Aluminum alloy foil and method for producing same

Abstract

This aluminum alloy foil is characterized by: comprising an aluminum alloy having a composition of Fe: 0.8 mass% to 2.0 mass%, Si: 0.2 mass% or less, with the remainder being Al and inevitable impurities; demonstrating a maximum tensile strength of 85 MPa or more, a 0.2% proof stress of 45 MPa or more, and an elongation of 15% or more in a tensile test at a 45° direction with respect to the rolling direction; and the ratio of the area ratio of the Cu orientation to the area ratio of the Cube orientation (Cu orientation / Cube orientation) in the area ratio of all orientations on the surface being 3 or more.

Description

Aluminum alloy foil and its manufacturing method

[0001] The present invention relates to an aluminum alloy foil and a method for producing the same.

[0002] Aluminum alloy foils used as packaging materials for food products, lithium-ion batteries, etc. are required to have high elongation because they are formed by being subjected to large deformations by press forming or the like.

[0003] For example, the following Patent Document 1 discloses a method for producing a foil made of an aluminum alloy containing 0.7 to 2.0% Fe as a method for producing an aluminum foil with excellent formability. The technology described in Patent Document 1 describes a technology in which, after hot rolling, a foil product is subjected to intensive processing at a processing rate of 97% or more without intermediate annealing during the cold rolling process, and then finish annealing is performed at 300 to 450 ° C. Furthermore, the following Patent Document 2 describes an aluminum alloy soft foil containing 0.7 to 1.4 mass% Fe, in which the average crystal grain size of crystal grains having an inclination angle of more than 5 ° is 3.5 μm or less. The technology described in Patent Document 2 describes a technology for producing a soft foil that exhibits excellent strength by homogenizing an ingot at 400 to 500 ° C, hot rolling at a hot rolling end temperature of 300 ° C or higher, cold rolling without intermediate annealing, and final annealing at 220 to 275 ° C.

[0004] JP 2-080541 A JP 2017-160509 A

[0005] In producing this type of aluminum alloy foil for packaging, an ingot is obtained by casting a molten alloy having a required composition, and the ingot is subjected to a homogenization treatment, followed by hot rolling and cold rolling, and then final annealing to obtain a packaging material having the desired mechanical properties. In view of the above-mentioned background regarding packaging materials produced through such processes, the present inventors have been conducting research and development into aluminum alloy foils suitable for use as packaging materials such as exterior foils for batteries.

[0006] Based on this research, the present inventors believe that in order to obtain an aluminum alloy foil with high formability, it is important to be able to suppress surface roughness during deformation. Furthermore, as a result of the present inventors' research on aluminum alloy foil for packaging, they have found that with regard to surface roughness during deformation, the ratio of the area ratio of Cu orientation to the area ratio of Cube orientation in the crystal grain structure of the packaging material is important.

[0007] Therefore, the present inventors have reviewed the manufacturing method and examined the crystal structure of aluminum alloy foil for packaging material, with the aim of providing an aluminum alloy foil that can improve productivity and has excellent formability.

[0008] "1" The aluminum alloy foil of this embodiment is an aluminum alloy foil made of an aluminum alloy having a composition containing Fe: 0.8% by mass or more and 2.0% by mass or less, Si: 0.2% by mass or less, with the remainder being Al and unavoidable impurities, and is characterized in that in a tensile test in a direction at an angle of 45° to the rolling direction, the maximum tensile strength is 85 MPa or more, the 0.2% proof stress is 45 MPa or more, and the elongation is 15% or more, and the ratio of the area ratio of Cu orientation to the area ratio of Cube orientation in the area ratios of each orientation on the surface (Cu orientation / Cube orientation) is 3 or more.

[0009] [2] In the aluminum alloy foil according to [1] of the present embodiment, the initial surface roughness Ra ０ and the surface roughness Ra at 25% strain in the tensile test ２５ The difference between the surface roughness (Ra ２５ -Ra ０ ) is preferably 0.30 μm or less. "3" In the aluminum alloy foil according to "1" or "2" of this embodiment, it is preferable that the average grain size of crystal grains surrounded by an orientation difference of 5° or more on the surface is 4.0 μm or less. "4" In the aluminum alloy foil according to this embodiment, it is preferable that the ratio of grain boundary lengths in the same field of view obtained by performing crystal orientation analysis by EBSD method on the surface of the aluminum alloy foil according to "1" or "2" satisfies the following formula (1): grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° / grain boundary length of crystal grains with an orientation difference of 15° or more > 0.5... formula (1)

[0010] [5] In the aluminum alloy foil of this embodiment, it is preferable that the ratio of grain boundary lengths in the same field of view, obtained by performing crystal orientation analysis by EBSD on the surface of the aluminum alloy foil described in [3], satisfies the following formula (1): grain boundary length of crystal grains with misorientation of 2° or more and less than 15° / grain boundary length of crystal grains with misorientation of 15° or more > 0.5... formula (1)

[0011] "6" A method for producing an aluminum alloy foil according to this embodiment is an aluminum alloy foil made of an aluminum alloy having a composition containing 0.8% by mass or more and 2.0% by mass or less of Fe, 0.2% by mass or less of Si, the balance being Al and unavoidable impurities, and characterized in that in a tensile test at 45° to the rolling direction, the maximum tensile strength is 85 MPa or more, the 0.2% proof stress is 45 MPa or more, and the elongation is 15% or more, and the ratio of the area fraction of Cu orientation to the area fraction of Cube orientation in the area fractions of each orientation on the surface (Cu orientation / Cube orientation) is 3 or more, and it is preferable that an ingot of an aluminum alloy having the above composition is subjected to homogenization treatment, hot rolling, and cold rolling, and then foil rolling without intermediate annealing and final annealing. "7" In the method for producing an aluminum alloy foil according to this embodiment, it is preferable that the homogenization treatment is performed under conditions of holding at 480 to 540°C for 6 hours or more.

[0012] According to the aluminum alloy foil of the present invention, it is possible to provide an aluminum alloy foil having high formability.

[0013] It is a plan view showing a first embodiment of the aluminum alloy foil according to the present invention. It is a diagram showing the planar shape of a square punch used in a limit forming height test in Examples of the present invention.

[0014] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the drawings used in the following description may show characteristic portions enlarged for convenience in order to make the characteristics easier to understand.

[0015] Fig. 1 is a plan view showing one embodiment of an aluminum alloy foil according to the present invention. The aluminum alloy foil 1 shown in Fig. 1 is a foil obtained by hot rolling, cold rolling, and foil rolling of an ingot obtained by a casting method, and is depicted in Fig. 1 as a strip having a constant width and a longitudinal direction oriented left and right. The rolling direction of this aluminum alloy foil 1 is the left-right direction shown in Fig. 1 (the longitudinal direction of the strip-shaped foil). For convenience, the direction at 0° to the rolling direction refers to the left-right direction in Fig. 1, the direction at 45° to the rolling direction refers to the direction of the arrow labeled 45° in Fig. 1, and the direction at 90° to the rolling direction refers to the direction of the arrow labeled 90° in Fig. 1. In other words, the 90° direction to the rolling direction of the aluminum alloy foil 1 refers to the width direction of the strip-shaped aluminum alloy foil 1 (the vertical direction in the plane of Fig. 1).

[0016] The aluminum alloy foil 1 shown in FIG. 1 is formed to a thickness of, for example, approximately 0.01 mm to 0.2 mm. The thickness of the aluminum alloy foil 1 may be a typical thickness used for foils. For example, it is formed to a thickness of approximately 0.04 mm (40 μm). In this specification, when "to" is used to indicate a range by describing upper and lower limits, the range includes the upper and lower limits unless otherwise specified. Therefore, 0.01 mm to 0.2 mm means 0.01 mm or more and 0.2 mm or less. As an example, this aluminum alloy foil 1 is made of an aluminum alloy having a composition containing 0.8 mass % to 2.0 mass % Fe, 0.2 mass % or less Si, the balance being Al and unavoidable impurities.

[0017] As an example, this aluminum alloy foil 1 has a maximum tensile strength of 85 MPa or more, a 0.2% yield strength of 45 MPa or more, and an elongation of 15% or more in a tensile test in a direction at 45° to the rolling direction, and the ratio of the area ratio of Cu orientation to the area ratio of Cube orientation in the area ratio of each orientation on the surface (Cu orientation / Cube orientation) is 3 or more. In the aluminum alloy foil 1, it is preferable that the average crystal grain size surrounded by an orientation difference of 5° or more is 4 μm or less. In the aluminum alloy foil 1, the initial surface roughness Ra ０ and the surface roughness Ra at 25% strain in the tensile test ２５ The difference between the surface roughness (Ra ２５ -Ra０ The surface roughness measurement will be described in detail in the examples below.

[0018] In the aluminum alloy foil 1, it is preferable that the ratio of grain boundary lengths in the same field of view obtained by performing crystal orientation analysis by the EBSD method satisfies the following formula (1): grain boundary length of grains with orientation misorientation of 2° or more and less than 15° / grain boundary length of grains with orientation misorientation of 15° or more > 0.5 (1) Furthermore, it is preferable that the aluminum alloy foil 1 has elongation of 10% or more in both the 0° direction and the 90° direction relative to the rolling direction.

[0019] The reasons for limiting the composition, properties, and structure of the aluminum alloy constituting the aluminum alloy foil 1 are explained below. Fe: 0.8% by mass or more and 2.0% by mass or less. Fe crystallizes as Al-Fe intermetallic compounds during casting. If the size of these compounds is appropriate, they serve as recrystallization sites during annealing, effectively refining the recrystallized grains. If the Fe content is less than 0.8% by mass, the distribution density of the intermetallic compounds decreases, the grain refinement effect decreases, the final recrystallized grains become coarse, and the grain boundary density of grains with an orientation misorientation of 2° to less than 15° decreases. If the Fe content exceeds 2.0% by mass, the grain refinement effect saturates or decreases. Furthermore, the size of the Al-Fe intermetallic compounds generated during casting becomes very large, resulting in reduced elongation, formability, and productivity of the foil. A particularly preferred range for the Fe content is 1.2% by mass or more and 1.8% by mass or less. Si: 0.20% by mass or less Si forms intermetallic compounds with Fe, but excessive addition of Si leads to coarsening of the compound size and a decrease in distribution density. If the content exceeds the upper limit, there is a concern that coarse crystals will cause a decrease in elongation and formability, and further that the uniformity of the recrystallized grain size distribution after final annealing will decrease. For these reasons, the Si content is set to 0.20% by mass or less. For the same reasons, it is more preferable to set the upper limit of the Si content to 0.04% by mass.

[0020] The balance of the components constituting the aluminum alloy foil according to the present invention consists of Al and inevitable impurities. These inevitable impurities refer to elements that are inevitably mixed in during the production of the aluminum alloy foil. These inevitable impurities may be contained to a degree that does not affect the properties of the aluminum alloy foil according to the present invention. Examples of the inevitable impurities include elements such as magnesium (Mg), chromium (Cr), manganese (Mn), copper (Cu), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), boron (B), and zirconium (Zr). One or more of these elements may each be contained in an amount of 500 ppm by mass or less.

[0021] "In a tensile test in a direction 45° from the rolling direction, the maximum tensile strength is 85 MPa or more, the 0.2% yield strength is 45 MPa or more, and the elongation is 15% or more." Aluminum alloy foil used in packaging materials is subjected to three-dimensional deformation during press forming. Therefore, it is required to have good mechanical properties not only in the rolling direction but also in various directions. The inventors have discovered that mechanical properties in a direction 45° from the rolling direction are particularly important during press forming. Regarding the maximum tensile strength and 0.2% yield strength, in order to maintain the shape during forming and ensure strength after forming, it is preferable that the maximum tensile strength be 85 MPa or more and the 0.2% yield strength be 45 MPa. Although there are no particular upper limits, if the maximum tensile strength and 0.2% yield strength are too high, handling during forming becomes difficult. Therefore, it is more preferable that the maximum tensile strength be 130 MPa or less and the 0.2% yield strength be 85 MPa or less. Elongation is most closely correlated with formability, and it has been confirmed that in this product, a high elongation value, especially in the 45° direction, indicates good formability. The elongation in the direction at 45° to the rolling direction is preferably 15% or more, and most preferably 20% or more.

[0022] "Orientation area ratio" In the aluminum alloy foil 1, the ratio of the area ratio of the Cu orientation to the Cube orientation (Cu orientation area ratio / Cube orientation area ratio) is preferably 3 or more. The (Cu orientation area ratio / Cube orientation area ratio) can be, for example, 5.0 or more and 31 or less. After electrolytic polishing of the foil surface, crystal orientation analysis can be performed using a scanning electron microscope (SEM)-EBSD to calculate the area ratio of each orientation. TSL Solutions' OIM Analysis can be used for the analysis. The deviation from the ideal orientation is limited to 15°. From the obtained area ratio, the ratio of the area ratio of the Cu orientation to the Cube orientation (Cu orientation area ratio / Cube orientation area ratio) can be calculated. The ideal orientation of each orientation is shown below. The details of the method for calculating the orientation area ratio will be described in detail in the Examples. In the aluminum alloy foil of this embodiment, aligning the crystal orientations in the same direction can suppress surface roughness and improve formability. In the alloy foil of this embodiment, the Cu orientation and the Cube orientation are particularly the main crystal orientations, and the inventors have found that aligning them to the Cu orientation is particularly important. Furthermore, even if the proportion of Cu orientation increases, if there is a large amount of Cube orientation, surface roughness is likely to occur, which is a factor that deteriorates formability. Therefore, it was decided to index the ratio of the area ratios of Cu orientation and Cube orientation. As a result of investigation, it was confirmed that the ratio of the area ratios of Cu orientation and Cube orientation (Cu orientation area ratio / Cube orientation area ratio) is preferably 3 or more. More preferably, it is 5 or more. If it is less than 3, even if the crystal grains are fine, the aluminum alloy foil surface is likely to become rough, resulting in a decrease in the limit forming height and other deterioration in formability. Cu orientation {112}<111> Cube orientation {001}<100> These ideal orientations are expressed as orientations that include all equivalent orientations.

[0023] When the aluminum alloy foil of this embodiment is plastically deformed, surface roughness (unevenness) occurs on the surface of the material. The surface roughness is considered to be unevenness in thickness, and by suppressing it, it is possible to prevent a decrease in the limit forming height. With respect to the three-dimensional deformation when used as a packaging material, the surface roughness Ra at the initial stage before plastic deformation is ０and the surface roughness Ra at 25% strain in the tensile test ２５ The difference between the surface roughness (Ra ２５ -Ra ０ The inventors have found that the surface roughness (Ra ２５ -Ra ０ The surface roughness (Ra) is preferably 0.30 μm or less, and more preferably 0.25 μm or less. ２５ -Ra ０ If the thickness exceeds 0.30 μm, the limit forming height decreases.

[0024] "The average grain size of crystal grains surrounded by a misorientation of 5° or more is 4.0 μm or less." The fine grains of soft aluminum foil can suppress surface roughness during deformation, allowing for high elongation and high formability. One factor affecting this surface roughness is grain size. To achieve high elongation and the associated high formability, it is desirable for the average grain size of crystal grains surrounded by grain boundaries with a misorientation of 5° or more to be 4.0 μm or less. The inventors have also found that when the average grain size exceeds 4.0 μm, surface roughness during forming becomes significant, and controlling the grain structure is also important for suppressing surface roughness. In the aluminum alloy foil 1, the average grain size is preferably 4.0 μm or less, and more preferably 3.5 μm or less. Electron backscatter diffraction (EBSD) can be used to analyze the crystal orientation per unit area to obtain a grain boundary map depicting crystal grains with a misorientation of 5° or more. The method for calculating the average crystal grain size will be described in detail in the Examples.

[0025] Grain boundary length (LAGB) of crystal grains with misorientation of 2° or more and less than 15° / grain boundary length (HAGB) of crystal grains with misorientation of 15° or more > 0.5 In order to suppress surface roughness of aluminum alloy foil, it is considered important that a high density of crystal grains with a misorientation of 2° or more and less than 15° is present on the surface of the aluminum alloy foil. Therefore, the relationship of grain boundary length (LAGB) of crystal grains with misorientation of 2° or more and less than 15° / grain boundary length (HAGB) of crystal grains with a misorientation of 15° or more > 0.5 is defined as equation (1), and it is preferable to satisfy this relationship (1). If the relationship of grain boundary length (LAGB) of crystal grains with misorientation of 2° or more and less than 15° / grain boundary length (HAGB) of crystal grains with a misorientation of 15° or more ≦ 0.5 is satisfied, surface roughness of the foil occurs, resulting in a decrease in the limit forming height and other deterioration in formability. More preferably, the grain boundary length (LAGB) of crystal grains with a misorientation of 2° or more but less than 15° / the grain boundary length (HAGB) of crystal grains with a misorientation of 15° or more>0.6.

[0026] "Method for manufacturing aluminum alloy foil" To manufacture the aluminum alloy foil 1 shown in Fig. 1, a molten aluminum alloy satisfying the above-mentioned composition is prepared, and an aluminum alloy ingot is obtained by a casting method using this molten aluminum alloy. Next, this aluminum alloy ingot is subjected to a homogenization treatment, and processed to a target thickness by hot rolling, cold rolling, and foil rolling, and finally annealed to obtain the aluminum alloy foil 1.

[0027] Homogenization treatment: Holding at 480-540°C for 6 hours or more. It is desirable to perform homogenization treatment on the resulting ingot by holding it at 480-540°C for 6 hours or more. Below 480°C, Fe precipitation is minimal and intermetallic compounds are not sufficiently grown. On the other hand, above 540°C, intermetallic compounds grow significantly, resulting in a significant decrease in the density of fine intermetallic compounds with particle sizes of 0.1 μm to 1 μm. Therefore, it is more preferable to select a temperature range of 500-540°C. In such homogenization treatment at around 500°C, a long heat treatment time is required to precipitate fine intermetallic compounds at a high density, and a minimum of 6 hours or more must be ensured. Precipitation for less than 6 hours may result in insufficient precipitation, potentially resulting in a decrease in the density of the fine intermetallic compounds. While there is no particular upper limit to the homogenization treatment time, a time of 16 hours or less is desirable from the perspective of production costs.

[0028] Hot rolling: finishing temperature of 240°C or higher and lower than 300°C In hot rolling, it is desirable to set the finishing temperature to less than 300°C to suppress recrystallization. By setting the hot rolling finishing temperature to less than 300°C, the hot-rolled sheet has a uniform fibrous structure. If the hot-rolling finishing temperature is 300°C or higher, recrystallization occurs in part of the hot-rolled sheet, resulting in a structure in which fibrous structure and recrystallized structure are mixed, which may result in non-uniform recrystallized grain size during final annealing. When hot-rolling is finished at less than 240°C, the temperature during hot rolling is also extremely low, which may cause cracks to easily occur on the sides of the rolled sheet, resulting in a significant decrease in productivity. Therefore, the finishing temperature of hot rolling is preferably in the range of 240°C or higher and lower than 300°C. The finished sheet thickness is not particularly limited, but it is preferably 3.0 mm or higher in order to reduce the final cold-rolling reduction ratio.

[0029] Final cold rolling reduction: 98% or more. The higher the cold rolling reduction from hot rolling to the final foil thickness, the greater the amount of strain accumulated in the material, resulting in finer recrystallized grains after final annealing. By performing cold rolling the required number of times at the required reduction rate and then foil rolling, an aluminum alloy foil 1 having a thickness of approximately 10 μm to 0.2 mm, for example, 40 μm, can be obtained. When performing cold rolling the required number of times, it is preferable to perform final foil rolling without intermediate annealing and then final annealing. Furthermore, when performing final annealing after cold rolling, the final annealing conditions are preferably heating to 220°C to 350°C for approximately 30 minutes to 20 hours, followed by slow cooling.

[0030] The obtained aluminum alloy foil 1 contains a predetermined amount of Fe, which affects the texture of the aluminum alloy and contributes to refinement of the crystal grain size. Although the aluminum alloy contains 0.8 to 2.0 mass % of Fe, by performing foil rolling as final cold rolling without intermediate annealing at the final stage of cold rolling and then final annealing, the aluminum alloy has good elongation even with an Fe content within the above range. The aluminum alloy used here may contain approximately 0.2 mass % or less of Si in addition to Fe. Even if the aluminum alloy foil 1 of this embodiment contains Si within the above range, an aluminum alloy foil that can achieve the purpose can be obtained.

[0031] By the manufacturing method described above, it is possible to obtain an aluminum alloy foil 1 having a maximum tensile strength of 85 MPa or more, a 0.2% proof stress of 45 MPa or more, an elongation of 15% or more in a tensile test in a direction 45° to the rolling direction, and a ratio of the area ratio of Cu orientation to the area ratio of Cube orientation in the area ratios of each orientation on the surface (Cu orientation / Cube orientation) of 3 or more. The aluminum alloy foil 1 described above is suitable for food packaging or for formed packaging materials for lithium ion batteries, and can provide an aluminum alloy foil suitable for applications requiring large deformation by press forming and applications requiring high elongation and formability. Furthermore, since it can be produced without intermediate annealing after cold rolling, it is possible to obtain an aluminum alloy foil 1 with excellent productivity.

[0032] Ingots of aluminum alloys having the compositions shown in Tables 1 and 2 (the balance being Al and other unavoidable impurities) were produced by semi-continuous casting. The resulting ingots were then subjected to homogenization, hot rolling, cold rolling, and final annealing under the manufacturing conditions shown in Tables 1 and 2 (homogenization conditions, hot rolling finish temperature, hot rolling finish thickness, and cold rolling finish foil thickness), to produce aluminum alloy foils. The final annealing conditions were 300°C x 20 hours. The final thicknesses of the aluminum alloy foils were those shown in Tables 1 and 2 (foil thickness). For samples that underwent intermediate annealing, the intermediate annealing was performed under the conditions of 360°C x 3 hours. In Tables 1 and 2, samples that were not subjected to intermediate annealing are marked with an "X" in the intermediate annealing column, and samples that were subjected to intermediate annealing are marked with an "O".

[0033]

[0034]

[0035] The following measurements and evaluations were performed on the obtained aluminum alloy foil. Tensile strength (MPa) and elongation (%) were both measured by tensile testing. The tensile test conformed to JIS Z2241. JIS No. 5 test pieces were punched out of the aluminum alloy foil samples (using a Super Dumbbell (registered trademark) manufactured by Dumbbell Co., Ltd.) so that the elongation in the 45° direction relative to the rolling direction could be measured. The tensile test was performed using a universal tensile testing machine (AGS-X 10 kN manufactured by Shimadzu Corporation) at a tensile speed of 2 mm / min. The elongation percentage was calculated as follows. First, before the test, two lines were marked in the longitudinal center of the test piece in the direction perpendicular to the test piece, spaced 50 mm apart, which is the gauge length. After the test, the fracture surfaces of the aluminum alloy foil were butted together to measure the distance between the marks. The gauge length (50 mm) was subtracted from the distance to obtain the elongation amount (mm), and the resulting value was divided by the gauge length (50 mm) to determine the elongation percentage (%).

[0036] - Orientation area ratio Prior to crystal orientation analysis, the foil surface was mirror-finished by electrolytic polishing. A solution of perchloric acid:ethanol = 1:4 (volume ratio) was used for electrolytic polishing, and the treatment was performed at a voltage of 20 V for 5 seconds. After electrolytic polishing of the foil surface, crystal orientation analysis was performed using a scanning electron microscope (SEM)-EBSD, and the area ratio of each orientation was calculated. An FE-SEM (JSM-7900F manufactured by JEOL Ltd.) was used as the SEM, and OIM Analysis (Ver. 8.0) from TSL Solutions was used for the analysis. Deviation from the ideal orientation was limited to 15°.

[0037] The measurement conditions were: observation magnification: 900x, acceleration voltage: 15 kV, sample tilt angle: 70°, step size: 0.3 μm. The observation area was 50,000 μm in total, obtained by connecting the images measured at 900x. ２ CI (Confidence Index) values ​​of 0.1 or less were excluded, and Minimum Grain Size [points]: 2 and Anti Grains: 2 were adopted.

[0038] (Orientation Analysis) The area ratio of each orientation was calculated using the Crystal Orientation function. The tolerance was set to less than 15°, and the Orientation Euler Angles and Orientation{hk(i)l}<uv(t)w> of each orientation were defined as shown in Table 3 below to obtain the area ratio. From the obtained area ratios, (Cu orientation area ratio / Cube orientation area ratio) was calculated to obtain the area ratio ratio.

[0039]

[0040] Surface Roughness In this example, plastic processing was performed using a tensile test. Similar to the elongation measurement in the previous section, the tensile test was performed using a JIS No. 5 test piece, applying tensile strain using the universal tensile tester. The surface roughness of the test material was measured in accordance with JIS B0601:2001. The actual measurements were performed using a confocal laser microscope (Keyence Corporation, VK-X100) and analyzed using an analysis application (Keyence Corporation, VK-H1XA). The observation magnification was 500x, the field of view size was 1000 x 500 μm, and the measurement location was the center of the width and length of the JIS No. 5 test piece. The data scanned using the laser microscope was subjected to noise removal and tilt correction, and the surface roughness was measured. For noise removal, the noise detection level was set to "Normal," and for tilt correction, the correction method was set to "Surface tilt correction (profile)." The surface roughness parameter was calculated based on JIS B0601:2001 using the arithmetic mean roughness of the surface roughness. First, the surface condition of the test piece before the test was observed with a confocal laser microscope. ０ After that, a tensile test is carried out. The test is stopped midway when the strain during plastic deformation reaches 25%, and the surface properties (surface roughness measurement) are again carried out on the test piece after plastic deformation at the same location as before the test. This is called R ２５ The same test piece measured using the above procedure is ０ and R ２５ Using (R ２５ -R ０ The measurement was carried out for n=5 or more for the same level, and the average value excluding the maximum and minimum values ​​was used as the calculated value of surface roughness.

[0041] Average crystal grain size After electrolytic polishing of the foil surface, crystal orientation analysis was performed using SEM-EBSD, and crystal grains surrounded by grain boundaries with a tilt angle of more than 5° were analyzed using the Number method (number average crystal grain size) under the following conditions to calculate the average crystal grain size. Details of the analysis conditions are as follows: Grain Tolerance Angle: 5° Minimum Grain Size [points]: 2 Anti Grains: 2 Minimum Confidence Index: 0 Multiple rows required: All OFF Apply partition before calculation: OFF Include grains at edges of scan in statistics: OFF The average crystal grain size calculated by the Number method is the diameter of a circle calculated by dividing the measurement area by the number of crystal grains. The measurement conditions were the same as in the case of the orientation area ratio described above: observation magnification: 900x, total area: 50,000 μm ２ and

[0042] LAGB length / HAGB length After electrolytic polishing of the foil surface, crystal orientation analysis was performed using SEM-EBSD to observe high-angle grain boundaries (HAGBs) with an orientation misorientation between crystal grains of 15° or more and low-angle grain boundaries (LAGBs) with an orientation misorientation of 2° or more and less than 15°. Three fields of view with a field size of 45×90 μm were measured at a magnification of 900x, and the lengths of the HAGBs and LAGBs within the fields of view were determined, and the ratio was calculated. The measurement conditions were the same as in the case of the orientation area ratio described above: observation magnification: 900x, total area: 50,000 μm ２ In EBSD, by specifying boundaries in Grain-MAP, it is possible to perform analysis on grain boundaries with any misorientation. Note that since grain boundaries with a misorientation of less than 2° may contain noise, they were excluded from the calculation. In this application, the analysis was performed by specifying a misorientation of 2° or more but less than 15° (=LAGB) as min: 2° - max: 15°, and a misorientation of 15° or more (=HAGB) as min: 15° (- max: 90°), and the grain boundary length obtained by the analysis was used to calculate LAGB / HAGB.

[0043] Limit Forming Height: The forming height was evaluated in a square tube forming test. The test was performed using a universal sheet metal forming tester (Model 142 / 20 manufactured by ERICHSEN) and a square punch (side length D = 37 mm, corner chamfer diameter R = 4.5 mm) 2 with a 40 μm thick aluminum foil having the shape shown in Figure 2. The test conditions were a wrinkle suppression force of 10 kN, a scale of 1 for the punch rising speed (forming speed), and mineral oil applied as a lubricant to one side of the foil (the surface that the punch contacts). The aluminum alloy foil was formed by the punch rising from the bottom of the device. The maximum punch rising height that could be formed without cracks or pinholes after three consecutive forming runs was defined as the limit forming height (mm) of that aluminum alloy foil. The punch height was varied in 0.1 mm increments. In this example, samples with a formed height of 11.0 mm or more were designated as excellent products and were indicated with the symbol A, samples with a formed height of 10.0 mm or more but less than 11.0 mm were designated as acceptable products and were indicated with the symbol B, and samples with a formed height of less than 10.0 mm were designated as unacceptable products and were indicated with the symbol C.

[0044] Using the alloy compositions shown in Tables 1 and 2 and the manufacturing conditions shown in Tables 1 and 2, Examples No. 1 to 22 and Comparative Examples No. 23 to 31 were prepared. All of the Examples are examples that satisfy the aforementioned desirable compositions or manufacturing conditions. All of the Comparative Examples are examples that do not satisfy either of the aforementioned desirable compositions or manufacturing conditions. For Samples No. 1 to 31, the tensile strengths (MPa) in the 0°, 45°, and 90° directions are shown in Tables 1 and 2. Furthermore, the yield strengths (MPa) in the 0°, 45°, and 90° directions, the elongations (%) in the 0°, 45°, and 90° directions, the Cu orientation area fraction, the Cube orientation area fraction, and the area fraction ratio (Cu orientation area fraction / Cube orientation area fraction), the average crystal grain size (μm), and the surface roughness (ΔRa ２５ -ΔRa ０ The values ​​of (LAGB length / HAGB length) and limit forming height (mm) were determined. The measurement results and evaluations are shown in Tables 4 and 5.

[0045]

[0046]

[0047] As shown in the results shown in Tables 1, 2, 4, and 5, the aluminum alloy foils made of aluminum alloys containing 0.8% by mass or more and 2.0% by mass or less of Fe, 0.2% by mass or less of Si, with the remainder being Al and unavoidable impurities, had a maximum tensile strength of 85 MPa or more, a 0.2% proof stress of 45 MPa or more, and an elongation of 15% or more in a tensile test at 45° to the rolling direction, and had a ratio of the area fraction of Cu orientation to the area fraction of Cube orientation (Cu / Cube) of 3 or more on the surface. These samples (Examples) had small surface roughness and excellent limit forming height. Furthermore, the samples of these Examples had an average crystal grain size of 4 μm or less, which was sufficiently small. Furthermore, the samples of these Examples had a small surface roughness (Ra ２５ -Ra ０ ) is 0.30 μm or less, which is sufficiently small.

[0048] The Fe content of the example samples is 0.82% or more and 1.96% or less, and the Si content is 0.03% or more and 0.19% or less. The foil thickness of the example samples is 25 μm or more and 80 μm or less. The maximum tensile strength of the example samples in a tensile test in a 45° direction relative to the rolling direction is 86 MPa or more and 101 MPa or less. The 0.2% proof stress in a 45° direction relative to the rolling direction of the example samples is 48 MPa or more and 74 MPa or less. The Cu orientation / Cube orientation value of the example samples is 5.8 or more and 30.8 or less. The average crystal grain size of the example samples is 2.53 μm or more and 3.42 μm or less. The surface roughness of the example samples is 0.17 μm or more and 0.29 μm or less. The LAGB / HAGB value of the example samples is 0.52 or more and 0.88 or less. In the example samples, the limit forming height is 10.1 mm or more and 12.5 mm.

[0049] In comparison with these examples, samples No. 23 and No. 24 had Fe contents outside the above-mentioned range, but exhibited lower tensile strength, lower proof stress, and lower elongation than the example samples when compared in the same direction. Furthermore, they also tended to have greater surface roughness and a lower limit forming height. Samples No. 25 and No. 26 had Si contents outside the above-mentioned range, but exhibited lower tensile strength, lower proof stress, and lower elongation than the example samples when compared in the same direction. Furthermore, their limit forming heights were also lower. Samples No. 27, No. 28, and No. 29 were subjected to intermediate annealing, but exhibited lower tensile strength, lower proof stress, and lower elongation than the example samples when compared in the same direction. Furthermore, these samples No. 27 to No. 29 had larger average grain sizes, greater surface roughness, smaller (LAGB / HAGB) values, and lower limit forming heights than the example samples.

[0050] Sample No. 30 was a sample in which the homogenization temperature was higher than the desired range, but it had low yield strength, a slightly larger average crystal grain size than the example samples, slightly greater surface roughness, and a worse limit forming height.Sample No. 31 was a sample in which the homogenization temperature was lower than the desired range, but it had a slightly larger average crystal grain size than the example samples, slightly greater surface roughness, and a worse limit forming height than the example samples.

[0051] 1...aluminum alloy foil, 2...punch

Claims

1. An aluminum alloy foil made of an aluminum alloy containing 0.8% by mass or more and 2.0% by mass or less of Fe, 0.2% by mass or less of Si, with the remainder being Al and unavoidable impurities, characterized in that in a tensile test at 45° to the rolling direction, the maximum tensile strength is 85 MPa or more, the 0.2% proof stress is 45 MPa or more, and the elongation is 15% or more, and the ratio of the area ratio of Cu orientation to the area ratio of Cube orientation in the area ratios of each orientation on the surface (Cu orientation / Cube orientation) is 3 or more.

2. Initial surface roughness Ra ０ and the surface roughness Ra at 25% strain in the tensile test ２５ The difference between the surface roughness (Ra ２５ -Ra ０ 2. The aluminum alloy foil according to claim 1, wherein the thickness of the aluminum alloy foil is 0.30 μm or less.

3. An aluminum alloy foil according to claim 1 or 2, characterized in that the average crystal grain size of crystal grains surrounded by an orientation difference of 5° or more on the surface is 4.0 μm or less.

4. The aluminum alloy foil according to claim 1 or 2, characterized in that the ratio of grain boundary lengths in the same field of view obtained by performing crystal orientation analysis on the surface by the EBSD method satisfies the following formula (1): grain boundary length of grains with orientation difference of 2° or more and less than 15° / grain boundary length of grains with orientation difference of 15° or more > 0.5 ... formula (1) 5. The aluminum alloy foil according to claim 3, characterized in that the ratio of grain boundary lengths in the same field of view obtained by performing crystal orientation analysis on the surface by the EBSD method satisfies the following formula (1): grain boundary length of grains with orientation difference of 2° or more and less than 15° / grain boundary length of grains with orientation difference of 15° or more > 0.5 ... formula (1) 6. A method for producing an aluminum alloy foil comprising an aluminum alloy containing 0.8% by mass or more and 2.0% by mass or less of Fe, 0.2% by mass or less of Si, with the remainder being Al and unavoidable impurities, the aluminum alloy foil having a maximum tensile strength of 85 MPa or more, a 0.2% yield strength of 45 MPa or more, and an elongation of 15% or more in a tensile test at 45° to the rolling direction, and a ratio of the area rate of Cu orientation to the area rate of Cube orientation in the area rate of each orientation on the surface (Cu orientation / Cube orientation) of 3 or less, the method for producing an aluminum alloy foil comprising the steps of: subjecting an ingot of an aluminum alloy having the above composition to homogenization treatment, hot rolling, and cold rolling; and then subjecting the ingot to foil rolling without intermediate annealing, and final annealing.

7. The method for producing an aluminum alloy foil according to claim 6, characterized in that the homogenization treatment is carried out under conditions in which the temperature is maintained at 480 to 540° C. for 6 hours or more.

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