Aluminum alloy foil and method for manufacturing the same

Abstract

To provide an aluminum alloy foil.SOLUTION: This aluminum alloy foil comprises an aluminum alloy having a composition of Fe: 0.8 mass% mor more to 2.0 mass% or less, Si: 0.2 mass% or less, with the balance being Al and inevitable impurities; having an elongation of 10% or more in a 0° direction with respect to the rolling direction, an elongation of 15% or more in a 45° direction with respect to the rolling direction, and an elongation of 10% or more in a 90° direction with respect to the rolling direction; having an average crystal grain size of 3.5 μm or less of crystal grains surrounded by a misorientation of 5° or more on the surface; and, on the surface, satisfying the following formula (1) for the ratio of crystal grain boundary lengths obtained by performing crystal orientation analysis by an EBSD method in the same field of view. Formula (1): crystal grain boundary length of crystal grains having a misorientation of 2° or more and less than 15° / crystal grain boundary length of crystal grains having a misorientation of 15° or more>0.5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Aluminum alloy foil used in packaging for food products and lithium-ion batteries is formed by press molding and other processes that subject it to significant deformation, and therefore requires high elongation.

[0003] For example, Patent Document 1 discloses a method for manufacturing aluminum foil with excellent formability, specifically a foil made from an aluminum alloy containing 0.7-2.0% Fe. The technology described in Patent Document 1 involves hot rolling followed by cold rolling, in which intermediate annealing is omitted, and the foil product is strongly processed to a processing rate of 97% or more, followed by finish annealing at 300-450°C. Furthermore, Patent Document 2 describes an aluminum alloy foil containing 0.7 to 1.4 mass% Fe, wherein the average grain size of crystal grains with an inclination angle exceeding 5° is 3.5 μm or less. The technology described in Patent Document 2 describes a technique for producing a soft foil exhibiting excellent strength by homogenizing an ingot at 400 to 500°C, hot rolling with a hot rolling completion temperature of 300°C or higher, cold rolling without intermediate annealing, and finally annealing at 220 to 275°C. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2-080541 [Patent Document 2] Japanese Patent Publication No. 2017-160509 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When manufacturing aluminum alloy foil for this type of packaging material, an ingot is obtained by casting from a molten alloy of the required composition, the ingot is subjected to homogenization treatment, then hot-rolled and cold-rolled, and finally annealed to obtain packaging material with the desired mechanical properties. In light of the aforementioned background, the inventors are conducting research and development on aluminum alloy foil suitable for use as packaging material, such as battery outer foil, for packaging materials manufactured through such processes.

[0006] Based on this research, the inventors believe that suppressing surface roughness during deformation is important in order to obtain aluminum alloy foil with high formability. Furthermore, as a result of the inventor's research on aluminum alloy foil for packaging materials, it was found that 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 in relation to surface roughness during deformation.

[0007] Therefore, the present inventors aim to provide aluminum alloy foil for packaging materials that offers improved productivity and excellent formability by reviewing the manufacturing method and examining the crystal structure. [Means for solving the problem]

[0008] "1" The aluminum alloy foil of this embodiment is 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 unavoidable impurities, and has an elongation of 10% or more in the 0° direction relative to the rolling direction, an elongation of 15% or more in the 45° direction relative to the rolling direction, an elongation of 10% or more in the 90° direction relative to the rolling direction, and on the surface, the average grain size of crystal grains surrounded by an orientation difference of 5° or more is 3.5 μm or less. On the surface, the ratio of the area ratio of the Cu orientation to the area ratio of the Cube orientation in each orientation (Cu orientation / Cube orientation) is 3 or more. The surface is characterized in that the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD, satisfies the following equation (1). The grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° / the grain boundary length of crystal grains with an orientation difference of 15° or more > 0.5 ... (1)

[0009] In the aluminum alloy foil of the "2" embodiment, it is preferable that the maximum tensile strength in a tensile test conducted at a 45° angle to the rolling direction is 85 MPa or higher. "3" In this form of aluminum alloy foil, Instead of equation (1) above, it is preferable that the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD on the surface, satisfies the following equation (2). 0.52 ≤ grain boundary length of grains with an orientation difference of 2° or more and less than 15° / grain boundary length of grains with an orientation difference of 15° or more ≤ 0.88 ... (2)

[0010] " 4 In this form of aluminum alloy foil, the initial surface roughness Ra0 and the surface roughness Ra at 25% strain in the tensile test are... 25 The difference is the surface roughness (Ra 25 It is preferable that the -Ra0) value is 0.30 μm or less. " 5 In this embodiment of aluminum alloy foil, the surface roughness (Ra 25 It is preferable that the -Ra0) value is between 0.17 μm and 0.29 μm.

[0011] " 6 The present invention relates to an aluminum alloy foil having a composition of Fe: 0.8% to 2.0% by mass, Si: 0.2% by mass or less, with the remainder being Al and unavoidable impurities, wherein the elongation in the 0° direction relative to the rolling direction is 10% or more, the elongation in the 45° direction relative to the rolling direction is 15% or more, the elongation in the 90° direction relative to the rolling direction is 10% or more, and on the surface, the average grain size of crystal grains surrounded by an orientation difference of 5° or more is 3.5 μm or less. On the surface, the ratio of the area ratio of the Cu orientation to the area ratio of the Cube orientation in each orientation (Cu orientation / Cube orientation) is 3 or more. A method for manufacturing aluminum alloy foil, characterized in that the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD on the surface, satisfies the following equation (1), characterized in that an aluminum alloy ingot of the above composition is subjected to a homogenization treatment by heating and holding at 480 to 540°C for 8 hours or more and then cooling, hot rolling is performed to a finishing temperature of 240°C or more and less than 300°C, cold rolling is performed to a rolling ratio of 98% or more, foil rolling is performed without intermediate annealing, and final annealing is performed by heating at 220 to 350°C for 30 minutes to 20 hours. 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)

[0012] " 7 " In the method for producing an aluminum alloy foil according to the present embodiment, it is preferable that the maximum tensile strength is 85 MPa or more in a tensile test in a direction at 45° to the rolling direction.

[0013] " 8 " In the method for producing an aluminum alloy foil according to the present embodiment, the initial surface roughness Ra0 and the surface roughness Ra at a strain of 25% in a tensile test 25 , which is the difference in surface roughness (Ra 25 -Ra0), is preferably 0.30 µm or less.

[0014] " 9 " In the method for producing an aluminum alloy foil according to the present embodiment, instead of the above formula (1), it is preferable to produce an aluminum alloy foil whose ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by the EBSD method on the surface, satisfies the following formula (2). 0.52 ≦ 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 ≦ 0.88 ... Formula (2) " 10 " In the method for producing an aluminum alloy foil according to the present embodiment, it is preferable that the homogenization treatment is performed under the condition of heating and holding at 480 to 540°C for 8 hours or more and 16 hours or less, followed by cooling.

Effects of the Invention

[0015] According to the aluminum alloy foil of the present invention, an aluminum alloy foil having high formability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [Figure 1] It is a plan view showing a first embodiment of the aluminum alloy foil according to the present invention. [Figure 2]This figure shows the planar shape of the square punch used in the limit forming height test in an embodiment of the present invention. [Modes for carrying out the invention]

[0017] An example of an embodiment of the present invention will be described in detail below based on the attached drawings. Note that, for convenience, the drawings used in the following description may show enlarged versions of key features to make them easier to understand.

[0018] Figure 1 is a plan view showing one embodiment of the aluminum alloy foil according to the present invention. The aluminum alloy foil 1 shown in Figure 1 is a foil obtained by hot rolling, cold rolling, and foil rolling from an ingot obtained by a casting method. In Figure 1, it is depicted as a strip-shaped body with a constant width and its length oriented from left to right. The rolling direction of this aluminum alloy foil 1 is the left-right direction (length direction of the strip-shaped foil) as shown in Figure 1. For convenience, the direction at 0° to the rolling direction means the left-right direction in Figure 1, the direction at 45° to the rolling direction means the direction of the arrow labeled 45° in Figure 1, and the direction at 90° to the rolling direction means the direction of the arrow labeled 90° in Figure 1. In other words, the direction at 90° to the rolling direction in aluminum alloy foil 1 means the width direction of the strip-shaped aluminum alloy foil 1 (up-down direction on the paper in Figure 1).

[0019] The aluminum alloy foil 1 shown in Figure 1 is formed to a thickness of, for example, 0.01 mm to 0.2 mm. The thickness of the aluminum alloy foil 1 can be any thickness that is typical for foils. For example, it can be formed to a thickness of about 0.04 mm (40 μm). In this specification, when "~" is used to indicate a range by specifying an upper and lower limit, it refers to a range that includes both 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. This aluminum alloy foil 1, as an example, consists of an aluminum alloy containing Fe: 0.8% to 2.0% by mass, Si: 0.2% by mass or less, with the remainder being Al and unavoidable impurities.

[0020] 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 conducted at a 45° angle 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 each orientation on the surface is 3 or more. In the aluminum alloy foil 1, it is preferable that the average grain size enclosed by an orientation difference of 5° or more is 4 μm or less. In the aluminum alloy foil 1, the initial surface roughness Ra0 and the surface roughness Ra at 25% strain in the tensile test are 25 The difference is the surface roughness (Ra 25 It is preferable that the Ra0 value is 0.30 μm or less. Details of the surface roughness measurement will be explained in the examples below.

[0021] Furthermore, in aluminum alloy foil 1, it is preferable that the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD, satisfies the following equation (1). The grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° / the grain boundary length of crystal grains with an orientation difference of 15° or more > 0.5 ... (1) Furthermore, it is more preferable that the following equation (2) is satisfied instead of the relationship in equation (1) mentioned above. 0.52 ≤ grain boundary length of grains with an orientation difference of 2° or more and less than 15° / grain boundary length of grains with an orientation difference of 15° or more ≤ 0.88 ... (2) Furthermore, it is preferable that the aluminum alloy foil 1 has an elongation of 10% or more in the 0° direction and an elongation of 10% or more in the 90° direction relative to the rolling direction.

[0022] The following explains the reasons for limiting the composition, properties, and structure of the aluminum alloy constituting aluminum alloy foil 1. ·Fe: 0.8% by mass or more and 2.0% by mass or less Fe crystallizes as Al-Fe intermetallic compounds during casting, and if the size of these compounds is suitable, they act as recrystallization sites during annealing, resulting in the refinement of recrystallized grains. If the Fe content is less than 0.8 mass%, the distribution density of intermetallic compounds decreases, reducing the grain refinement effect, resulting in coarser final recrystallized grains, and a lower grain boundary density for grains with an orientation difference of 2° to less than 15°. If the Fe content exceeds 2.0 mass%, the grain refinement effect saturates or decreases, and the size of the Al-Fe intermetallic compounds generated during casting becomes very large, reducing the elongation, formability, and productivity of the foil. A particularly preferable range for Fe content is 1.2 mass% or more and 1.8 mass% or less. ·Si: 0.20% by mass or less Si forms intermetallic compounds with Fe, but excessive addition 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 precipitates will reduce elongation and formability, and furthermore, that the uniformity of the recrystallized grain size distribution will decrease after final annealing. For these reasons, the Si content should be set to 0.20 mass% or less. For the same reasons, it is more preferable to set the upper limit of the Si content to 0.04 mass%.

[0023] The remainder of the components constituting the aluminum alloy foil according to the present invention consists of Al and unavoidable impurities. These unavoidable impurities refer to elements that are inevitably mixed in during the manufacturing of the aluminum alloy foil. These unavoidable impurities may be included in a range that does not affect the properties of the aluminum alloy foil according to the present invention. Examples of these unavoidable 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), and one or more of these may be included in amounts of 500 ppm by mass or less of each.

[0024] • "In a tensile test conducted at a 45° angle to the rolling direction, the maximum tensile strength is 85 MPa or higher, the 0.2% yield strength is 45 MPa or higher, and the elongation is 15% or higher." Aluminum alloy foil used in packaging materials is subjected to three-dimensional deformation through press molding. Therefore, it is required to have good mechanical properties not only in the rolling direction but also in various other directions. The inventors have found that the mechanical properties in the 45° direction relative to the rolling direction are particularly important during press forming. Regarding the maximum tensile strength and 0.2% yield stress, to ensure shape retention during forming and strength after forming, it is preferable that the maximum tensile strength be 85 MPa or higher and the 0.2% yield stress be 45 MPa. While there is no particular upper limit, if the maximum tensile strength and 0.2% yield stress are too high, handling during forming becomes difficult; therefore, it is more preferable that the maximum tensile strength be 130 MPa or lower and the 0.2% yield stress be 85 MPa or lower. Elongation is most correlated with formability, and in this product, it has been confirmed that a high elongation value in the 45° direction results in good formability. It is preferable that the elongation in the 45° direction relative to the rolling direction be 15% or higher, and most preferably 20% or higher.

[0025] "Azimuth area ratio" In 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 ratio (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 by SEM (Scanning Electron Microscope)-EBSD, and the area fraction of each orientation can be calculated. OIM Analysis manufactured by TSL Solutions can be used for the analysis. The deviation from the ideal orientation is defined as up to 15°. From the obtained area fractions, the ratio of the area fraction of Cu orientation to the area fraction of Cube orientation (Cu orientation area fraction / Cube orientation area fraction) can be calculated. The ideal orientations of each orientation are shown below. Details of the method for calculating the orientation area fraction will be described in Examples. In the aluminum alloy foil of the present embodiment, by aligning crystal orientations in the same direction, surface roughness can be suppressed and formability can be improved. The present inventors have found that in the alloy foil of the present embodiment, Cu orientation and Cube orientation are the main crystal orientations, and among these, alignment to Cu orientation is particularly important. Further, even if the proportion of Cu orientation increases, the presence of a large amount of Cube orientation tends to cause surface roughness, which becomes a factor that degrades formability. Therefore, it was decided to use the ratio of the area fractions of Cu orientation and Cube orientation as an index. As a result of the study, it was confirmed that the ratio of the area fraction of Cu orientation to the area fraction of Cube orientation (Cu orientation area fraction / Cube orientation area fraction) is preferably 3 or more. More preferably, it is 5 or more. When the ratio is less than 3, even if the crystal grains are fine, surface roughening of the aluminum alloy foil is likely to occur, leading to a decrease in formability such as a reduction in limiting forming height. Cu orientation {112}<111> Cube orientation {001}<100> With respect to these ideal orientations, they are expressed as orientations that also include all equivalent orientations.

[0026] When the aluminum alloy foil of the present embodiment is plastically deformed, surface roughness (unevenness) occurs on the material surface. Surface roughness can be regarded as non-uniformity in thickness, and suppressing it makes it possible to prevent a decrease in limiting forming height. For three-dimensional deformation when used as a packaging material, the surface roughness Ra0 in the initial state before plastic deformation and the surface roughness Ra at a strain of 25% in a tensile test 25 that is, the difference in surface roughness (Ra 25The inventors found that surface roughness (Ra0) is important. 25 Surface roughness (Ra0) is preferably 0.30 μm or less, and more preferably 0.25 μm or less. 25 When Ra0 exceeds 0.30 μm, the limiting molding height decreases.

[0027] • "The average grain size of crystal grains enclosed by an orientation difference of 5° or more is 4.0 μm or less." By making the crystal grains of soft aluminum foil finer, surface roughness during deformation can be suppressed, leading to high elongation and consequently high formability. One of the factors influencing this surface roughness is crystal grain size. To achieve high elongation characteristics and the resulting high formability, it is desirable that the average crystal grain size of crystal grains surrounded by grain boundaries with an orientation difference of 5° or more be 4.0 μm or less. The inventors have also found that when the average crystal grain size exceeds 4.0 μm, surface roughness during molding becomes significant, indicating that controlling the crystal grain structure is also important for suppressing surface roughness. In 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) allows for the creation of grain boundary maps when grains with an orientation difference of 5° or more are depicted by analyzing the crystal orientation per unit area. Details of the method for calculating the average grain size are described in the examples.

[0028] • Grain boundary length of grains with an orientation difference of 2° or more but less than 15° (LAGB) / Grain boundary length of grains with an orientation difference of 15° or more (HAGB) > 0.5 To suppress surface roughness of aluminum alloy foil, it is considered important that the density of crystal grains with an orientation difference of 2° or more and less than 15° is high on the surface of the aluminum alloy foil. Therefore, it is preferable to satisfy the relationship (1) given by equation (1), where the grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° (LAGB) / the grain boundary length of crystal grains with an orientation difference of 15° or more (HAGB) > 0.5. When the relationship between the grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° / the grain boundary length of crystal grains with an orientation difference of 15° or more is ≤ 0.5, surface roughness occurs on the foil, leading to a decrease in formability, such as a lower limit formable height. More preferably, the grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° (LAGB) / the grain boundary length of crystal grains with an orientation difference of 15° or more (HAGB) > 0.6.

[0029] "Method for manufacturing aluminum alloy foil" To manufacture the aluminum alloy foil 1 shown in Figure 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, processed to the desired thickness by hot rolling, cold rolling and foil rolling, and finally annealed to obtain the aluminum alloy foil 1.

[0030] • Homogenization treatment: Hold at 480-540°C for 6 hours or more. It is desirable to perform a homogenization treatment on the obtained ingot by heating and holding it at 480-540°C for 6 hours or more, followed by cooling. Below 480°C, Fe precipitation is small and the growth of intermetallic compounds is insufficient. On the other hand, above 540°C, the growth of intermetallic compounds is significant, and the density of fine intermetallic compounds with a particle size of 0.1 μm to less than 1 μm decreases greatly. For this reason, it is more preferable to select a temperature range of, for example, 500-540°C. In homogenization processes at around 500°C, prolonged heat treatment is necessary to precipitate fine intermetallic compounds at high density, requiring a minimum of 6 hours. Less than 6 hours may result in insufficient precipitation and a decrease in the density of fine intermetallic compounds. While there is no specific upper limit for the homogenization process time, from a production cost perspective, 16 hours or less is desirable.

[0031] • Hot rolling: Finishing temperature between 240°C and 300°C In hot rolling, it is desirable to keep the finishing temperature below 300°C to suppress recrystallization. By keeping the hot rolling finishing temperature below 300°C, the hot-rolled sheet will have a uniform fiber structure. If the hot rolling finishing temperature is 300°C or higher, recrystallization will occur in some parts of the hot-rolled sheet, resulting in a structure in which fiber structure and recrystallized structure coexist, and there is a risk that the recrystallized grain size will become non-uniform during the final annealing. Finishing hot rolling at a temperature below 240°C requires extremely low temperatures during hot rolling, which increases the likelihood of cracks forming on the sides of the rolled sheet, raising concerns about a significant decrease in productivity. Therefore, it is preferable that the hot rolling finishing temperature be in the range of 240°C to less than 300°C. While there are no particular limitations on the finished sheet thickness, it is preferable to make it 3.0 mm or more in order to lower the final cold rolling ratio.

[0032] • Final cold rolling ratio: 98% or higher The higher the cold rolling ratio 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 processing rate and then foil rolling, an aluminum alloy foil 1 with a thickness of approximately 10 μm to 0.2 mm, for example, 40 μm, can be obtained. When cold rolling is performed the required number of times, it is preferable to perform the final foil rolling without intermediate annealing, followed by final annealing. Furthermore, when performing final annealing after cold rolling, it is desirable that the final annealing conditions be such that the material is heated to 220°C to 350°C for 30 minutes to 20 hours, followed by slow cooling.

[0033] The resulting aluminum alloy foil 1 contains a predetermined amount of Fe, which influences the texture of the aluminum alloy and contributes to the refinement of the grain size. Although the aluminum alloy contains 0.8 to 2.0 mass% Fe, by performing foil rolling as the final cold rolling without intermediate annealing in the final stage of cold rolling, and then performing final annealing, it is possible to obtain good elongation even with the Fe content within the above range. Furthermore, the aluminum alloy used here may contain Si in addition to Fe in an amount of 0.2% by mass or less. Even if the aluminum alloy foil 1 of this embodiment contains Si within the above range, an aluminum alloy foil that can achieve the objective can be obtained.

[0034] By the manufacturing method described above, an aluminum alloy foil 1 can be obtained in which, in a tensile test at a 45° angle to the rolling direction, the maximum tensile strength is 85 MPa or more, the 0.2% yield strength is 45 MPa or more, the elongation is 15% or more, 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 each orientation on the surface is 3 or more. The aluminum alloy foil 1 described above is suitable for food packaging or as a molded packaging material for lithium-ion batteries. It is suitable for applications requiring large deformation by press molding, 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. [Examples]

[0035] Aluminum alloy ingots having the compositions shown in Tables 1 and 2 (the remainder being Al and other unavoidable impurities) were produced by a semi-continuous casting method. Subsequently, the obtained ingots were subjected to homogenization treatment, hot rolling, cold rolling, and final annealing according to the manufacturing conditions (homogenization treatment conditions, hot rolling finish temperature, hot rolling finish thickness, and cold rolling finish foil thickness) shown in Tables 1 and 2 to produce aluminum alloy foil. The final annealing conditions were 300°C for 20 hours. The final thickness of the aluminum alloy foil was as shown in Tables 1 and 2. For samples that underwent intermediate annealing, the intermediate annealing was performed at 360°C for 3 hours. In Tables 1 and 2, samples that did not undergo intermediate annealing are marked with an "x" in the intermediate annealing column, and samples that underwent intermediate annealing are marked with a "○".

[0036] [Table 1]

[0037] [Table 2]

[0038] The following measurements and evaluations were performed on the obtained aluminum alloy foil. • Tensile strength (MPa), elongation (percentage) All measurements were performed using tensile testing. In accordance with JIS Z2241, JIS No. 5 test specimens were punched out from aluminum alloy foil samples (using Super Dumbbell®, manufactured by Dumbbell Co., Ltd.) to measure elongation at a 45° angle to the rolling direction. Tensile testing was then performed on a universal tensile testing machine (AGS-X 10kN, manufactured by Shimadzu Corporation) at a tensile speed of 2 mm / min. The calculation of elongation was as follows: First, before the test, two lines were marked perpendicular to the length of the specimen at a distance of 50 mm from the center of the specimen. After the test, the fracture surfaces of the aluminum alloy foil were joined together and the distance between the marks was measured. The elongation (mm), obtained by subtracting the gauge length (50 mm) from this distance, was then divided by the gauge length (50 mm) to obtain the elongation (%).

[0039] ·Azimuth area ratio Prior to crystal orientation analysis, the foil surface was mirror-polished by electrolytic polishing. For electrolytic polishing, a perchloric acid:ethanol solution of 1:4 (volume ratio) was used, and the process was performed at 20V for 5 seconds. After electrolytic polishing, crystal orientation analysis was performed using SEM (Scanning Electron Microscope)-EBSD, and the area fraction for each orientation was calculated. A FE-SEM (JEOL JSM-7900F) was used, and OIM Analysis (Ver. 8.0) from TSL Solutions was used for the analysis. A deviation from the ideal orientation was limited to 15°.

[0040] The measurement conditions were: observation magnification: 900x, acceleration voltage: 15kV, sample tilt angle: 70°, step size: 0.3μm. The observation area was calculated by stitching together images measured at 900x magnification, resulting in a total area of ​​50,000 μm². 2The above was the conclusion. Confidence Index (CI) values ​​below 0.1 were excluded, and Minimum Grain Size [points]: 2, Anti-Grains: 2 were adopted.

[0041] (Azimuth analysis) The area ratio for each direction was calculated using the Crystal Orientation function. Tolerance was set to less than 15°, and the Orientation Euler Angles and Orientation{hk(i)l} for each direction were calculated.<uv(t)w> The area ratios were determined as shown in Table 3 below. The ratio of the area ratios was calculated by (Cu orientation area ratio / Cube orientation area ratio) from the obtained area ratios.

[0042] [Table 3]

[0043] • Surface roughness In this embodiment, plastic deformation was performed by tensile testing. Similar to the elongation measurement described in the previous section, the tensile test was performed using a JIS No. 5 test specimen and by applying tensile strain using the universal tensile testing machine. Surface roughness measurements of the test material were performed in accordance with JIS B0601:2001. The actual measurements were performed using a confocal laser microscope (Keyence Corporation, VK-X100), and the results were analyzed using an analysis application (Keyence Corporation, VK-H1XA). The observation magnification was 500x, the field of view was 1000x500 μm, and the measurement points were the center of the width and length of the JIS No. 5 test specimen. Surface roughness was measured after applying noise reduction and tilt correction to data scanned using a laser microscope. For noise reduction, the noise detection level was set to [Normal], and for tilt correction, the correction method was selected as [Surface Tilt Correction (Profile)]. The surface roughness parameter was calculated using the arithmetic mean roughness, based on JIS B0601:2001. First, the surface properties of the specimen before testing are observed using a confocal laser microscope and defined as R0. Then, a tensile test is performed. The test is stopped prematurely when the strain reaches 25% during plastic deformation, and the surface properties (surface roughness measurement) are observed again at the same location on the specimen after plastic deformation, and this is defined as R0. 25 In the same test specimen measured using the above procedure, R0 and R 25 Using (R 25 The value of R0 was calculated. This was performed for n=5 or more times at the same level, and the average value among those excluding the maximum and minimum was used as the calculated surface roughness value.

[0044] ·Average grain size After electropolishing the foil surface, crystal orientation analysis was performed using SEM-EBSD. Crystal grains surrounded by grain boundaries with an inclination angle greater than 5° were analyzed using the number method (number-mean grain size) under the following conditions, and the average grain size was calculated. The 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 grain size calculated using the Number method is the diameter of a circle, assuming the area obtained by dividing the measurement region by the number of grains is a circle. The measurement conditions are the same as for the orientation area ratio described above: observation magnification: 900x, total area: 50,000 μm². 2 That's what I decided.

[0045] ·LAGB length / HAGB length After electropolishing the foil surface, crystal orientation analysis was performed using SEM-EBSD to observe large-angle grain boundaries (HAGBs) with an orientation difference of 15° or more, and small-angle grain boundaries (LAGBs) with an orientation difference of 2° or more and less than 15°. Three fields of view were measured at a magnification of ×900 with a field size of 45 × 90 μm. The lengths of HAGBs and LAGBs within each field of view were determined, and their ratio was calculated. The measurement conditions were the same as for the orientation area ratio described above: observation magnification: 900x, total area: 50,000 μm. 2 That's what I decided. In EBSD, by defining Boundaries in the Grain-MAP, it is possible to perform analysis on grain boundaries with arbitrary orientation differences. However, grain boundaries with orientation differences of less than 2° may contain noise, so they were excluded from the calculation. In this application, for orientation differences of 2° or more and less than 15° (=LAGB), min:2°-max:15° was defined, and for orientation differences of 15° or more (=HAGB), min:15°(-max:90°) was defined, and the analysis was performed. The LAGB / HAGB was calculated using the grain boundary lengths obtained from the analysis.

[0046] • Limit forming height The forming height was evaluated using a rectangular tube forming test. The test was performed using a universal thin sheet forming tester (ERICHSEN Model 142 / 20), and a rectangular punch (side length D=37mm, corner chamfer diameter R=4.5mm) with the shape shown in Figure 2 was used on 40μm thick aluminum foil. The test conditions were a wrinkle-suppressing force of 10kN, a punch lifting speed (forming speed) scale of 1, and mineral oil applied as a lubricant to one side of the foil (the side that the punch contacts). A punch rising from the bottom of the device strikes the aluminum alloy foil, forming the foil. The maximum punch height at which the foil could be formed without cracks or pinholes during three consecutive forming attempts was defined as the limit forming height (mm) for that aluminum alloy foil. The punch height was varied in 0.1 mm increments. In this embodiment, samples with a molded height of 11.0 mm or more were designated as excellent products with the symbol A, samples with a molded height of 10.0 mm or more and less than 11.0 mm were designated as acceptable products with the symbol B, and samples with a molded height of less than 10.0 mm were designated as unacceptable products with the symbol C.

[0047] Using either the alloy composition shown in Tables 1 and 2, or the manufacturing conditions shown in Tables 1 and 2, we created Examples No. 1-22 and Comparative Examples No. 23-31. All of the Examples satisfy the desired composition or manufacturing conditions described above. All of the Comparative Examples do not satisfy either the desired composition or manufacturing conditions described above. Tables 1 and 2 show the tensile strength (MPa) in the 0°, 45°, and 90° directions for samples No. 1 to 31. Furthermore, the yield strength (MPa) in the 0°, 45°, and 90° directions, the elongation (%) in the 0°, 45°, and 90° directions, the Cu orientation area ratio, the Cube orientation area ratio, and the area ratio ratio (Cu orientation area ratio / Cube orientation area ratio), as well as the average grain size (μm) and surface roughness (ΔRa). 25 The values ​​of -ΔRa0 (μm), (LAGB length / HAGB length), and limiting molding height (mm) were determined. The measurement results and evaluations are shown in Tables 4 and 5.

[0048] [Table 4]

[0049] [Table 5]

[0050] As shown in the results in Tables 1, 2, 4, and 5, the aluminum alloy foils No. 1 to 22 (Examples), which consist of an aluminum alloy containing Fe: 0.8% to 2.0% by mass, Si: 0.2% by mass or less, with the remainder being Al and unavoidable impurities, exhibited 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 a 45° angle to the rolling direction, and had a ratio of the area ratio of the Cu orientation to the area ratio of the Cube orientation (Cu / Cube) of 3 or more on the surface, showed minimal surface roughness and excellent limit forming height. Furthermore, the samples in these examples have an average grain size of 4 μm or less, which is sufficiently small. In addition, the samples in these examples have surface roughness (Ra 25 The -Ra0 value is 0.30 μm or less, which is sufficiently small.

[0051] The Fe content of the example sample is between 0.82% and 1.96%, and the Si content is between 0.03% and 0.19%. The foil thickness of the example sample is between 25 μm and 80 μm. The maximum tensile strength of the example sample measured in a tensile test at a 45° angle to the rolling direction is between 86 MPa and 101 MPa. The 0.2% yield strength of the example sample at a 45° angle to the rolling direction is between 48 MPa and 74 MPa. The Cu orientation / Cube orientation value of the example sample is between 5.8 and 30.8. The average grain size of the example sample is between 2.53 μm and 3.42 μm. The surface roughness of the example sample is between 0.17 μm and 0.29 μm. The LAGB / HAGB value of the example sample is between 0.52 and 0.88. The limiting molding height of the example sample is between 10.1 mm and 12.5 mm.

[0052] Compared to these examples, samples No. 23 and 24, whose Fe content fell outside the aforementioned range, exhibited lower tensile strength, lower yield strength, and lower elongation in the same direction compared to the example samples. Furthermore, they tended to have greater surface roughness and lower limit molding height. Samples No. 25 and 26, whose Si content fell outside the aforementioned range, exhibited lower tensile strength, lower yield strength, and lower elongation compared to the example samples in the same direction. Furthermore, their limiting molding height was lower. Samples No. 27, 28, and 29, which underwent intermediate annealing, showed lower tensile strength, lower yield strength, and lower elongation compared to the example samples in the same direction. Furthermore, compared to the example samples, samples No. 27-29 had a larger average grain size, greater surface roughness, a smaller (LAGB / HAGB) value, and a lower limit forming height.

[0053] Sample No. 30 was obtained by raising the homogenization temperature above the desired range, but it had low yield strength, a slightly larger average grain size than the example sample, slightly greater surface roughness, and a worsened limit molding height. Sample No. 31 was obtained by lowering the homogenization treatment temperature below the desired range. However, its average grain size was slightly larger than that of the example sample, its surface roughness was slightly greater, and its limiting molding height was worse than that of the example sample. [Explanation of Symbols]

[0054] 1...Aluminum alloy foil, 2...Punch.

Claims

1. This aluminum alloy foil is made of an aluminum alloy containing Fe: 0.8% to 2.0% by mass, Si: 0.2% by mass or less, with the remainder being Al and unavoidable impurities. It has an elongation of 10% or more in the 0° direction relative to the rolling direction, an elongation of 15% or more in the 45° direction relative to the rolling direction, and an elongation of 10% or more in the 90° direction relative to the rolling direction. On the surface, the average grain size of the crystal grains surrounded by an orientation difference of 5° or more is 3.5 μm or less. On the surface, the ratio of the area ratio of the Cu direction to the area ratio of the Cube direction in the area ratio of each direction (Cu direction / Cube direction) is 3 or more. An aluminum alloy foil characterized in that the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD on the surface, satisfies the following equation (1). The grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° / the grain boundary length of crystal grains with an orientation difference of 15° or more > 0.5 ... (1)

2. The aluminum alloy foil according to claim 1, characterized in that the maximum tensile strength in a tensile test conducted at a 45° angle to the rolling direction is 85 MPa or more.

3. The aluminum alloy foil according to claim 1 or 2, characterized in that, instead of equation (1) above, the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD on the surface, satisfies the following equation (2). 0.52 ≤ grain boundary length of grains with an orientation difference of 2° or more and less than 15° / grain boundary length of grains with an orientation difference of 15° or more ≤ 0.88 ... (2)

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

5. The aforementioned surface roughness (Ra ２５ -Ra ０ The aluminum alloy foil according to claim 4, characterized in that the thickness of the ) is 0.17 μm or more and 0.29 μm or less.

6. This aluminum alloy foil is made of an aluminum alloy containing Fe: 0.8% to 2.0% by mass, Si: 0.2% by mass or less, with the remainder being Al and unavoidable impurities. It has an elongation of 10% or more in the 0° direction relative to the rolling direction, an elongation of 15% or more in the 45° direction relative to the rolling direction, and an elongation of 10% or more in the 90° direction relative to the rolling direction. On the surface, the average grain size of the crystal grains surrounded by an orientation difference of 5° or more is 3.5 μm or less. On the surface, the ratio of the area ratio of the Cu direction to the area ratio of the Cube direction in the area ratio of each direction (Cu direction / Cube direction) is 3 or more. A method for manufacturing aluminum alloy foil, characterized in that the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD on the surface, satisfies the following equation (1): A method for manufacturing aluminum alloy foil, characterized by subjecting an aluminum alloy ingot of the above composition to a homogenization treatment in which an ingot is heated and held at 480 to 540°C for 8 hours or more and then cooled; hot rolling to a finished temperature of 240°C or more and less than 300°C; cold rolling to a rolling ratio of 98% or more; foil rolling without intermediate annealing; and final annealing by heating at 220 to 350°C for 30 minutes to 20 hours. The grain boundary length of crystal grains with an orientation difference of 2° or more and less than 15° / the grain boundary length of crystal grains with an orientation difference of 15° or more > 0.5 ... (1)

7. The method for manufacturing aluminum alloy foil according to claim 6, characterized in that the maximum tensile strength in a tensile test conducted at a 45° angle to the rolling direction is 85 MPa or more.

8. Initial surface roughness Ra ０ and the surface roughness Ra at a strain of 25% in a tensile test ２５ which is the difference in surface roughness (Ra ２５ -Ra ０ ) being 0.30 µm or less. The method for producing an aluminum alloy foil according to claim 6 or 7, characterized in that

9. The method for manufacturing an aluminum alloy foil according to claim 6 or 7, characterized in that, instead of using equation (1) above, an aluminum alloy foil is manufactured in which the ratio of grain boundary lengths within the same field of view, obtained by performing crystal orientation analysis by EBSD on the surface, satisfies the following equation (2). 0.52 ≤ grain boundary length of grains with an orientation difference of 2° or more and less than 15° / grain boundary length of grains with an orientation difference of 15° or more ≤ 0.88 ... (2)

10. The method for producing aluminum alloy foil according to claim 6 or 7, characterized in that the homogenization treatment is carried out under conditions of heating and holding at 480 to 540°C for 8 hours or more and 16 hours or less, followed by cooling.

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