Aluminum alloys and aluminum alloy components, and methods for manufacturing the same.

Abstract

To provide an aluminum alloy that can selectively impart excellent plastic workability and high proof stress, among other properties, to an aluminum alloy member through proper heat treatment, and an aluminum alloy member composed of the aluminum alloy, and a simple and efficient production method for the aluminum alloy member.SOLUTION: An aluminum alloy comprises Cu: 1.0-1.9 wt.%, Mg: 1.2-1.8 wt.%, Zn: 5.0-7.0 wt.%, Zr: 0.05-0.25 wt.%, and Ti: 0.01-0.10 wt.%, with the balance being Al and unavoidable impurities. Preferably, the content of Mg is 1.3-1.7 wt.%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aluminum alloy member, an efficient manufacturing method thereof, and an aluminum alloy suitably used for the aluminum alloy member.

Background Art

[0002] Aluminum alloy members have various applications. For example, hollow extruded materials made of aluminum alloy are used as various pipes and structural members made of aluminum alloy. In addition to being lightweight, hollow extruded materials made of aluminum alloy have excellent strength, reliability, corrosion resistance, etc. Therefore, for example, they are used as pipes for heat exchangers such as automotive air conditioners, oil coolers, radiators, heaters, and photosensitive drums of electrophotographic devices such as copiers, printers, and fax machines.

[0003] However, in recent years, in addition to the shape of the desired hollow extruded material made of aluminum alloy becoming more complex, higher strength and reliability are required. In contrast, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2020-180353), "an aluminum alloy pipe material for a heat exchanger, which contains Mg: 0.7% by mass or more and less than 2.5% by mass, and Ti: more than 0% by mass and 0.15% by mass or less, and the balance is Al and inevitable impurities, and a Zn-containing layer disposed on the outer surface of the pipe material body portion and having Zn diffused in the Al-Mg alloy by 0.1% by mass or more" is disclosed.

[0004] In the aluminum alloy pipe material described in Patent Document 1 above, it is stated that "by subjecting an aluminum alloy pipe material extruded by adjusting alloy components to Zn spraying having a specific range of Zn adhesion amount and then performing diffusion heat treatment, a Zn-containing layer with high strength can be disposed on the outer surface to achieve strength improvement."

[0005] Furthermore, Patent Document 2 (Japanese Unexamined Patent Publication No. 2020-143339) discloses "an aluminum alloy characterized by having a composition containing Si: 0.060~0.080 mass%, Fe: 0.10~0.70 mass%, Cu: 0.050~0.20 mass%, and Mn: 1.0~1.5 mass%, with the remainder being Al and unavoidable impurities."

[0006] In the aluminum alloy described in Patent Document 2 above, "By setting the content of each element constituting the composition of the aluminum alloy within a predetermined range, for example, the surface of the extruded material obtained by extruding the aluminum alloy billet can be formed into a highly smooth surface. Furthermore, since Mg is not subject to control, manufacturing costs can be reduced. In addition, since the Si content is 0.060 to 0.080 mass%, there is no need to use high-purity metal, thus reducing manufacturing costs." [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-180353 [Patent Document 2] Japanese Patent Publication No. 2020-143339 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the aluminum alloy piping material described in Patent Document 1 above increases surface strength through Zn diffusion, and does not adequately guarantee the overall strength and reliability of the aluminum alloy piping material. Furthermore, it does not consider the creation of complex shapes, such as variations in wall thickness, for the aluminum alloy piping material.

[0009] Furthermore, while the aluminum alloy described in Patent Document 2 above can form a highly smooth surface on the resulting extruded material, it is deficient in elements that contribute to precipitation strengthening, and therefore cannot impart high strength or yield strength to the extruded material. In addition, when shaping the resulting extruded material by cold working or the like, the plasticity of the extruded material is not considered.

[0010] In view of the problems of the prior art described above, the object of the present invention is to provide an aluminum alloy that can selectively impart good plastic workability and high yield strength to an aluminum alloy member by appropriate heat treatment, an aluminum alloy member made of the aluminum alloy, and a simple and efficient method for manufacturing the aluminum alloy member. [Means for solving the problem]

[0011] To achieve the above objectives, the inventors of the present invention have diligently researched aluminum alloys, aluminum alloy components, and methods for manufacturing them. As a result, they have found that adding appropriate amounts of Cu, Mg, and Zn, which contribute to increasing the strength of aluminum alloy components, while keeping the Mg content as low as possible, is extremely effective in achieving good plastic workability, and have arrived at the present invention. Here, the content of Cu, Mg, and Zn is defined within a very narrow range in order to obtain the desired effects.

[0012] In other words, the present invention is Cu: 1.0~1.9 wt%, Mg: 1.2~1.8 wt%, Zn: 5.0~7.0 wt%, Zr: 0.05~0.25 wt%, It contains Ti: 0.01~0.10 wt%, The remainder consists of Al and unavoidable impurities. We provide an aluminum alloy characterized by the following.

[0013] The aluminum alloy of the present invention contains Cu, Mg, and Zn, which contribute to precipitation strengthening, while the Mg content is controlled to a low value. Generally, the addition of Mg to aluminum alloys is aimed at increasing strength through precipitates such as MgCuAl and MgZn2, and there is a tendency to add as much as possible to achieve this effect. Furthermore, in Al-Mg aluminum alloys, the addition of Mg increases work hardening, so from the viewpoint of providing good formability, the adverse effect of adding Mg in cold working is not significant. In contrast, in the aluminum alloy of the present invention, the upper limit of the Mg content is restricted to 1.8 wt% with the aim of providing excellent shock absorption to the final aluminum alloy member, thereby suppressing the decrease in ductility.

[0014] Furthermore, the aluminum alloy of the present invention uses Zr as an essential additive element. Zr has the effect of suppressing recrystallization through a pinning effect on the compound, thereby stabilizing the fibrous structure, which is the processed structure. As a result, high yield strength and plastic workability can be imparted to aluminum alloy components.

[0015] Furthermore, the aluminum alloy of this invention also includes Ti as an essential additive element, and the addition of Ti can refine the cast structure. As a result, high yield strength and plastic workability can be reliably imparted to aluminum alloy components.

[0016] In the aluminum alloy of the present invention, it is preferable that the Mg content is 1.3 to 1.7 wt%. By setting the Mg content to 1.3 to 1.7 wt%, it is possible to achieve a higher level of balance between the yield strength and plastic workability of the aluminum alloy member.

[0017] Furthermore, in the aluminum alloy of the present invention, it is preferable that the Zr content is 0.12 to 0.20 wt%. By setting the Zr content to 0.12 to 0.20 wt%, the effect of suppressing recrystallization can be more reliably exhibited, the fibrous structure which is the processed structure can be stabilized, and the decrease in ductility due to the coarsening of the compound can be suppressed.

[0018] Further, the present invention also provides an aluminum alloy member which is an extruded material or a cold-worked material made of the aluminum alloy of the present invention, and has a tensile strength of 500 MPa or more, a 0.2% proof stress value of 470 MPa or more, and an elongation of 12% or more.

[0019] Since the aluminum alloy member of the present invention is made of an aluminum alloy containing an appropriate amount of Cu, Mg, and Zn, by performing solution treatment and artificial aging treatment under appropriate conditions, tensile characteristics can be imparted such that the tensile strength is 500 MPa or more, the 0.2% proof stress value is 470 MPa or more, and the elongation is 12% or more.

[0020] In the aluminum alloy member of the present invention (an extruded material or a cold-worked material made of the aluminum alloy of the present invention), it is preferable that the thickness of the region including the recrystallized structure formed on the outermost surface is 500 μm or less. By setting the thickness of the region including the recrystallized structure to 500 μm or less, a decrease in cold workability can be suppressed.

[0021] Further, the present invention also provides an aluminum alloy member which is an annealed material made of the aluminum alloy of the present invention, has a 0.2% proof stress value of 110 MPa or less, and has a fibrous structure on the entire surface. By performing annealing treatment under appropriate conditions, the 0.2% proof stress value of the aluminum alloy member can be made 110 MPa or less while maintaining the fibrous structure. Here, the elongation of the aluminum alloy member is preferably 22% or more. By setting the elongation of the aluminum alloy member to 22% or more, good plastic workability can be more reliably exhibited.

[0022] In the aluminum alloy member of the present invention (an annealed material made of the aluminum alloy of the present invention), since the 0.2% proof stress value is 110 MPa or less and no recrystallized structure is formed, for example, cold working with a large cross-sectional reduction rate (wall thickness reduction rate) can be performed.

[0023] Furthermore, the present invention An extrusion step of subjecting a billet made of the aluminum alloy of the present invention to extrusion to obtain an extruded material made of an aluminum alloy, A solution heat treatment step, An aging step, and having, In the aging step, two-stage aging treatment is performed, and the first stage in the two-stage aging treatment is 4 to 10 hours at 100 to 110 ° C, and the second stage is 2 to 10 hours at 150 to 170 ° C, A method for manufacturing a member made of an aluminum alloy, characterized by also providing.

[0024] The temperature and extrusion speed of the billet in the extrusion process are not particularly limited as long as the effects of the present invention are not impaired, and may be appropriately determined according to the performance of the extrusion device, etc., but the temperature of the billet is 350 to 450 ° C, and the extrusion speed is 10 m / min or less, It is preferable. By performing the extrusion process under these conditions, a fibrous structure can be formed throughout the aluminum alloy member after the extrusion process.

[0025] Also, by making the aging treatment two-stage aging, the first-stage treatment conditions are 4 to 10 hours at 100 to 110 ° C, and the second-stage treatment conditions are 2 to 10 hours at 150 to 170 ° C, the strength and ductility can be made compatible at a high level.

[0026] The temperature of the solution heat treatment is not particularly limited as long as the effects of the present invention are not impaired, and may be appropriately determined according to the composition of the extruded material made of an aluminum alloy and the desired mechanical properties, but it is preferably 430 ° C or higher. By performing two-stage aging treatment after the solution heat treatment at 430 ° C or higher, tensile properties with a tensile strength of 500 MPa or more, a 0.2% proof stress value of 470 MPa or more, and an elongation of 12% or more can be surely imparted to the hollow extruded material made of an aluminum alloy. Further, the temperature of the solution heat treatment is preferably less than 470 ° C. Heating at 470 ° C or higher does not contribute to precipitation strengthening and may impair structure strengthening.

[0027] In the method for manufacturing a member made of an aluminum alloy of the present invention, The extruded material made of an aluminum alloy is made into a hollow extruded material made of an aluminum alloy, An annealing process in which the aforementioned hollow extruded aluminum alloy material is subjected to an annealing treatment, Preferably, the method includes a cold working step in which the hollow extruded aluminum alloy material after the annealing step is subjected to cold working.

[0028] The aluminum alloy of the present invention has an optimized composition to exhibit good plastic workability through annealing treatment (O treatment), and by applying annealing treatment to an aluminum alloy extruded material, a large reduction in cross-sectional area can be achieved through subsequent cold working processes.

[0029] The annealing conditions can be adjusted as appropriate depending on the composition and microstructure of the aluminum alloy extruded material. For example, it is possible to hold it at 410°C for 2 hours, and then furnace cool it to 240°C at a cooling rate of 25°C / hour or less. Furthermore, it is preferable to perform a heat treatment at around 250°C for about 4 hours after this heat treatment.

[0030] Furthermore, by converting aluminum alloy extruded material into aluminum alloy hollow extruded material, and then performing cold working on the aluminum alloy hollow extruded material after the annealing process, it is possible to manufacture aluminum alloy components with various complex cross-sectional shapes.

[0031] Furthermore, in the method for manufacturing aluminum alloy members of the present invention, it is preferable to perform drawing in the cold working step. By performing drawing, high dimensional accuracy can be imparted to the aluminum alloy member. In addition, by appropriately controlling the wall thickness of the aluminum alloy member, desired shock absorption can be imparted to the necessary areas. Moreover, the surface condition can be controlled, and a glossy finish can be obtained through surface treatment. [Effects of the Invention]

[0032] According to the present invention, it is possible to provide an aluminum alloy that can selectively impart good plastic workability and high yield strength to an aluminum alloy member by appropriate heat treatment, an aluminum alloy member made of the aluminum alloy, and a simple and efficient method for manufacturing the aluminum alloy member. [Brief explanation of the drawing]

[0033] [Figure 1] This is a schematic cross-sectional view of an annealed aluminum alloy hollow extruded material. [Figure 2] This is a schematic cross-sectional view of an aluminum alloy hollow extruded material that has undergone solution treatment and aging treatment after cold working. [Figure 3] This is an example of a process diagram relating to the manufacturing method of an aluminum alloy component of the present invention. [Figure 4] This is a micrograph of the L-section of the aluminum alloy extruded material obtained as Example 13 (after annealing). [Figure 5] This is a microstructure image of the LT cross section in Example 13 (after cold working + T6 heat treatment). [Figure 6] This is a microstructure image of the LT cross section in Example 16 (after cold working + T6 heat treatment). [Figure 7] This is a microstructure image of the L section in Example 13 (after cold working and T6 heat treatment). [Figure 8] This is a microstructure image of the L section in Example 16 (after cold working and T6 heat treatment). [Figure 9] This is a microstructure image of the L section in Example 13 (large reduction in cross-sectional area after cold working + T6 heat treatment). [Figure 10] This is a micrograph of the L section in Example 13 (after extrusion T6 heat treatment). [Modes for carrying out the invention]

[0034] The following describes in detail representative embodiments of the aluminum alloy and aluminum alloy components of the present invention, as well as their manufacturing methods, with reference to the drawings, but the present invention is not limited to these embodiments. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions may be omitted. Also, since the drawings are for conceptual explanation of the present invention, the dimensions of each component shown and their ratios may differ from those of actual components.

[0035] 1. Aluminum alloy The aluminum alloy of the present invention is characterized by containing Cu: 1.0~1.9 wt%, Mg: 1.2~1.8 wt%, Zn: 5.0~7.0 wt%, Zr: 0.05~0.25 wt%, and Ti: 0.01~0.10 wt%, with the remainder being Al and unavoidable impurities. Each component element will be described below.

[0036] (1) Essential additive elements Cu: 1.0~1.9 wt% (preferably 1.4~1.8 wt%) Cu has the effect of improving strength through solid solution strengthening, and when subjected to aging treatment, it precipitates as an Al-Cu compound, improving mechanical strength. By setting the Cu content to 1.0 wt% or more, solid solution strengthening and precipitation strengthening can be sufficiently exhibited, and by setting it to 1.9 wt% or less, the decrease in ductility caused by the coarsening of the Al-Cu compound can be suppressed. Furthermore, by setting the Cu content to 1.4 to 1.8 wt%, these effects can be exhibited more significantly. If the Cu content is further increased to over 1.9 wt%, strength and yield strength will increase, but good plastic workability cannot be imparted to the aluminum alloy component.

[0037] Mg: 1.2-1.8 wt% (preferably 1.3-1.7 wt%) Mg has the effect of improving strength through solid solution strengthening, and when subjected to aging treatment, it precipitates as an Al-Zn-Mg compound, improving mechanical strength. By setting the content to 1.2 wt% or more, solid solution strengthening and precipitation strengthening can be sufficiently exhibited. Furthermore, by setting it to 1.8 wt% or less, the decrease in ductility caused by the coarsening of the Zn-Mg compound can be suppressed, making it possible to achieve both yield strength and ductility in aluminum alloy members, as well as improving corrosion resistance. Moreover, by regulating the upper limit of Mg content to 1.8 wt% and suppressing the decrease in ductility, excellent shock absorption can be imparted to the final aluminum alloy member.

[0038] Zn: 5.0~7.0 wt% (preferably 5.5~6.5 wt%) When Zn undergoes aging treatment, it precipitates as Zn-Mg and Al-Zn-Mg-Cu compounds, improving the mechanical strength of the aluminum alloy. This precipitation strengthening can be achieved by increasing the Zn content to 5.0 wt% or more, while reducing it to 7.0 wt% or less suppresses the decrease in ductility caused by compound coarsening. These effects can be more pronounced by setting the Zn content to 5.5-6.5 wt%. Further increasing the Zn content to over 7.0 wt% increases strength and yield strength, but it does not provide good plastic workability to the aluminum alloy component.

[0039] Zr: 0.05~0.25 wt% (preferably 0.12~0.20 wt%) Zr has the effect of suppressing recrystallization and structuring through its pinning effect on compounds, thereby stabilizing the fibrous structure, which is the processed structure. This effect can be fully expressed by having a Zr content of 0.05 wt% or more, and by having a Zr content of 0.25 wt% or less, the decrease in ductility associated with the coarsening of the compound can be suppressed. Furthermore, these effects can be more pronounced by having a Zr content of 0.12 to 0.20 wt%.

[0040] Ti: 0.01~0.10 wt% The addition of Ti can refine the microstructure of a cast alloy. This refinement effect can be fully achieved by using a Ti content of 0.01 wt% or more, and by using a Ti content of 0.10 wt% or less, the decrease in ductility caused by the formation of coarse compounds can be suppressed. In order to obtain the refinement effect of the cast microstructure, it is preferable to add Ti to the molten alloy immediately before casting.

[0041] (2) Any additive element Cr:0.30wt% or less Cr has the effect of suppressing recrystallization through its pinning effect on the compound, thereby stabilizing the fibrous structure, which is a processed structure. By keeping the Cr content below 0.30 wt%, the decrease in ductility associated with the coarsening of the compound can be suppressed.

[0042] Mn: 0.40wt% or less Mn has the effect of suppressing recrystallization and structuring through its pinning effect on the compound, thereby stabilizing the fibrous structure, which is a processed structure. By keeping the Mn content below 0.40 wt%, the decrease in ductility associated with the coarsening of the compound can be suppressed.

[0043] Be:0.001~0.1% by mass Be is effective in preventing the depletion of Mg due to oxidation and can be used as any additive element. When adding Be, amounts less than 0.001% by mass do not provide sufficient protection against Mg depletion, and adding more than 0.1% by mass increases costs because sufficient protection against Mg depletion has already been achieved.

[0044] (3) Inevitable impurities Insofar as it does not impair the effects of the present invention, the presence of unavoidable impurities is permissible. For example, it may contain 0.20 wt% or less of Si and 0.25 wt% or less of Fe. Here, it is preferable that the Si and Fe content be 0.10 wt% or less.

[0045] 2. Aluminum alloy components The following provides a detailed explanation of aluminum alloy components, using hollow extruded aluminum alloy materials as a representative example.

[0046] The hollow extruded aluminum alloy of the present invention is made of the aluminum alloy of the present invention, and by heat treatment, it is possible to selectively exhibit high strength and yield strength (tensile strength of 500 MPa or more, 0.2% yield strength of 470 MPa or more, and elongation of 12% or more) or low yield strength and good ductility (0.2% yield strength of 110 MPa or less, and elongation of 22% or more).

[0047] When imparting high strength and yield strength to hollow extruded aluminum alloy materials, it is preferable to apply solution treatment and aging treatment to the hollow extruded aluminum alloy materials to achieve a tensile strength of 530 MPa or higher, and more preferably 560 MPa or higher. Furthermore, it is preferable to have a 0.2% yield strength of 490 MPa or higher, and more preferably 510 MPa or higher. In addition, it is preferable to have an elongation of 16% or higher, and more preferably 17% or higher.

[0048] When imparting low yield strength and good ductility to a hollow extruded aluminum alloy, it is preferable to anneal the aluminum alloy hollow extruded material and set the 0.2% yield strength to 100 MPa or less, and more preferably to 90 MPa or less. In addition, it is preferable to set the elongation to 23% or more, and more preferably to 24% or more.

[0049] Figure 1 shows a schematic LT cross-section of an annealed hollow aluminum alloy extruded material. The annealed hollow aluminum alloy extruded material 1 has a fibrous structure throughout its entire surface, achieving low yield strength and good ductility. Here, "fibrous structure throughout the entire surface" means that a state in which a recrystallized structure is formed on the very outermost surface is acceptable, and specifically, the thickness of the region including the recrystallized structure formed on the outermost surface should be 100 μm or less. Here, there are no particular limitations on the method of observing the microstructure of the aluminum alloy hollow extruded material, but it is sufficient to observe the microstructure on a cross-section parallel to the extrusion direction (L direction) (L cross-section) or a cross-section perpendicular to the L direction (LT cross-section).

[0050] Figure 2 shows a schematic cross-sectional view of an aluminum alloy hollow extruded material that has undergone cold working, solution treatment, and aging treatment. In the aluminum alloy hollow extruded material 2 that has undergone cold working, solution treatment, and aging treatment, a region 4 containing a recrystallized structure is formed on the outermost surface. Here, the thickness of the region 4 containing the recrystallized structure is 500 μm or less. Preferably, the thickness of the region 4 containing the recrystallized structure is 400 μm or less, and more preferably 200 μm or less. In the case of an aluminum alloy hollow extruded material, the region 4 containing the recrystallized structure is formed on the outermost surface of the circumferential circumference and the innermost surface (not shown), but the thickness of the region 4 containing the recrystallized structure is restricted by the maximum value of these regions.

[0051] The length, outer diameter, and inner diameter of the aluminum alloy hollow extruded material 1 and the aluminum alloy hollow extruded material 2 are not particularly limited as long as they do not impair the effects of the present invention, and may be set appropriately depending on the application.

[0052] 3. Manufacturing method for aluminum alloy components The method for manufacturing aluminum alloy components of the present invention will be described in detail below, with the case of manufacturing a hollow extruded aluminum alloy material being a representative example.

[0053] Figure 3 shows an example of a process diagram relating to the manufacturing method of an aluminum alloy member of the present invention. The process diagram in Figure 3 consists of a homogenization heat treatment step (S01) for homogenizing a billet made of aluminum alloy, an extrusion step (S02) for extruding the billet to obtain a hollow aluminum alloy extruded material, an annealing step (S03) for annealing the hollow aluminum alloy extruded material, a cold working step (S04) for cold working the hollow aluminum alloy extruded material, a solution treatment step (S05) for solution treatment, and a two-stage aging step (S06). Each step will be described below.

[0054] (1) Homogenization heat treatment process (S01) As a pretreatment for the extrusion process (S02), it is preferable to subject the aluminum alloy material to be extruded to a homogenization heat treatment. Furthermore, it is preferable that the temperature of the homogenization heat treatment process be 460 to 480°C and the holding time be 1 to 12 hours.

[0055] By performing a homogenization heat treatment at 460-480°C for 1-12 hours, the particle size and spacing of Al3Zr dispersed in the aluminum base material can be adjusted to an appropriate state, thereby imparting good extrudeability and strength to the aluminum alloy billet.

[0056] (2) Extrusion process (S02) A hollow aluminum alloy extruded material can be obtained by subjecting the aluminum alloy billet obtained in (1) to extrusion. Here, the billet temperature is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately determined according to the billet shape and extrusion shape, etc., but for example, it is preferable to heat the billet to 350 to 450°C and then extrude it. By heating the temperature to 350°C or higher, the recovery of processing strain can be promoted and the formation of a recrystallized structure layer can be prevented. Also, by heating the temperature to 450°C or lower, deterioration of surface properties can be suppressed.

[0057] Here, it is preferable to cool the extruded material immediately after it comes out of the die at a cooling rate of 1°C / s or more using air or nitrogen, as forced cooling can be expected to suppress recrystallization.

[0058] Furthermore, a larger extrusion ratio results in greater processing strain, which facilitates recrystallization during solution treatment. Therefore, it is preferable to keep the extrusion ratio below 100. A more preferable extrusion ratio is below 75, and the most preferable is below 60. The extrusion speed can be adjusted as appropriate from the viewpoint of suppressing recrystallization and production efficiency, but it is preferable to keep the extrusion speed below 10 m / min. By performing the extrusion process under these conditions, the formation of recrystallization throughout the entire hollow extruded aluminum alloy material after extrusion can be suppressed.

[0059] (3) Annealing process (S03) The annealing process (S03) is a process that imparts good plastic workability to the hollow extruded aluminum alloy material, enabling a large reduction in cross-sectional area in the cold working process (S05).

[0060] The annealing conditions can be adjusted as appropriate depending on the composition and microstructure of the aluminum alloy extruded material, but a temperature of 380 to 420°C is preferable. The holding time at 380 to 420°C does not need to be long; holding for 1 hour is sufficient to obtain the desired effect. Furthermore, it is preferable to perform a heat treatment at around 250°C for about 4 hours after the initial heat treatment. By performing the annealing treatment under these conditions, it is possible to maintain the fibrous microstructure of the aluminum alloy hollow extruded material while achieving a 0.2% yield strength of 110 MPa or less and an elongation of 22% or more immediately after the annealing treatment.

[0061] (4) Cold working process (S04) The cold working process (S04) is a process for applying cold working to a hollow extruded aluminum alloy material to impart a desired shape.

[0062] For example, by adjusting the wall thickness of the aluminum alloy hollow extruded material in the cold working process (S04), it is possible to accommodate even cases where the aluminum alloy hollow extruded material 1 has a complex shape.

[0063] The type of cold working is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known cold working methods can be used. Examples of such cold working methods include drawing and deep drawing.

[0064] (5) Solution treatment process (S05) By applying a solution treatment to an aluminum alloy hollow extruded material having a desired shape under appropriate conditions, good tensile properties can be imparted to the aluminum alloy hollow extruded material in the subsequent aging process (S06).

[0065] The solution treatment temperature is preferably 430°C or higher, more preferably 450°C or higher, and most preferably 460°C or higher. The duration of holding at these temperatures is not particularly limited, as long as the predetermined temperature is reached. Furthermore, it is preferable to use water cooling for cooling after holding at the temperature. In addition, it is preferable that the solution treatment temperature be below 470°C. Heating above 470°C does not contribute to precipitation strengthening and may impair structural strengthening.

[0066] (6) Aging process (S06) The aging process (S06) is a process in which the hollow extruded aluminum alloy material, after solution treatment, is subjected to aging treatment to impart good tensile properties (tensile strength of 500 MPa or more, 0.2% yield strength of 470 MPa or more, and elongation of 12% or more) to the final aluminum alloy component.

[0067] By using a two-stage aging process, with the first stage being 100-110°C for 4-10 hours and the second stage being 150-170°C for 2-10 hours, it is possible to achieve a high level of both strength and ductility.

[0068] The precipitation distribution of the reinforcing phase compound is greatly influenced by the GP zone of the precursor structure. In aluminum alloy components, the precipitates can be dispersed finely and densely by growing the GP zone. High strength is obtained in the first aging treatment, and the precipitation structure is further controlled in the second aging treatment, contributing to either strength or ductility.

[0069] By holding the second stage at a temperature of 150°C or higher to allow sufficient precipitate growth, good strength, ductility, and corrosion resistance can be obtained. Alternatively, by keeping the temperature below 170°C, excessive growth of the precipitate phase can be suppressed, thereby preventing a decrease in strength.

[0070] Although typical embodiments of the present invention have been described above, the present invention is not limited to these, and various design modifications are possible, all of which fall within the technical scope of the present invention. [Examples]

[0071] Examples Molten aluminum alloys (Examples 1 to 16) having the composition (wt%) listed in Table 1 were subjected to degassing and filtration treatments, and then billets were obtained by DC continuous casting. Si and Fe were present as unavoidable impurities. Next, the billets were subjected to homogenization heat treatment (S01) and then extruded (S02) to obtain aluminum alloy extruded material. The homogenization heat treatment conditions and extrusion shape are as shown in Table 2, and the extrusion conditions were a billet temperature of 380 to 430°C and an extrusion speed of 5 m / min or less.

[0072] Next, in Examples 1 to 12, the obtained aluminum alloy extruded material was subjected to solution treatment (S05) and aging treatment (S06) to impart high tensile properties to the aluminum alloy extruded material and obtain the aluminum alloy component of the present invention. The conditions shown in Table 2 were used for each heat treatment. In addition, water cooling was used for cooling during the solution treatment.

[0073] In Examples 13 to 16, the obtained aluminum alloy extruded material was subjected to annealing (S03) to impart good plastic workability and obtain the aluminum alloy member (annealed material) of the present invention. Next, after cold working (S04) to the cross-sectional reduction ratio shown in Table 2, the aluminum alloy extruded material was subjected to solution treatment (S05) and aging treatment (S06) to impart high tensile properties to the aluminum alloy extruded material and obtain the aluminum alloy member of the present invention. The conditions shown in Table 2 were used for each heat treatment. In the annealing treatment, the material was furnace-cooled from the treatment temperature to 240°C at a cooling rate of 25°C / hour or less. In the solution treatment, water cooling was used for cooling.

[0074] [Table 1]

[0075] [Table 2]

[0076] ≪Comparative Example≫ Aluminum alloy extruded materials were obtained from aluminum alloys (Comparative Examples 1 to 3) having the compositions (wt%) listed in Table 1, in the same manner as in the examples. All comparative examples were subjected to annealing, and comparative examples 2 and 3 were subjected to cold working. The treatment conditions applied are shown in Table 2.

[0077] [evaluation] (1) Tensile test Tensile test specimens (14B specimens according to JIS Z 2201) were taken from annealed aluminum alloy extruded materials, and their tensile properties were evaluated according to the tensile test method of JIS Z 2241. The results are shown in Table 3. Three test cycles were used, and the average value was calculated.

[0078] Furthermore, the tensile properties of aluminum alloy extruded materials after aging treatment were evaluated in the same manner as those of aluminum alloy extruded materials after annealing treatment. The results are shown in Table 3.

[0079] (2) Tissue observation Samples for microstructural observation were taken from annealed aluminum alloy extruded materials. After polishing the LT surface, the samples were anodized in Barker reagent at 15V for 2 minutes, and the crystalline structure was observed using an optical microscope with a polarizing filter. For annealed aluminum alloy extruded materials, if a fibrous structure was observed in the entire LT surface area, it was indicated as "fibrous structure" in Table 3. For aged aluminum alloy extruded materials, the thickness of the region containing the recrystallized structure formed on the outermost surface was measured, and the maximum value obtained is shown in Table 3.

[0080] Figure 4 shows a microstructure photograph of the LT cross-section of the aluminum alloy extruded material obtained as Example 13, representing a typical microstructure observation result of the aluminum alloy extruded material after annealing. A region containing a recrystallized structure is formed on the very outermost surface, but the thickness of this region is 100 μm or less, and no coarsening of the recrystallized grains is observed. This result indicates that the aluminum alloy extruded material of Example 13 has a fibrous structure.

[0081] [Table 3]

[0082] In all cases, the aluminum alloy members (aluminum alloy extruded materials) that are embodiments of the present invention have a 0.2% yield strength of 110 MPa or less and an elongation of 22% or more after annealing. In contrast, in the case of the composition of Comparative Example 3, which has a high content of Cu and Zn, the 0.2% yield strength after annealing is high at 115 MPa, and the elongation is low at 20%.

[0083] Furthermore, in all cases, the aluminum alloy members (aluminum alloy extruded materials) that are embodiments of the present invention exhibit a tensile strength of 500 MPa or more, a 0.2% yield strength of 470 MPa or more, and an elongation of 12% or more after aging treatment. In contrast, in the case of Comparative Example 1, which has a low Cu content, the 0.2% yield strength of the aluminum alloy member (aluminum alloy extruded material) after aging treatment is a low value of 442 MPa. In addition, in the case of Comparative Example 2, which has a high Mg content, the elongation of the aluminum alloy member (aluminum alloy extruded material) after aging treatment is a low value of 11.4%.

[0084] Furthermore, regarding the microstructure of the aluminum alloy members, in the embodiments of the present invention, the microstructure after annealing is entirely fibrous. In addition, in the case where solution treatment and aging treatment are performed after cold working, an extremely thin region containing a recrystallized structure is formed on the outermost surface, but the thickness of this region is 500 μm or less. Representative observation results are shown in Figures 5 and 6, respectively, of the LT cross-section of Examples 13 and 16. Also, the microstructure photographs of the L cross-section of Examples 13 and 16 are shown in Figures 7 and 8, respectively. The thickness of the region containing the recrystallized structure is 200 μm or less in both the LT direction and the L direction in both Examples 13 and 16.

[0085] Figure 9 shows a microstructure photograph of the LT cross-section of the aluminum alloy member obtained as Example 13, in a region where the processing rate was locally high (cross-sectional reduction rate: 66%). Even when the cross-sectional reduction rate was large, the thickness of the region containing the recrystallized structure remained at 320 μm, which is less than 500 μm.

[0086] Furthermore, Figure 10 shows a microstructure photograph of the LT cross-section of the aluminum alloy extruded material obtained as Example 3, which is a typical microstructure when solution treatment and aging treatment are performed after extrusion without cold working. Although a region consisting of a coarse recrystallized structure is formed on the very outermost surface, the thickness of this region is 50 μm or less. In addition, the thickness of the region consisting of the recrystallized structure is 200 μm or less. In other words, for the aluminum alloy component of the present invention, regardless of whether or not cold working is performed, the thickness of the region containing the recrystallized structure after T6 heat treatment is suppressed to 500 μm or less.

[0087] From the above results, it can be seen that by strictly controlling the amounts of Cu, Mg, and Zn added, which contribute to increasing the strength of aluminum alloy components, and by keeping the Mg content as low as possible from the viewpoint of exhibiting good plastic workability, good plastic workability can be imparted to annealed materials, and excellent tensile properties (strength, yield strength, and elongation) can be imparted to T6 heat-treated materials. [Explanation of Symbols]

[0088] 1. Hollow extruded aluminum alloy material after annealing treatment. 2. Hollow extruded aluminum alloy material 2, which has been cold-worked and then subjected to solution treatment and aging treatment. 4. Region containing recrystallized tissue.

Claims

1. An extruded material, drawn material, or drawn material made of an aluminum alloy, The tensile strength is 500 MPa or more, the 0.2% proof stress is 470 MPa or more, and the elongation is 12% or more. The aforementioned aluminum alloy Cu: 1.0 to 1.9 wt%, Mg: 1.2 to 1.8 wt%, Zn: 5.0 to 7.0 wt%, Zr: 0.05-0.25wt%, It contains Ti: 0.01 to 0.10 wt%, The remainder consists of Al and unavoidable impurities. An aluminum alloy component characterized by the following.

2. The Mg content is 1.3 to 1.7 wt%, The aluminum alloy member according to claim 1, characterized by the above.

3. The Zr content is 0.12 to 0.20 wt%, An aluminum alloy member according to claim 1 or 2, characterized by the above.

4. The thickness of the region including the recrystallized structure formed on the outermost surface is 500 μm or less. An aluminum alloy member according to claim 1 or 2, characterized by the above.

5. An annealed material obtained by annealing an extruded material made of an aluminum alloy, The 0.2% proof stress value is 110 MPa or less. The entire surface is fibrous tissue, The aforementioned aluminum alloy Cu: 1.0 to 1.9 wt%, Mg: 1.2 to 1.8 wt%, Zn: 5.0 to 7.0 wt%, Zr: 0.05-0.25wt%, It contains Ti: 0.01 to 0.10 wt%, The remainder consists of Al and unavoidable impurities. An aluminum alloy component characterized by the following.

6. The Mg content is 1.3 to 1.7 wt%, The aluminum alloy member according to claim 5, characterized in that

7. An extrusion step of obtaining an aluminum alloy extruded material by extruding a billet made of an aluminum alloy, Solution treatment process, It has a aging process, In the aforementioned aging process, a two-stage aging treatment is performed, with the first stage being at 100-110°C for 4-10 hours and the second stage being at 150-170°C for 2-10 hours. The aforementioned aluminum alloy Cu: 1.0 to 1.9 wt%, Mg: 1.2 to 1.8 wt%, Zn: 5.0 to 7.0 wt%, Zr: 0.05-0.25wt%, It contains Ti: 0.01 to 0.10 wt%, The remainder consists of Al and unavoidable impurities. A method for manufacturing aluminum alloy components characterized by the following.

8. The Mg content is 1.3 to 1.7 wt%, A method for manufacturing an aluminum alloy member according to claim 7, characterized by the above.

9. The aluminum alloy extruded material is made into an aluminum alloy hollow extruded material. After the extrusion process, an annealing process is performed on the hollow extruded aluminum alloy material, The process includes a cold working step, after the annealing step, in which the hollow extruded aluminum alloy material is subjected to drawing or drawing. A method for manufacturing an aluminum alloy member according to claim 7 or 8, characterized by the above.

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