphs showing the relationship between the depth from the outermost surface and the element concentration at approximately the center in the width direction of the laser-irradiated region in the aluminum alloy material after laser irradiation in Experimental Example 1. FIG. 9(a) is a graph showing the relationship between the depth from the outermost surface and the aluminum concentration. FIG. 9(b) is a graph showing the relationship between the depth from the outermost surface and the copper concentration. FIG. 9(c) is a graph showing the relationship between the depth from the outermost surface and the magnesium concentration. FIG. 9(d) is a graph showing the relationship between the depth from the outermost surface and the zinc concentration. [Figure 10]Figures 10(a) to 10(e) are laser microscope photographs of the cross section of the aluminum alloy material after removal from the etching solution of Experimental Example 2. The central parts in the horizontal direction in Figures 10(a) to 10(e) are the areas irradiated with the laser. Figure 10(a) is a photograph of an area where the YAG laser output was 10 W. Figure 10(b) is a photograph of an area where the YAG laser output was 20 W. Figure 10(c) is a photograph of an area where the YAG laser output was 30 W. Figure 10(d) is a photograph of an area where the YAG laser output was 40 W. Figure 10(e) is a photograph of an area where the YAG laser output was 50 W. [Figure 11] FIG. 11 is a graph showing the relationship between the width and depth of the grooves formed in the aluminum alloy material of Experimental Example 2 and the output of the YAG laser. [Figure 12] Figures 12(a) to 12(h) are laser microscope photographs of the cross section of the aluminum alloy material after removal from the etching solution of Experimental Example 3. The central parts in the horizontal direction in Figures 12(a) to 12(h) are the areas irradiated with the laser. Figure 12(a) is a photograph after an immersion time of 1 minute. Figure 12(b) is a photograph after an immersion time of 2 minutes. Figure 12(c) is a photograph after an immersion time of 4 minutes. Figure 12(d) is a photograph after an immersion time of 5 minutes. Figure 12(e) is a photograph after an immersion time of 6 minutes. Figure 12(f) is a photograph after an immersion time of 7 minutes. Figure 12(g) is a photograph after an immersion time of 9 minutes. Figure 12(h) is a photograph after an immersion time of 30 minutes. [Figure 13] FIG. 13 is a graph showing the relationship between the width and depth of the grooves formed in the aluminum alloy material of Experimental Example 3 and the immersion time. [Figure 14] 14(a) and 14(b) are laser microscope photographs of the cross section of the aluminum alloy material after it was removed from the etching solution of Experimental Example 4. [Figure 15] FIG. 15 is an image showing the shape of the aluminum alloy material after being taken out of the etching solution of Experimental Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0027] The method for processing an aluminum alloy material and the aluminum alloy material of the present invention will be described in detail below with reference to the drawings. The scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. Furthermore, when multiple upper and lower limit values ​​are specified for a specific parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range.

[0028] <Aluminum alloy material> FIG. 2 is a schematic cross-sectional view showing an example of an aluminum alloy material produced using the method for processing an aluminum alloy material of this embodiment, as viewed from a direction perpendicular to the extending direction of the grooves. As shown in FIG. 2, an aluminum alloy material 10A of this embodiment is made of an aluminum alloy raw material 10 and has grooves 10B on a surface 11 thereof.

[0029] The grooves 10B extend linearly in plan view, and may extend linearly or curvedly in plan view. As shown in FIG. 2, the groove 10B has a generally arcuate cross-sectional shape that protrudes from the surface 11 in the depth direction.

[0030] The width D1 of the groove 10B can be in the range of 5 μm or more and is determined depending on the application of the aluminum alloy material 10A. Since the width D1 of the groove 10B is 5 μm or more, it can be formed using the processing method described later. Since it can be easily formed using the processing method described later, the width D1 of the groove 10B is preferably 80 μm or more. Furthermore, the width D1 of the groove 10B can be 1 mm or less, and may be 330 μm or less. Grooves 10B having a width D1 of 1 mm or less are difficult to form in an aluminum alloy material 10 by a machining method, and there has not been an aluminum alloy material 10 having grooves 10B having a width D1 of 1 mm or less. Therefore, there has not been an aluminum alloy material 10 having fine grooves 10B having a width D1 of 330 μm or less. An aluminum alloy material 10A having fine grooves 10B having a width D1 of 1 mm or less, preferably 330 μm or less, can be suitably used for applications such as improving the sliding properties and wear resistance of the aluminum alloy material, improving the bondability to other members such as carbon fiber reinforced plastics, and adding a function of storing oil at sealed locations.

[0031] In this embodiment, the width D1 of groove 10B means the distance between the edges of groove 10B that are arranged opposite surface 11 when groove 10B extends linearly in a planar view, and means the length in a direction perpendicular to the extension direction of groove 10B.

[0032] The depth D2 of the grooves 10B can be, for example, in the range of 10 μm or more, and is determined depending on the application of the aluminum alloy material 10A. The grooves 10B having a width D1 in the range of 5 μm to 1 mm and a depth D2 of 10 μm or more can be formed using the processing method described later. The grooves 10B having a width D1 in the range of 5 μm to 330 μm and a depth D2 in the range of 10 μm to 125 μm can be easily formed using the processing method described later.

[0033] In this embodiment, the depth D2 of the groove 10B means the distance between the surface 11 and the position on the inner surface of the groove 10B that is farthest from the surface 11 in the direction perpendicular to the surface 11 in a cross-sectional view.

[0034] A surface oxide film formed after the grooves 10B are formed may be present on the outermost surface of the aluminum alloy material 10A of this embodiment (the upper surface of the aluminum alloy base material 10 and the outermost surface inside the grooves 10B).

[0035] The aluminum alloy material 10 forming the aluminum alloy material 10A of the present embodiment contains copper (Cu), magnesium (Mg), and aluminum (Al). The aluminum alloy material 10 may also contain copper, magnesium, aluminum, and zinc (Zn).

[0036] The aluminum alloy material 10 preferably comprises copper, magnesium, aluminum, and optionally one or more elements selected from zinc, silicon (Si), iron (Fe), manganese (Mn), chromium (Cr), and titanium (Ti), as well as inevitable impurities. Specific examples of aluminum alloy materials 10 having such a composition include alloy numbers A2017, A2024, and A7075.

[0037] In the aluminum alloy material 10A of this embodiment, the aluminum alloy material 10 contains 1.2 mass % to 4.9 mass % copper and 87.0 mass % to 94.0 mass % aluminum. Therefore, in the manufacturing process of the aluminum alloy material 10A, a surface oxide film is removed from the aluminum alloy material 10 to expose the work surface, and a laser is irradiated to the work surface, thereby forming a dendritic structure layer 1 and a high-concentration aluminum layer 2 (see FIG. 1 ) provided in contact with the outer surface of the dendritic structure layer 1. As a result, grooves 10B can be formed in the surface 11 of the aluminum alloy material 10 by a manufacturing method described below.

[0038] In this embodiment, the aluminum alloy material 10 contains 1.2 mass% or more of copper. Therefore, the aluminum alloy material 10 is not easily dissolved in hydrochloric acid. Therefore, in the manufacturing process of the aluminum alloy material 10A, the aluminum alloy material 10 arranged in contact with the high-concentration aluminum layer 2 (see FIG. 1) formed by laser irradiation functions as an etching stopper layer when the groove formation region after laser irradiation is removed using an etching solution containing hydrochloric acid. Furthermore, since the copper content of the aluminum alloy material 10 is 1.2 mass% or more, the effect of including copper in improving the strength of the aluminum alloy material 10A can be sufficiently obtained. The aluminum alloy material 10 preferably contains 3.8 mass% or more of copper to obtain an aluminum alloy material 10A with even higher strength.

[0039] The copper content of the aluminum alloy material 10 is 4.9% by mass or less. Therefore, in the manufacturing process of the aluminum alloy material 10A, the high-concentration aluminum layer 2 (see FIG. 1 ) formed by irradiating a laser onto the workpiece surface exposed by removing a surface oxide film from the aluminum alloy material 10 has a sufficiently low copper content. As a result, the high-concentration aluminum layer 2 is easily dissolved in hydrochloric acid, and the difference in ease of dissolution in hydrochloric acid (difference in etching rate) between the high-concentration aluminum layer 2 and the base aluminum alloy material 10 is large. Therefore, grooves 10B can be formed on the surface 11 of the aluminum alloy material 10 by the manufacturing method described below. The copper content of the aluminum alloy material 10 is preferably 2.0% by mass or less because the high-concentration aluminum layer 2 is easily dissolved by hydrochloric acid and grooves 10B can be easily formed on the surface 11 of the aluminum alloy material 10 by the manufacturing method described below.

[0040] The content of magnesium in the aluminum alloy material 10 is 0.4 mass % to 2.9 mass %. Since the content of magnesium in the aluminum alloy material 10 is 0.4 mass % or more, the aluminum alloy material 10A can be sufficiently improved in strength by containing magnesium. The aluminum alloy material 10 preferably contains 1.2 mass % or more of magnesium to provide an aluminum alloy material 10A with even higher strength.

[0041] Furthermore, since the content of magnesium contained in the aluminum alloy material 10 is 2.9 mass% or less, a high-strength aluminum alloy material 10 containing copper, such as alloy number A2017, alloy number A2024, or alloy number A7075, can be used as the aluminum alloy material 10.

[0042] The aluminum alloy material 10 contains 87.0 mass % to 94.0 mass % aluminum. Because the aluminum content is 87.0 mass % or more, in the manufacturing process of the aluminum alloy material 10A, a high-concentration aluminum layer 2 (see FIG. 1 ) is formed by irradiating a laser onto the work surface exposed by removing a surface oxide film from the aluminum alloy material 10. This high-concentration aluminum layer 2 has a sufficiently high aluminum concentration and is more easily dissolved in hydrochloric acid than the aluminum alloy material 10, which is the base material. As a result, grooves 10B can be formed with high precision on the surface 11 of the aluminum alloy material 10 by the manufacturing method described below. The aluminum content of the aluminum alloy material 10 is preferably 90.0 mass % or more, because this makes the high-concentration aluminum layer 2 more easily dissolved in hydrochloric acid and allows grooves 10B to be easily formed on the surface 11 of the aluminum alloy material 10 by the manufacturing method described below.

[0043] Furthermore, since the aluminum content in the aluminum alloy material 10 is 94.0 mass % or less, an aluminum alloy material 10A containing a sufficient amount of copper can be obtained. Therefore, by a manufacturing method described later, grooves 10B can be formed on the surface 11 of the aluminum alloy material 10. Furthermore, since the aluminum content is 94.0 mass % or less, an aluminum alloy material 10A in which the strength-improving effect due to the inclusion of copper and magnesium can be fully exerted can be obtained.

[0044] The aluminum alloy material 10 preferably contains copper and magnesium in a total amount of 3.4 mass% to 5.3 mass%. When the total amount of copper and magnesium is 3.4 mass% or more, an aluminum alloy material 10A with higher strength can be obtained. When the total amount of copper and magnesium is 5.3 mass% or less, the aluminum alloy material is further suppressed from undergoing stress corrosion cracking.

[0045] Examples of the aluminum alloy material 10 containing 3.4 mass % to 5.3 mass % of copper and magnesium in total include duralumin (alloy number: A2017), super duralumin (alloy number: A2024), and extra super duralumin (alloy number: A7075).

[0046] The aluminum alloy material 10 may further contain 5.1 mass % to 6.1 mass % of zinc. When the content of zinc in the aluminum alloy material 10 is 5.1 mass % or more, the effect of improving the strength of the aluminum alloy material 10A due to the inclusion of zinc is sufficiently obtained, and an aluminum alloy material 10A with higher strength is obtained. When the content of zinc in the aluminum alloy material 10 is 6.1 mass % or less, the aluminum alloy material 10A is one in which stress corrosion cracking is suppressed.

[0047] An example of the aluminum alloy material 10 containing 3.4 mass % to 5.3 mass % of copper and magnesium in total and further containing 5.1 mass % to 6.1 mass % of zinc is extra super duralumin (alloy number: A7075).

[0048] <Aluminum alloy processing method> Fig. 3 is a flowchart illustrating an example of a method for processing an aluminum alloy material according to the present embodiment. Fig. 4(a) to Fig. 4(e) are process diagrams illustrating a manufacturing process of the aluminum alloy material 10A shown in Fig. 2, as an example of a method for processing an aluminum alloy material according to the present embodiment.

[0049] As shown in FIG. 3 , the method for processing an aluminum alloy material 10 of the present embodiment includes an oxide film removing step S1 of removing a surface oxide film from the aluminum alloy material 10 to expose a work surface, a laser irradiation step S3 of irradiating a groove formation region of the work surface with a laser, and an etching step S5 of removing the groove formation region after the laser irradiation with an etching solution containing hydrochloric acid.

[0050] As shown in Fig. 3, in the method for processing an aluminum alloy material 10 of the present embodiment, it is preferable to perform a pretreatment step S2 of providing a heat absorption layer on the processing surface of the aluminum alloy material 10 before the laser irradiation step S3. Furthermore, as shown in Fig. 3, when the pretreatment step S2 is performed, it is preferable to perform a posttreatment step S4 of removing the heat absorption layer after the laser irradiation step S3 and before the etching step S5.

[0051] (Oxide film removal process) In the method for processing the aluminum alloy material 10 of the present embodiment, the aluminum alloy material 10 used as the material for the aluminum alloy material 10A has the above-described composition. The shape of the aluminum alloy material 10 can be a shape depending on the application of the aluminum alloy material 10A, and is not particularly limited.

[0052] The aluminum alloy material 10 is preferably used after being solution-quenched by a known method under conditions corresponding to the composition to dissolve the additive elements such as copper and magnesium contained in the aluminum alloy material 10. Generally, an aluminum alloy material 10 used as a starting material has a surface oxide film 10a formed on its surface, as shown in Fig. 4(a). In the oxide film removing step S1, the surface oxide film 10a formed on the surface of the aluminum alloy material 10 is removed.

[0053] In the oxide film removal step S1, the surface oxide film 10a is removed from the aluminum alloy material 10 to expose the workpiece surface 10b. Therefore, in the laser irradiation step S3, the surface oxide film 10a, which has high thermal conductivity, does not prevent heat generated by laser irradiation from being conducted in the depth direction from the workpiece surface 10b. As a result, by irradiating the groove formation region of the workpiece surface 10b with a laser in the laser irradiation step S3, a dendritic structure layer 1 having a generally arc-shaped cross section is formed in a convex shape in the depth direction of the workpiece surface 10b, as shown in FIG. 4(c), and a high-concentration aluminum layer 2 is formed in contact with the outer surface of the dendritic structure layer 1 and has a generally uniform thickness.

[0054] The method for removing the surface oxide film 10a from the aluminum alloy material 10 may be any method that can remove the surface oxide film 10a from the aluminum alloy material 10 to expose the work surface 10b, and any known method can be used depending on the shape of the aluminum alloy material 10. Specific examples include a method of polishing the surface of the aluminum alloy material 10 using emery paper with grit sizes of 320 to 2000, and a machining method of cutting the surface of the aluminum alloy material 10 using a tool such as a milling cutter.

[0055] (Pretreatment process) In the pretreatment step S2, as shown in Fig. 4(b), a heat absorption layer 12 is provided on the work surface 10b of the aluminum alloy material 10. The heat absorption layer 12 may be provided on the entire work surface 10b, or may be provided only in the groove formation region of the work surface 10b.

[0056] By providing the heat absorption layer 12, the heat generated by the laser irradiation in the laser irradiation step S3 is absorbed by the heat absorption layer 12, facilitating thermal conduction in the depth direction from the workpiece surface 10b. Therefore, when the pretreatment step S2 is performed, the amount of energy required for laser irradiation can be reduced compared to when the pretreatment step S2 is not performed. Furthermore, when the pretreatment step S2 is performed, the dimension of the depth D2 relative to the width D1 of the dendritic structure layer 1 formed by irradiating the workpiece surface 10b with the laser can be made longer compared to when the pretreatment step S2 is not performed, and grooves 10B with a longer dimension of the depth D2 relative to the width D1 can be formed.

[0057] Examples of the heat absorption layer 12 include a heat absorption layer made of a carbon material and a heat absorption layer made of a plating film formed by a plating process. Among these heat absorption layers 12, a heat absorption layer 12 made of a carbon material is preferable. This is because the heat absorption layer 12 made of a carbon material is black and has high light absorption properties over a wide wavelength range. Therefore, by providing a heat absorption layer 12 made of a carbon material on the workpiece surface 10b, high energy conversion efficiency from laser light to heat can be achieved, effectively reducing the amount of energy required for laser irradiation. Furthermore, a heat absorption layer 12 made of a carbon material is preferable because it can be easily manufactured by applying a paint containing a carbon material to the workpiece surface and drying it. The thickness of the heat absorption layer 12 made of a carbon material is preferably sufficient to obtain a black heat absorption layer 12 with a sufficiently low brightness and to ensure that the heat absorption effect of the heat absorption layer 12 is fully exhibited.

[0058] (Laser irradiation process) In the laser irradiation step S3 in this embodiment, a laser is irradiated onto a groove formation region on the workpiece surface 10b provided with the heat absorption layer 12. By performing the laser irradiation step S3, a dendritic structure layer 1 having a generally arc-shaped cross section and projecting in the depth direction of the workpiece surface 10b is formed below the heat absorption layer 12, as shown in Fig. 4(c), and a high-concentration aluminum layer 2 is formed in contact with the outer surface of the dendritic structure layer 1.

[0059] The groove formation region can be any position on the workpiece surface 10b exposed in the oxide film removal step S1. The groove formation region corresponds to a position on the workpiece surface 10b of the aluminum alloy material 10 where the groove 10B is desired to be formed, and is determined depending on the application of the aluminum alloy material 10A, etc.

[0060] Examples of the laser used in the laser irradiation step S3 include a YAG laser, a CO2 laser, an excimer laser, and a fiber laser, and it is preferable to use a YAG laser. In the laser irradiation step S3, the groove formation region on the workpiece surface 10b may be irradiated with a laser in the atmosphere, or the groove formation region on the workpiece surface 10b may be irradiated with a YAG laser in water.

[0061] When a YAG laser is used as the laser, the laser irradiation conditions can be appropriately determined depending on the planar shape and cross-sectional shape of the grooves 10B corresponding to the application of the aluminum alloy material 10A. Examples of the laser irradiation conditions include output, scanning speed, scanning method, angle, number of scans, and trajectory. In this embodiment, the laser is irradiated approximately perpendicularly to the surface of the aluminum alloy material 10 along a trajectory that moves linearly in the extension direction of the grooves 10B. The trajectory for laser irradiation may be, for example, a trajectory (tilt irradiation) in which the laser moves in the extension direction of the grooves 10B while rotating along a trajectory of a substantially ellipse with predetermined major and minor axis lengths in a plan view.

[0062] As the output power of the YAG laser is increased, a wider and deeper dendritic structure layer 1 is formed, and a thick high-concentration aluminum layer 2 is formed in contact with the outer surface of the dendritic structure layer 1. Therefore, as the output power of the YAG laser is increased, grooves 10B with a wider width D1 and a deeper depth D2 can be formed. For example, when forming grooves 10B with a width D1 of 50 μm to 400 μm and a depth D2 of 10 μm to 150 μm, the output power of the YAG laser is preferably set to 10 W to 50 W.

[0063] As the scanning speed of the YAG laser is slowed, a wider and deeper dendritic structure layer 1 is formed, and a thick high-concentration aluminum layer 2 is formed in contact with the outer surface of the dendritic structure layer 1. This allows the formation of grooves 10B with a wide width D1 and a deep depth D2. For example, when forming grooves 10B with a width D1 of 50 μm to 400 μm and a depth D2 of 10 μm to 150 μm, the scanning speed of the YAG laser is preferably set to 10 mm / s to 400 mm / s.

[0064] (Post-processing process) In the post-treatment step S4, it is preferable to remove the heat absorption layer 12 formed on the workpiece surface 10b of the aluminum alloy material 10 by performing the pre-treatment step S2 after the laser irradiation step S3 and before the etching step S5, as shown in Fig. 4(d). The reason for this is that the heat absorption layer 12 does not prevent contact between the groove formation region and the etching solution after laser irradiation, allowing the etching step S5 to be performed efficiently and the grooves 10B to be formed with high precision.

[0065] In the post-treatment step S4, a known method can be used to remove the heat absorption layer 12. Specifically, the method can be determined appropriately depending on the type of the heat absorption layer 12, such as a method of polishing the heat absorption layer with emery paper of 320 to 2000 grit. When a heat absorption layer 12 made of a carbon material is formed as the heat absorption layer 12 in the pre-treatment step S2, it is preferable to remove the heat absorption layer 12 by polishing using emery paper of 320 to 2000 grit in the post-treatment step S4.

[0066] (etching process) In the etching step S5, the groove formation region after the laser irradiation is removed using an etching solution 13 containing hydrochloric acid. As a method for removing the groove formation region using an etching solution, a known method can be used, and it is preferable to use a method in which the aluminum alloy material 10 having the groove formation region after the laser irradiation is immersed in the etching solution 13, as shown in Fig. 4(e). As the etching solution 13 containing hydrochloric acid, it is preferable to use an aqueous solution of hydrogen chloride.

[0067] The groove formation region after laser irradiation tends to be more easily dissolved in hydrochloric acid as the aluminum alloy material 10 has a lower copper concentration, and more difficult to dissolve in hydrochloric acid as the aluminum alloy material 10 has a higher copper concentration. Therefore, the concentration of hydrochloric acid contained in the hydrochloric acid-containing etching solution 13 can be appropriately determined depending on the copper concentration in the aluminum alloy material 10 and the immersion time for immersing the aluminum alloy material 10 having the groove formation region after laser irradiation in the etching solution.

[0068] In the etching step S5 of this embodiment, it is preferable to use 2 vol% to 8 vol% hydrochloric acid as the etching solution 13. When the etching solution 13 is 2 vol% or more hydrochloric acid, the dendrite structure layer 1 and the high-concentration aluminum layer 2 in the groove formation region can be efficiently removed. In particular, when the copper concentration in the aluminum alloy material 10 is 2.0 mass% or more, it is preferable to use 2 vol% or more hydrochloric acid as the etching solution 13 in order to efficiently remove the groove formation region after laser irradiation. Furthermore, when the copper concentration in the aluminum alloy material 10 is 4.5 mass% or more, it is preferable to use 4 vol% or more hydrochloric acid as the etching solution 13. It is preferable to use 8 vol% or less hydrochloric acid as the etching solution 13 in order to prevent the aluminum alloy material 10 (see FIG. 4(d)) from being corroded more than necessary.

[0069] The etching conditions in the etching step S5, such as the temperature of the etching solution 13 and the immersion time for immersing the aluminum alloy material 10 in the etching solution 13, are determined depending on the sizes of the dendritic structure layer 1 and the high-concentration aluminum layer 2, the concentration of copper contained in the aluminum alloy material 10, the concentration of hydrochloric acid contained in the etching solution 13, etc.

[0070] For example, as shown in FIG. 4(e), when a method is used in which an aluminum alloy material 10 having a groove formation region after laser irradiation is immersed in an etching solution 13, and 2 vol% to 8 vol% hydrochloric acid is used as the etching solution 13, the temperature of the etching solution 13 can be room temperature (25°C).

[0071] 4(e), when a method of immersing an aluminum alloy material 10 having a groove formation region after laser irradiation in an etching solution 13 is used, and 2 vol% to 8 vol% hydrochloric acid at room temperature (25°C) is used as the etching solution 13 to form grooves 10B having a width D1 of 50 μm to 400 μm and a depth D2 of 10 μm to 150 μm, the immersion time is preferably 5 to 10 minutes. In this case, an immersion time of 5 minutes or more can sufficiently remove the high-concentration aluminum layer 2 together with the dendritic structure layer 1. Furthermore, an immersion time of 7 minutes or less allows the aluminum alloy material 10 to effectively function as an etching stopper layer, and the grooves 10B can be formed with high precision.

[0072] By carrying out the above steps, the aluminum alloy material 10A of this embodiment is obtained, which is made of an aluminum alloy material 10 and has fine grooves 10B on the surface 11 with a width D1 of 5 μm to 1 mm, which are difficult to form by machining.

[0073] As shown in FIG. 3 , the method for processing an aluminum alloy material 10 of this embodiment includes an oxide film removing step S1 in which a surface oxide film 10a is removed from an aluminum alloy material 10 containing 1.2 mass % to 4.9 mass % copper, 0.4 mass % to 2.9 mass % magnesium, and 87.0 mass % to 94.0 mass % aluminum to expose a work surface 10b, a laser irradiation step S3 in which a laser is irradiated onto a groove formation region of the work surface 10b, and an etching step S5 in which the groove formation region after the laser irradiation is removed using an etching solution 13 containing hydrochloric acid.

[0074] Therefore, according to the processing method of the present embodiment, grooves 10B can be formed on the surface 11 of the copper-containing aluminum alloy material 10 by utilizing laser irradiation, and the width D1 and depth D2 of the grooves 10B can be adjusted by changing the laser irradiation conditions in the laser irradiation step S3. Thus, according to the processing method of the present embodiment, the aluminum alloy material 10A of the present embodiment can be formed having fine grooves 10B with a width D1 of 5 μm to 1 mm, for example, on the surface 11 of a high-strength copper-containing aluminum alloy material 10 such as duralumin (alloy number: A2017), super duralumin (alloy number: A2024), or extra super duralumin (alloy number: A7075).

[0075] (Other examples) In the above-described embodiment, as shown in Fig. 3, a pre-treatment step S2 of providing a heat absorption layer 12 on the workpiece surface 10b of the aluminum alloy material 10 is performed before the laser irradiation step S3, but the pre-treatment step S2 does not have to be performed. Also, as shown in Fig. 3, when the pre-treatment step S2 is performed, it is preferable to perform a post-treatment step S4 of removing the heat absorption layer 12 after the laser irradiation step S3 and before the etching step S5, but the post-treatment step S4 does not have to be performed.

[0076] Furthermore, the method for processing an aluminum alloy material of this embodiment has been described using an example in which an aluminum alloy material 10A having grooves 10B extending linearly in a planar view as shown in FIG. 2 is produced. However, the method for processing an aluminum alloy material of the present invention can be suitably used not only in the case of producing an aluminum alloy material 10A having grooves 10B as shown in FIG. 2 but also in the case of forming grooves having various shapes on the surface of an aluminum alloy material, such as fine grooves having a planar view of 5 μm to 1 mm, and grooves in which a part of the inner surface is formed at a position outside the opening in a cross-sectional view.

[0077] When the groove is a planar-view shape (hole-like), examples include a groove that is approximately circular in plan view, a groove that is approximately elliptical in plan view, and a groove that is shaped like a stack of multiple circles with different center positions in plan view. When the groove is planar (i.e., not planar), the width of the groove is the distance between the edges of the groove that face the surface, and means the maximum length between the edges of the groove. For example, when the groove is circular in plan view, it means the diameter of the groove on the surface.

[0078] Furthermore, in the present embodiment, as an example of the aluminum alloy material of the present invention, aluminum alloy material 10A shown in FIG. 2 has been described as being made of aluminum alloy material 10 and having groove 10B on surface 11 that is approximately arc-shaped in cross section. However, the cross-sectional shape of the groove in aluminum alloy material 10A is not limited to being approximately arc-shaped in cross section, and may be, for example, a shape formed by overlapping a plurality of arc-shaped shapes in cross section that have different centers and / or radii.

[0079] Fig. 5 is a schematic cross-sectional view showing another example of the aluminum alloy material of the present invention, viewed from a direction perpendicular to the extending direction of the groove. Groove 101B of aluminum alloy material 10C shown in Fig. 5 can have a width D1 of 5 μm to 1 mm and a depth D2 of 10 μm or more, similar to groove 10B of aluminum alloy material 10A shown in Fig. 2. However, as shown in Fig. 5, the cross-sectional shape of groove 101B of aluminum alloy material 10C differs from groove 10B of aluminum alloy material 10A shown in Fig. 2 in that it has a shape formed by two overlapping arc-shaped cross-sectional shapes having different centers and radii.

[0080] The aluminum alloy material 10C shown in Fig. 5 can be produced by appropriately changing the laser irradiation conditions, such as the output, scanning speed, scanning method, angle, number of scans, and trajectory, in the laser irradiation step S3 in the processing method of the present embodiment described above. Specifically, the groove 101B in the aluminum alloy material 10C shown in Fig. 5 can be formed by combining, as the trajectory for laser irradiation, a trajectory in which the laser moves in the extension direction of the groove while rotating about a trajectory of a substantially ellipse having a predetermined major axis length and minor axis length in a plan view (flat irradiation) with a trajectory in which the laser moves linearly with respect to the extension direction of the groove.

[0081] Furthermore, the aluminum alloy material of the present invention may be made of the same aluminum alloy material as in the above-described embodiment, have a groove on the surface, and have a part of the inner surface of the groove formed at a position outside the opening in a cross-sectional view. 6(a) and 6(b) are schematic cross-sectional views showing other examples of the aluminum alloy material of the present invention, as viewed from a direction perpendicular to the extending direction of the grooves.

[0082] The groove 102B of the aluminum alloy material 10D in Fig. 6(a) has, in a cross-sectional view, a first wall surface and a second wall surface that are inclined relative to the surface and arranged opposite to each other, and a semicircular bottom surface that is connected to the ends of the first wall surface and the second wall surface and forms the bottom surface of the groove. The bottom surface has a substantially symmetrical shape with respect to the center line between the first wall surface and the second wall surface. The groove 102B of the aluminum alloy material 10D in Fig. 6(a) has the bottom surface and one of the first wall surface and the second wall surface formed at a position outside the opening 102 in a cross-sectional view.

[0083] The width D1 of the groove 102B of the aluminum alloy material 10D in Fig. 6(a) is not particularly limited and can be, for example, 5 µm or more. The width D1 of the groove 102B may be, for example, 1 mm or less, or 330 µm or less. The depth D2 of the groove 102B is also not particularly limited and can be, for example, 10 µm or more.

[0084] The groove 103B of the aluminum alloy material 10E in Fig. 6(b) has, in a cross-sectional view, an inner surface shape that is substantially arc-shaped and has its center at a position closer to the bottom surface than the opening 103. As shown in Fig. 6(b), in the aluminum alloy material 10E, a part of the inner surface of the groove 103B is formed at a position outside the opening 103 in a cross-sectional view.

[0085] The width D1 of the groove 103B of the aluminum alloy material 10E in FIG. 6(b) (in other words, the width of the opening 103) is not particularly limited and can be, for example, 5 μm or more. The width D1 of the groove 103B may be, for example, 1 mm or less, or 330 μm or less. The depth D2 of the groove 103B is also not particularly limited and can be, for example, 10 μm or more.

[0086] The aluminum alloy material 10D shown in Figure 6(a) and the aluminum alloy material 10E shown in Figure 6(b) can also be manufactured by appropriately changing the laser irradiation conditions such as output, scanning speed, scanning method, angle, number of scans, and trajectory in the laser irradiation step S3 in the processing method of this embodiment described above.

[0087] Specifically, for example, by setting the angle of the laser irradiated onto the surface of the aluminum alloy material to a first angle inclined with respect to the surface of the aluminum alloy material, the aluminum alloy material 10D shown in FIG. 6(a) can be formed. Furthermore, for example, aluminum alloy material 10E shown in Figure 6(b) can be formed by irradiating a laser onto the surface of the aluminum alloy material from a first angle inclined with respect to the surface of the aluminum alloy material and from a second angle inclined with respect to the surface of the aluminum alloy material and different from the first angle.

[0088] Furthermore, the method for processing an aluminum alloy material of this embodiment has been described using an example of producing aluminum alloy material 10A of this embodiment shown in FIG. 2, which is an example of an aluminum alloy material of the present invention. However, the method for processing an aluminum alloy material of the present invention can be suitably used not only when producing the aluminum alloy material of the present invention, but also when forming grooves having various shapes on the surface of an aluminum alloy material.

[0089] Furthermore, in this embodiment, the aluminum alloy material 10A shown in FIG. 2 having only one groove 10B has been described as an example of the aluminum alloy material of the present invention. However, the aluminum alloy material of the present invention may have one or more grooves, and the number of grooves is not particularly limited. When the aluminum alloy material of the present invention has multiple grooves, the planar shapes and cross-sectional shapes of the multiple grooves may be different from one another, or some or all of them may be the same. It is preferable that the cross-sectional shapes of the multiple grooves are all the same, as this allows for efficient formation. Furthermore, the planar shapes, such as the arrangement, length, and pitch of one or more grooves, are not particularly limited, and can be shaped according to the application of the aluminum alloy material. [Example]

[0090] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0091] [Experimental Example 1] An aluminum alloy material of Experimental Example 1 was prepared, measuring 10 mm in width, 30 mm in length, and 3 mm in thickness, and having a composition corresponding to extra super duralumin (alloy number: A7075) consisting of 1.2 mass% to 2.0 mass% copper, 2.1 mass% to 2.9 mass% magnesium, 5.1 mass% to 6.1 mass% zinc, 0.40 mass% silicon, 0.50 mass% iron, 0.06 mass% to 0.30 mass% manganese, 0.18 mass% to 0.28 mass% chromium, 0.2 mass% titanium, 0.05 mass% or less of unavoidable impurities, and the remainder being aluminum.

[0092] The aluminum alloy material of Experimental Example 1 was heated in an electric furnace at 480°C for 15 minutes and then subjected to solution quenching by holding at 120°C for 24 hours. Thereafter, the surface of the aluminum alloy material was polished with emery paper of No. 320 to No. 2000 to remove the surface oxide film and expose the processed surface (oxide film removal step), and grinding dust was removed from the surface with acetone.

[0093] Next, a paint containing a carbon material (product name: Black Guard Spray, manufactured by Fine Chemical Japan Co., Ltd.) was applied to the entire surface of the exposed work surface of the aluminum alloy material of Experimental Example 1 and dried to provide a heat absorption layer made of carbon material (pretreatment step).

[0094] Next, a YAG laser processing machine (product name: ML-7064A, manufactured by Amada Miyachi) was moved along the length direction from one end to the other end of a region approximately in the center of the width direction on the heat absorption layer provided on the processing surface of the aluminum alloy material of Experimental Example 1, and a laser was irradiated under the conditions shown below (laser irradiation process). <Laser irradiation conditions> Waveform; Continuous wave Output: 30W Scanning speed: 10 mm / s Number of scans: 1

[0095] The top surface and cross section of the aluminum alloy material of Experimental Example 1 after laser irradiation were observed and analyzed using a shape analysis laser microscope (product name: VK-X150, manufactured by KEYENCE). The results are shown in Figure 7(a) and Figure 7(b). The cross section was observed after cutting the aluminum alloy material in a direction approximately perpendicular to the longitudinal direction, polishing the resulting cut surface, and then etching it with an etching solution prepared by adding an appropriate amount of 48 mass % hydrofluoric acid (Showa Grade 1) to 100 mL of water.

[0096] Fig. 7(a) is a laser microscope photograph of the top surface of the aluminum alloy material after laser irradiation in Experimental Example 1. The central part in the vertical direction in Fig. 7(a) is the region irradiated with the laser. Figure 7(b) is a laser microscope photograph of the cross section of the aluminum alloy material after laser irradiation in Experimental Example 1. The center in the left-right direction in Figure 7(b) is the center of the area irradiated with the laser.

[0097] Furthermore, the top surface and cross section of the aluminum alloy material of Experimental Example 1 after the laser irradiation were observed and analyzed using an energy dispersive X-ray analysis scanning electron microscope (product name: EDS-SEM, JSM-7100F, manufactured by JEOL Ltd.) The results are shown in Figures 8(a) to 8(e) and Figures 9(a) to 9(d).

[0098] FIG. 8(a) is a scanning electron microscope photograph of the cross section of the aluminum alloy material of Experimental Example 1 after laser irradiation, and is a photograph of the cross section taken at approximately the center in the width direction of the laser-irradiated area. FIGS. 8(b) to 8(e) are photographs showing the results of elemental mapping by energy dispersive X-ray spectroscopy (EDS) of the same cross section as the photograph of FIG. 8(a). FIG. 8(b) shows the results of aluminum mapping. FIG. 8(c) shows the results of copper mapping. FIG. 8(d) shows the results of magnesium mapping. FIG. 8(e) shows the results of zinc mapping.

[0099] 9(a) to 9(d) are graphs showing the relationship between the depth from the outermost surface and the element concentration at approximately the center in the width direction of the laser-irradiated region in the aluminum alloy material after laser irradiation in Experimental Example 1. FIG. 9(a) is a graph showing the relationship between the depth from the outermost surface and the aluminum concentration. FIG. 9(b) is a graph showing the relationship between the depth from the outermost surface and the copper concentration. FIG. 9(c) is a graph showing the relationship between the depth from the outermost surface and the magnesium concentration. FIG. 9(d) is a graph showing the relationship between the depth from the outermost surface and the zinc concentration.

[0100] As shown in Figures 7(a) and 7(b) and Figures 8(a) to 8(e), it was confirmed that a dendrite structure layer that was approximately arc-shaped in cross section and convex in the depth direction of the processed surface was formed in the aluminum alloy material of Experimental Example 1 after laser irradiation. As shown in Figures 8(a) to 8(e) and 9(a) to 9(d), aluminum has a higher concentration in the range of more than 7 μm deep from the outermost surface than in the range of 7 μm deep or less from the outermost surface. In contrast, copper, magnesium, and zinc all have the highest concentration at a depth of about 7 μm from the outermost surface, and their concentrations are lower in the range of more than 7 μm to 17 μm deep from the outermost surface than in the range of 7 μm deep or less from the outermost surface. Furthermore, as shown in Figures 8(a) to 8(e) and 9(a) to 9(d), aluminum, copper, magnesium, and zinc all have a smaller concentration change in the range of more than 17 μm deep from the outermost surface.

[0101] From these findings, it was confirmed that in the aluminum alloy material of Experimental Example 1, a dendritic structure layer was formed in a depth range of 7 μm or less from the outermost surface at approximately the center in the width direction of the area irradiated with the laser, a high-concentration aluminum layer containing a higher concentration of aluminum than the aluminum alloy material was formed in a depth range of more than 7 μm to 17 μm from the outermost surface in contact with the outer surface of the dendritic structure layer, and an aluminum alloy material, which is a base material containing higher concentrations of copper and magnesium than the high-concentration aluminum layer, was arranged in a depth range of more than 17 μm from the outermost surface.

[0102] [Experimental Example 2] As the aluminum alloy material of Experimental Example 2, five sheets of the same aluminum alloy material as in Experimental Example 1 were prepared, and the steps up to the pretreatment step of providing a heat absorption layer made of a carbon material were carried out in the same manner as in Experimental Example 1.

[0103] Next, for each of the five aluminum alloy materials in Experimental Example 2, a laser was irradiated onto the region approximately in the center of the width direction on the heat absorption layer provided on the surface to be processed, from one end to the other along the length direction, while moving a YAG laser processing machine (product name: ML-7064A, manufactured by Amada Miyachi) under the conditions shown below with different output powers (laser irradiation process).

[0104] <Laser irradiation conditions> Waveform; Continuous wave Output: 10W, 20W, 30W, 40W, 50W Scanning speed: 10 mm / s Number of scans: 1

[0105] After the laser irradiation, the surface of the aluminum alloy material of Experimental Example 2 was polished with No. 2000 emery paper to remove the heat absorbing agent (post-treatment step). Thereafter, the aluminum alloy material of Experimental Example 2 from which the heat absorbing agent had been removed after the laser irradiation was immersed in an etching solution of 2 vol % hydrochloric acid at room temperature (25° C.) for 20 minutes (etching step).

[0106] The aluminum alloy material of Experimental Example 2 was removed from the etching solution and cross-sections of each region were observed using a shape analysis laser microscope (product name: VK-X150, manufactured by KEYENCE) with a YAG laser output of 10 W, 20 W, 30 W, 40 W, and 50 W. The results are shown in Figures 10(a) to 10(e). The cross-sections were observed after the aluminum alloy material was cut in a direction approximately perpendicular to the longitudinal direction, the cut surface was polished, and then the material was etched using an etching solution prepared by adding an appropriate amount of 48 mass% hydrofluoric acid (Showa Grade 1) to 100 mL of water.

[0107] Figures 10(a) to 10(e) are laser microscope photographs of the cross section of the aluminum alloy material after removal from the etching solution of Experimental Example 2. The central parts in the horizontal direction in Figures 10(a) to 10(e) are the areas irradiated with the laser. Figure 10(a) is a photograph of an area where the YAG laser output was 10 W. Figure 10(b) is a photograph of an area where the YAG laser output was 20 W. Figure 10(c) is a photograph of an area where the YAG laser output was 30 W. Figure 10(d) is a photograph of an area where the YAG laser output was 40 W. Figure 10(e) is a photograph of an area where the YAG laser output was 50 W.

[0108] Furthermore, the width and depth of the grooves formed in each aluminum alloy material were measured from Figures 10(a) to 10(e) using the method described below. The results are shown in Figure 11. The width and depth of the grooves formed in an area of ​​870 μm in length and 650 μm in width in each aluminum alloy material were observed at several points using a laser microscope, and the maximum values ​​were taken as the width and depth of the groove. FIG. 11 is a graph showing the relationship between the width and depth of the grooves formed in the aluminum alloy material of Experimental Example 2 and the output of the YAG laser.

[0109] As shown in Figures 10(a) to 10(e) and 11, it was confirmed that the wider and deeper grooves can be formed as the YAG laser output is increased. Furthermore, as shown in Figures 10(a) to 10(e), it was confirmed that grooves of approximately similar shapes in cross section can be formed by varying only the YAG laser output.

[0110] [Experimental Example 3] A plurality of aluminum alloy materials after laser irradiation in Experimental Example 1 were prepared, and the heat absorbing agent was removed from the surface of each of them in the same manner as in Experimental Example 2 (post-treatment step). Thereafter, the aluminum alloy material of Experimental Example 3 from which the heat absorbing agent had been removed after laser irradiation was immersed in an etching solution consisting of 2 vol% hydrochloric acid at room temperature (25°C) for different immersion times ranging from 1 minute to 30 minutes (etching process).

[0111] The aluminum alloy materials of Experimental Example 3 were removed from the etching solution and their cross sections were observed using a shape analysis laser microscope (product name: VK-X150, manufactured by KEYENCE). The results are shown in Figures 12(a) to 12(h). The cross sections were observed after the aluminum alloy materials were cut in a direction approximately perpendicular to the longitudinal direction, the cut surfaces were polished, and then the materials were etched using an etching solution prepared by adding an appropriate amount of 48 mass% hydrofluoric acid (Showa Grade 1) to 100 mL of water.

[0112] Figures 12(a) to 12(h) are laser microscope photographs of the cross section of the aluminum alloy material after removal from the etching solution of Experimental Example 3. The central parts in the horizontal direction in Figures 12(a) to 12(h) are the areas irradiated with the laser. Figure 12(a) is a photograph after an immersion time of 1 minute. Figure 12(b) is a photograph after an immersion time of 2 minutes. Figure 12(c) is a photograph after an immersion time of 4 minutes. Figure 12(d) is a photograph after an immersion time of 5 minutes. Figure 12(e) is a photograph after an immersion time of 6 minutes. Figure 12(f) is a photograph after an immersion time of 7 minutes. Figure 12(g) is a photograph after an immersion time of 9 minutes. Figure 12(h) is a photograph after an immersion time of 30 minutes.

[0113] Furthermore, for the aluminum alloy materials of Experimental Example 3, in which the immersion time was varied within the range of 1 minute to 30 minutes, the width and depth of the grooves formed in each aluminum alloy material were measured using the laser microscope photographs of the cross sections taken with the shape analysis laser microscope, using the method described below. The results are shown in Figure 13. The width and depth of the grooves formed in an area of ​​870 μm in length and 650 μm in width of each aluminum alloy material were observed at several points using the laser microscope, and the maximum values ​​were taken as the groove width and depth. FIG. 13 is a graph showing the relationship between the width and depth of the grooves formed in the aluminum alloy material of Experimental Example 3 and the immersion time.

[0114] 12(a) to 12(g) and 13, the width and depth of the grooves gradually increased when the immersion time was 9 minutes or less. This confirmed that immersion in the etching solution allowed the etching solution to reach the high-concentration aluminum layer through the dendritic structure layer, gradually removing the high-concentration aluminum layer along with the dendritic structure layer.

[0115] Furthermore, as shown in Figures 12(g), 12(h), and 13, when the immersion time exceeded 9 minutes, the change in the width and depth of the grooves due to the change in immersion time became smaller. This confirmed that when the immersion time was about 9 minutes, the high-concentration aluminum layer dissolved, allowing the etching solution to reach the aluminum alloy material, and the etching rate decreased due to the aluminum alloy material's function as an etching stopper layer.

[0116] [Experimental Example 4] As the aluminum alloy material of Experimental Example 4, the same aluminum alloy material as in Experimental Example 1 was prepared, and the steps up to the pretreatment step of providing a heat absorption layer made of a carbon material were carried out in the same manner as in Experimental Example 1.

[0117] Next, for the aluminum alloy material of Experimental Example 4, the region approximately in the center in the longitudinal direction on the heat absorption layer provided on the work surface was irradiated from one end to the other end along the width direction (laser irradiation process). The laser irradiation was carried out using a YAG laser processing machine (product name: ML-7064A, manufactured by Amada Miyachi) under the conditions shown below.

[0118] <Laser irradiation conditions> Waveform; Continuous wave Output: 30W (1st orbit), 50W (2nd orbit) Number of scans: 1

[0119] The laser irradiation was performed in a first orbit (tilt irradiation) in which the laser was rotated and moved in the groove extension direction at a scanning speed of 10 mm / s along a nearly circular orbit in a plan view. The diameter of the nearly circular orbit in the first orbit was determined in advance by experiments and was set to a dimension that would allow the formation of a groove approximately 200 μm wide after the etching process.

[0120] Then, the laser was irradiated along a second orbit that moved linearly in the extension direction of the groove at a scanning speed of 10 mm / s along the first orbit, leaving a gap of 100 μm from the center position of the first orbit in the extension direction of the groove in the width direction of the aluminum alloy material. Thereafter, laser irradiation was performed four times on the first and second orbits, with a gap of 0.5 mm between adjacent first orbits in the width direction of the aluminum alloy material.

[0121] After the laser irradiation, the surface of the aluminum alloy material of Experimental Example 4 was polished with No. 2000 emery paper to remove the heat absorbing agent (post-treatment step). Thereafter, the aluminum alloy material of Experimental Example 4 from which the heat absorbing agent had been removed after the laser irradiation was immersed in an etching solution of 2 vol % hydrochloric acid at room temperature (25° C.) for 20 minutes (etching step).

[0122] The aluminum alloy material of Experimental Example 4, which had been removed from the etching solution, was subjected to cross-sectional observation using a shape analysis laser microscope (product name: VK-X150, manufactured by KEYENCE). The results are shown in Figures 14(a) and 14(b). The cross-sectional observation was performed after the aluminum alloy material was cut in a direction substantially perpendicular to the longitudinal direction, the cut surface obtained was polished, and then the material was corroded using an etching solution prepared by adding an appropriate amount of 48 mass% hydrofluoric acid (Showa Grade 1) to 100 mL of water.

[0123] Figures 14(a) and 14(b) are laser microscope photographs of the cross section of the aluminum alloy material after removal from the etching solution of Experimental Example 4. The width and depth of the groove formed in an area of ​​870 μm in length and 650 μm in width of the aluminum alloy material, which corresponds to an area of ​​158 mm in length and 122 mm in width on the laser microscope photograph of Figure 14(b), were observed at several points, and the maximum values ​​were taken as the groove width and depth. As a result, the groove width was 617 μm and the groove depth was 125 μm.

[0124] Furthermore, the aluminum alloy material of Experimental Example 4 that had been removed from the etching solution was photographed using a shape analysis laser microscope (product name: VK-X150, manufactured by KEYENCE), and image analysis was performed. The results are shown in FIG. FIG. 15 is an image showing the shape of the aluminum alloy material after being taken out of the etching solution of Experimental Example 4.

[0125] As shown in Figures 14(a), 14(b), and 15, it was confirmed that a groove could be formed in an aluminum alloy material, which had a cross-sectional shape formed by two overlapping arc-shaped cross-sectional shapes with different centers and radii, and which extended linearly in a planar view, with a width of 617 μm and a depth of 125 μm.

[0126] [Examples 1 to 4, Comparative Examples 1 to 5] Nine pieces of each of aluminum alloy material 1 to aluminum alloy material 3 having the following compositions and measuring 10 mm in width, 30 mm in length and 3 mm in thickness were prepared and subjected to solution quenching under the following conditions.

[0127] [Aluminum alloy material 1] It consists of 4.5 mass% copper, 0.4 mass% to 0.8 mass% magnesium, 0.25 mass% zinc, 0.20 mass% to 0.8 mass% silicon, 0.7 mass% iron, 0.4 mass% to 1.0 mass% manganese, 0.10 mass% chromium, 0.15 mass% titanium, 0.05 mass% or less of unavoidable impurities, and the remainder aluminum (duralumin; alloy number: corresponds to A2017). The aluminum alloy material 1 was heated at 500°C for 15 minutes using an electric furnace and then subjected to solution quenching by holding the heated material at room temperature (25°C) for 96 hours.

[0128] [Aluminum alloy material 2] It consists of 3.8 to 4.9 mass% copper, 1.2 to 1.8 mass% magnesium, 0.25 mass% zinc, 0.50 mass% silicon, 0.50 mass% iron, 0.30 to 0.9 mass% manganese, 0.10 mass% chromium, 0.15 mass% titanium, 0.05 mass% or less of unavoidable impurities, and the remainder aluminum (super duralumin; alloy number: corresponds to A2024). The aluminum alloy material 2 was heated at 500°C for 15 minutes using an electric furnace and then subjected to solution quenching by holding the heated material at room temperature (25°C) for 96 hours.

[0129] [Aluminum alloy material 3] It consists of 0.18 to 0.28 mass% copper, 2.1 to 2.9 mass% magnesium, 5.1 to 6.1 mass% zinc, 0.40 mass% silicon, 0.50 mass% iron, 0.06 to 0.30 mass% manganese, 0.18 to 0.28 mass% chromium, 0.20 mass% titanium, 0.05 mass% or less of unavoidable impurities, and the remainder being aluminum (extra super duralumin; alloy number: corresponds to A7075). The aluminum alloy material 3 was heated at 480°C for 15 minutes using an electric furnace, and then solution quenched by holding the heated material at 120°C for 24 hours using an electric furnace.

[0130] For the above aluminum alloy materials 1 to 3, the surface was polished using emery paper with grit sizes ranging from 320 to 2000 to remove the surface oxide film and expose the processed surface (oxide film removal step), and grinding dust was removed from the surface using acetone. Next, a paint containing a carbon material (product name: Black Guard Spray, manufactured by Fine Chemical Japan Co., Ltd.) was applied to the entire surface of the exposed processed surface of the aluminum alloy materials 1 to 3 and then dried to form a heat absorption layer made of a carbon material (pretreatment process).

[0131] Next, for each of the aluminum alloy materials 1 to 3, a laser was irradiated to a region approximately in the center of the width direction on the heat absorption layer provided on the surface to be processed from one end to the other along the length direction while moving a YAG laser processing machine (product name: ML-7064A, manufactured by Amada Miyachi) under the conditions shown below (laser irradiation process).

[0132] <Laser irradiation conditions> Waveform; Continuous wave Output: 30W Scanning speed: 10 mm / s Number of scans: 1

[0133] After the laser irradiation, the surfaces of the aluminum alloy materials 1 to 3 were polished with No. 2000 emery paper to remove the heat absorbing agent (post-treatment step). Thereafter, the aluminum alloy materials 1 to 3 from which the heat absorbing agent had been removed after the laser irradiation were immersed in etching solutions consisting of aqueous solutions of the types and concentrations shown in Table 1 at room temperature (25°C) for the immersion times shown in Table 1 to form grooves (etching process).

[0134] The raw materials used for the etching solutions shown in Table 1 were as follows: Hydrochloric acid; Showa Grade 1, content 35% by volume Sulfuric acid; Showa Grade 1, content 97.0% by volume Nitric acid; pure first grade, content 60% by volume Sodium hydroxide; Showa Grade 1, content 93.0% by mass

[0135] The cross sections of the aluminum alloy materials 1 to 3 removed from the etching solution were observed using a shape analysis laser microscope (product name: VK-X150, manufactured by KEYENCE). The cross sections were observed after cutting the aluminum alloy material in a direction substantially perpendicular to the longitudinal direction, polishing the resulting cut surface, and then etching it with an etching solution prepared by adding an appropriate amount of 48% by mass of hydrofluoric acid (Showa Grade 1) to 100 mL of water. The grooves were then evaluated according to the following criteria. The results are shown in Table 1.

[0136] <Groof evaluation criteria> ◎: Grooves were formed on the surface of the aluminum alloy material along the path of laser irradiation. ○: The surface of the aluminum alloy material was etched (corroded) in spots along the path of the laser irradiation. △: The end of the track where the laser was irradiated on the surface of the aluminum alloy material was etched (corroded). ×: No change was observed on the surface of the aluminum alloy material irradiated with the laser, or the entire surface of the aluminum alloy material was etched (corroded).

[0137] [Table 1]

[0138] As shown in Table 1, in Examples 1 to 4, in which an etching solution containing hydrochloric acid was used, grooves were successfully formed on the surfaces of aluminum alloy materials 1 to 3 made of duralumin (alloy number: A2017), super duralumin (alloy number: A2024), and extra super duralumin (alloy number: A7075). Furthermore, from Examples 2 to 4, it was confirmed that it is preferable to use 4 vol% to 8 vol% hydrochloric acid as an etching solution containing hydrochloric acid.

[0139] In contrast, in Comparative Examples 1, 2, 4, and 5, in which sulfuric acid or nitric acid was used as the etching solution, corrosion of the aluminum alloy materials 1 to 3 did not progress. Therefore, as shown in Table 1, the groove evaluation was poor in Comparative Examples 1, 2, 4, and 5. Furthermore, in Comparative Example 3, in which sodium hydroxide was used as the etching solution, the entire surfaces of the aluminum alloy materials 1 to 3 were corroded. Therefore, the groove evaluation in Comparative Example 3 was poor. [Explanation of symbols]

[0140] 1 Dendrite structure layer, 2 High-concentration aluminum layer, 10 Aluminum alloy material, 10A Aluminum alloy material, 10B Groove, 10a Surface oxide film, 10b Workpiece surface, 11 Surface, 12 Heat absorption layer, 13 Etching solution.

Claims

1. an oxide film removing step of removing a surface oxide film from an aluminum alloy material containing 1.2 mass% to 4.9 mass% copper, 0.4 mass% to 2.9 mass% magnesium, and 87.0 mass% to 94.0 mass% aluminum to expose a work surface; a laser irradiation step of irradiating a laser onto a groove formation region of the workpiece surface; an etching step of removing the groove formation region after the laser irradiation using an etching solution containing hydrochloric acid.

2. 2. The method for processing an aluminum alloy material according to claim 1, wherein the etching solution is 2 vol% to 8 vol% hydrochloric acid.

3. The method for processing an aluminum alloy material according to claim 1, wherein the aluminum alloy material contains 3.4 mass% to 5.3 mass% of copper and magnesium in total.

4. The method for processing an aluminum alloy material according to claim 1, wherein the aluminum alloy material further contains 5.1% by mass to 6.1% by mass of zinc.

5. 2. The method for processing an aluminum alloy material according to claim 1, further comprising the step of: performing a pretreatment step of providing a heat absorption layer on the surface to be processed before the laser irradiation step.

6. 6. The method for processing an aluminum alloy material according to claim 5, further comprising the step of performing a post-treatment of removing the heat absorption layer after the laser irradiation step and before the etching step.

7. 2. The method for processing an aluminum alloy material according to claim 1, wherein the laser is a YAG laser.

8. an aluminum alloy material containing 1.2 mass% to 4.9 mass% copper, 0.4 mass% to 2.9 mass% magnesium, and 87.0 mass% to 94.0 mass% aluminum; An aluminum alloy material with grooves of 5 μm to 1 mm in width on the surface.

9. an aluminum alloy material containing 1.2 mass% to 4.9 mass% copper, 0.4 mass% to 2.9 mass% magnesium, and 87.0 mass% to 94.0 mass% aluminum; An aluminum alloy material having a groove on its surface, with a portion of the inner surface of the groove being formed at a position outside an opening in a cross-sectional view.

10. The aluminum alloy material according to claim 8 or claim 9, wherein the aluminum alloy material contains 3.4 mass% to 5.3 mass% of copper and magnesium in total.

11. The aluminum alloy material according to claim 8 or claim 9, wherein the aluminum alloy material further contains 5.1 mass% to 6.1 mass% of zinc.

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