Aluminum alloy material

Abstract

To provide an aluminum alloy material enabling increase of strength of any of Al-Zn-Mg-Cu based alloy and Al-Zn-Mg based alloy.SOLUTION: An aluminum alloy material 1 is composed of a 7000 based aluminum alloy having a chemical component including 0.05 mass% or more and 0.20 mass% or less of Sc and 0.05 mass% or more and 0.20 mass% or less of Zr. The aluminum alloy material has metallographic structure in which an Al-Sc-Zr based deposit 3 including Sc and Zr exists in an Al parent l phase 2 and the number of Al-Sc-Zr based deposit 3 having a major axis of 2 nm or more and 20 nm or less, out of the Al-Sc-Zr based deposit, per unit volume 3 is 3.0×1021 pieces / m3 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 7000 series aluminum alloys containing zinc (Zn) and magnesium (Mg) have high strength for an aluminum alloy, and are therefore used in a variety of fields, such as aircraft structural materials and motorcycle structural materials.

[0003] For example, Patent Document 1 describes an invention relating to an aluminum alloy for welded structures that contains, as essential components, 3.2 to 5.0% Zn, 1.0 to 2.8% Mg, 0.13 to 0.29% Cu, 0.3 to 0.18% V, and 0.03 to 0.24% Ti, with one or more of 0.06 to 0.26% Cr, 0.10 to 0.50% Mn, 0.06 to 0.26% Zr, and 0.0001 to 0.01% B added, with the balance being Al, and that has excellent toughness and stress corrosion cracking resistance in the thickness direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 48-71711 Summary of the Invention [Problem to be solved by the invention]

[0005] 7000 series aluminum alloys are broadly divided into Al-Zn-Mg-Cu (aluminum-zinc-magnesium-copper) alloys, which have higher strength, and Al-Zn-Mg alloys, which have excellent weldability. Because the basic chemical compositions of Al-Zn-Mg-Cu alloys and Al-Zn-Mg alloys are different, alloy design studies to improve strength have traditionally been conducted for each alloy system, which has been a time-consuming and labor-intensive process. Therefore, there is a need for technology to improve the strength of both alloy systems, making alloy design easier.

[0006] The present invention has been made in view of the above background, and aims to provide an aluminum alloy material having high strength. [Means for solving the problem]

[0007] One aspect of the present invention reference The present invention relates to a 7000 series aluminum alloy having a chemical composition including Sc (scandium): 0.05% by mass or more and 0.20% by mass or less and Zr (zirconium): 0.05% by mass or more and 0.20% by mass or less, Al-Sc-Zr-based precipitates containing Sc and Zr are present in an Al matrix, and the number of the Al-Sc-Zr-based precipitates per unit volume having a major axis of 2 nm or more and 20 nm or less is 3.0 × 10 21 pieces / m 3 The aluminum alloy material has the above-described metal structure. [Effects of the Invention]

[0008] The aluminum alloy material is made of a 7000 series aluminum alloy containing both Sc and Zr elements, and the contents of these elements are within the specific ranges. The aluminum alloy material also contains 3.0 × 10 Al-Sc-Zr-based precipitates having a major axis of 2 nm or more and 20 nm or less. 21 pieces / m 3The Al-Sc-Zr-based precipitates of the specific embodiment can improve the strength of the aluminum alloy material by precipitation strengthening, whether the aluminum alloy material is an Al-Zn-Mg-Cu-based alloy or an Al-Zn-Mg-based alloy.

[0009] As described above, according to the above-described embodiment, an aluminum alloy material having high strength can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a dark-field image obtained by TEM observation of the aluminum alloy material of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] The 7000 series aluminum alloy constituting the aluminum alloy material may be an Al-Zn-Mg-Cu alloy containing Zn (zinc), Mg (magnesium), and Cu (copper), or an Al-Zn-Mg alloy containing Zn and Mg. Regardless of the type of alloy, by setting the Sc and Zr contents within the above-mentioned specific ranges, fine Al-Sc-Zr precipitates can be formed in the aluminum alloy material. Below, examples of the chemical components of an Al-Zn-Mg-Cu alloy and an Al-Zn-Mg alloy will be described.

[0012] (Al-Zn-Mg-Cu alloy) When the 7000 series aluminum alloy constituting the aluminum alloy material is an Al-Zn-Mg-Cu alloy, the 7000 series aluminum alloy contains Zn: 9.0 mass % or more and 11.0 mass % or less, Mg: 2.0 mass % or more 2.63 % by mass or less, Cu: 1.2% by mass or more and 1.8% by mass or less, Sc: 0.05% by mass or more and 0.20% by mass or less, and Zr: 0.05% by mass or more and 0.20% by mass or less, with the remainder being Al and unavoidable impurities.

[0013] ·Zn: 9.0 mass% or more and 11.0 mass% or less and Mg: 2.0 mass% or more and 3.0 mass% or less Zn and Mg have the effect of forming Zn-Mg-based precipitates containing these elements in the aluminum alloy material and improving the strength of the aluminum alloy material by precipitation strengthening. By setting the Zn content and the Mg content in the aluminum alloy material within the above-mentioned specific ranges, fine Zn-Mg-based precipitates can be formed in the aluminum alloy material, and the strength of the aluminum alloy material can be improved.

[0014] If at least one of the Zn content and the Mg content is lower than the specific range, the amount of Zn-Mg-based precipitates formed in the aluminum alloy material may be insufficient, which may result in a decrease in the strength of the aluminum alloy material. On the other hand, if at least one of the Zn content and the Mg content is higher than the specific range, casting cracks may be more likely to occur during the production process of the aluminum alloy material.

[0015] ·Cu: 1.2 mass% or more and 1.8 mass% or less Cu has the effect of improving the strength of the aluminum alloy material by precipitating together with Zn-Mg-based precipitates. By setting the Cu content in the aluminum alloy material within the above-mentioned specific range, the strength of the aluminum alloy material can be improved.

[0016] If the Cu content is less than the specific range, precipitation strengthening by Cu may be insufficient, which may result in a decrease in the strength of the aluminum alloy material, whereas if the Cu content is more than the specific range, casting cracks may be more likely to occur during the manufacturing process of the aluminum alloy material.

[0017] ·Sc: 0.05 mass% or more and 0.20 mass% or less and Zr: 0.05 mass% or more and 0.20 mass% or less Sc and Zr have the effect of forming Al-Sc-Zr-based precipitates in an aluminum alloy material and improving the strength of the aluminum alloy material through precipitation strengthening. Examples of Al-Sc-Zr-based precipitates include intermetallic compounds containing Al, Sc, and Zr, such as Al3(Sc,Zr). By setting the Sc content and Zr content in the aluminum alloy material within the above-mentioned specific ranges, Al-Sc-Zr-based precipitates can be formed in the aluminum alloy material, and the strength of the aluminum alloy material can be improved.

[0018] When at least one of the Sc content and the Zr content is lower than the specific range, the amount of Al-Sc-Zr-based precipitates formed in the aluminum alloy material is insufficient, which may result in a decrease in the strength of the aluminum alloy material. On the other hand, when at least one of the Sc content and the Zr content is higher than the specific range, coarse crystals are likely to be formed in the aluminum alloy material. As a result, the effect of precipitation strengthening is reduced, and the ductility and toughness of the aluminum alloy may be reduced.

[0019] From the viewpoint of improving the strength of the aluminum alloy material, the Sc content in the Al-Zn-Mg-Cu alloy is more preferably 0.05% by mass to 0.17% by mass, even more preferably 0.06% by mass to 0.15% by mass, and particularly preferably 0.07% by mass to 0.13% by mass. Similarly, the Zr content is more preferably 0.06% by mass to 0.18% by mass, even more preferably 0.07% by mass to 0.16% by mass, and particularly preferably 0.08% by mass to 0.14% by mass.

[0020] Furthermore, when the 7000 series alloy is an Al-Zn-Mg-Cu alloy, the mass ratio of Zr content to Sc content, Zr / Sc, is preferably 0.7 or more and 4.0 or less, more preferably 0.8 or more and 3.0 or less, even more preferably 1.0 or more and 2.0 or less, and particularly preferably 1.1 or more and 1.5 or less. In an Al-Zn-Mg-Cu alloy, by setting the mass ratio of Zr content to Sc content within the above-mentioned specific range, the Al-Sc-Zr precipitates formed in the Al matrix can be made finer. As a result, the strength of the aluminum alloy material can be further improved.

[0021] In addition to the essential elements Zn, Mg, Cu, Sc, and Zr, the Al-Zn-Mg-Cu alloy may contain other optional elements such as Mn (manganese), Cr (chromium), and Ti (titanium).

[0022] ·Mn: More than 0 mass% and 1.0 mass% or less The Al-Zn-Mg-Cu alloy may contain more than 0 mass % and not more than 1.0 mass % Mn as an optional element. When the aluminum alloy material is a rolled material, adding Mn in the specific range to the Al-Zn-Mg-Cu alloy can refine recrystallized grains. When the aluminum alloy material is an extruded material, adding Mn in the specific range to the Al-Zn-Mg-Cu alloy can improve the strength and stress corrosion cracking resistance of the aluminum alloy material.

[0023] ·Cr: More than 0% by mass and 0.3% by mass or less The Al-Zn-Mg-Cu alloy may contain, as an optional element, more than 0 mass % but not more than 0.3 mass % of Cr. When the aluminum alloy material is a rolled material, adding Cr in the specific range to the Al-Zn-Mg-Cu alloy can refine recrystallized grains. When the aluminum alloy material is an extruded material, adding Cr in the specific range to the Al-Zn-Mg-Cu alloy can improve the strength and stress corrosion cracking resistance of the aluminum alloy material.

[0024] ·Ti: more than 0% by mass and less than 1.0% by mass The Al-Zn-Mg-Cu alloy may contain more than 0 mass % but not more than 0.05 mass % Ti as an optional element, which can refine the cast structure and suppress casting cracks.

[0025] Other elements The aluminum alloy material may contain elements other than those mentioned above, provided that the above-mentioned effects are not impaired. For example, the aluminum alloy material may contain elements such as Fe (iron) and Si (silicon). The Fe and Si contents may be, for example, 0.5% by mass or less. The Fe and Si contents are preferably 0.3% by mass or less.

[0026] ·Metal structure The aluminum alloy material has a metal structure in which Al-Sc-Zr-based precipitates and the like are dispersed in an Al matrix. The number of Al-Sc-Zr-based precipitates with a major axis of 2 nm or more and 20 nm or less contained in the aluminum alloy material per unit volume is 3.0 × 10 21 pieces / m 3 That is all. By setting the number of Al-Sc-Zr-based precipitates having a major axis of 2 nm or more and 20 nm or less contained in the aluminum alloy material to the specific range, the precipitation strengthening effect of the Al-Sc-Zr-based precipitates can be sufficiently enhanced. Furthermore, the precipitation strengthening effect of the Al-Sc-Zr-based precipitates and the effects of other elements act synergistically, thereby improving the strength of the aluminum alloy material.

[0027] When the number per unit volume of the Al-Sc-Zr-based precipitates contained in the aluminum alloy material is smaller than the specific range, the precipitation strengthening effect of the Al-Sc-Zr-based precipitates becomes insufficient, which may lead to a decrease in strength of the aluminum alloy material.

[0028] (Al-Zn-Mg alloy) The 7000 series aluminum alloy constituting the aluminum alloy material may be an Al-Zn-Mg alloy. When the 7000 series aluminum alloy constituting the aluminum alloy material is an Al-Zn-Mg alloy, the 7000 series aluminum alloy preferably has a chemical composition containing 4.0% by mass or more and 6.0% by mass or less of Zn, 1.0% by mass or more and 2.0% by mass or less of Mg, 0.05% by mass or more and 0.20% by mass or less of Sc, and 0.05% by mass or more and 0.20% by mass or less of Zr, with the balance being Al and unavoidable impurities.

[0029] ·Zn: 4.0 mass% or more and 6.0 mass% or less and Mg: 1.0 mass% or more and 2.0 mass% or less The effects of Zn and Mg in Al-Zn-Mg alloys are similar to those of these elements in Al-Zn-Mg-Cu alloys. That is, Zn and Mg form Zn-Mg-based precipitates containing these elements in the aluminum alloy material, and have the effect of improving the strength of the aluminum alloy material through precipitation strengthening. By setting the Zn content and Mg content in the aluminum alloy material within the above-mentioned specific ranges, fine Zn-Mg-based precipitates can be formed in the aluminum alloy material, and the strength of the aluminum alloy material can be improved.

[0030] If at least one of the Zn content and the Mg content is lower than the specific range, the Zn-Mg-based precipitates formed in the aluminum alloy material may be insufficient, which may result in a decrease in strength of the aluminum alloy material. On the other hand, if the Zn content is higher than the specific range, it may result in a decrease in stress corrosion cracking resistance. Furthermore, if the Mg content is higher than the specific range, it may result in a decrease in hot workability.

[0031] ·Sc: 0.05 mass% or more and 0.20 mass% or less and Zr: 0.05 mass% or more and 0.20 mass% or less The effects of Sc and Zr in Al-Zn-Mg alloys and the reasons for limiting the contents of these elements are similar to those of Al-Zn-Mg-Cu alloys. That is, Sc and Zr have the effect of forming Al-Sc-Zr-based precipitates in an aluminum alloy material and improving the strength of the aluminum alloy material through precipitation strengthening. By setting the Sc content and Zr content in the aluminum alloy material within the specific ranges, Al-Sc-Zr-based precipitates can be formed in the aluminum alloy material, improving the strength of the aluminum alloy material. If at least one of the Sc content and Zr content in the aluminum alloy material deviates from the specific range, the strength of the aluminum alloy material may be reduced.

[0032] From the viewpoint of improving the strength of the aluminum alloy material, the Sc content in the Al-Zn-Mg alloy is more preferably 0.05% by mass to 0.17% by mass, even more preferably 0.06% by mass to 0.15% by mass, and particularly preferably 0.07% by mass to 0.13% by mass. Similarly, the Zr content is more preferably 0.08% by mass to 0.20% by mass, even more preferably 0.10% by mass to 0.20% by mass, and particularly preferably 0.12% by mass to 0.20% by mass.

[0033] Furthermore, when the 7000 series alloy is an Al-Zn-Mg alloy, the mass ratio of Zr to Sc, Zr / Sc, is preferably 0.7 to 4.0, more preferably 0.9 to 3.0, even more preferably 1.1 to 2.0, and particularly preferably 1.3 to 1.8. In an Al-Zn-Mg alloy, by setting the mass ratio of Zr to Sc within the above-mentioned specific range, the Al-Sc-Zr precipitates formed in the Al matrix can be made finer. As a result, the strength of the aluminum alloy material can be further improved.

[0034] In addition to the essential elements Zn, Mg, Sc, and Zr, the Al-Zn-Mg alloy may contain other optional elements such as Mn (manganese), Cr (chromium), and Ti (titanium).

[0035] ·Mn: More than 0 mass% and 1.0 mass% or less The Al-Zn-Mg alloy may contain more than 0 mass % and 1.0 mass % or less of Mn as an optional element. When the aluminum alloy material is a rolled material, adding Mn in the specific range to the Al-Zn-Mg alloy can refine recrystallized grains. When the aluminum alloy material is an extruded material, adding Mn in the specific range to the Al-Zn-Mg alloy can improve the strength and stress corrosion cracking resistance of the aluminum alloy material.

[0036] ·Cr: More than 0% by mass and 0.3% by mass or less The Al-Zn-Mg alloy may contain, as an optional element, more than 0 mass % but not more than 0.3 mass % of Cr. When the aluminum alloy material is a rolled material, adding Cr in the specific range to the Al-Zn-Mg alloy can refine recrystallized grains. When the aluminum alloy material is an extruded material, adding Cr in the specific range to the Al-Zn-Mg alloy can improve the strength and stress corrosion cracking resistance of the aluminum alloy material.

[0037] ·Ti: more than 0% by mass and less than 1.0% by mass The Al-Zn-Mg alloy may contain more than 0 mass % but not more than 0.05 mass % of Ti as an optional element, which can refine the cast structure and suppress casting cracks.

[0038] Other elements The aluminum alloy material may contain elements other than those mentioned above, provided that the above-mentioned effects are not impaired. For example, the aluminum alloy material may contain elements such as Fe (iron) and Si (silicon). The Fe and Si contents may be, for example, 0.5% by mass or less. The Fe and Si contents are preferably 0.3% by mass or less.

[0039] ·Metal structure The aluminum alloy material has a metal structure in which Al-Sc-Zr-based precipitates and the like are dispersed in an Al matrix. The number of Al-Sc-Zr-based precipitates with a major axis of 2 nm or more and 20 nm or less contained in the aluminum alloy material per unit volume is 3.0 × 10 21 pieces / m 3 That is all. By setting the number of Al-Sc-Zr-based precipitates having a major axis of 2 nm or more and 20 nm or less contained in the aluminum alloy material to the specific range, the precipitation strengthening effect of the Al-Sc-Zr-based precipitates can be sufficiently enhanced. Furthermore, the precipitation strengthening effect of the Al-Sc-Zr-based precipitates and the effects of other elements, precipitates, etc. act synergistically, thereby improving the strength of the aluminum alloy material.

[0040] When the number of the Al-Sc-Zr-based precipitates contained in the aluminum alloy material is smaller than the specific range, the precipitation strengthening effect of the Al-Sc-Zr-based precipitates becomes insufficient, which may lead to a decrease in strength of the aluminum alloy material.

[0041] (Method of manufacturing aluminum alloy material) In producing the aluminum alloy material, for example, an ingot made of the 7000 series aluminum alloy is prepared, and then the ingot is subjected to a homogenization treatment.

[0042] The method for producing the ingot is not particularly limited, and various methods such as continuous casting and semi-continuous casting can be used.

[0043] After preparing the ingot by the various methods described above, the ingot is heated and homogenized. The holding temperature during homogenization is 250°C or higher. 400 °C or less. By setting the holding temperature in the homogenization treatment within the specific range, it is possible to finally form fine Al-Sc-Zr-based precipitates in the aluminum alloy material. As a result, an aluminum alloy having high strength can be easily obtained.

[0044] The holding time in the homogenization treatment is not particularly limited, but from the viewpoint of sufficiently homogenizing the ingot, it is preferably 2 hours or more and 24 hours or less, and more preferably 5 hours or more and 24 hours or less.

[0045] The ingot after the homogenization treatment may be used as an aluminum alloy material as it is, or may be subjected to wrought processing or heat treatment as necessary to obtain an aluminum alloy material having a desired shape and mechanical properties. Examples of wrought processing include hot rolling, hot extrusion, cold rolling, and drawing. Examples of heat treatment include annealing, solution treatment, and artificial aging treatment. These wrought processing and heat treatments can be performed alone or in appropriate combination depending on the desired form of the aluminum alloy material. [Example]

[0046] Examples of the aluminum alloy material will be described below. Note that the specific aspects of the aluminum alloy material according to the present invention are not limited to the aspects of the examples shown below, and the configuration can be appropriately changed within the scope of the present invention.

[0047] Example 1 In this example, an example of an aluminum alloy material made of an Al-Zn-Mg-Cu alloy will be described. The aluminum alloy material of this example is a 7000 series aluminum alloy containing Zn: 9.0% by mass to 11.0% by mass, Mg: 2.0% by mass to 3.0% by mass, Cu: 1.2% by mass to 1.8% by mass, Sc: 0.05% by mass to 0.20% by mass, and Zr: 0.05% by mass to 0.20% by mass, with the balance being Al and unavoidable impurities. Furthermore, the aluminum alloy material of this example is configured such that Al-Sc-Zr precipitates containing Sc and Zr are present in an Al matrix, and the number per unit volume of the Al-Sc-Zr precipitates having a major axis of 2 nm to 20 nm is 3.0 × 10 21 pieces / m 3 The metal structure is as described above.

[0048] The aluminum alloy material of this example can be produced, for example, by the following method. First, a billet with a diameter of 90 mm having the chemical composition shown in alloy symbol A1 in Table 1 is produced by DC casting. In Table 1, "Bal." is a symbol indicating the balance, and "-" is a symbol indicating that the element in question is not included.

[0049] Next, the billet is held at 400°C for 10 hours for homogenization. During the homogenization, the temperature is increased at a rate of 50°C / hour until the temperature reaches 400°C. After the homogenization is complete, the billet is cooled to room temperature by air cooling.

[0050] After the homogenization treatment, hot extrusion is performed. The temperature of the billet at the start of hot extrusion is 400°C, and the extrusion ratio, i.e., the ratio of the cross-sectional area of ​​the billet before extrusion to the cross-sectional area of ​​the extruded material after extrusion, is approximately 99.

[0051] Next, the extruded material is subjected to solution treatment. In the solution treatment, the extruded material is held in a salt bath furnace at 470°C for 1 hour, and then water quenched. Thereafter, the extruded material is held at a temperature of 120°C for 24 hours to undergo artificial aging treatment. In the artificial aging treatment, the temperature is increased at a rate of 50°C / hour until the temperature reaches 120°C. After the artificial aging treatment is completed, the billet is cooled to room temperature by air cooling. Through the above steps, the aluminum alloy material of this example can be obtained.

[0052] FIG. 1 shows an example of the metallographic structure of the aluminum alloy material of this example. FIG. 1 is a dark-field image obtained by observing a thin section, 500 nm long, 500 nm wide, and 2 nm thick, taken from the aluminum alloy material of this example using a transmission electron microscope (TEM). As shown in FIG. 1, the aluminum alloy material 1 of this example has a metallographic structure in which Al-Sc-Zr-based precipitates 3 are dispersed in an Al matrix 2. The Al-Sc-Zr-based precipitates 3 in FIG. 1 are black areas surrounded by an annular region 4 with a relatively bright contrast. The annular region 4 in FIG. 1 is thought to be the Al matrix in which strain has occurred due to the Al-Sc-Zr-based precipitates 3.

[0053] The number of Al-Sc-Zr precipitates with a long diameter of 2 nm to 20 nm per unit volume in an aluminum alloy material (N (unit: pieces / m 3 ) is the number n (unit: pieces) of Al-Sc-Zr-based precipitates with a major axis of 2 nm to 20 nm present in the field of view of the TEM image and the field area. S (unit: m 2 The number N of Al-Sc-Zr-based precipitates per unit volume present in the aluminum alloy material of this example is the value shown in Table 2. N=(S / n) -3 / 2 ···(1)

[0054] The mechanical properties of the aluminum alloy material of this example can be evaluated based on the results of a tensile test performed in accordance with JIS Z2241: 2011. Table 2 shows the 0.2% yield strength, tensile strength, and elongation of the aluminum alloy material of this example.

[0055] Table 2 shows the 0.2% yield strength, tensile strength and elongation values ​​of the aluminum alloy material of this example.

[0056] (Comparative Example 1) Comparative Example 1 is an example of an aluminum alloy material made of an Al-Zn-Mg-Cu alloy that does not contain Sc. The aluminum alloy material of this example has the chemical composition shown by alloy symbol A2 in Table 1. Since the chemical composition of the aluminum alloy material of this example does not contain Sc, no Al-Sc-Zr precipitates are formed in the aluminum alloy material. The method for producing the aluminum alloy material of Comparative Example 1 is the same as the method for producing the aluminum alloy material of Example 1, except for the chemical composition.

[0057] Table 2 shows the 0.2% yield strength, tensile strength and elongation values ​​of the aluminum alloy material of this example.

[0058] Example 2 In this example, an aluminum alloy material made of an Al-Zn-Mg alloy will be described. The aluminum alloy material in this example is a 7000 series aluminum alloy containing 4.0% by mass or more and 6.0% by mass or less of Zn, 1.0% by mass or more and 2.0% by mass or less of Mg, 0.05% by mass or more and 0.20% by mass or less of Sc, and 0.05% by mass or more and 0.20% by mass or less of Zr, with the balance being Al and unavoidable impurities.

[0059] More specifically, the aluminum alloy material of this example has the chemical composition shown in alloy symbol A3 in Table 1. The aluminum alloy material of this example can be produced, for example, by the following method: First, a billet having a diameter of 90 mm and having the chemical composition shown in alloy symbol A3 in Table 1 is produced by DC casting.

[0060] Next, the billet is held at 400°C for 8 hours to undergo homogenization. During the homogenization, the temperature is increased at a rate of 50°C / hour until the temperature reaches 400°C. After the homogenization is complete, the billet is cooled to room temperature by air cooling.

[0061] After the homogenization treatment, the billet is hot extruded. The temperature of the billet at the start of the hot extrusion is 450°C, and the extrusion ratio is about 99.

[0062] Next, the extruded material is subjected to artificial aging treatment by being held at a temperature of 120°C for 24 hours. In the artificial aging treatment, the temperature is increased at a rate of 50°C / hour until the temperature reaches 120°C. After the artificial aging treatment is completed, the billet is cooled to room temperature by air cooling. In this manner, the aluminum alloy material of this example can be obtained.

[0063] Table 2 shows the 0.2% yield strength, tensile strength and elongation values ​​of the aluminum alloy material of this example.

[0064] (Comparative Example 2) Comparative Example 2 is an example of an aluminum alloy material made of an Al-Zn-Mg alloy that does not contain Sc. The aluminum alloy material of this example has the chemical composition shown in alloy symbol A4 in Table 1. Since the chemical composition of the aluminum alloy material of this example does not contain Sc, no Al-Sc-Zr precipitates are formed in the aluminum alloy material. The method for producing the aluminum alloy material of this example is the same as the method for producing the aluminum alloy material of Example 2, except for the chemical composition.

[0065] Table 2 shows the 0.2% yield strength, tensile strength and elongation values ​​of the aluminum alloy material of this example.

[0066] [Table 1]

[0067] [Table 2]

[0068] As described above, the aluminum alloy material of Example 1 has a metal structure in which Al-Sc-Zr-based precipitates are finely dispersed in the Al matrix. In contrast, the aluminum alloy material of Comparative Example 1 does not contain Sc, and therefore no Al-Sc-Zr-based precipitates are formed in the Al matrix. In Table 2, comparing Example 1 and Comparative Example 1, which have similar chemical compositions except for the presence or absence of Sc, the aluminum alloy material of Example 1 has higher 0.2% proof stress and tensile strength than the aluminum alloy material of Comparative Example 1, which does not contain Sc. From these results, it can be understood that in an aluminum alloy material made of an Al-Zn-Mg-Cu alloy, the strength can be improved by finely precipitating Al-Sc-Zr-based precipitates.

[0069] Furthermore, when Example 2 and Comparative Example 2, which have similar chemical compositions except for the presence or absence of Sc, are compared, the aluminum alloy material of Example 2, which is made of an Al-Zn-Mg alloy containing Zr and Sc, has higher 0.2% proof stress and tensile strength than the aluminum alloy material of Comparative Example 2, which does not contain Sc. From these results, it can be inferred that fine Al-Sc-Zr-based precipitates are precipitated in the Al matrix also in Example 2. It can also be understood that the strength can be improved by finely precipitating Al-Sc-Zr-based precipitates in an aluminum alloy material made of an Al-Zn-Mg alloy.

[0070] As described above, by adding the specific amounts of Sc and Zr to the 7000 series alloy and by forming the metal structure in the specific form, it is possible to increase the strength of both the Al-Zn-Mg-Cu alloy and the Al-Zn-Mg alloy. [Explanation of symbols]

[0071] 1. Aluminum alloy material 2 Al matrix 3. Al-Sc-Zr precipitates

Claims

1. a 7000 series aluminum alloy having a chemical composition containing Zn: 9.0% by mass or more and 11.0% by mass or less, Mg: 2.0% by mass or more and 2.63% by mass or less, Cu: 1.2% by mass or more and 1.8% by mass or less, Sc: 0.05% by mass or more and 0.20% by mass or less, and Zr: 0.05% by mass or more and 0.20% by mass or less, with the balance being Al and unavoidable impurities; Al-Sc-Zr-based precipitates containing Sc and Zr are present in an Al matrix, and the number of the Al-Sc-Zr-based precipitates having a major axis of 2 nm or more and 20 nm or less per unit volume is 3.0 × 10 ２１ pieces / m ３ An aluminum alloy material having the above metal structure.

2. 2. The aluminum alloy material according to claim 1, wherein the 7000 series aluminum alloy further contains one or more elements selected from the group consisting of more than 0 mass% and 1.0 mass% or less of Mn, more than 0 mass% and 0.3 mass% or less of Cr, and more than 0 mass% and 0.05 mass% or less of Ti.

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