Aluminum alloy foil

Abstract

The present invention aims to provide aluminum alloy foil. [Solution] The present invention relates to an aluminum alloy foil having a composition containing Fe: 1.0% to 1.5% by mass, Mn: 0.08% to 0.16% by mass, Cu: 0.15% to 0.25% by mass, Si: 0.07% by mass or less, with the remainder being Al and unavoidable impurities, characterized in that it has a tensile strength of 120 MPa or more in the rolling direction, a 0.2% yield strength of 70 MPa or more in the rolling direction, elongation of 15% or more in each of the directions of 0°, 45°, and 90° with respect to the rolling direction, an average grain size of grains surrounded by grain boundaries with an orientation difference of 2° or more is 5.5 μm or less, a grain size ratio expressed as maximum grain size / average grain size is 3.0 or less, and a Cu orientation density of 30 or more.

Description

[Technical Field]

[0001] This invention relates to aluminum alloy foil. [Background technology]

[0002] Aluminum alloy foil, used in packaging for food products and lithium-ion batteries, is processed into product shapes through processes such as press molding, which involves significant deformation. Recently, with the expansion of applications and environments, product shapes, including those that are difficult to process, have become diverse.

[0003] For example, as described in Patent Document 1 below, an aluminum alloy foil is known that contains Fe, Mn, and Si, with the Fe and Mn content in a predetermined ratio, an average crystal grain size of 5 μm or less, and a grain size ratio expressed as maximum crystal grain size / average crystal grain size of 3.5 or less. Furthermore, as described in Patent Document 2 below, the foil contains predetermined amounts of Mn, Fe, Si, and Cu, and the number of second-phase particles exceeding 1.5 μm on the surface of the foil is 1000 particles / mm². 2 The following is measured by the EBSD method on the foil surface. <100> The ratio of crystal orientations is 0.01 or less. <101> Aluminum alloy foils with a directional ratio of 0.05 or higher are known. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6456654 [Patent Document 2] Japanese Patent Publication No. 2022-063563 [Overview of the project] [Problems that the invention aims to solve]

[0005] Given the wide variety of product shapes, including the aforementioned difficult-to-process shapes, high formability is required for the aluminum alloy foil to prevent fracture during processing under harsh conditions. Furthermore, when using aluminum alloy foil products, it is anticipated that they will be subjected to impacts such as drops and collisions, so impact resistance is also required to prevent them from being destroyed by impacts.

[0006] This invention was made to solve the above-mentioned problems and aims to provide an aluminum alloy foil with excellent formability and impact resistance. [Means for solving the problem]

[0007] "1" The aluminum alloy foil of this embodiment is an aluminum alloy foil having a composition containing Fe: 1.0 mass% to 1.5 mass%, Mn: 0.08 mass% to 0.16 mass%, Cu: 0.15 mass% to 0.25 mass%, Si: 0.07 mass%, with the remainder being Al and unavoidable impurities, and is characterized by having a tensile strength of 120 MPa or more in the rolling direction, a 0.2% yield strength of 70 MPa or more in the rolling direction, elongation of 15% or more in each direction of 0°, 45°, and 90° with respect to the rolling direction, an average grain size of grains surrounded by grain boundaries with an orientation difference of 2° or more being 5.5 μm or less, a grain size ratio expressed as maximum grain size / average grain size being 3.0 or less, and a Cu orientation density of 30 or more.

[0008] In the aluminum alloy foil described in "1" of this embodiment, the number density of intermetallic compounds with an equivalent circular diameter of 1.5 to 2.5 μm is 4000 particles / mm². 2 It is preferable that the above conditions are met. "3" In the aluminum alloy foil described in "1" or "2" of this embodiment, the number density of intermetallic compounds with an equivalent circular diameter of 3.5 μm or more is 500 particles / mm 2 The following is preferable: [Effects of the Invention]

[0009] The aluminum alloy foil according to the present invention provides an aluminum alloy foil that has high formability and excellent impact resistance. [Brief explanation of the drawing]

[0010] [Figure 1] It is a plan view showing a first embodiment of an aluminum alloy foil according to the present invention. [Figure 2] It is a figure showing the planar shape of a square punch used in a limiting drawing height test in an example of the present invention.

Mode for Carrying Out the Invention

[0011] Hereinafter, an example of an embodiment of the present invention will be described in detail based on the accompanying drawings. In the drawings used in the following description, for the sake of easy understanding of the features, there are cases where the characteristic portions are enlarged and shown for convenience.

[0012] FIG. 1 is a plan view showing an 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 subjecting a cast ingot obtained by a casting method to a homogenization treatment and a soaking treatment, and then undergoing hot rolling and cold rolling. In FIG. 1, it is depicted as a strip having a certain width and with the length direction oriented horizontally. The rolling direction of this aluminum alloy foil 1 is the horizontal direction (the length direction of the strip-like foil) shown in FIG. 1. For convenience, the direction of 0° with respect to the rolling direction means the horizontal direction in FIG. 1, the direction of 45° with respect to the rolling direction means the direction of the arrow marked 45° shown in FIG. 1, and the direction of 90° with respect to the rolling direction means the direction of the arrow marked 90° shown in FIG. 1. In the aluminum alloy foil 1, the direction of 90° with respect to the rolling direction, in other words, means the width direction (the vertical direction on the paper surface of FIG. 1) of the strip-like aluminum alloy foil 1.

[0013] The aluminum alloy foil 1 shown in FIG. 1 is formed to have a thickness of, for example, about 0.02 mm to 0.1 mm. The thickness of the aluminum alloy foil ¹ can be a general thickness used as a foil. For example, it is formed to have a thickness of about 0.04 mm (40 μm). This aluminum alloy foil 1 is made of an aluminum alloy having a composition consisting of Fe: 1.0% by mass or more and 1.5% by mass or less, Mn: 0.08% by mass or more and 0.16% by mass or less, Cu: 0.15% by mass or more and 0.25% by mass or less, Si: 0.07% by mass or less, with the balance being Al and inevitable impurities.

[0014] As an example, for the aluminum alloy foil 1, it is preferable that the elongation in the 0° direction, 45° direction, and 90° direction with respect to the rolling direction are all 15% or more. Also, it is preferable that the average crystal grain size of the crystal grains surrounded by grain boundaries with an azimuth difference of 2° or more is 5.5 μm or less, and the grain size ratio represented by the maximum crystal grain size / average crystal grain size is 3.0 or less. Also, as an example, for the aluminum alloy foil 1, it is preferable that the tensile strength in the rolling direction is 120 MPa or more, and the 0.2% proof stress is 70 MPa or more.

[0015] The aluminum alloy foil 1 described above has excellent formability and excellent impact resistance. Formability requires not only in one direction but also the elongation in the 0° direction, 45° direction, and 90° direction with respect to the rolling direction. Regarding impact resistance, the strength that does not break even when an impact is applied is required. However, simply increasing the strength alone is insufficient for impact resistance, and a cohesive strength (≈toughness) having elongation together with the strength is necessary. Therefore, it is necessary to achieve both strength and elongation.

[0016] Hereinafter, the reasons for limiting the composition, the reasons for limiting the properties, and the reasons for limiting the structure of the aluminum alloy constituting the aluminum alloy foil 1 will be described. · Fe: 1.0% by mass or more and 1.5% by mass or less Fe crystallizes as an Al-Fe-based intermetallic compound during casting. These crystallized substances have a different deformation ability from the aluminum matrix in the rolling process, so they have the effect of inhibiting the deformation of the aluminum matrix, dividing the crystal grains, and making them finer. However, if the Fe content is too low, the distribution density of intermetallic compounds will be low, resulting in a reduced effect of fine fragmentation and an uneven final grain size distribution. On the other hand, if the Fe content is too high, the size of the Al-Fe intermetallic compounds generated during casting will be very large, reducing the ductility and rollability of the aluminum alloy foil. For this reason, the lower limit of the Fe content is set at 1.0 mass%, and the upper limit at 1.5 mass%. For similar reasons, it is more desirable to set the lower limit at 1.2 mass% and the upper limit at 1.4 mass%.

[0017] ·Mn: 0.08 mass% or more and 0.16 mass% or less The addition of manganese (Mn) can improve the tensile strength and yield strength of aluminum alloy foil. Furthermore, the addition of Mn suppresses the recovery and recrystallization during cold rolling, as well as the resulting excessive work softening, which have been reported in Al-Fe alloys. However, if the Mn content is too low, these effects cannot be fully obtained. On the other hand, if the Mn content exceeds 0.16 mass%, coarse intermetallic compounds of the Al-Fe-Mn(-Si) system are easily formed, reducing the ductility and rollability of the aluminum alloy foil. Therefore, it is preferable to set the lower limit of the Mn content at 0.08 mass% and the upper limit at 0.16 mass%. More preferably, the lower limit of the Mn content is 0.1 mass% and the upper limit at 0.14 mass%.

[0018] ·Cu: 0.15 mass% or more and 0.25 mass% or less Cu is also an additive element that improves the strength of aluminum alloy foil through solid solution strengthening and suppresses recovery and recrystallization during rolling. Therefore, if the Cu content is too low, these effects cannot be fully obtained. On the other hand, if the Cu content is too high, the elongation decreases significantly, cracks occur frequently during rolling, and the rollability deteriorates. For this reason, it is preferable to set the lower limit of the Cu content to 0.15 mass% and the upper limit to 0.25 mass%. More preferably, the lower limit is 0.18 mass% and the upper limit is 0.23 mass%.

[0019] ·Si: 0.07% by mass or less Si crystallizes into coarse intermetallic compounds during casting. To prevent the formation of these coarse intermetallic compounds, it is desirable to limit its content. Excessive Si content can lead to coarser intermetallic compounds and a decrease in density, potentially resulting in reduced rollability and elongation properties. Therefore, it is desirable to limit the Si content to 0.07 mass%. More preferably, the Si content should be limited to 0.05 mass%.

[0020] 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), 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.

[0021] • Tensile strength: 120 MPa or higher, 0.2% yield strength: 70 MPa or higher Existing soft foils made of aluminum alloys have low strength and yield strength, and even slight external forces cause wrinkles and bending of the foil, resulting in poor handling during and after molding. Furthermore, aluminum alloy foil may break even with minor impacts such as dropping. By increasing the tensile strength of the aluminum alloy foil to 120 MPa or higher and the 0.2% yield strength to 70 MPa or higher, handling during molding, shape retention after molding, and resistance to impacts from drops and collisions are improved.

[0022] • Elongation of 15% or more in the 0°, 45°, and 90° directions relative to the rolling direction. In the molding process of packaging materials, deformation is applied in multiple directions, not just stretching in one direction. By satisfying the above elongation characteristics, excellent elongation characteristics in all directions can be expected. Furthermore, even when subjected to impact, the material is expected to have excellent impact resistance, being less prone to breakage due to its high strength and deformability. For this reason, it is preferable that the elongation in the three directions of 0°, 45°, and 90° be 15% or more in each direction. If the aluminum alloy foil does not meet these conditions, it will not be possible to achieve sufficient molding height, difficult-to-process shapes, or high impact resistance.

[0023] • Average grain size of grains surrounded by grain boundaries with an orientation difference of 2° or more: 5.5 μm or less • Particle size ratio expressed as maximum particle size / average particle size: 3.0 or less When metals are plastically deformed, irregularities (surface roughness) occur on the material surface. In particular, in thin materials such as aluminum alloy foil, surface roughness can be seen as thickness non-uniformity, and by suppressing this non-uniformity, the localization of stress / deformation can be mitigated, preventing a decrease in the forming limit. Refining the grain size is effective in suppressing surface roughness, and it is desirable that the average grain size of grains surrounded by grain boundaries with an orientation difference of 2° or more be 5.5 μm or less. Furthermore, since non-uniform particle size in aluminum alloy foils contributes to surface roughness and localization of stress / deformation, it is desirable that the particle size ratio, expressed as maximum particle size / average particle size, be 3.0 or less.

[0024] ·Cu orientation density Crystal orientation also affects surface roughness in aluminum alloy foil. Surface roughness occurs frequently near grain boundaries and is therefore related to deformation and non-uniformity at the grain level. If there is a large variation in crystal orientation, non-uniformity occurs in the deformation and rotation of each crystal grain during plastic deformation, leading to the development of surface roughness. Therefore, it is preferable for crystal orientations to be concentrated. Aluminum alloy foil has a relatively high rolling rate during its manufacturing process, and a rolling texture tends to develop easily. Therefore, it is desirable to concentrate crystal orientations in relation to the Cu orientation density, and to make the orientation density 30 or higher.

[0025] • Number density of intermetallic compounds with an equivalent circle diameter of 1.5-2.5 μm is 4000 particles / mm² 2 That's all. • Number density of intermetallic compounds with an equivalent circle diameter of 3.5 μm or more is 500 particles / mm² 2 below Intermetallic compounds, having different deformability from the aluminum substrate during the rolling process, inhibit the deformation of the aluminum substrate and have the effect of fragmenting and refining the crystal grains. However, if the size of the intermetallic compounds is small or their distribution density is sparse, the effect of refining the grains will be reduced or only partial. On the other hand, if the size of intermetallic compounds is too large, it can easily lead to a decrease in rollability, elongation, and formability, such as pinholes during rolling and voids during forming. Therefore, the number density of intermetallic compounds with an equivalent circle diameter of 1.5 to 2.5 μm should be 4000 / mm². 2 The above conditions must be met, and the number density of intermetallic compounds with an equivalent circular diameter of 3.5 μm or more must be 500 particles / mm². 2 The following is preferable:

[0026] <Manufacturing method for 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 homogenization treatment and soaking treatment, processed to the desired thickness by hot rolling, cold rolling and foil rolling, and finally annealed to obtain the aluminum alloy foil 1.

[0027] • Homogenization treatment: 480℃~540℃ for 7 hours or more A homogenization treatment is applied to the ingot after casting. The purpose of this homogenization treatment is to eliminate microsegregation in the ingot and adjust the distribution of intermetallic compounds, and it is an important treatment for obtaining a fine and uniform grain structure in the aluminum alloy foil after final annealing. If the homogenization temperature is below 480°C, the diffusion / precipitation of solid solution atoms is insufficient, resulting in a high solid solution content. Furthermore, the growth of intermetallic compounds tends to be insufficient. Intermetallic compounds are effective in promoting grain fragmentation during cold rolling, and insufficient growth reduces the grain refinement effect due to fragmentation. On the other hand, if the homogenization temperature exceeds 540°C, the growth of intermetallic compounds is significant, leading to a decrease in their density. In homogenization treatment held at a temperature range of 480-540°C, prolonged heat treatment is necessary to achieve an appropriate distribution of intermetallic compounds. Therefore, it is preferable to hold the homogenization treatment for 7 hours or more. If the holding time is less than 7 hours, the solid solution elements cannot be sufficiently diffused / deposited, the distribution of intermetallic compounds becomes non-uniform, and it becomes impossible to properly control the grain size after final annealing.

[0028] <Hot rolling> • Heat treatment: 400℃~450℃ × 1 hour In the soaking treatment before hot rolling, similar to the homogenization treatment, microsegregation is eliminated and the distribution of intermetallic compounds is adjusted. In addition, reheating is preferable to ensure hot rolling suitability in the next process. However, insufficient temperature control may result in non-uniformity in the grain size distribution. Therefore, to suppress recrystallization during hot rolling and to control the grain structure uniformly, the soaking treatment temperature is set to 400°C to 450°C. If the soaking temperature exceeds 450°C, recrystallization occurs in some areas during hot rolling, driven by the processing strain introduced during hot rolling, resulting in a non-uniform grain structure. This non-uniformity of the structure during hot rolling affects the structure of the final product, making it difficult to obtain a fine and uniform grain structure. On the other hand, if the temperature is below 400°C, the temperature during hot rolling is also low, which may cause cracks to form on the sides of the aluminum alloy sheet, leading to a significant decrease in productivity. For this reason, the soaking temperature should ideally be within the above range.

[0029] • Hot rolling finishing temperature: 230℃~280℃ To maintain a uniform grain structure during hot rolling, the finishing temperature after hot rolling is also important. It is necessary to appropriately adjust the finishing temperature to suppress recrystallization. If the finishing temperature exceeds 280°C, recrystallization occurs in some areas after hot rolling, resulting in a non-uniform structure where fiber grains and recrystallized grains are mixed. This non-uniform structure affects the grain structure of the final product and may lead to a decrease in formability. On the other hand, finishing the rolling temperature below 230°C requires extremely low temperatures during hot rolling, raising concerns from a rollingability standpoint. Therefore, the finishing temperature of hot rolling is desirable within the above range.

[0030] <Cold rolling> Intermediate annealing: None, or 300-400°C for 3 hours or more. If it is necessary to soften (restore rollability) a material hardened by cold rolling, annealing may be applied during cold rolling. However, if the temperature is below 300°C, recrystallization may not be completed, and there is a risk of non-uniform grain structure. Also, if the intermediate annealing temperature exceeds 400°C, recrystallized grains will coarseen, and the final grain size will also be larger. Even if the processing time is less than 3 hours, there is a risk that recrystallization will be incomplete. Intermediate annealing is performed using batch annealing, where the coils are placed in a furnace and held for a certain period of time.

[0031] In batch annealing, conditions of 300-400°C for 3 hours or more can be used. However, this embodiment is not limited to the presence or absence of intermediate annealing.

[0032] • Final cold rolling ratio: 98% or higher The grain size is refined even during the cold rolling process due to the high rolling load; therefore, the higher the final cold rolling ratio, the finer the grain size. For this reason, a high final cold rolling ratio is desirable, specifically, a final cold rolling ratio of 98% or higher is desirable. If the final cold rolling ratio is less than 98%, the grain size after final annealing becomes coarser or non-uniform, making it difficult to achieve the desired strength and ductility.

[0033] • Thickness of aluminum alloy foil The aluminum alloy foil can be made to the desired thickness by the final cold rolling process. In this embodiment, the thickness is not particularly limited, but for example, it can be 20 to 100 μm thick.

[0034] <Final annealing> Annealing temperature: 250℃~350℃ for 10 hours or more Final annealing is performed to restore the ductility of aluminum alloy foil after final cold rolling. For example, the final annealing after foil rolling should be carried out at 250°C to 350°C. If the final annealing temperature is too low, the ductility will be insufficient. On the other hand, if the annealing temperature exceeds 350°C, increased costs and other problems arise. If the final annealing time is less than 10 hours, the effect of the final annealing will be insufficient.

[0035] By the manufacturing method described above, an aluminum alloy foil can be obtained having a tensile strength of 120 MPa or more in the rolling direction, a 0.2% yield strength of 70 MPa or more in the rolling direction, elongation of 15% or more in each direction of 0°, 45°, and 90° relative to the rolling direction, an average grain size of grains surrounded by grain boundaries with an orientation difference of 2° or more of 5.5 μm or less, a grain size ratio expressed as maximum grain size / average grain size of 3.0 or less, and a Cu orientation density of 30 or more. The aluminum alloy foil 1 described above is suitable for food packaging or as a molded packaging material for lithium-ion batteries, and provides an aluminum alloy foil suitable for applications where large deformation is required by press molding, and where high elongation and formability are required. [Examples]

[0036] Aluminum alloy ingots of samples No. 1 to 20 with the compositions shown in Tables 1 and 2 below were obtained. Each ingot was then subjected to the soaking treatment shown in Tables 1 and 2, followed by hot rolling and cold rolling under the conditions shown in Tables 1 and 2, intermediate annealing as necessary, and finally cold rolling under the conditions shown in Tables 1 and 2 to obtain aluminum alloy foil. For each aluminum alloy foil, the tensile strength, 0.2% yield strength, elongation in the 0° direction, elongation in the 45° direction, and elongation in the 90° direction were determined based on the conditions described below. In addition, for each aluminum alloy foil, the average grain size, the grain size ratio (expressed as the ratio of the maximum grain size to the average grain size), the intermetallic compound density, the Cu orientation density, and the rectangular tube overhang height were measured based on the conditions described below.

[0037] "Evaluation Method" <Tensile strength> Tensile strength and 0.2% proof stress were measured using tensile tests in accordance with JIS Z2241. <Extension in the 0° direction, extension in the 45° direction, extension in the 90° direction> For elongation in the 0° direction, 45° direction, and 90° direction, JIS No. 5 test specimens were taken from 0°, 45°, and 90° directions relative to the rolling direction, and after processing to the test specimen shape, annealing was performed. The annealing here was performed under the same conditions as the final annealing described above. The annealed test specimens were measured using a universal tensile testing machine (Shimadzu Corporation AGS-X 10kN) at a tensile speed of 5 mm / min. The elongation rate was calculated by marking two lines at 50 mm intervals (gauge length) in the longitudinal center of the test specimen before the test, measuring the distance between the marks (l) by joining the fracture surfaces after the test, and dividing the elongation amount (mm) by the gauge length (l0:50 mm) using the following formula. ((l-l0) / l0)×100

[0038] <Crystal grain size> The grain size was determined by smoothing the cross-section of the aluminum alloy foil using a cross-section polisher (CP), and then performing crystal orientation analysis using a scanning electron microscope (SEM) and electron-beam diffraction (EBSD). In the analysis results, grain boundaries were defined as those with an orientation difference of 2° or more, and the average grain size was calculated by analyzing the area method under the following conditions. The analysis software used was OIM Analysis from TSL Solutions. In the Area method, the diameter of the area calculated by considering the relative abundance of each crystal grain within the measurement region, assuming it to be a circle, was defined as the crystal grain size. The observation magnification was set to 1000 times, and the field size was 150×38 μm. The average value was obtained by observing three fields. Other conditions of the electron microscope were an acceleration voltage of 15 kV, a sample tilt angle of 70°, and a step size of 0.5 μm.

[0039] The conditions of the EBSD detector were as follows. Analysis software: OIM Analysis (Ver.7.0) of TSL Solutions Area: The field size was 150 μm×38 μm, and three fields were analyzed. CI value (Confidence Index): Measurement points with a CI value of 0.1 or less were excluded. Minimum Grain Size (points): 2 Anti Grains: 2 (Measurement and calculation conditions for average crystal grain size) Grain Tolerance Angle: 2° Minimum Grain Size (points): 2 Anti Grains: 2 Minimum Confidence Index: 0.1 Multiple rows required: All were set to OFF. Apply partition before calculation: Set to OFF. Include grains at edges of scan in statistics: Set to ON.

[0040] <Cu orientation density> The Cu orientation density was obtained by X-ray diffraction method. An incomplete pole figure was obtained, and it was obtained from the incomplete pole figure by crystal orientation function analysis software. For the surface of the aluminum alloy foil sample, incomplete pole figures of {111}, {200}, and {220} were measured by X-ray diffraction method. Using the measurement results, a three-dimensional orientation distribution function (ODF) was calculated to calculate the Cu orientation density. The Cu orientation has {112}<111> as the representative orientation. As an example, a circular sample with a diameter of 40 mm is taken from an aluminum alloy foil such that the foil surface becomes the measurement surface. Next, using an X-ray diffractometer (SmartLab manufactured by Rigaku Corporation), the Schulz reflection method (α = 20° to 90°, β = 0° to 360°, measurement interval 5.0°) is carried out at a tube voltage of 40 kV and a tube current of 50 mA for the Cu tube target with respect to the measurement surface, and incomplete pole figures of (220), (200), and (111) are obtained. From these incomplete pole figures, using crystal orientation distribution function analysis software (StandardODF manufactured by Norm Engineering Co., Ltd.), the crystal orientation distribution function f(ψ1, φ, ψ2) is determined by the series expansion method with an expansion order of 22. The orientation density of the Cu orientation is taken as the numerical values of ψ1 = 90°, φ = 35°, and ψ2 = 45°.

[0041] <Number density of intermetallic compounds> The number density of intermetallic compounds is observed with a scanning electron microscope (SEM) after mechanically polishing the surface (RD-TD surface) of the aluminum alloy foil. The images obtained by observing at the following magnifications and ranges are subjected to particle analysis using analysis software to calculate the density. Observation magnification: 500 times Observation range: Total area of 400000 μm 2 Observation is carried out in multiple fields so as to be as described above. SEM: JSM-IT200LA (JEOL) Image analysis software: SMILE VIEW TM Lab

[0042] <Height of the corner cylinder protrusion> The height of the corner cylinder protrusion is carried out using a universal thin plate forming tester (model 142 / 20 manufactured by ERICHSEN) as the testing machine and using a square punch 2 having the shape shown in Fig. 2 (side length D = 37 mm, chamfered diameter at the corner R = 4.5 mm). · Test conditions: The wrinkle suppression force is 10 kN, and the scale of the upward speed (forming speed) of the punch is 1 Mineral oil is applied as a lubricant to one side of the aluminum alloy foil (the side where punch 2 hits). The punch height was varied in 0.2 mm increments while measurements were taken to determine the limit of the rectangular tube overhang height that would not cause cracks or pinholes.

[0043] The rectangular tube overhang height is a measure of processability when the aluminum alloy foil is processed into a three-dimensional shape, such as for battery packaging. It is determined by the degree of deformation that is possible when the aluminum alloy foil is formed. For example, if lubricating oil is supplied as described above and the aluminum alloy foil is formed at a constant speed using punch 2, the maximum punch height at which the foil can be formed without cracking or pinholes can be defined as the rectangular tube overhang height. A larger rectangular tube overhang height indicates that the aluminum alloy foil has superior processability.

[0044] Tables 1 and 2 show the composition ratios, homogenization treatment conditions, soaking treatment conditions, hot rolling conditions, intermediate annealing conditions, and cold rolling ratios for each aluminum alloy foil sample described above. Furthermore, for each aluminum alloy foil sample, the following data is provided: tensile strength (MPa), 0.2% yield strength (MPa), elongation in the 0° direction (%), elongation in the 45° direction (%), elongation in the 90° direction (%), average grain size (μm), grain size ratio expressed as the maximum grain size to the average grain size, and intermetallic compound number density (×10) for a circle equivalent diameter of 1.5 to 2.5 μm. 3 pieces / mm 2 ), number density of intermetallic compounds with an equivalent circle diameter of 3.5 μm or more (× compounds / mm²) 2 The results of measurements for Cu orientation density and rectangular tube overhang height (mm) are shown in Tables 3 and 4 below.

[0045] [Table 1]

[0046] [Table 2]

[0047] [Table 3]

[0048] [Table 4]

[0049] As shown in Tables 3 and 4, samples No. 1 to 10 are aluminum alloy foils made of an aluminum alloy having a composition containing Fe: 1.0% to 1.5% by mass, Mn: 0.08% to 0.16% by mass, Cu: 0.15% to 0.25% by mass, and Si: 0.07% by mass or less, with the remainder being Al and unavoidable impurities. Samples No. 1 to 10 have an average grain size of 5.5 μm or less for grains surrounded by grain boundaries with an orientation difference of 2° or more, a grain size ratio expressed as maximum grain size / average grain size of 3.0 or less, and a Cu orientation density of 30 or more. Samples No. 1 to 10 had a tensile strength of 120 MPa or more in the rolling direction, a 0.2% yield strength of 70 MPa or more in the rolling direction, and elongation of 15% or more in each direction at 0°, 45°, and 90° relative to the rolling direction.

[0050] Samples No. 1-2 and 5-10 have a number density of 4000 intermetallic compounds with an equivalent circular diameter of 1.5-2.5 μm. 2 That concludes the report. Furthermore, these samples have a number density of 500 intermetallic compounds with an equivalent circular diameter of 3.5 μm or larger. 2 The following applies: The intermetallic compounds in samples No. 3 and No. 4 have a number density of 4000 particles / mm² with an equivalent circular diameter of 1.5-2.5 μm. 2 Number density of less than 500 particles / mm² or with a circular equivalent diameter of 3.5 μm or more 2 This is in line with the desired results. While samples No. 3 and 4 differ from samples No. 1-2 and 5-10 in terms of the number density of intermetallic compounds, their particle size ratio, Cu orientation density, tensile strength, 0.2% yield strength, and elongation were within the aforementioned desirable range.

[0051] Compared to these samples, sample No. 11 contained more Si than the desired range, but its elongation in the 0° direction was less than 15%, its average grain size was larger, and its rectangular tube overhang height was less than 10 mm. Furthermore, sample No. 11 had a number density of 500 intermetallic compounds with an equivalent circle diameter of 3.5 μm or more. 2 It exceeds that. Sample No. 12, which had an Fe content lower than the desired range, exhibited an elongation in the 0° direction of less than 15%, resulting in a larger average grain size, insufficient Cu orientation density, and a rectangular tube overhang height of less than 10 mm. Furthermore, sample No. 12 also showed an intermetallic compound number density of 4000 particles / mm² with an equivalent circle diameter of 1.5-2.5 μm. 2 It fell below this amount.

[0052] Sample No. 13, which has an Fe content higher than the desired range, exhibits an elongation in the 0° direction of less than 15%, a larger grain size ratio, and a rectangular tube overhang height of less than 10 mm. Furthermore, sample No. 13 has a number density of 500 intermetallic compounds with an equivalent circle diameter of 3.5 μm or larger. 2 It exceeds that. Sample No. 14, which has a Mn content higher than the desired range, exhibits an elongation in the 0° direction of less than 15%, resulting in increased average grain size and grain size ratio, insufficient Cu orientation density, and a rectangular tube overhang height of less than 10 mm. Sample No. 14 also has a number density of 4000 particles / mm² of intermetallic compounds with an equivalent circle diameter of 1.5-2.5 μm. 2 It fell below this amount.

[0053] Sample No. 15, which had a Cu content higher than the desired range, exhibited an elongation of less than 15% in the 0° direction and a rectangular tube overhang height of less than 10 mm. Sample No. 16 was a sample in which the Mn and Cu content was lower than the desired range, but it lacked tensile strength and Cu orientation density. Sample No. 17 uses an aluminum alloy with a desirable composition, but the homogenization treatment time was short at 4.5 hours. As a result, the elongation in the 0° direction was less than 15%, the grain size ratio was large, and the protruding height of the rectangular tube was less than 10 mm. In addition, the number density of intermetallic compounds with an equivalent circle diameter of 1.5 to 2.5 μm in sample No. 17 was 4000 particles / mm². 2 It fell below this amount.

[0054] Sample No. 18 uses an aluminum alloy with the desired composition, but because the soaking temperature is higher than the desired temperature, the elongation in the 0° direction is less than 15%, both the average grain size and grain size ratio are large, and the protruding height of the rectangular tube is less than 10 mm. Sample No. 19 uses an aluminum alloy with Si and Mn content higher than the desired range, and the soaking temperature is higher than the desired temperature. Furthermore, the hot finishing temperature is also higher than the desired range, resulting in an elongation in the 0° direction of less than 15%, a larger grain size ratio, and a rectangular tube overhang height of less than 10 mm. Sample No. 19 has a number density of 500 intermetallic compounds with an equivalent circle diameter of 3.5 μm or larger. 2 It exceeds that. Sample No. 20 used an aluminum alloy with a Cu content lower than the desired range, and the cold rolling rate was also low. As a result, the tensile strength was insufficient, the Cu orientation density was low, and the rectangular tube overhang height was less than 10 mm. [Explanation of Symbols]

[0055] 1...Aluminum alloy foil, 2...Punch.

Claims

1. This aluminum alloy foil is made of an aluminum alloy having a composition containing Fe: 1.0% to 1.5% by mass, Mn: 0.08% to 0.16% by mass, Cu: 0.15% to 0.25% by mass, and Si: 0.07% by mass or less, with the remainder being Al and unavoidable impurities. An aluminum alloy foil characterized by having a tensile strength of 120 MPa or more in the rolling direction, a 0.2% yield strength of 70 MPa or more in the rolling direction, elongation of 15% or more in each of the 0°, 45°, and 90° directions relative to the rolling direction, an average grain size of grains surrounded by grain boundaries with an orientation difference of 2° or more of 5.5 μm or less, a grain size ratio expressed as maximum grain size / average grain size of 3.0 or less, and a Cu orientation density of 30 or more.

2. The number density of intermetallic compounds with an equivalent circular diameter of 1.5 to 2.5 μm is 4000 particles / mm². ２ The aluminum alloy foil according to claim 1, characterized in that it is as described above.

3. Number density of intermetallic compounds with an equivalent circular diameter of 3.5 μm or more is 500 particles / mm² ２ The aluminum alloy foil according to claim 1 or 2, characterized in that it is as follows:

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