Aluminum alloy, aluminum alloy hot worked material, and method of making same

Abstract

An aluminum alloy having the following chemical composition: containing Sc: 0.01 mass% or more and 0.40 mass% or less, Mg: 0 mass% or more and 2.5 mass% or less, Zr: 0 mass% or more and 0.4 mass% or less, with the remainder including Al and unavoidable impurities. A compression deformation resistance calculated from a true stress when deforming the aluminum alloy by compressing it at a temperature of 450°C at a strain rate of 1 s ‑1 62 MPa or less.

Description

Technical Field

[0001] This invention relates to aluminum alloys, aluminum alloy hot working materials, and methods for manufacturing the same. Background Technology

[0002] Aluminum materials (including pure aluminum and aluminum alloys), with their high specific strength and excellent machinability, are used in various fields such as materials for transportation aircraft (vehicles, aircraft, ships), building materials, and general mechanical components. In these applications, such as in vehicle materials, high strength is required for vehicle weight reduction. Furthermore, vehicle materials are sometimes formed into complex cross-sectional shapes and fine structures. To meet these requirements, aluminum materials used in vehicles must possess a yield strength of 0.2% or higher of 140 MPa and excellent hot workability. Aluminum alloys that meet these requirements include the 6000 series alloys containing Al (aluminum), Mg (magnesium), and Si (silicon), and the 7000 series alloys containing Al, Mg, and Zn (zinc).

[0003] However, 6000 series alloys are unsuitable for applications requiring welding due to their low weld joint coefficient. Additionally, 7000 series alloys suffer from low corrosion resistance.

[0004] On the other hand, aluminum materials with excellent weld joint coefficient and corrosion resistance are known to include 1000 series aluminum and 5000 series alloys containing Al (aluminum) and Mg (magnesium) (e.g., Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6446124 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, 1000 series aluminum suffers from low strength due to its low content of alloying elements. Furthermore, to improve the strength of 5000 series alloys, simply increasing the Mg content could be considered. However, if the Mg content increases, the deformation resistance during hot working processes such as hot rolling and hot extrusion will increase, potentially making it difficult to shape the 5000 series alloys into the desired form.

[0010] The present invention was made in view of the above background, and aims to provide an aluminum alloy, an aluminum alloy hot workable material containing the aluminum alloy, and a method for manufacturing the same, wherein the aluminum alloy can achieve both excellent hot workability and high strength even when it does not contain Mg or when the Mg content is low.

[0011] Technical solutions for solving technical problems

[0012] One aspect of the present invention is an aluminum alloy having the following chemical composition: containing Sc (scandium): 0.01% by mass or more and 0.40% by mass, Mg (magnesium): 0% by mass or more and 2.5% by mass, Zr (zirconium): 0% by mass or more and 0.4% by mass, with the remainder comprising Al (aluminum) and unavoidable impurities, based on a 1s... -1 The compressive deformation resistance calculated from the true stress when the aluminum alloy is deformed by compressing at the strain rate is less than 62 MPa.

[0013] Another aspect of the present invention is an aluminum alloy hot-working material having the following chemical composition: containing Sc: 0.01% by mass or more and 0.40% by mass or less, Mg: 0% by mass or more and 2.5% by mass or less, Zr: 0% by mass or more and 0.4% by mass or less, with the remainder comprising Al and unavoidable impurities.

[0014] The material contains Al-Sc second-phase particles dispersed in the Al parent phase, and the number density of these Al-Sc second-phase particles is 3000 particles / μm. 3 above.

[0015] Another aspect of the present invention is a method for manufacturing an aluminum alloy hot-working material, comprising: a hot-working step, wherein the aluminum alloy of the above-described manner is hot-working performed at a temperature within a range of 350°C to 550°C; and

[0016] The heat treatment process, wherein, in at least one of the above-mentioned heat treatment process and the above-mentioned heat treatment process, the aluminum alloy is held at a holding temperature of 250°C or higher and 550°C or lower for a total of 30 minutes or more.

[0017] Invention Effects

[0018] The aforementioned aluminum alloy contains Sc as an essential component and Mg and Zr as optional components. Sc in the aforementioned aluminum alloy exists as a solid-soluble element dissolved in the Al matrix phase and as Al-Sc system second-phase particles dispersed within the Al matrix phase. Even in any of these states, Sc has a small effect on deformation resistance during hot working. Therefore, the aforementioned aluminum alloy can suppress the increase in deformation resistance and avoid deterioration of hot workability, even when it does not contain Mg or contains Mg within the aforementioned specific range.

[0019] Furthermore, Sc, as a solid solution element, precipitates as Al-Sc-based second-phase particles in the Al parent phase through the aforementioned specific heat treatment process. This precipitation strengthening of the Al-Sc-based second-phase particles enhances the strength of the aluminum alloy.

[0020] As mentioned above, the aluminum alloys described above can achieve both excellent hot workability and high strength when Mg is absent or present in a small amount.

[0021] Furthermore, the aforementioned aluminum alloy hot-working material possesses the specific chemical composition described above, and the number density of Al-Sc-based second-phase particles dispersed in the Al matrix phase is within the specific range described above. By achieving the specific number density of Al-Sc-based second-phase particles within the aforementioned range, the aforementioned aluminum alloy hot-working material can easily achieve high strength.

[0022] Furthermore, the method for manufacturing the aforementioned aluminum alloy hot-working material includes a hot-working step of performing hot working on the aluminum alloy as described above, and a heat treatment step of heating the aluminum alloy under the aforementioned specific conditions. In the heat treatment step, by heating the aluminum alloy under the aforementioned specific conditions, Sc dissolved in the aluminum alloy can precipitate as Al-Sc-based second-phase particles. This allows for easy improvement of the strength of the final obtained aluminum alloy hot-working material. Detailed Implementation

[0023] (Aluminum alloy)

[0024] The chemical composition of the aforementioned aluminum alloy and the reasons for its limitations are explained.

[0025] •Sc: ≥0.01% by mass and ≤0.40% by mass

[0026] The aforementioned aluminum alloy contains 0.01% to 0.40% by mass of Sc as an essential component. As described above, the Sc in the aluminum alloy exists in the form of a solid-solubilized element dissolved in the Al matrix phase, or Al-Sc-based second-phase particles. When the aluminum alloy is held at a holding temperature of 250°C to 550°C, the Sc dissolved in the Al matrix phase precipitates in the Al matrix phase as Al-Sc-based second-phase particles. Furthermore, the Al-Sc-based second-phase particles dispersed in the Al matrix phase have the effect of increasing the strength of the aluminum alloy through precipitation strengthening.

[0027] The aforementioned aluminum alloy is configured such that, by setting the Sc content within the specific range described above, the number density of Al-Sc-based second-phase particles present in the Al matrix phase is within the specific range described above. Therefore, the strength of the aforementioned aluminum alloy can be easily improved. Furthermore, as mentioned above, both Sc dissolved in the Al matrix phase and the Al-Sc-based second-phase particles have minimal impact on hot workability. Therefore, even in the presence of Al-Sc-based second-phase particles, the aforementioned aluminum alloy can suppress the increase in deformation resistance during hot working.

[0028] The content of Sc is preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.07% by mass or more. By increasing the Sc content in the above-mentioned aluminum alloy, the number density of Al-Sc-based second-phase particles after heat treatment can be further improved. As a result, the strength of the above-mentioned aluminum alloy can be further improved. When the Sc content is less than 0.01% by mass, it may become difficult to increase the number density of Al-Sc-based second-phase particles, and thus difficult to improve the strength.

[0029] On the other hand, if the Sc content is too high, it exceeds the solid solution limit, making it difficult to dissolve Sc in the aforementioned aluminum alloy. As a result, the strength improvement effect brought about by the Al-Sc second-phase particles may not be obtained. From the viewpoint of avoiding this problem, the Sc content is set to 0.40% by mass or less. From the same viewpoint, the Sc content is preferably 0.35% by mass or less, more preferably 0.30% by mass or less, even more preferably 0.25% by mass or less, and particularly preferably 0.15% by mass or less.

[0030] ·Mg: ≥0% by mass and ≤2.5% by mass

[0031] The aforementioned aluminum alloy may contain up to 2.5% by mass of Mg as an arbitrary component. Mg in the aforementioned aluminum alloy exists as a solid-solubilized element in the Al matrix phase, and thus enhances the strength of the aluminum alloy. By setting the Mg content in the aforementioned aluminum alloy within the specific range described above, the increase in deformation resistance during hot working can be suppressed, and the strength improvement effect brought about by Mg can be obtained.

[0032] From the viewpoint of further enhancing the strength improvement effect brought about by Mg, the Mg content is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, even more preferably 0.8% by mass or more, particularly preferably 1.0% by mass or more, and most particularly preferably 1.2% by mass or more. On the other hand, from the viewpoint of further improving hot workability, the Mg content is preferably 2.2% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.8% by mass or less.

[0033] • Zr: ≥0% by mass and ≤0.40% by mass

[0034] The aforementioned aluminum alloy may contain up to 0.40% by mass of Zr as an arbitrary component. Zr in the aforementioned aluminum alloy exists as a solid-soluble element dissolved in the Al matrix phase, or as Zr-based precipitates. When the aforementioned aluminum alloy is held at a temperature between 250°C and 550°C, Zr dissolved in the Al matrix phase precipitates out in a manner that surrounds Al-Sc second-phase particles. These Zr-based precipitates thus suppress the coarsening of Al-Sc second-phase particles. Furthermore, by suppressing the coarsening of Al-Sc second-phase particles through Zr-based precipitates, finer Al-Sc second-phase particles can be precipitated in large quantities within the Al matrix phase. These results further enhance the strength improvement effect brought about by Al-Sc second-phase particles.

[0035] From the viewpoint of further enhancing the aforementioned effects brought about by Zr, the Zr content is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, even more preferably 0.06% by mass or more, and particularly preferably 0.09% by mass or more.

[0036] On the other hand, if the Zr content is too high, it exceeds the solid solution limit, making it difficult for Zr to dissolve in the aforementioned aluminum alloy. As a result, the aforementioned effects brought about by Zr-based precipitates may not be obtained. From the viewpoint of avoiding this problem, the Zr content is set to 0.40% by mass or less. From the same viewpoint, the Zr content is preferably 0.35% by mass or less, more preferably 0.30% by mass or less, and even more preferably 0.25% by mass or less.

[0037] Cu (copper): greater than 0% by mass and less than 1.0% by mass

[0038] The aforementioned aluminum alloy may contain Cu as an arbitrary component, which is greater than 0% by mass and less than 1.0% by mass. In this case, the strength of the aforementioned aluminum alloy can be further improved. From the viewpoint of further improving the strength improvement effect brought about by Cu, the Cu content is preferably 0.10% by mass or more, more preferably 0.20% by mass or more, and even more preferably 0.30% by mass or more.

[0039] On the other hand, if the Cu content is too high, it may lead to a decrease in corrosion resistance. From the viewpoint of avoiding a decrease in corrosion resistance and obtaining the effect of increased strength brought about by Cu, the Cu content is preferably 0.90% by mass or less, more preferably 0.80% by mass or less, and even more preferably 0.70% by mass or less.

[0040] Mn (manganese): greater than 0% by mass and less than 1.0% by mass; Cr (chromium): greater than 0% by mass and less than 0.30% by mass.

[0041] The above aluminum alloy may contain one or both of Mn at more than 0% by mass and 1.0% by mass or less and Cr at more than 0% by mass and 0.30% by mass or less as optional components. By setting the content of these elements within the above-specified ranges, coarsening of the crystal grain structure during the manufacturing process of the above aluminum alloy can be more effectively suppressed.

[0042] · Ti (titanium): more than 0% by mass and 0.10% by mass or less, B (boron): more than 0% by mass and 0.10% by mass or less

[0043] The above aluminum alloy may contain one or both of Ti at more than 0% by mass and 0.10% by mass or less and B at more than 0% by mass and 0.10% by mass or less as optional components. These elements have the effect of refining the crystal grains when the molten metal solidifies during the manufacturing process of the above aluminum alloy. By setting the content of Ti and B within the above-specified ranges, the crystal grains of the above aluminum alloy can be sufficiently refined, further improving the strength of the finally obtained aluminum alloy hot-worked material.

[0044] · Inevitable impurities

[0045] As the inevitable impurities contained in the above aluminum alloy, elements such as Fe (iron), Si (silicon), etc. can be cited. The content of Fe as an inevitable impurity is 0.50% by mass or less, and the content of Si is 0.50% by mass or less. In addition, for inevitable impurities other than Fe and Si, the content of each element is 0.05% by mass or less. If the content of the elements as inevitable impurities is within the above ranges, it is possible to easily avoid impairing the above effects due to inevitable impurities.

[0046] · Compressive deformation resistance: 62 MPa or less

[0047] The aluminum alloy having the chemical composition within the above-specified ranges has a compressive deformation resistance of 62 MPa or less. It should be noted that the compressive deformation resistance in this specification is the compressive deformation resistance calculated based on the true stress when the aluminum alloy is deformed by compression at a strain rate of 1 s -1 at a temperature of 450 °C.

[0048] By setting the compressive deformation resistance of the above aluminum alloy within the above-specified ranges, the hot workability of the aluminum alloy can be improved. In addition, an aluminum alloy having the compressive deformation resistance within the above-specified ranges can also be applied to, for example, porthole extrusion (Japanese: ポートホール押出), that is, a forming method such as extruding an aluminum alloy from a die formed by combining a male die and a female die, which particularly requires high hot workability.

[0049] (Aluminum alloy hot-worked material)

[0050] By subjecting the aforementioned aluminum alloy to hot processing such as hot rolling and hot extrusion, aluminum alloy hot-working materials (hereinafter referred to as "hot-working materials") can be obtained. The chemical composition of the aforementioned hot-working materials is the same as that of the aluminum alloy used as raw material.

[0051] In the aforementioned hot-working material, Al-Sc system second-phase particles, i.e., second-phase particles containing Al and Sc, are dispersed within the Al parent phase. Specifically, the Al-Sc system second-phase particles consist of Al3Sc and Al3(Sc) x Zr 1-x It is composed of intermetallic compounds such as Al3(Sc). It should be noted that Al3(Sc) is composed of... x Zr 1-x In Al3(Sc), the value of x is 0 < x < 1. x Zr 1-x The value of x in () varies depending on the Zr content in the aluminum alloy and the heating conditions in the heat treatment process.

[0052] The preferred number density of Al-Sc second-phase particles in the aforementioned heat-working material is 3000 particles / μm. 3 The above describes the effect of Al-Sc second-phase particles in improving the strength of hot-worked materials through precipitation strengthening. By setting the number density of Al-Sc second-phase particles in the hot-worked material within the specific range described above, the strength of the hot-worked material can be improved.

[0053] Regarding the precipitation enhancement effect brought about by the second phase particles, it can be predicted to some extent according to the following equation (1) recorded in CBFuller et al., ActaMaterialia 51 (2003) 4803-4814.

[0054] σ=2.8 / λ(lnλ+5.4)+σ0 . . . (1)

[0055] It should be noted that in the above formula, σ is the 0.2% yield strength [MPa] of the aluminum alloy after being strengthened by the precipitation of second phase particles, λ is the average particle spacing [μm] of the second phase particles, and σ0 is the 0.2% yield strength [MPa] of the aluminum alloy without second phase particles.

[0056] The average interparticle spacing λ of the second phase particles in equation (1) above can be expressed as the number density N [particles / μm] of the second phase particles per unit volume. 3 ], as shown in the following formula (2).

[0057] λ=N -1 / 3 ... (2)

[0058] As σ0, if the typical 0.2% yield strength of JIS A1100 aluminum is 35 MPa, then the above equation (1) can be expressed as equation (3) below.

[0059] σ = 2.8N 1 / 3 (lnN -1 / 3 +5.4)+35 . . . (3)

[0060] Furthermore, if N in the above equation (3) is set to 3000 per μm 3 Therefore, the 0.2% yield strength σ is approximately 145 MPa. Thus, by setting the number density of Al-Sc second-phase particles to the aforementioned specific range, even without the presence of Mg, it is possible to expect the 0.2% yield strength of the aluminum alloy to be above 140 MPa.

[0061] From the perspective of further improving the strength of hot-working materials, the number density of Al-Sc second-phase particles is more preferably 5000 particles / μm. 3 The above is further optimized to 7000 per μm. 3 The above. It should be noted that the upper limit of the number density of Al-Sc second-phase particles can be naturally determined based on the amount of Sc contained in the aforementioned hot-working aluminum alloy materials.

[0062] The number density of Al-Sc second-phase particles in the aforementioned heat-processed material can be calculated based on the results of microstructural observation using transmission electron microscopy (TEM). More specifically, firstly, after taking a test sample from the aforementioned heat-processed material, the thickness of the test sample is reduced to 0.1 μm through electrolytic grinding. The test sample is then observed using TEM, and the number of Al-Sc second-phase particles with an equivalent circle diameter of 0.5 nm or more and less than 10 nm within the field of view is counted. Then, the number of Al-Sc second-phase particles present in the field of view is converted to a density per μm. 3 The number of volumes is used as the number density of the second-phase particles in the Al-Sc system.

[0063] The shape of the aforementioned hot-working aluminum alloy material is not particularly limited; for example, it can take various shapes such as sheet, bar, tube, strip, and extruded profile. The aforementioned hot-working aluminum alloy material is preferably produced by split extrusion. The hot-extruded material produced by split extrusion has at least one hollow portion surrounded by a wall containing aluminum alloy. Alternatively, at least one weld surface can be formed in the wall portion of the hot-extruded material produced by split extrusion, where the aluminum alloys are fused together.

[0064] As described above, the aluminum alloy possesses hot workability capable of being subjected to split extrusion. Therefore, by using the aluminum alloy described above, it is possible to easily produce hot-extruded materials with complex cross-sectional shapes or fine structures that can be achieved through split extrusion.

[0065] (Manufacturing method of aluminum alloy hot-working materials)

[0066] The manufacturing method of the above-mentioned aluminum alloy hot-working material includes: a hot-working step, wherein the aluminum alloy is hot-working in a temperature range of 350°C or higher and 550°C or lower; and

[0067] The heat treatment process, wherein, at least one of the above-mentioned heat treatment process and the above-mentioned heat treatment process is performed, the aluminum alloy is held at a holding temperature of 250°C or higher and 550°C or lower for a total of 30 minutes or more.

[0068] • Hot working process

[0069] As an aluminum alloy for hot working processes, aluminum alloys prepared by conventional methods can be used. For example, the aluminum alloy can be an ingot obtained by casting molten metal with the above-mentioned specific chemical composition by methods such as DC casting and CC casting, or it can be a billet.

[0070] Hot working, as a hot processing step, can be achieved through various methods such as hot rolling, hot extrusion, and hot forging. In the aforementioned manufacturing methods, aluminum alloys with the specific chemical composition described above and excellent hot workability can be used. Therefore, as a hot processing step, the aforementioned manufacturing method can employ split extrusion. Then, by performing split extrusion, hot-extruded materials with complex cross-sectional shapes or fine structures can be easily obtained.

[0071] The starting temperature for hot working in the hot working process is set to be above 350°C and below 550°C. When the starting temperature is below 350°C, the deformation resistance of the aluminum alloy becomes too high, making hot working difficult. On the other hand, when the starting temperature is above 550°C, the aluminum alloy may easily melt locally during hot working due to the heat generated.

[0072] Heat treatment process

[0073] In the above manufacturing method, a heat treatment process is performed on the heated aluminum alloy. The holding temperature in the heat treatment process is set to 250°C or higher and 550°C or lower. Furthermore, the holding time in the heat treatment process is set to a total of 30 minutes or more. By setting the holding temperature and holding time in the heat treatment process to the aforementioned specific ranges, fine and abundant Al-Sc-based second-phase particles can be precipitated in the Al matrix, thereby improving the strength of the heat-worked material.

[0074] When the holding temperature during the heat treatment process is less than 250°C, or the total holding time is less than 30 minutes, the precipitation of Al-Sc second-phase particles becomes insufficient, which may lead to a decrease in the strength of the heat-worked material. When the holding temperature during the heat treatment process is greater than 550°C, local melting of the aluminum alloy may occur.

[0075] The heat treatment process can be performed before or after the hot working process. Alternatively, it can be performed both before and after the hot working process. As mentioned above, Al-Sc second-phase particles have little impact on hot workability. Therefore, even if the heat treatment process is performed before the hot working process, hot working of aluminum alloys with precipitated Al-Sc second-phase particles can be easily performed.

[0076] Example

[0077] The following describes embodiments of the aforementioned aluminum alloy, the aforementioned aluminum alloy hot-working material, and the manufacturing method thereof. It should be noted that the specific embodiments of the aluminum alloy, aluminum alloy hot-working material, and the manufacturing method thereof involved in this invention are not limited to those described in the embodiments, and appropriate modifications can be made without prejudice to the spirit of this invention.

[0078] In this example, firstly, molten metal of an aluminum alloy with the chemical composition shown in Table 1 is cast using conventional methods to produce a cylindrical billet with a diameter of 90 mm and a length of 200 mm. It should be noted that the symbol "Bal." in Table 1 indicates the remaining portion. The billet is then held at a holding temperature of 300°C for 10 hours, followed by a holding temperature of 400°C for 10 hours (heat treatment process).

[0079] After the heat treatment process, the billet is heated to 450℃ for hot extrusion (hot working process). The container temperature and die temperature are both set to 450℃, and the extrusion speed is set to 1.0 m / min. Through this process, test materials A to F can be obtained. It should be noted that test materials A to F are strips with a width of 35 mm and a thickness of 2 mm.

[0080] In addition, the billet was heated to 500°C and hot-extruded under the conditions of container temperature 500°C, die temperature 500°C, and extrusion speed 1.4 m / min to obtain test material G. It should be noted that test material G is a strip with a width of 35 mm and a thickness of 2.6 mm.

[0081] In addition, test materials H and I shown in Table 1 are test materials used for comparison with test materials A to G. The manufacturing methods of test materials H and I are the same as those of test materials A to F, except for the difference in the chemical composition of the aluminum alloy.

[0082] The physical properties of each test material and the aluminum alloys used in the preparation of the test materials can be evaluated using the following methods.

[0083] • Compression resistance of aluminum alloys

[0084] After the heat treatment process, a cylindrical compression test piece with a diameter of 8 mm and a length of 12 mm is taken from the blank before heat working. Using this test piece, a compression test is performed at a temperature of 450℃ and a strain rate of 1 second. -1 Compression tests were conducted under the specified conditions to obtain load-displacement curves. Based on these curves, assuming uniform deformation of the test specimens during the compression tests, the true strain and true stress were calculated. Then, the arithmetic mean of the true stresses within the range of true strain greater than 0.3 and less than 0.6 was taken as the compressive deformation resistance. The compressive deformation resistances of each test material are shown in Table 2.

[0085] • Number density of Al-Sc second-phase particles present in the experimental material

[0086] After cutting the experimental material into appropriate sizes, a 0.1 μm thick test piece was prepared by electrolytic grinding. Three randomly selected locations on the test piece were observed using TEM, obtaining dark-field images with a field of view of 2 μm × 2 μm. Then, the number of Al-Sc second-phase particles with an equivalent circular diameter greater than 0.5 nm and less than 10 nm present in these three dark-field images was converted to a per 1 μm... 3 The number of particles in the second phase of the Al-Sc system is calculated from the volume of particles.

[0087] The number density of Al-Sc second-phase particles in experimental material A is 10,000 particles / μm. 3 Furthermore, it is presumed that the number density of Al-Sc second-phase particles present in test materials B to G is similar to that in test material A.

[0088] Mechanical properties of the test materials

[0089] Test pieces No. 5 as specified in JIS Z2241:2011 were selected from the test materials. Tensile tests were performed using these test pieces, and the tensile strength and 0.2% yield strength were calculated. The tensile strength and 0.2% yield strength of each test material are shown in Table 2.

[0090] • Extrusive

[0091] The extrudability was evaluated using the following method. First, the billet after heat treatment was heated to 520°C. Then, the billet was subjected to split extrusion using a die configured to form a square tube with a cross-sectional shape of 31 mm on each side and a wall thickness of 2.5 mm surrounding the hollow portion. The container temperature and die temperature were both set to 450°C, and the extrusion speed was set to 1.0 m / min.

[0092] In Table 2, the "Extrudability" column indicates that square tubes can be produced under the above conditions when performing split extrusion, and the "B" indicates that square tubes cannot be produced.

[0093] [Table 1]

[0094] (Table 1)

[0095]

[0096]

[0097] [Table 2]

[0098] (Table 2)

[0099]

[0100] As shown in Tables 1 and 2, the aluminum alloys used in test materials A through G possess the aforementioned specific chemical compositions, and the compressive deformation resistance of the billets is below 62 MPa. Therefore, these test materials exhibit excellent hot workability and can be subjected to split extrusion. Furthermore, due to the aforementioned specific chemical compositions, test materials A through G, through heat treatment, can achieve an Al-Sc second-phase particle number density of 3000 particles / μm. 3 The results show that the 0.2% yield strength of the heat-treated test materials A to G is above 140 MPa.

[0101] On the other hand, test material H is composed of an aluminum alloy that does not contain Sc, and therefore no Al-Sc second-phase particles were formed in the heat-treated billet. Consequently, the 0.2% yield strength of test material H is lower than that of test material A.

[0102] To achieve a higher strength than test material H, test material I contains a significantly higher amount of Mg compared to test material H in its aluminum alloy composition. However, the increased Mg content leads to a rise in the compressive deformation resistance of the aluminum alloy and a deterioration in its hot extrusion properties. Consequently, test material I is difficult to extrude using a split-flow die. Furthermore, while the 0.2% yield strength of test material I is higher than that of test material H, it is lower than that of test materials A through G.

Claims

1. An aluminum alloy for use in split extrusion, having the following chemical composition: containing Sc: ≥0.01% by mass and ≤0.40% by mass, Mg: ≥0.2% by mass and ≤2.5% by mass, Zr: ≥0.01% by mass and ≤0.4% by mass, with the remainder being Al and unavoidable impurities. Based on a temperature of 450℃ and a time of 1 second -1 The compressive deformation resistance, calculated from the true stress when the aluminum alloy is deformed by compressing it at a certain strain rate, is below 62 MPa. The aluminum alloy hot-working material produced by split extrusion has Al-Sc system second-phase particles dispersed in the Al matrix phase, and the number density of the Al-Sc system second-phase particles is 3000 / 3000. μ m 3 above, The equivalent circular diameter of the Al-Sc second-phase particles is greater than 0.5 nm and less than 10 nm.

2. The aluminum alloy according to claim 1, wherein, The aluminum alloy further contains one or more elements selected from the group consisting of Cu: greater than 0% by mass and less than 1.0% by mass, Mn: greater than 0% by mass and less than 1.0% by mass, Cr: greater than 0% by mass and less than 0.30% by mass, Ti: greater than 0% by mass and less than 0.10% by mass, and B: greater than 0% by mass and less than 0.10% by mass.

3. An aluminum alloy hot-working material having the following chemical composition: containing Sc: 0.01% by mass or more and 0.40% by mass, Mg: 0.2% by mass or more and 2.5% by mass, Zr: 0.01% by mass or more and 0.4% by mass, with the remainder being Al and unavoidable impurities. The aluminum alloy hot-working material has at least one hollow portion surrounded by a wall portion containing aluminum alloy, and at least one weld surface is formed in the wall portion where the aluminum alloys are fused together. The aluminum alloy hot-working material has Al-Sc system second-phase particles dispersed in the Al matrix phase, and the number density of the Al-Sc system second-phase particles is 3000 / 3000. μ m 3 above, The equivalent circular diameter of the Al-Sc second-phase particles is greater than 0.5 nm and less than 10 nm.

4. The aluminum alloy hot-working material according to claim 3, wherein, The aluminum alloy hot-working material further contains one or more elements selected from the group consisting of Cu: greater than 0% by mass and less than 1.0% by mass, Mn: greater than 0% by mass and less than 1.0% by mass, Cr: greater than 0% by mass and less than 0.30% by mass, Ti: greater than 0% by mass and less than 0.10% by mass, and B: greater than 0% by mass and less than 0.10% by mass.

5. A method for manufacturing an aluminum alloy hot-working material, comprising: The heat treatment process, among which, The aluminum alloy of claim 1 or 2 is subjected to split extrusion as a hot working process in a state where its temperature is above 350°C and below 550°C; and The heat treatment process, wherein, in at least one of the heat treatment process and the heat treatment process, the aluminum alloy is held at a holding temperature of 250°C or higher and 550°C or lower for a total of 30 minutes or more.

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