Aluminum alloy foil

Abstract

To provide aluminum alloy foil with high strength and formability. [Solution] An aluminum alloy foil is used, characterized by the following composition: Si: 0.15 mass% or less, Fe: 1.00 to 1.70 mass%, Cu, Mn, Mg, Cr, and Ni: 0.0005 mass% or more each, Cu+Mn+Mg+Cr+Ni: 0.0500 to 0.1000 mass% in total, and the remainder being Al and impurities, with an average crystal grain size of 3.0 to 9.0 μm.

Description

Technical Field

[0001] The present disclosure relates to aluminum alloy foils. More specifically, it relates to aluminum alloy foils having high strength and formability.

Background Art

[0002] Aluminum alloys are used in various forming applications because of their excellent formability. For example, Patent Document 1 discloses an aluminum alloy foil having a composition containing Fe: 1.2 mass% or more and 1.6 mass% or less, Si: 0.05 mass% or more and 0.14 mass% or less, Cu: 0.005 mass% or more and 0.1 mass% or less, regulated to Mn: 0.01 mass% or less, with the balance being Al and other inevitable impurities, wherein the average crystal grain size of the aluminum alloy foil is 20 to 30 μm, the maximum crystal grain size / average crystal grain size ≦ 3.0, the Cube orientation density is 10 or more, the Cu orientation density is 20 or less, and the R orientation density is 15 or less. Patent Document 1 discloses that the above aluminum alloy foil has high elongation characteristics.

[0003] From the viewpoint of improving the strength and formability of aluminum alloy foils, there is still room for further improvement.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide an aluminum alloy foil having high strength and formability.

Means for Solving the Problems

[0006] The gist of this disclosure is as follows: [1]Si: 0.15% by mass or less, Fe: 1.00~1.70% by mass, Cu, Mn, Mg, Cr, and Ni: 0.0005% by mass or more each, Cu+Mn+Mg+Cr+Ni: Total of 0.0500~0.1000 mass%, and, The remainder consists of Al and impurities. An aluminum alloy foil characterized by having an average crystal grain size of 3.0 to 9.0 μm. [2] The aluminum alloy foil according to [1], characterized in that the total elongation is 15.0% or more and the tensile strength is 100 MPa or more. [3] The aluminum alloy foil according to [1] or [2], characterized in that the Erichsen value is 6.0 mm or more. [4] An aluminum alloy foil according to any one of [1] to [3], characterized in that the equivalent plastic strain in the equibiaxial tensile region measured by the Marciniak method is 0.300 or more. [Effects of the Invention]

[0007] According to this disclosure, by incorporating desired amounts of Cu, Mn, Mg, Cr, and Ni, it is possible to provide an aluminum alloy foil with high strength and formability. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view showing an example of an aluminum alloy foil according to the present invention. [Modes for carrying out the invention]

[0009] In order to obtain an aluminum alloy foil with high strength and formability, the inventors conducted research and obtained the following findings. By controlling the elemental composition range and grain size to a desired range, high formability can be achieved. Furthermore, by including desired amounts of Cu, Mn, Mg, Cr, and Ni, which have not been previously considered, a grain refinement effect can be obtained. Including these elements in desired amounts contributes to improving the formability of aluminum alloy foil. Moreover, the inclusion of these elements also improves tensile strength, making it a useful material for containers and other applications where shape retention is required.

[0010] Hereinafter, an example of an aluminum alloy foil according to an embodiment of the present invention will be described in detail based on the attached drawings. Note that, for convenience, the drawings used in the following description may show enlarged portions of key features to make them easier to understand.

[0011] Figure 1 is a plan view showing an example of an aluminum alloy foil according to this embodiment. The aluminum alloy foil 1 shown in Figure 1 is a foil obtained by hot rolling and cold rolling of 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.

[0012] The rolling direction of aluminum alloy foil 1 is the left-right direction (the 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 (the vertical direction on the page of Figure 1).

[0013] The aluminum alloy foil 1 according to this embodiment will be described in detail below. Reference numerals in the drawings may be omitted in the following description. Note that the numerical ranges indicated by "~" below include both a lower limit and an upper limit. Numbers indicated as "less than" or "greater than" are not included in the numerical range.

[0014] First, the chemical composition of the aluminum alloy foil will be described. The aluminum alloy foil contains Si: 0.15 mass% or less, Fe: 1.00 - 1.70 mass%, Cu, Mn, Mg, Cr, and Ni: each 0.0005 mass% or more, Cu + Mn + Mg + Cr + Ni: a total of 0.0500 - 0.1000 mass%, and the balance: Al and impurities. Next, each element will be described in detail.

[0015] Si: 0.15 mass% or less Si is an element that forms intermetallic compounds together with Fe. If the Si content exceeds 0.15 mass%, coarse intermetallic compounds will be generated, which may lead to a decrease in rolling properties and elongation characteristics, and further a concern about the deterioration of the uniformity of the recrystallized grain size after final annealing. Therefore, the Si content should be 0.15 mass% or less. The Si content is preferably 0.11 mass% or less. The lower limit of the Si content is not particularly limited, but it may be 0.00 mass% or 0.01 mass% or more.

[0016] Fe: 1.00 - 1.70 mass% Fe crystallizes as an Al - Fe - based intermetallic compound during casting. When its size is large, it serves as a recrystallization site during annealing and has the effect of refining recrystallized grains. If the Fe content is less than 1.00 mass%, the distribution density of coarse intermetallic compounds will be low, the effect of its refinement will be low, and the uniformity of the recrystallized grain size after final annealing will decrease. Therefore, the Fe content should be 1.00 mass% or more. The Fe content is preferably 1.20 mass% or more. On the other hand, if the Fe content exceeds 1.70 mass%, the effect of grain refinement will saturate or decrease, and furthermore, the size of the Al - Fe - based intermetallic compound generated during casting will become significantly larger, resulting in a decrease in the elongation, formability, and rolling properties of the aluminum alloy foil. Therefore, the Fe content should be 1.70 mass% or less. The Fe content is preferably 1.60 mass% or less.

[0017] Cu, Mn, Mg, Cr, and Ni: each 0.0005 mass% or more Cu is an element that increases the strength of the aluminum alloy foil and decreases its elongation. By containing an appropriate amount of Cu, the effect of grain refinement can also be obtained. If the Cu content is less than 0.0005% by mass, the effect of strength improvement and the effect of grain refinement become low, and it cannot withstand use as a container. Therefore, the Cu content should be 0.0005% by mass or more. The Cu content is preferably 0.0010% by mass or more, 0.0020% by mass or more, 0.0030% by mass or more, or 0.0050% by mass or more.

[0018] Mn is an element that dissolves in aluminum to increase strength and decrease elongation. If the Mn content is less than 0.0005% by mass, the effect of strength improvement becomes low, and it cannot withstand use as a container. Therefore, the Mn content should be 0.0005% by mass or more. The Mn content is preferably 0.0010% by mass or more, 0.0020% by mass or more, 0.0030% by mass or more, or 0.0050% by mass or more.

[0019] Mg is an element that dissolves in aluminum to increase strength and decrease elongation. By containing an appropriate amount of Mg, the effect of grain refinement can also be obtained. If the Mg content is less than 0.0005% by mass, the effect of strength improvement and the effect of grain refinement become low, and it cannot withstand use as a container. Therefore, the Mg content should be 0.0005% by mass or more. The Mg content is preferably 0.0010% by mass or more, 0.0020% by mass or more, 0.0030% by mass or more, or 0.0050% by mass or more.

[0020] Cr is an element that dissolves in aluminum to increase strength and decrease elongation. If the Cr content is less than 0.0005% by mass, the effect of strength improvement becomes low, and it cannot withstand use as a container. Therefore, the Cr content should be 0.0005% by mass or more. The Cr content is preferably 0.0010% by mass or more, 0.0020% by mass or more, 0.0030% by mass or more, or 0.0050% by mass or more.

[0021] Ni is an element that dissolves in aluminum, increasing its strength and decreasing its elongation. If the Ni content is less than 0.0005% by mass, the effect of increasing strength becomes low, and the aluminum cannot withstand use as a container. Therefore, the Ni content should be 0.0005% by mass or more. Preferably, the Ni content is 0.0010% by mass or more, 0.0020% by mass or more, 0.0030% by mass or more, or 0.0050% by mass or more.

[0022] Cu + Mn + Mg + Cr + Ni: Total mass 0.0500~0.1000% As described above, the aluminum alloy foil according to this disclosure contains 0.0005% by mass or more of Cu, Mn, Mg, Cr, and Ni, and the total content of these elements is 0.0500 to 0.1000% by mass. If the total content of Cu, Mn, Mg, Cr, and Ni is less than 0.0500%, the effects of grain refinement, resulting elongation, improved formability, and improved strength cannot be obtained. Therefore, the total content of Cu, Mn, Mg, Cr, and Ni is 0.0500% by mass or more. Preferably, the total content of Cu, Mn, Mg, Cr, and Ni is 0.0550% by mass or more, 0.0600% by mass or more, or 0.0700% by mass or more. On the other hand, if the total content of Cu, Mn, Mg, Cr, and Ni exceeds 0.1000% by mass, the moldability decreases significantly along with the decrease in elongation. Therefore, the total content of Cu, Mn, Mg, Cr, and Ni should be 0.1000% by mass or less. Preferably, the total content of Cu, Mn, Mg, Cr, and Ni is 0.0900% by mass or less, or 0.0800% by mass or less.

[0023] Remainder: Al and impurities The remainder of the chemical composition of the aluminum alloy foil according to this embodiment consists of Al and (unavoidable) impurities. In this embodiment, unavoidable impurities refer to elements that are inevitably mixed in during the manufacturing of the aluminum alloy foil. Unavoidable impurities may be included in amounts that do not affect the properties of the aluminum alloy foil according to this embodiment. Examples of unavoidable impurities include elements such as zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), boron (B), and zirconium (Zr). One or more of these elements may be included in amounts of 0.0500% by mass or less for each. Furthermore, it is preferable that the total amount of unavoidable impurities be 0.500% by mass or less.

[0024] Average grain size: 3.0~9.0μm The average grain size of aluminum alloy foil affects elongation and surface roughness during plastic deformation. If the average grain size is less than 3.0 μm, the structure will retain subgrain boundaries, reducing elongation and moldability. Therefore, the average grain size should be 3.0 μm or larger. Preferably, the average grain size is 4.0 μm or larger, or 5.0 μm or larger. On the other hand, if the average grain size exceeds 9.0 μm, the elongation and moldability will decrease due to surface roughness during plastic deformation. Therefore, the average grain size should be 9.0 μm or less. Preferably, the average grain size is 8.5 μm or less, 7.5 μm or less, or 7.0 μm or less.

[0025] The average grain size is measured by the following method. After electropolishing the surface of the aluminum alloy foil, crystal orientation analysis is performed using SEM-EBSD. In the crystal orientation analysis, boundaries where the crystal orientation difference between measurement points is 5° or more are considered grain boundaries, and the region enclosed by these grain sizes is defined as a crystal grain. The average crystal grain size is obtained by determining the average equivalent circle diameter for each crystal grain using the Area method.

[0026] The measurement and analysis conditions for EBSD are as follows. (Measurement conditions) Observation magnification: 900x Acceleration voltage: 15kV Sample tilt angle: 70° Step Size: 0.5 μm (Analysis conditions) Analysis software: OIM Analysis (Ver. 8.0) by TSL Solutions Area: Images measured at 900x magnification were stitched together to create a total area of ​​50,000 μm². 2 That's all. Confidence Index (CI): Exclude values ​​below 0.1 Minimum Grain Size [points]: 2 Anti-grains: 2

[0027] The measurement conditions for crystal grain size were set as follows. Grain Tolerance Angle: 5° Minimum Grain Size[points]:2 Anti Grains:2 Minimum Confidence Index: 0.1 Multiple rows required: All OFF Apply partition before calculation:OFF Include grains at edges of scan in statistics:OFF

[0028] Total growth: 15.0% or more Tensile strength: 100 MPa or more The aluminum alloy foil relating to this disclosure preferably has a total elongation of 15.0% or more and a tensile strength of 100 MPa or more. Total elongation is a characteristic value related to the limit of forming during plastic deformation. High formability can be obtained by achieving a total elongation of 15.0% or more. Tensile strength is a characteristic value related to the durability of a container when used. By setting the tensile strength to 100 MPa or higher, it is possible to prevent the container from breaking due to its inability to withstand use.

[0029] Total elongation and tensile strength are obtained by performing tensile tests. Tensile testing will be conducted in accordance with JIS Z 2241:2022, using JIS No. 5 test specimens taken from aluminum alloy foil to measure the total elongation in the 0° direction relative to the rolling direction. The collected test specimens will be subjected to tensile testing at a tensile speed of 2 mm / min using a universal tensile testing machine (Shimadzu AGS-X 10kN). The tensile strength will be the maximum stress. The total elongation is calculated using the following method. First, before the tensile test, two lines are marked perpendicular to the specimen at the center of the specimen's longitudinal axis, at intervals of 50 mm (gauge length). After the tensile test, the fracture surfaces of the aluminum alloy foil are joined together to measure the distance between the marks (l). The elongation (mm), obtained by subtracting the gauge length (l0: 50 mm) from this distance, is then divided by the gauge length (50 mm) to calculate the total elongation (%) using the following formula. Note that total elongation refers to "elongation at break" as defined in JIS Z 2241:2022. ((l-l0) / l0)×100

[0030] Erichsen value: 6.0 mm or higher The aluminum alloy foil relating to this disclosure preferably has an Erichsen value of 6.0 mm or more. The Erichsen value obtained using an Erichsen tester is used as an indicator of formability in stretch molding. If the Erichsen value is 6.0 mm or more, it can be determined that the foil has high formability in this disclosure.

[0031] The Erichsen value is determined by performing an Erichsen test using a universal thin sheet forming tester (ERICHSEN Model 142 / 20). For the Erichsen test, a metal punch with a radius of 10 mm is used, and mineral oil is applied to the surface of the aluminum alloy foil in contact with the punch for lubrication. The aluminum alloy foil is fixed to the apparatus with a wrinkle-holding force of 10 kN, and stretch forming is performed with the punch rising at a rate of 3.0 mm / min. The forming height at which cracks appear in the aluminum alloy foil is defined as the maximum stretch height, i.e., the Erichsen value (mm).

[0032] Equivalent plastic strain in the equibiaxial tensile region according to the Marciniak method: 0.300 or greater In this disclosure, if the equivalent plastic strain in the equibiaxial tensile region measured by the Marciniak method is 0.300 or higher, it can be determined that the material has high formability.

[0033] The equivalent plastic strain in the equibiaxial tensile region, obtained by the Marciniak method, is obtained by the following method. A universal thin sheet forming tester (ERICHSEN Model 142 / 20) and DIC (analysis using Correlated Solutions software Vic-3D8) are used to simulate equibiaxial tensile strain. Strains in the range of strain ratio 0.9 to 1.0 are applied to aluminum alloy foil using the Marciniak method, and the equivalent plastic strain at the point of cracking in the aluminum alloy foil is determined. A metal punch with a diameter of φ40 mm and a radius of R4 mm is used. To create a frictionless area on the test surface of the aluminum alloy foil, a resin drive plate with a hole in the center is placed between the punch and the aluminum alloy foil. Forming is performed with the punch rising at a rate of 8 mm / min, and the change in strain during forming is analyzed by DIC to determine the equivalent plastic strain at the time of fracture.

[0034] The Marciniak method, commonly known as flat-head overhanging, uses a drive plate to achieve frictionless top surface. Appropriate selection of the drive plate is necessary to prevent friction and cracking. Fluoropolymers are preferably used as the drive plate, with polytetrafluoroethylene (PTFE) being particularly suitable. The thickness is not particularly limited, but for example, plates with a thickness of 10 to 200 μm can be used. Surface lubricant can be applied to the front and back surfaces of the test specimen and the drive plate. The shape of the drive plate is not particularly limited, but circular, ISO proportional shapes (dogbone type), etc., can be used.

[0035] Before testing, a random pattern can be applied to the test material by spraying, and the increase or decrease in strain before and after plastic deformation can be measured using the Marciniak method for evaluation. In the DIC analysis method, a quick-drying paint is applied to the test material using a spray or similar method to create a random pattern on the surface. When the material is plastically deformed, the change in the pattern is read by an optical sensor to measure the strain distribution during deformation. The pattern change can be continuously photographed, for example, with a camera. DIC can obtain localized strain by measuring the strain between small gauge points.

[0036] The aluminum alloy foil relating to this disclosure may have a thickness of, for example, about 0.01 to 0.10 mm. The thickness of the aluminum alloy foil may be a general thickness used for foil. For example, a thickness of about 0.04 mm (40 μm) is acceptable.

[0037] Next, a preferred manufacturing method for producing the aluminum alloy foil relating to this disclosure will be described. In the preferred method for manufacturing aluminum alloy foil according to this disclosure, An aluminum alloy ingot having the above-described component composition is obtained, and a homogenization treatment is performed by holding it at a temperature range of 480-540°C for 6 hours or more. After homogenization, hot rolling is performed so that the finished temperature is in the range of 230-300°C. The final cold rolling ratio is 80.0% or more and less than 98.0%. The final annealing is performed at a temperature range of 200-350°C for 10 hours or more. Furthermore, any intermediate annealing may be performed between hot rolling and final cold rolling. The following provides a detailed explanation of each step.

[0038] Homogenization treatment: Holding at a temperature range of 480-540°C for 6 hours or more. An aluminum alloy ingot having the above-described component composition is obtained by casting. The obtained ingot is preferably subjected to a homogenization treatment, which involves holding it at a temperature of 480-540°C for 6 hours or more. If the holding temperature is below 480°C, Fe precipitation is insufficient, and the growth of intermetallic compounds is inadequate. On the other hand, if the holding temperature exceeds 540°C, the growth of intermetallic compounds is significant, and the density of fine intermetallic compounds with a particle size of 0.1 μm or more and less than 1.0 μm decreases greatly. Since long heat treatment is required to precipitate fine intermetallic compounds at high density during such a homogenization treatment around 500°C, it is preferable to hold it for 6 hours or more. By holding it for 6 hours or more, sufficient precipitation of fine intermetallic compounds can be achieved.

[0039] Hot rolling: Finished temperature range of 230-300°C In hot rolling, it is preferable to keep the finishing temperature below 300°C to suppress recrystallization. By keeping the finishing temperature below 300°C, the hot-rolled sheet will have a uniform fiber structure. By suppressing recrystallization after hot rolling in this way, the amount of strain accumulated during subsequent cold rolling increases, and a recrystallized grain structure with uniform grain size can be obtained. This also leads to uniformity in the final grain size. If the finishing temperature exceeds 300°C, recrystallization will occur in some parts of the hot-rolled sheet, resulting in a mixture of fiber structure and recrystallized grain structure. This leads to non-uniformity in the recrystallized grain size during intermediate annealing, which in turn leads to non-uniformity in the final grain size. Finishing at below 230°C requires extremely low temperatures during hot rolling, raising concerns about crack formation on the sides of the sheet and a significant decrease in productivity.

[0040] Final cold rolling ratio: 80.0% or more, less than 98.0% The higher the final cold rolling ratio (reduction ratio in the final stage of cold rolling) from intermediate annealing to the final thickness, the greater the amount of strain accumulated in the material, resulting in finer recrystallized grains after final annealing and more pronounced development of Cu orientation. If the final cold rolling ratio is too low, it can cause coarsening and non-uniformity of the recrystallized grains. If the final cold rolling ratio is less than 80.0%, the decrease in accumulated strain may cause coarsening and non-uniformity of the crystal grain size after final annealing. On the other hand, if the final cold rolling ratio is 98.0% or higher, work hardening progresses, and fracture may occur during cold rolling. Therefore, it is preferable that the final cold rolling ratio be between 80.0% and 98.0%. It is even more preferable that the final cold rolling ratio be 97.9% or lower. The final cold rolling ratio can be expressed as (t0-t1) / t0 × 100 (%), where t0 is the thickness of the entry side of the final stage and t1 is the thickness of the exit side of the final stage.

[0041] Final annealing: 10 hours or more at a temperature range of 200-350°C. After the final cold rolling, a final annealing is performed to completely soften the aluminum alloy foil. If the holding temperature is below 200°C or the holding time is less than 10 hours, softening may be insufficient. If the holding temperature exceeds 350°C, problems such as deformation of the aluminum alloy foil and a decrease in economic efficiency may occur. From the viewpoint of economic efficiency, the upper limit of the holding time is preferably less than 150 hours.

[0042] The manufacturing method described above makes it possible to stably produce the aluminum alloy foil related to this disclosure. [Examples]

[0043] Next, the effects of one aspect of this disclosure will be described in more detail by reference to examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effectiveness of this disclosure, and this disclosure is not limited to these examples of conditions. This disclosure may adopt various conditions as long as they do not depart from the gist of this disclosure and achieve the objectives of this disclosure.

[0044] Aluminum alloy foil was manufactured using the chemical composition and manufacturing conditions shown in Tables 1 and 2. Underlined text in the tables indicates that the information is outside the scope of this disclosure, the manufacturing conditions are undesirable, or the characteristic values ​​are undesirable.

[0045] For aluminum alloy foil, the average grain size, total elongation, tensile strength, Erichsen value, and equivalent plastic strain in the equibiaxial tensile region were measured using the method described above. The results are shown in Table 3.

[0046] If the tensile strength was 100 MPa or higher, it was judged to have high strength and passed the test. On the other hand, if the tensile strength was less than 100 MPa, it was judged to have insufficient strength and failed the test. If the Erichsen value was 6.0 mm or higher, and the equivalent plastic strain in the equibiaxial tensile region measured by the Marciniak method was 0.300 or higher, the material was judged to have high formability and was deemed acceptable. On the other hand, if either condition was not met, the material was judged to lack high formability and was deemed unacceptable.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3]

[0050] As shown in Tables 1-3, the aluminum alloy foil according to the examples exhibits high strength and formability. On the other hand, the aluminum alloy foil according to the comparative examples does not exhibit high strength and / or formability. [Explanation of symbols]

[0051] 1…Aluminum alloy foil

Claims

1. Si: 0.15% by mass or less, Fe: 1.00 to 1.70% by mass, Cu, Mn, Mg, Cr, and Ni: 0.0005% by mass or more, Cu + Mn + Mg + Cr + Ni: Total of 0.0500 to 0.1000 mass%, and, The remainder consists of Al and impurities. An aluminum alloy foil characterized by having an average crystal grain size of 3.0 to 9.0 μm.

2. The aluminum alloy foil according to claim 1, characterized in that the total elongation is 15.0% or more and the tensile strength is 100 MPa or more.

3. The aluminum alloy foil according to claim 1 or 2, characterized in that the Erichsen value is 6.0 mm or more.

4. The aluminum alloy foil according to claim 1 or 2, characterized in that the equivalent plastic strain in the equibiaxial tensile region measured by the Marciniak method is 0.300 or more.

5. The aluminum alloy foil according to claim 3, characterized in that the equivalent plastic strain in the equibiaxial tensile region measured by the Marciniak method is 0.300 or more.

Images