Aluminum alloy plate

Abstract

To provide an aluminum alloy sheet having excellent adhesion and vibration-damping properties with a coated film or a resin and having high strength.SOLUTION: There is provided an aluminum alloy sheet 1 which has a base material 2 having a chemical composition comprising 0.10 mass% or more and 3.0 mass% or less of Fe, 0.10 mass% or more and 3.0 mass% or less of Mn and the balance Al with inevitable impurities and an anodic oxide film 3 provided on at least one surface of the base material 2. The aluminum alloy sheet 1 has a Young's modulus after heating at a temperature of 100°C or more and 300°C or less for 0.5 hour or more and 10 hours or less of 70 GPa or more, a 0.2% proof stress of 100 MPa or more and a decrement in damped free vibration of 1.5×10-3 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy sheet. [Background technology]

[0002] Steel materials have traditionally been used for automobile bodies. Car bodies are painted for the purposes of rust prevention and improving design. However, in recent years, there has been a strong demand for further weight reduction in automobile bodies to meet the increasing demand for electrification of automobiles and further improvement in fuel efficiency. Therefore, aluminum alloy materials have begun to be used for automobile bodies instead of steel materials.

[0003] As aluminum alloy materials used in automobiles, sheet materials made of Al-Mg based alloys (e.g., Patent Document 1) and Al-Mg-Si based alloys (e.g., Patent Document 2), which have relatively high strength among aluminum alloys, are widely used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-165538 [Patent Document 2] Japanese Patent Application Publication No. 11-71623 Summary of the Invention [Problem to be solved by the invention]

[0005] While an automobile is running, various vibrations occur, such as those generated by the power source and those caused by uneven road surfaces. If these vibrations are transmitted to various parts of the vehicle via the body, etc., problems may arise due to the vibrations. Therefore, there is a need to further improve the vibration-damping properties of Al-Mg and Al-Mg-Si alloys used in vehicles.

[0006] Furthermore, when an aluminum alloy material is used for a body panel or the like, it is desirable that the adhesion between the coating film and the aluminum alloy material is excellent. One possible method for improving the adhesion to the coating film is to anodize the aluminum alloy material to provide an anodized film on the surface of the aluminum alloy material. However, when the chemical composition of an aluminum alloy material made of an Al-Mg alloy or an Al-Mg-Si alloy is changed to improve the vibration damping properties, the types of intermetallic compounds present in the alloy change, which may make it difficult to uniformly apply a surface treatment to the surface of the aluminum alloy material.

[0007] The present invention has been made in view of the above background, and aims to provide an aluminum alloy sheet which has excellent adhesion to coatings and resins, excellent vibration damping properties, and high strength. [Means for solving the problem]

[0008] One aspect of the present invention is Fe (iron): 0.10 mass % or more and 3.0 mass % or less 、 Mn (manganese): 0.10% by mass or more and 3.0% by mass or less , Si (silicon): 0.10% by mass or more and 0.40% by mass or less, Cu (copper): 0.005% by mass or more and 0.100% by mass or less, Cr (chromium): 0.01% by mass or more and 1.00% by mass or less, and Zn (zinc): 0.01% by mass or more and 0.50% by mass or less (excluding Zn: 0.1% by mass or less) A substrate having a chemical composition containing the above, with the remainder being Al (aluminum) and unavoidable impurities; an anodic oxide coating provided on at least one surface of the substrate, 250℃ At a temperature of 3 hours After heating, the Young's modulus becomes 70 GPa or more, the 0.2% proof stress becomes 100 MPa or more, and the damping rate in damped free vibration becomes 1.5 × 10 -3 The aluminum alloy plate has the above properties. [Effects of the Invention]

[0009] The aluminum alloy sheet has a substrate having the specific chemical composition and an anodized film formed on at least one surface of the substrate. By adjusting the chemical composition of the substrate to fall within the specific range, the anodized film can be uniformly formed on the substrate. Furthermore, by providing the anodized film on the substrate, the aluminum alloy sheet can improve adhesion to paint films and resins.

[0010] Furthermore, the aluminum alloy sheet has at least the specific chemical components, and therefore the Young's modulus, 0.2% proof stress, and damping rate of damped free vibration can be set within the specific ranges after heating at a temperature of 100° C. to 300° C. for 0.5 hours to 10 hours. The aluminum alloy sheet having such properties can exhibit high strength and excellent vibration damping properties after undergoing heat treatment, for example, for baking a coating film.

[0011] As described above, according to the above-mentioned embodiment, an aluminum alloy sheet having excellent adhesion to coating films and resins, excellent vibration damping properties, and high strength can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing a main part of an aluminum alloy plate according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram that schematically shows the attenuation rate measuring device used in the examples. [Figure 3] FIG. 3 is an explanatory diagram showing a method for calculating the attenuation rate in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (aluminum alloy plate) The aluminum alloy plate has a substrate and an anodized film formed on one or both sides of the substrate.

[0014] [Base material] First, the chemical composition of the substrate of the aluminum alloy plate and the reasons for limiting it will be explained.

[0015] Fe (iron): 0.10% by mass or more and 3.0% by mass or less The substrate contains 0.10% by mass or more and 3.0% by mass or less of Fe as an essential component. Fe is mainly present in the Al matrix as second-phase particles such as Al-Fe intermetallic compounds. The Al-Fe intermetallic compounds in the Al matrix improve the vibration damping properties of the aluminum alloy sheet and also improve the strength of the aluminum alloy sheet through dispersion strengthening. The remainder of the Fe is present as a solid solution element in the Al matrix and improves the strength of the aluminum alloy sheet.

[0016] The mechanism by which second-phase particles such as Al-Fe intermetallic compounds improve the vibration-damping properties of aluminum alloy sheets is thought to be, for example, as follows. That is, when vibrations are applied to the aluminum alloy sheet from the outside, viscous flow occurs at the interface between the Al matrix and the second-phase particles. It is thought that this viscous flow absorbs the vibration energy, resulting in early damping of the vibrations.

[0017] By setting the Fe content in the substrate to 0.10% by mass or more, the strength and vibration-damping properties of the aluminum alloy sheet can be improved. From the viewpoint of further improving the vibration-damping properties and increasing the strength of the aluminum alloy sheet, the Fe content in the substrate is preferably 0.40% by mass or more, and more preferably 1.0% by mass or more. If the Fe content in the substrate is less than 0.10% by mass, the number of second-phase particles such as Al-Fe-based intermetallic compounds formed in the substrate will be insufficient, which may lead to a decrease in the strength and vibration-damping properties of the aluminum alloy sheet.

[0018] Furthermore, by setting the Fe content in the substrate to 3.0 mass% or less, preferably 2.0 mass% or less, and more preferably 1.7 mass% or less, a uniform anodic oxide film can be easily formed on the substrate. As a result, the adhesion between the aluminum alloy sheet and the coating or resin can be improved. If the Fe content in the substrate is excessively high, coarse Al-Fe intermetallic compounds are likely to be formed in the substrate. If coarse Al-Fe intermetallic compounds are present in the substrate, reactions around the coarse Al-Fe intermetallic compounds are likely to be promoted during anodization, which may make it difficult to form a uniform anodic oxide film on the substrate.

[0019] Mn (manganese): 0.10% by mass or more and 3.0% by mass or less The substrate contains 0.10% by mass or more and 3.0% by mass or less of Mn as an essential component. Mn is mainly present in the Al matrix as second-phase particles such as Al-Mn intermetallic compounds. The Al-Mn intermetallic compounds in the Al matrix, like the Al-Fe intermetallic compounds, have the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet. Mn can also form Al-Fe-Mn intermetallic compounds in the substrate together with Fe. The Al-Fe-Mn intermetallic compounds have a small potential difference with the Al matrix, and therefore have the effect of suppressing local cell reactions during the formation of an anodic oxide film. By suppressing the local cell reactions during the formation of an anodic oxide film, a uniform anodic oxide film can be easily formed on the substrate.

[0020] By setting the Mn content in the substrate to 0.10% by mass or more, preferably 0.20% by mass or more, and more preferably 0.40% by mass or more, the strength and vibration-damping property of the aluminum alloy sheet can be improved and a uniform anodic oxide coating can be easily formed on the substrate. If the Mn content in the substrate is less than 0.10% by mass, the number of second-phase particles such as Al-Mn-based intermetallic compounds formed in the substrate will be insufficient, which may lead to a decrease in the strength and vibration-damping property of the aluminum alloy sheet.

[0021] Furthermore, by setting the Mn content in the substrate to 3.0% by mass or less, preferably 2.0% by mass or less, and more preferably 1.0% by mass or less, it is possible to form a uniform anodic oxide film on the substrate. As a result, it is possible to improve the adhesion between the aluminum alloy sheet and the coating or resin. If the Mn content in the substrate is excessively high, coarse Al-Mn intermetallic compounds are likely to be formed in the substrate. Similar to Al-Fe intermetallic compounds, coarse Al-Mn intermetallic compounds have the effect of accelerating the reaction when forming the anodic oxide film. Therefore, in this case, it may be difficult to form a uniform anodic oxide film on the substrate.

[0022] The base material is 、F In addition to e and Mn, Si (silicon), Cu (copper), Cr (chromium), Zn (zinc) The substrate contains It may contain one or more elements selected from the group consisting of Ti (titanium), B (boron), V (vanadium) and Ni (nickel) as an optional component.

[0023] ·Si: 0.10 mass% or more and 0.40 mass% or less The base material is 、0 Contains 0.10 mass% or more and 0.40 mass% or less of Si There are Si forms second-phase particles such as Si particles in the substrate, and has the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet, similar to Al-Fe intermetallic compounds. Si can also form Al-Si-Mn intermetallic compounds in the substrate together with Mn. Al-Si-Mn intermetallic compounds have a small potential difference with the Al parent phase, so they have the effect of suppressing local cell reactions when forming an anodic oxide film. By suppressing local cell reactions when forming an anodic oxide film, a uniform anodic oxide film can be easily formed on the substrate.

[0024] By setting the Si content in the substrate to 0.10 mass% or more and 0.40 mass% or less, more preferably 0.15 mass% or more and 0.30 mass% or less, the strength and vibration damping property of the aluminum alloy plate can be further improved, and an anodized coating can be more uniformly formed on the substrate.

[0025] ·Cu: 0.005 mass% or more and 0.100 mass% or less The base material is 、0 Contains 0.005% by mass or more and 0.100% by mass or less of Cu There are Cu forms second-phase particles such as Al-Cu intermetallic compounds in the substrate, and has the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet, similar to Al-Fe intermetallic compounds. However, while Al-Cu intermetallic compounds improve vibration-damping properties, they may precipitate at the grain boundaries of the Al matrix upon heat treatment, causing intergranular corrosion. By setting the Cu content in the substrate to 0.005% by mass or more and 0.100% by mass or less, more preferably 0.010% by mass or more and 0.070% by mass or less, it is possible to further improve the strength and vibration-damping properties of the aluminum alloy sheet while suppressing the occurrence of intergranular corrosion.

[0026] ·Cr: 0.01 mass% or more and 1.00 mass% or less The base material is 、0 Contains 0.01% by mass or more and 1.00% by mass or less of Cr There are Cr forms second phase particles such as Al-Cr based intermetallic compounds in the base material, and has the effect of improving the strength and vibration damping properties of the aluminum alloy sheet, similar to Al-Fe based intermetallic compounds.

[0027] On the other hand, if the Cr content in the substrate is excessively high, coarse Al-Cr intermetallic compounds are likely to be formed in the substrate. Since coarse Al-Cr intermetallic compounds have the effect of accelerating the reaction when forming an anodic oxide film, the presence of excessively large coarse Al-Cr intermetallic compounds in the substrate may make it difficult to form a uniform anodic oxide film on the substrate. By setting the Cr content in the substrate to 0.01 mass% or more and 1.00 mass% or less, more preferably 0.10 mass% or more and 0.50 mass% or less, the strength and vibration damping properties of the aluminum alloy sheet can be further improved, and the formation of coarse Al-Cr intermetallic compounds in the substrate can be suppressed, allowing a more uniform anodic oxide film to be formed on the substrate.

[0028] ·Zn: 0.01 mass% or more and 0.50 mass% or less (However, Zn: 0.1 mass% or less is excluded) The base material is 、0 .01 mass% or more and 0.50 mass% or less (excluding 0.1% by mass or less) Contains Zn There are A portion of the Zn forms second-phase particles in the Al matrix together with other alloying elements, which has the effect of further improving the strength and vibration-damping properties of the aluminum alloy sheet. The remaining Zn dissolves in the Al matrix to lower the potential of the substrate, thereby improving the reactivity when forming an anodized film. However, if the Zn content is excessively high, the substrate may become more susceptible to corrosion. The Zn content in the substrate should be kept between 0.01% and 0.50% by mass. (excluding 0.1% by mass or less) , and more preferably 0.10 mass % or more and 0.40 mass % or less (excluding 0.1% by mass or less) By doing so, the strength and vibration-damping property of the aluminum alloy plate can be further improved, and the potential of the substrate can be made appropriately less noble, thereby further accelerating the formation of the anodic oxide film.

[0029] ·Ti, B and V: Total 0.005 mass% or more and 0.500 mass% or less The substrate may contain, as an optional component, one or more elements selected from the group consisting of Ti, B, and V. These elements have the effect of refining the crystal grains of the ingot during the manufacturing process of the aluminum alloy sheet. By setting the total content of Ti, B, and V within the specific range, the crystal grains of the ingot can be refined and the variation in size of second-phase particles formed in the substrate can be reduced. As a result, the variation in vibration-damping properties of the aluminum alloy sheet can be reduced. Furthermore, the reduced variation in size of second-phase particles reduces the variation in reactivity during the formation of an anodized film, allowing the anodized film to be formed more uniformly on the substrate. From the viewpoint of further enhancing these effects, the total content of Ti, B, and V is more preferably 0.20 mass% or less.

[0030] ·Ni: 0.10% by mass or less The substrate may contain 0.10 mass% or less of Ni as an optional component. Ni forms second-phase particles such as Al-Ni intermetallic compounds in the substrate, and has the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet, similar to Al-Fe intermetallic compounds. However, while Al-Ni intermetallic compounds improve vibration-damping properties, they may become cathode sites when exposed to corrosive substances, accelerating corrosion. Furthermore, since Al-Ni intermetallic compounds have the effect of accelerating the reaction when forming an anodized film, if the number of Al-Ni intermetallic compounds present on the surface of the substrate increases, it may become difficult to form a uniform anodized film on the substrate.

[0031] By setting the Ni content in the substrate to 0.10% by mass or less, more preferably 0.05% by mass or less, the strength and vibration-damping properties of the aluminum alloy sheet can be further improved while suppressing the occurrence of corrosion, and in this case, a uniform anodic oxide film can be more easily formed on the substrate.

[0032] Other elements In addition to the elements mentioned above, the base material contains unavoidable impurities that are inevitably mixed in during the manufacturing process. Elements contained as unavoidable impurities include, for example, Zr (zirconium), Pb (lead), Ga (gallium), and Sn (tin). The content of each element as an unavoidable impurity is 0.1% by mass or less for each element, and the total content of the unavoidable impurities is 0.2% by mass or less.

[0033] [Anodic oxide film] An anodized film is provided on the substrate. By adjusting the chemical composition of the substrate to fall within the specific range, second-phase particles such as Al-Fe intermetallic compounds can be formed in the substrate. These second-phase particles can improve the strength and vibration-damping properties of the aluminum alloy sheet. Furthermore, the second-phase particles formed in the substrate of the aluminum alloy sheet are unlikely to interfere with the dissolution and growth reactions of aluminum oxide during anodizing. Therefore, by adjusting the chemical composition of the substrate to fall within the specific range, an anodized film can be uniformly formed on the substrate, and the second-phase particles can improve the strength and vibration-damping properties of the aluminum alloy sheet after heating.

[0034] In the aluminum alloy sheet, by providing an anodized film on the substrate, oxidation of the substrate is suppressed, and fine irregularities are formed on the surface of the aluminum alloy sheet, which can improve adhesion to coating films and resins by an anchor effect. From the viewpoint of further enhancing the effect of improving adhesion to coating films and resins, the thickness of the anodized film is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more.

[0035] The anodized film on the aluminum alloy sheet is preferably a porous anodized film having a large number of pores. In this case, when a paint is applied to the aluminum alloy sheet, the paint can easily penetrate into the pores of the anodized film. This further improves adhesion to the paint film and resin. In this case, it is also possible to color the aluminum alloy sheet by encapsulating a dye in the pores of the anodized film.

[0036] [Physical properties of aluminum alloy sheets] The aluminum alloy plate is 250℃ At a temperature of 3 hours After heating, the Young's modulus becomes 70 GPa or more, the 0.2% proof stress becomes 100 MPa or more, and the damping rate in damped free vibration becomes 1.5 × 10 -3It has the above characteristics. Aluminum alloy sheets with a high Young's modulus and a high damping rate in damped free vibration can efficiently damp externally applied vibrations. Furthermore, aluminum alloy sheets with a high 0.2% yield strength can improve the rigidity of final products such as automobile bodies, and can also suppress the occurrence of cracks and wrinkles during forming processes.

[0037] Therefore, an aluminum alloy sheet having Young's modulus, 0.2% proof stress, and damping rate of damped free vibration each falling within the above-mentioned specific ranges after heating under the above-mentioned specific conditions can exhibit excellent vibration-damping properties after heat treatment such as baking performed after painting. Furthermore, an aluminum alloy sheet having such properties is particularly suitable for automobile bodies.

[0038] From the viewpoint of further improving the vibration damping property of the aluminum alloy plate, the aluminum alloy plate is 250℃ At a temperature of 3 hours The damping rate of the damped free vibration after heating is 2.0×10 -3 The specific method for measuring the damping rate of damped free vibration will be explained in detail in the examples.

[0039] [Application] As described above, the aluminum alloy sheet has improved adhesion to paint films and resins and has excellent vibration-damping properties after heating, due to the chemical composition of the substrate being within the above-mentioned specific range and the anodized coating being provided on the substrate, and is therefore suitable for applications requiring excellent vibration-damping properties after paint baking, such as automobile body panel materials.

[0040] When the aluminum alloy sheet is heated during paint baking or the like, it is preferable that the heating temperature is 300° C. or less and the heating time is 10 hours or less. If the heating temperature of the aluminum alloy sheet is excessively high or the heating time is excessively long, the strength of the aluminum alloy sheet may be reduced.

[0041] (Method of manufacturing aluminum alloy plate) In producing the aluminum alloy plate, a substrate made of an aluminum alloy having the specific chemical composition is cold-rolled to a desired thickness, and then the substrate is anodized to form an anodized coating.

[0042] The method for producing the substrate is not particularly limited. For example, the substrate may be produced by DC casting an ingot having the specific chemical composition, heating the ingot for homogenization as needed, and then hot rolling the ingot.

[0043] In DC casting, the cooling rate of the ingot after casting is preferably in the range of 0.1°C / sec to 1000°C / sec. When homogenization treatment is performed, the ingot is held at a temperature of 500°C to 650°C for 0.5 hours or more.

[0044] When hot rolling an ingot without homogenizing treatment, it is preferable to start rolling while the temperature of the ingot is in the range of 300°C or higher and 550°C or lower. When hot rolling an ingot after homogenizing treatment, it is preferable to start rolling while the temperature of the ingot is in the range of 300°C or higher and lower than 380°C. In either case, the temperature of the substrate at the end of hot rolling should be 100°C or higher and lower than 380°C.

[0045] Alternatively, a plate material having the specific chemical composition produced by CC casting can be used as the substrate. The cooling rate of the substrate after CC casting is preferably in the range of 0.1°C / sec to 1000°C / sec.

[0046] The substrate thus obtained is subjected to cold rolling to reduce the thickness of the substrate to a desired thickness. The thickness of the substrate after cold rolling may be appropriately set within a range of, for example, 1.0 mm to 2.0 mm. Furthermore, the total rolling ratio in cold rolling, i.e., the ratio of the thickness reduction of the substrate due to cold rolling to the thickness of the substrate before cold rolling, is preferably 10% to 95%.

[0047] Furthermore, when cold rolling the substrate, the substrate can be heated and annealed as necessary. Annealing may be performed before cold rolling or during cold rolling. Annealing may also be performed both before cold rolling and during cold rolling. When performing annealing, a batch annealing furnace or a continuous annealing furnace may be used. For example, when annealing is performed using a batch annealing furnace, it is preferable to hold the substrate at a temperature of 200°C or higher and lower than 380°C for 0.1 hours to 10 hours.

[0048] The aluminum alloy sheet can be obtained by anodizing the substrate after cold rolling to form an anodic oxide film on the substrate. In the anodizing process, the substrate and a counter electrode are immersed in an acidic electrolyte such as sulfuric acid, oxalic acid, or phosphoric acid, and a direct current is passed between the substrate and the counter electrode, causing a dissolution reaction and a growth reaction of aluminum oxide to proceed in parallel. This allows a porous anodic oxide film with numerous pores to be formed on the substrate.

[0049] The thickness of the anodic oxide film can be controlled to some extent by the amount of electricity applied to the substrate. The amount of electricity applied to the substrate can be controlled by the magnitude of the voltage applied between the substrate and the counter electrode, the magnitude of the current flowing between the substrate and the counter electrode, and the duration of current flow. In the anodic oxidation treatment, for example, the voltage applied between the substrate and the counter electrode may be kept constant and the current may be varied, or the current applied between the substrate and the counter electrode may be kept constant and the voltage may be varied. In addition, both the voltage and the current may be varied in the anodic oxidation treatment. Furthermore, when attempting to form a porous anodic oxide film on a substrate, the diameter and number of pores per unit area formed in the anodic oxide film can be controlled to some extent by the type of electrolyte.

[0050] Anodizing treatment may be performed at any time between the completion of cold rolling and the coating. For example, anodizing treatment may be performed by unwinding a coiled substrate from the coil, bringing it into contact with an electrolyte together with a counter electrode, and passing a direct current through it. Alternatively, anodizing treatment may be performed by bringing a substrate cut to a desired size or a substrate after forming into a desired size into contact with an electrolyte together with a counter electrode, and passing a direct current through it. [Example]

[0051] An example of the aluminum alloy sheet will be described with reference to Figs. 1 to 3. As shown in Fig. 1, the aluminum alloy sheet 1 of this example has a substrate 2 having a chemical composition containing 0.10 to 3.0 mass% of Fe and 0.10 to 3.0 mass% of Mn, with the balance being Al and unavoidable impurities, and an anodized coating 3 provided on at least one surface of the substrate 2. Furthermore, as shown in Table 1, the aluminum alloy sheet 1 of this example has a Young's modulus of 70 GPa or more, a 0.2% proof stress of 100 MPa or more, and a damping ratio in damped free vibration of 1.5 × 10 after heating at a temperature of 100 °C to 300 °C for 0.5 to 10 hours. -3 It has the above characteristics.

[0052] To produce the aluminum alloy sheet 1 of this example, first, an ingot having the chemical composition shown in Table 1 is produced by DC casting. In Table 1, the symbol "Bal." indicates that the corresponding element is the balance, and the symbol "-" indicates that the corresponding element is not contained. The surface of the ingot is chamfered to remove the surface segregation layer, and then the ingot is held at a temperature of 520°C for 1 hour for homogenization treatment. Thereafter, hot rolling is started while the ingot temperature is 460°C, and a substrate 2 having a thickness of 3.0 mm is produced. The temperature of the substrate 2 at the completion of hot rolling is 280°C. Next, the substrate 2 is cold-rolled to reduce the thickness of the substrate 2 to 1.0 mm.

[0053] One side of the substrate 2 thus obtained is masked, and then the substrate 2 is immersed together with a counter electrode in a 15% by mass aqueous sulfuric acid solution at a temperature of 20° C. Then, the substrate 2 is used as the anode, and a current density of 10 mA / cm is applied between the substrate 2 and the counter electrode. 2 Anodizing treatment is performed by passing a direct current of 1000 kJ / s. The duration of current application in the anodizing treatment is as shown in Table 1. As a result, a porous anodic oxide film 3 is formed on the substrate 2, and test materials S1 to S3 shown in Table 1 can be obtained. The cross section of each test material was observed using an electron microscope, and the thickness of the anodic oxide film 3 was measured. The results are shown in Table 1.

[0054] Note that test materials R1 and R2 shown in Table 1 are test materials for comparison with test materials S1 to S3. Test material R1 has the same structure as test materials S1 to S3, except that the chemical composition of the substrate has been changed as shown in Table 1. Test material R2 has the same chemical composition as the substrate as shown in Table 1. For test material R2, even if the substrate is anodized under the same conditions as test materials S1 to S3, it is difficult to form a uniform anodic oxide film on the substrate. Therefore, for test material R2, the symbol "-" is entered in the anodized film thickness column in Table 1.

[0055] The Young's modulus, 0.2% proof stress and damping rate of damped free vibration of the aluminum alloy plate 1 of this example after heating were measured as follows.

[0056] ·Young's modulus and damping rate After heat treatment of each test material at the holding temperature and holding time shown in Table 2, strip-shaped test pieces measuring 80 mm in length and 8 mm in width were taken from the test material with the rolling direction and longitudinal direction parallel. These test pieces were attached to a free-resonance internal friction measuring device ("JE-RT" manufactured by Nippon Technoplus Co., Ltd.), and the Young's modulus and damping factor were measured using the damping method. The measuring device 4 used in this example, as shown in Figure 2, has a driving electrode 41 and an amplitude sensor 42 facing the driving electrode 41. The test piece S is horizontally placed between the driving electrode 41 and the amplitude sensor 42, and is fixed with a thin wire 43 at a vibration node position. In this state, an AC current is passed through the driving electrode 41, causing a Coulomb force to act on the test piece S, thereby vibrating the test piece S. The amplitude of the test piece S is then measured using the amplitude sensor 42, thereby obtaining a vibration waveform.

[0057] In this example, an AC current is applied to the driving electrode 41 to forcibly vibrate the test piece S, and then the AC current is stopped, allowing the test piece S to vibrate freely due to its restoring force. The vibration of the test piece S is what is known as damped free vibration, in which the amplitude exponentially decays while oscillating periodically with a period T, as shown in the waveform in Figure 3. In damped free vibration, it is believed that the amplitude decreases exponentially due to losses of vibration energy caused by atmospheric resistance and internal friction due to dislocations and grain boundaries within the test piece.

[0058] The method for calculating the value of the damping rate δ is as follows: First, the nth period (where n is a positive integer) and the n+mth period (where m is an integer of 2 or more) are arbitrarily selected from the waveform of the damped free vibration, and the amplitude a n and the amplitude a of the n+mth period n+m The decay rate δ is the amplitude a k and the amplitude of the next period a k+1 The natural logarithm of the ratio ln(a k / a k+1 ), so the amplitude a n and amplitude a n+m The natural logarithm of the ratio ln(a n / a n+m) can be expanded as follows: ln(a n / a n+m )=ln{(a n / a n+1 )×(a n+1 / a n+2 )×···×(a n+m-1 / a n+m )}=mδ

[0059] Therefore, the value of the attenuation rate δ is the amplitude a n and the amplitude a of the n+mth period n+m It can be expressed as follows using the value of δ=(1 / m)·ln(a n / a n+m )

[0060] The Young's modulus and damping rate of damped free vibration after heating for each test material are shown in Table 2. Note that for test material R2, the damping rate was not calculated, so the symbol "-" is entered in the damping rate column.

[0061] ·0.2% yield strength Each test material was heat-treated by heating at the holding temperature and holding time shown in Table 2, and then a JIS No. 5 test piece was taken from the test material so that the rolling direction and longitudinal direction were parallel. Using these test pieces, a tensile test was performed using a method in accordance with JIS Z2241:2011. The 0.2% yield strength of each test material was then calculated based on the load-displacement curve obtained from the tensile test. Table 2 shows the 0.2% yield strength of each test material after heating. Note that the 0.2% yield strength of test material R2 was not calculated, so the symbol "-" is entered in the 0.2% yield strength column.

[0062] [Table 1]

[0063] [Table 2]

[0064] As shown in Table 1, test materials S1 to S3 have a substrate 2 having the specific chemical components and an anodized coating 3 formed on the substrate 2, and therefore have excellent adhesion to paint films and resins. Furthermore, test materials S1 to S3 have properties such that after heat treatment at the temperatures and times shown in Table 2, their Young's modulus, 0.2% proof stress, and damping rate of damped free vibration are each within the specific ranges. Aluminum alloy sheets having such properties can exhibit high strength and excellent vibration damping after heating, such as paint baking, and are therefore suitable for use in automobile bodies.

[0065] In test material R1, the Fe content and Mn content in the substrate are lower than the specific ranges, so second-phase particles such as Al-Fe intermetallic compounds and Al-Mn intermetallic compounds are less likely to form in the substrate. As a result, test material R1 has a low Young's modulus and damping rate after heating, and is inferior in vibration damping performance to test material S1.

[0066] In test material R2, the Fe content and Mn content in the substrate are lower than the specific ranges, and the Si content is excessively high, making it difficult to form a uniform anodic oxide film on the substrate during anodizing treatment.

[0067] The above describes examples of specific configurations of the aluminum alloy plate according to the present invention, but the specific configurations of the aluminum alloy plate according to the present invention are not limited to the configurations of the examples, and the configurations can be changed as appropriate within the scope that does not detract from the spirit of the present invention. [Explanation of symbols]

[0068] 1. Aluminum alloy plate 2 Base material 3 Anodized coating

Claims

1. a base material having a chemical composition containing Fe: 0.10% by mass or more and 3.0% by mass or less, Mn: 0.10% by mass or more and 3.0% by mass or less, Si: 0.10% by mass or more and 0.40% by mass or less, Cu: 0.005% by mass or more and 0.100% by mass or less, Cr: 0.01% by mass or more and 1.00% by mass or less, and Zn: 0.01% by mass or more and 0.50% by mass or less (excluding Zn: 0.1% by mass or less), with the balance being Al and unavoidable impurities; an anodic oxide coating provided on at least one surface of the substrate, After heating at 250°C for 3 hours, the Young's modulus is 70 GPa or more, the 0.2% yield strength is 100 MPa or more, and the damping rate in damped free vibration is 1.5 × 10 －３ An aluminum alloy plate having the above properties.

2. 2. The aluminum alloy plate according to claim 1, wherein the base material further contains one or more elements selected from the group consisting of Ti, B, and V, and the total content of these elements is 0.005% by mass or more and 0.500% by mass or less.

3. The aluminum alloy plate according to claim 1 or 2, wherein the substrate further contains Ni: 0.10 mass % or less.

4. The aluminum alloy plate according to any one of claims 1 to 3, wherein the anodized film has a thickness of 2 µm or more.

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