JP2021143350A - Aluminum alloy foil and method for producing the same - Google Patents

Abstract

To provide an aluminum alloy foil that can suppress the breakage during production, and to provide a method for producing the same.SOLUTION: The aluminum alloy foil of the present invention contains Cu: 0.05 mass% or more and 0.2 mass% or less, Mn: 1.0 mass% or more and 1.5 mass% or less, and the balance is Al and unavoidable impurities. This aluminum alloy foil has a tensile strength of 240 MPa or more and less than 280 MPa, an elongation of 3% or more, and an interval of large-angle crystal grain boundary in the thickness direction of 0.5 μm or less.SELECTED DRAWING: Figure 1

Description

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

In recent years, lithium-ion batteries have been used as power sources for portable electronic devices such as mobile phones and laptop computers. The electrode material of this lithium ion battery is composed of a positive electrode plate, a separator, and a negative electrode plate, and is a material that has excellent electrical conductivity as a material for the positive electrode plate, does not affect the electrical efficiency of the secondary battery, and generates little heat. Aluminum alloy foil is used. As such an aluminum alloy foil, the aluminum alloy foils described in Patent Documents 1 to 3 are known.

For example, the aluminum alloy foil for a lithium ion battery electrode of Patent Document 1 contains Mn: 1.0 to 1.5% and Cu: 0.05 to 0.2% in mass%, and the balance Al and unavoidable impurities. The number of intermetallic compounds with a particle size of 0.1 to 1.0 μm present in the matrix is 1.5 × 10 ^{5 to} 6.0 × 10 ⁵ / mm ² , and liquid nitrogen is obtained by the double bridge method. The electric resistance value measured in the inside is 1.6 μΩcm or less.

Further, the aluminum alloy foil for a lithium ion secondary battery of Patent Document 2 has Si 0.01 to 0.60%, Fe 0.2 to 1.0%, Cu 0.05 to 0.50%, Mn 0. It contains 5 to 1.5%, the balance is composed of Al and unavoidable impurities, the tensile strength is 240 MPa or more, and the n value is 0.1 or more.

Further, the aluminum alloy foil for a lithium ion secondary battery of Patent Document 3 has Si 0.01 to 0.60%, Fe 0.2 to 1.0%, Cu 0.05 to 0.50%, Mn 0. It contains 5 to 1.5%, the balance is composed of Al and unavoidable impurities, the tensile strength is 240 MPa or more, the 0.2% proof stress after heat treatment at 100 ° C. for 30 minutes is 270 MPa or less, and The tensile strength after heat treatment at 180 ° C. for 30 minutes is 200 MPa or more.

Japanese Unexamined Patent Publication No. 2010-100919 Japanese Unexamined Patent Publication No. 2011-266656 Japanese Unexamined Patent Publication No. 2011-74433

By the way, since the aluminum alloy foils described in Patent Documents 1 to 3 are used as electrode materials for lithium ion secondary batteries, they are pressed after being coated with an active material on the surface by a battery maker or the like. In this case, if the elongation of the aluminum alloy foil is low, breakage may occur due to press working. Therefore, there is a demand for an aluminum alloy foil having excellent dislocation absorption ability due to deformation and higher elongation and deformation ability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aluminum alloy foil capable of suppressing fracture during production and a method for producing the same.

The aluminum alloy foil of the present invention contains Cu: 0.05% by mass or more and 0.2% by mass or less, Mn: 1.0% by mass or more and 1.5% by mass or less, and the balance is composed of Al and unavoidable impurities. The tensile strength is 240 MPa or more and less than 280 MPa, the elongation is 3% or more, and the interval between the large-angle crystal grain boundaries in the thickness direction is 0.5 μm or less.

In the present invention, since the tensile strength is 240 MPa or more and less than 280 MPa and the elongation is 3% or more, it is possible to suppress the breakage of the aluminum alloy foil during manufacturing or processing. If the tensile strength is less than 240 MPa, the tensile strength of the aluminum alloy foil is insufficient and breakage may occur due to processing during manufacturing, and if it is 280 MPa or more, breakage occurs due to a decrease in elongation. It will be easier. Further, since the elongation is 3% or more, breakage is less likely to occur. .. Further, by setting the interval between the large-angle crystal grain boundaries in the thickness direction to 0.5 μm or less, it is possible to provide an aluminum alloy foil having excellent dislocation absorption ability due to deformation and higher elongation and deformability. If the spacing between the large-angle crystal grain boundaries in the thickness direction exceeds 0.5 μm, grain boundary fracture is likely to occur.
The large-angle crystal grain boundary means a grain boundary with an orientation difference of 15 ° or more between adjacent crystals measured by the EBSD method.

Cu contributes to the improvement of the tensile strength and elongation of the aluminum alloy foil. If it is less than 0.05% by mass, sufficient tensile strength cannot be obtained, and if it exceeds 0.2% by mass, the tensile strength is high. If it becomes too large, the elongation is reduced and breakage is likely to occur.
Mn contributes to the improvement of the tensile strength of the aluminum alloy foil, and if it is less than 1.0% by mass, sufficient tensile strength cannot be obtained, and if it exceeds 1.5% by mass, the proportion of the metal compound increases. Therefore, when the tensile strength becomes too high, the elongation decreases and fracture is likely to occur.

As a preferred embodiment of the aluminum alloy foil of the present invention, Si: 0.1% by mass or more and 0.4% by mass or less and Fe: 0.2% by mass or more and 0.8% by mass or less may be further contained.
Si contributes to the improvement of elongation of the aluminum alloy foil, and if it is less than 0.1% by mass, sufficient elongation may not be obtained, and if it exceeds 0.4% by mass, the proportion of the metal compound increases. , May break during rolling in the manufacturing process of aluminum alloy foil.
Fe contributes to the improvement of the tensile strength and elongation of the aluminum alloy foil. If it is less than 0.2% by mass, sufficient tensile strength and elongation cannot be obtained, and if it exceeds 0.8% by mass, the metal compound The proportion may increase and break during rolling in the aluminum alloy foil manufacturing process.

The method for producing an aluminum alloy foil of the present invention contains Cu: 0.05% by mass or more and 0.2% by mass or less, Mn: 1.0% by mass or more and 1.5% by mass or less, and the balance is Al and unavoidable. After melt-casting an aluminum alloy composed of impurities, homogenization treatment is performed to hold it at 480 ° C. or higher and 550 ° C. or lower for 5 hours or longer, and soaking heat treatment is performed at 500 ° C. or higher and 540 ° C. or lower for 1 hour or longer, and then at 320 ° C. or lower. Hot rolling is performed, cold rolling with a rolling ratio of 70% or more and 80% or less is applied, intermediate annealing is performed at 480 ° C. or higher in a continuous tanning furnace, and foil rolling is performed to bring the final rolling ratio to 98% or higher.

In the present invention, a melt-cast aluminum alloy is subjected to homogenization treatment and soaking heat treatment, followed by hot rolling and cold rolling, which is then subjected to intermediate annealing and foil rolling. It contains 0.05% by mass or more and 0.2% by mass or less, Mn: 1.0% by mass or more and 1.5% by mass or less, the balance is composed of Al and unavoidable impurities, and the tensile strength is 240 MPa or more and less than 280 MPa. It is possible to produce an aluminum alloy foil having an elongation of 3% or more and an interval of large-angle crystal grain boundaries in the thickness direction of 0.5 μm or less.

If the holding temperature of the homogenization treatment is less than 480 ° C., a large amount of solid-solved elements are precipitated, and the strength of the foil becomes lower than 240 MPa due to the decrease of the solid-solved elements. On the other hand, if the holding temperature exceeds 550 ° C., local melting may occur and the surface texture may deteriorate, which is not preferable. Further, if the holding time is less than 5 hours, the precipitation of the solid-solved alloying elements is non-uniform, which causes variation from lot to lot, which is not preferable.
If the temperature of the soaking heat treatment is less than 500 ° C., the temperature during hot rolling becomes low, and solid-dissolving elements are precipitated during rolling, so that the concentration of solid-dissolving elements decreases. On the other hand, if it exceeds 540 ° C., the temperature becomes too high during hot rolling, and the temperature after rolling exceeds 320 ° C. Further, if the soaking time is less than 1 hour, the temperature does not rise to a temperature suitable for hot rolling and becomes low, or the entire plate becomes non-uniform.
When the temperature of hot rolling exceeds 320 ° C., the crystal grains after rolling become coarse, and the crystal grains in the foil do not become fine and the strength and elongation decrease. Further, if the rolling reduction ratio of cold rolling is less than 70%, the rolling ratio after intermediate annealing becomes high, the strength increases too much, and the elongation decreases. On the contrary, if it exceeds 80%, the strength cannot be increased because the rolling ratio after intermediate annealing is low.
Further, if the temperature of the intermediate annealing treatment is less than 480 ° C., sufficient solid solution of the additive element is not made, and the crystal grains become coarse.
Further, if the final rolling ratio by foil rolling is less than 98%, the rolling ratio is low and the refinement of crystal grains cannot be achieved.

As a preferred embodiment of the aluminum alloy foil of the present invention, the aluminum alloy further contains Si: 0.1% by mass or more and 0.4% by mass or less, and Fe: 0.2% by mass or more and 0.8% by mass or less. It is good to have.

According to the present invention, it is possible to provide an aluminum alloy foil capable of suppressing breakage during production.

It is a figure which shows the state that the aluminum alloy foil in the Example of this invention is cut out by punching the angle type test piece shape without a notch, and is pulled by a universal tensile tester.

Hereinafter, embodiments of the aluminum alloy foil according to the present invention will be described.

[Composition of aluminum alloy foil]
The aluminum alloy foil of the present embodiment is used, for example, as a material for the positive electrode plate among the positive electrode plate, the separator and the negative electrode plate constituting the electrode material of the lithium ion battery. This positive electrode plate is formed by applying an active material to the surface of an aluminum alloy foil and pressing it. Therefore, the aluminum alloy foil used as a material for the positive electrode plate is required to have high elongation and deformability in addition to the dislocation absorbing ability.
Therefore, the aluminum alloy foil of the present embodiment contains Cu: 0.05% by mass or more and 0.2% by mass or less, Mn: 1.0% by mass or more and 1.5% by mass or less, and the balance is Al and It consists of unavoidable impurities. Further, the aluminum alloy foil may further contain Si: 0.1% by mass or more and 0.4% by mass or less and Fe: 0.2% by mass or more and 0.8% by mass or less in addition to the above Cu and Mn. preferable.

"Cu" 0.05% by mass or more and 0.2% by mass or less Cu contributes to the improvement of the tensile strength and elongation of the aluminum alloy foil. Specifically, Cu prevents recrystallization during rolling and suppresses a decrease in strength.
If the Cu content is less than 0.05% by mass, the crystal grains become coarse during recrystallization and the structure becomes non-uniform, so that sufficient tensile strength cannot be obtained, and if it exceeds 0.2% by mass. If the tensile strength becomes too high, the elongation is reduced and breakage is likely to occur.

"Mn" 1.0% by mass or more and 1.5% by mass or less Mn contributes to the improvement of the tensile strength of the aluminum alloy foil. Specifically, Mn forms an Al—Mn—Fe-based intermetallic compound and exhibits a dispersion curing action by forming a crystallization phase and a dispersed phase, thereby improving tensile strength.
If the Mn content is less than 1.0% by mass, the amount of the intermetallic compound precipitated is small, and sufficient hardening characteristics cannot be obtained. Therefore, sufficient tensile strength cannot be obtained, and 1.5 If it exceeds% by mass, the proportion of the metal compound increases due to the dispersion hardening action and the precipitation hardening action, and the tensile strength becomes too high, so that the elongation decreases and fracture is likely to occur.

“Si” 0.1% by mass or more and 0.4% by mass or less Si contributes to the improvement of elongation of the aluminum alloy foil. Specifically, Si increases the amount of precipitation of the second phase particles and improves the elongation after foil rolling.
If the Si content is less than 0.1% by mass, sufficient elongation may not be obtained, and if it exceeds 0.4% by mass, the proportion of the metal compound increases, and the aluminum alloy foil manufacturing process. In addition to the possibility of breakage during rolling in the above, the second phase particles are coarsened to reduce the elongation after foil rolling.

"Fe" 0.2% by mass or more and 0.8% by mass or less Fe contributes to the improvement of the tensile strength and elongation of the aluminum alloy foil. Specifically, the tensile strength and elongation are improved by increasing the amount of precipitation of the Al-Mn-Fe-based intermetallic compound and subdividing the crystal.
If the Fe content is less than 0.2% by mass, sufficient tensile strength and elongation cannot be obtained, and if it exceeds 0.8% by mass, the proportion of the metal compound increases, and the manufacturing process of the aluminum alloy foil May break during rolling.

An aluminum alloy foil having such a composition has, for example, a thickness of 10 μm or more and 15 μm or less, a tensile strength of 240 MPa or more and less than 280 MPa, an elongation of 3% or more, and a large-angle grain boundary in the thickness direction. The interval between the two is 0.5 μm or less.
In the present embodiment, the tensile strength is 240 MPa or more and less than 280 MPa, and the elongation is 3% or more, so that it is possible to suppress breakage during manufacturing. If this tensile strength is less than 240 MPa, the tensile strength of the aluminum alloy foil is insufficient, and fracture may occur due to processing during manufacturing. If it is 280 MPa or more, the processability is lowered and the elongation is lowered. By doing so, breakage is likely to occur. Further, since the elongation is 3% or more, breakage is less likely to occur. Further, by setting the interval between the large-angle crystal grain boundaries in the thickness direction to 0.5 μm or less, it is possible to provide an aluminum alloy foil having excellent dislocation absorption ability due to deformation and higher elongation and deformability.
If the spacing between the large-angle crystal grain boundaries in the thickness direction exceeds 0.5 μm, grain boundary fracture may occur.

[Manufacturing method of aluminum alloy foil]
The aluminum alloy foil is manufactured by the following procedure. First, the aluminum alloy having the above composition is produced by subjecting it to melt casting, homogenization treatment, soaking heat treatment, hot rolling, cold rolling, intermediate annealing treatment, and foil rolling in this order. Hereinafter, a specific description will be given.

[Dissolution casting]
Cu: 0.05% by mass or more and 0.2% by mass or less, Mn: 1.0% by mass or more and 1.5% by mass or less, and the balance is an aluminum alloy by dissolving an aluminum alloy composed of Al and unavoidable impurities. Generates molten metal. Then, the molten aluminum alloy is cast by a semi-continuous casting method (DC casting).
The casting method is not limited to the semi-continuous casting method, and other conventional methods such as the continuous casting method may be used. Further, the aluminum alloy ingot may be surface-cut before and after the homogenization treatment.

[Homogenization treatment]
The ingot obtained by the semi-continuous casting method is homogenized for the purpose of removing inhomogeneous structures such as segregation. Due to the high-temperature homogenization treatment, additive elements supersaturated and solid-solved in the matrix during casting are precipitated as intermetallic compounds. Since the size and the amount of dispersion of the precipitated intermetallic compound are affected by the temperature and time of the homogenization treatment, it is necessary to select the heat treatment conditions according to the type of the additive element.

For example, since the aluminum alloy has the above composition, the obtained ingot is homogenized at a temperature of 480 ° C. or higher and 550 ° C. or lower for 5 hours or longer. This homogenization treatment is more preferably held at a temperature of 500 to 530 ° C. for 5 to 10 hours.
If the holding temperature of the homogenization treatment is less than 480 ° C., a large amount of solid-solved elements are precipitated, and the strength of the foil becomes lower than 240 MPa due to the decrease of the solid-solved elements. If the holding temperature exceeds 550 ° C., local melting may occur and the surface texture may be deteriorated, which is not preferable. Further, if the holding time is less than 5 hours, the precipitation of the solid-solved alloying elements is non-uniform, which causes variation from lot to lot, which is not preferable.

[Heat treatment]
A soaking heat treatment is performed on the ingot that has been homogenized. This soaking heat treatment is carried out after the ingot that has been homogenized has cooled to about room temperature (for example, 25 ° C.), and the ingot is raised to a temperature suitable for hot rolling before hot rolling. Will be executed.
In the present embodiment, since the hot rolling finish temperature is set to 320 ° C. or lower, for example, a soaking heat treatment that holds the temperature at 500 ° C. or higher and 540 ° C. or lower for 1 hour or longer is executed.

[Hot rolling]
Hot rolling is performed on the ingot that has undergone soaking heat treatment. This hot rolling is preferably completed at 320 ° C. or lower. Specifically, the total number of passes (the number of passes through the rolling mill) and the rolling reduction rate in each pass are controlled so that the temperature on the exit side of the final hot rolling pass is 250 ° C to 300 ° C, and the hot rolling is completed. The thickness of the latter plate material is set to 3 mm to 5 mm.

[Cold rolling]
Next, cold rolling is performed on the plate material after hot rolling. This cold rolling method is not particularly limited, but can be carried out, for example, by passing a plate material through a rolling mill. The rolling ratio of this cold rolling is 70% or more and 80% or less, and for example, the thickness of the plate material after cold rolling is, for example, 0.3 mm to 1.0 mm.

[Intermediate annealing treatment]
An intermediate annealing treatment is performed on the plate material after cold rolling. This intermediate annealing treatment is carried out in a continuous annealing furnace at a temperature of 480 ° C. or higher. Specifically, by executing rapid heating and rapid cooling in a continuous annealing furnace, the solid solubility of the added elements is increased, the formation of coarse precipitates is suppressed, and the crystal grains are refined after the final rolling. Facilitate.
If the temperature of the intermediate annealing treatment is less than 480 ° C., the additive elements are not sufficiently solid-solved, and the crystal grains become coarse.

[Foil rolling]
Finally, foil rolling is performed on the plate material that has been subjected to the intermediate annealing treatment. This method of foil rolling is not particularly limited, but can be carried out, for example, by passing a plate material through a rolling mill. In this foil rolling, the final rolling ratio is 98% or more, and the thickness of the aluminum alloy foil is 10 μm or more and 15 μm or less.

The aluminum alloy foil produced in this manner has a tensile strength of 240 MPa or more and 280 MPa or less, an elongation of 3% or more, and an interval of large angle grain boundaries in the thickness direction of 0.5 μm or less. ..

In the aluminum alloy foil of the present embodiment, since the tensile strength is set to 240 MPa or more and 280 MPa or less, it is possible to suppress the occurrence of breakage during manufacturing. Further, since the elongation of the aluminum alloy foil is 3% or more, breakage is less likely to occur. Further, by setting the interval between the large-angle crystal grain boundaries to 0.5 μm or less, the dislocation absorbing ability due to deformation is excellent, and the elongation and deformability can be further enhanced. Therefore, even if the aluminum alloy foil is coated with the active material and then pressed, the aluminum alloy foil does not break, so that it can be used as a material for the positive electrode plate of the lithium ion secondary battery. Manufacturing efficiency can be improved.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

The aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 10 were produced by the methods shown below, and the spacing, tensile strength and elongation of the large-angle grain boundaries in the thickness direction of each of the obtained samples were measured. This will be described in detail below.
The compositions (components) of the aluminum alloys used as the raw materials of Examples 1 to 5 and Comparative Examples 1 to 10 were as shown in Table 1. The composition of each of these aluminum alloys contains each component shown in Table 1, and the balance is Al and unavoidable impurities.

The aluminum alloys of Examples 1 to 5 and Comparative Examples 1 to 10 were melted to form a molten aluminum alloy, which was cast by semi-continuous casting. The ingot obtained by the semi-continuous casting method was subjected to a homogenization treatment of the temperature and time shown in Table 2, and then subjected to a soaking heat treatment at the temperature and time shown in Table 2, and the finishing temperature was 250 ° C to 300 ° C. It was hot-rolled in and cold-rolled with a rolling ratio of 76%. Then, in the furnace shown in Table 2, after intermediate annealing at the furnace and temperature shown in Table 2, foil rolling with a final rolling ratio of 98.2% was carried out to produce an aluminum alloy foil having a thickness of 13 μm. These were used as each sample.
The description of CAL in the intermediate annealing in Table 2 means annealing in a continuous annealing furnace, and the description of Batch means annealing in a batch furnace.

(Measurement of spacing between large-angle grain boundaries in the thickness direction)
The RD-ND surface of the aluminum alloy foil was cut by CP (cross section microscope), and this cut surface was analyzed by SEM (Scanning Electron Microscope) -EBSD. The entire thickness of the foil was observed at a magnification of × 4000 times, and when the particle size was actually measured, it was observed at × 10000 times. In the obtained orientation mapping image, the crystal grain spacing in the thickness direction of the foil was calculated by the line segment method from the grain map displaying the grain boundaries having an orientation difference of 15 ° or more. In addition, the observation of × 10000 times was performed in 3 fields of view with one sample, and the interval was taken as the average value.
In the crystal orientation analysis in SEM-EBSD, the crystal grain boundaries having an orientation difference of 15 ° or more between the crystal grains were defined as HAGBs (large tilt angle grain boundaries), and the intervals of HAGBs were measured. The visual field size of 15 × 40 μm was measured in three visual fields at a magnification of × 10000, and the grain boundary spacing in the thickness direction was calculated. For the calculation, the Area method (Average by Area Fraction Method) of EBSD was used. OIM Analysis of TSL Solutions was used for the analysis.

(Measurement of tensile strength and elongation)
The tensile strength and elongation were measured by a method according to JISZ2241. Specifically, a sample was cut out from each of the obtained samples in parallel with the rolling direction, and measurement was performed with a universal tensile tester (manufactured by Shimadzu Corporation) at a tensile speed of 2 mm / sec.

(Measurement of tear strength)
Regarding the tear strength, referring to the tear test (JIS K-6252) used for rubber, etc., an angle-type test piece shape without a notch as shown in FIG. 1 was cut out by punching, and a universal tensile tester (Shimadzu). The measurement was carried out at a tensile speed of 800 mm / sec, a distance between chucks of 70 mm, and a preload of 0.8 N. The dimensions and the like of each part of the angle type test piece in the tear test are as shown in the table at the bottom of FIG.
The value obtained by dividing the measured maximum load by the sample thickness was evaluated as the tear strength (kN / mm). A tear strength of 105 kN / mm or more was evaluated as "pass", and a tear strength of less than 105 kN / mm was evaluated as "fail".

As shown in Table 1, A1, B1, C1, D1 containing Cu: 0.05% by mass or more and 0.2% by mass or less and Mn: 1.0% by mass or more and 1.5% by mass or less. , E1 alloy is subjected to homogenization treatment for holding at 480 ° C. or higher and 550 ° C. or lower for 5 hours or longer, soaking heat treatment is applied at 500 ° C. or higher and 540 ° C. or lower for 1 hour or longer, and then hot-rolled at 320 ° C. or lower and rolled. The samples of Examples 1 to 5 subjected to cold rolling at a rate of 70% or more and 80% or less and subjected to intermediate annealing at 480 ° C. or higher in a continuous annealing furnace had a tensile strength of 240 MPa or more and less than 280 MPa. The elongation was 3% or more, the spacing between the large-angle grain boundaries in the thickness direction was 0.5 μm or less, and the tear strength was also evaluated as acceptable.
On the other hand, in Comparative Examples 1 to 4, since the Cu component or Mn component of the alloys F1, G1, H1 and I1 was out of the above range, the tensile strength and elongation were obtained even if the same treatment as in Examples 1 to 5 was performed. And at least one of the intervals between the large-angle grain boundaries was out of the above range, and in Comparative Examples 1 and 3, the tear strength was insufficient, and the evaluation was rejected. In Comparative Example 5, since the alloy A1 was used, the alloy composition was satisfied, but the homogenization holding time was insufficient, so that the elongation was lowered and the tear strength was also evaluated as unacceptable. Further, although the alloys A1 were used in Comparative Examples 6 to 8, the tensile strength was low in all of them because the temperature and time of the soaking heat treatment were out of the above range, and the elongation was lowered in Comparative Example 7, and Comparative Example 8 Then, the elongation decreased and the tear strength was also evaluated as unacceptable. Further, in Comparative Examples 9 and 10, although the alloy A1 is used, since the intermediate annealing temperature is low, the interval between the large-angle crystal grain sizes exceeds 0.5 μm and the elongation is 2.5 to 2.6. It was as small as%. Therefore, the evaluation of tear strength also failed.

Claims (4)

Cu: 0.05% by mass or more and 0.2% by mass or less, Mn: 1.0% by mass or more and 1.5% by mass or less, the balance is composed of Al and unavoidable impurities, and the tensile strength is 240 MPa or more and 280 MPa. An aluminum alloy foil having a elongation of less than 3%, an elongation of 3% or more, and an interval of large angle grain boundaries in the thickness direction of 0.5 μm or less. The aluminum alloy foil according to claim 1, further containing Si: 0.1% by mass or more and 0.4% by mass or less, and Fe: 0.2% by mass or more and 0.8% by mass or less. After melting and casting an aluminum alloy containing Cu: 0.05% by mass or more and 0.2% by mass or less, Mn: 1.0% by mass or more and 1.5% by mass or less, and the balance being Al and unavoidable impurities. It is homogenized by holding it at 480 ° C. or higher and 550 ° C. or lower for 5 hours or longer, and after soaking heat treatment at 500 ° C. or higher and 540 ° C. or lower for 1 hour or longer, it is hot-rolled at 320 ° C. or lower and the rolling ratio is 70% or higher and 80. A method for producing an aluminum alloy foil, which comprises loading% or less of cold rolling, performing intermediate annealing at 480 ° C. or higher in a continuous tanning furnace, and rolling the foil to a final rolling ratio of 98% or higher. The third aspect of claim 3, wherein the aluminum alloy further contains Si: 0.1% by mass or more and 0.4% by mass or less, and Fe: 0.2% by mass or more and 0.8% by mass or less. How to make aluminum alloy foil.

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