JP7172833B2 - Aluminum alloy material and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aluminum alloy extruded material and an aluminum alloy forged material for obtaining a forged member having a complicated shape, and a method for producing them.

Aluminum alloys are lightweight and have excellent strength and workability. When a complicated shape is required, it is necessary to consider the strength, reliability, surface appearance, etc. of the finally obtained aluminum alloy member, in addition to the efficiency and cost reduction of the manufacturing process.

On the other hand, for example, in Patent Document 1 (JP-A-9-125181), Si: 3 to 11%, Fe: 0.02 to 0.5%, Mg: 0.5 to 1.5%, or It contains Cu: 0.1 to 1.2%, and further contains one or two of Mn: 0.1 to 1.0% and Ti: 0.01 to 0.3%, An aluminum alloy for forging has been proposed, characterized in that the balance is Al and unavoidable impurities.

In the forging aluminum alloy of Patent Document 1, as a result of examining the combination of alloy components, etc., it has excellent hot forgeability, does not generate cracks even when forged into a complicated shape, and has excellent machinability and corrosion resistance. It is said that it is possible to provide aluminum alloys for forging that are also excellent in

In addition, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-298871), Si: 0.4 to 2.0% by weight, Mg: 0.4 to 2.0% by weight, and further Fe, Mn, Cr aluminum alloy powder containing 0.5 to 2.0% by weight in total of one or more of the above types, the balance being inevitable impurities, and 10 to 25% by weight of alumina mixed with aluminum alloy powder. proposed an aluminum alloy for plastic working, characterized by having a Young's modulus at room temperature of 80 GPa or more, a room temperature tensile strength of 300 MPa or more after water quenching, and an elongation of 5% or more. It is

The aluminum alloy for plastic working of Patent Document 2 has a high tensile strength and a high Young's modulus that are useful as highly functional members such as bicycle parts, fishing tackle, golf clubs, and snowboards. Even if the content is 10% by weight, it is less than 5%. There is.

JP-A-9-125181 JP 2005-298871 A

The aluminum alloy for forging described in Patent Document 1 is based on the composition of the 4000 series aluminum alloy, and has been studied for its alloying components. Not enough. In addition, the target value of tensile strength of the aluminum alloy for plastic working of Patent Document 2 is 300 MPa, and for example, it is used for power transmission members that require a tensile strength of 500 MPa or more. is difficult.

In addition, in the aluminum alloy for forging of Patent Document 1 and the aluminum alloy for plastic working of Patent Document 2, neither the surface appearance is considered, and the properties are sufficient for members that require good surface gloss. is not guaranteed.

In view of the problems in the prior art as described above, an object of the present invention is to provide an aluminum alloy extruded material with low flow stress that can efficiently produce an aluminum alloy forged member having a complicated shape. An object of the present invention is to provide an aluminum alloy extruded material which has higher strength than the alloy and can maintain a good surface gloss even after forming an anodized film. Further, the present invention provides an aluminum alloy forged material having a complicated shape, having higher strength than a 2000 series aluminum alloy, and capable of maintaining a good surface gloss even after forming an anodized film. It also aims to provide Another object of the present invention is to provide a simple and efficient method for producing these aluminum alloy extruded materials and aluminum alloy forged materials.

In order to achieve the above object, the present inventors have made intensive studies on the composition and structure of aluminum alloys. The inventors have found that reducing the area ratio is extremely effective, and have arrived at the present invention.

That is, the present invention
Zn: 6.0 to 7.0% by mass,
Mg: 1.2 to 1.6% by mass,
Mn: 0.1 to 0.4% by mass,
Cu: 0.1 to 0.3% by mass,
Fe: 0.05 to 0.2% by mass,
Zr: 0.05 to 0.2% by mass,
Si: 0 to 0.2% by mass,
Cr: 0 to 0.2% by mass,
Ti: 0 to 0.15% by mass,
An aluminum alloy with the balance being Al and inevitable impurities,
In observation of the cross-sectional structure, the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the base material is 0.1% or less,
An aluminum alloy extrusion characterized by:

In the aluminum alloy extruded material of the present invention, compared to extra super duralumin (A7075 aluminum alloy), which has extremely high tensile strength and yield strength among aluminum alloys, the content of Cu and Mg is mainly reduced, and the content of Zn is is increasing. By optimizing the components, the forgeability (low flow stress) superior to that of 2000 series aluminum alloys is realized while minimizing the strength reduction from A7075.

In addition, by setting the occupied area ratio of precipitates (intermetallic compounds) having an area of 0.05 μm ² or more existing in the grain boundaries of the base material to 0.1% or less, the surface after the formation of the anodized film is reduced. Shows a high gloss value.

The aluminum alloy extruded material of the present invention preferably has tensile strength of 500 MPa or more, 0.2% proof stress of 460 MPa or more, and elongation of 10% or more in terms of tensile properties in the extrusion direction (L direction). Since the aluminum alloy extruded material has these tensile properties, it is possible to ensure sufficient strength, yield strength and fatigue properties even when used as an important structural member as an aluminum alloy member.

Further, in the aluminum alloy extruded material of the present invention, it is preferable that the glossiness retention rate determined by the following relational expression (1) is 45% or more. Having a glossiness retention rate of 45% or more, it can be suitably used for aluminum alloy members where aesthetic appearance is important.
Glossiness retention rate = (glossiness after forming an anodized film having a thickness of approximately 5 µm by anodizing film treatment in a sulfuric acid bath/glossiness after mirror polishing) × 100 (1)

In addition, the present invention
Zn: 6.0 to 7.0% by mass,
Mg: 1.2 to 1.6% by mass,
Mn: 0.1 to 0.4% by mass,
Cu: 0.1 to 0.3% by mass,
Fe: 0.05 to 0.2% by mass,
Zr: 0.05 to 0.2% by mass,
Si: 0 to 0.2% by mass,
Cr: 0 to 0.2% by mass,
Ti: 0 to 0.15% by mass,
An aluminum alloy with the balance being Al and inevitable impurities,
In observation of the cross-sectional structure, the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the base material is 0.1% or less,
An aluminum alloy forging, characterized by:

The composition and structure of the aluminum alloy forged material of the present invention are basically the same as those of the aluminum alloy extruded material of the present invention, and can be obtained by forging the aluminum alloy extruded material of the present invention.

The aluminum alloy forged material of the present invention preferably has a tensile strength of 500 MPa or more, a 0.2% yield strength of 460 MPa or more, and an elongation of 10% or more. The tensile properties of forged materials are affected by the structure formed by forging, and there are cases where they differ depending on the location to be evaluated and the tensile direction. It is preferable that the strength is 500 MPa or more, the 0.2% yield strength is 460 MPa or more, and the elongation is 10% or more.

The aluminum alloy forged material of the present invention preferably has the same glossiness and glossiness retention rate as the above-described aluminum alloy extruded material of the present invention. Since the aluminum alloy forged material has these glossiness and glossiness retention rate, it can be suitably used, for example, for a member that requires a beautiful surface appearance in addition to a complicated shape and high strength.

In addition, the present invention
A method for producing an aluminum alloy extruded material by extruding an aluminum alloy billet,
The aluminum alloy is
Zn: 6.0 to 7.0% by mass,
Mg: 1.2 to 1.6% by mass,
Mn: 0.1 to 0.4% by mass,
Cu: 0.1 to 0.3% by mass,
Fe: 0.05 to 0.2% by mass,
Zr: 0.05 to 0.2% by mass,
Si: 0 to 0.2% by mass,
Cr: 0 to 0.2% by mass,
Ti: 0 to 0.15% by mass,
An aluminum alloy with the balance being Al and inevitable impurities,
There is also provided a method for producing an aluminum alloy extruded material, characterized by subjecting the extruded billet to solution treatment and then water cooling at a water temperature of 80° C. or less.

By using the aluminum alloy having the above composition for the billet, the flow stress can be made lower than that of the A7075 aluminum alloy, for example, and extrusion can be performed relatively easily. In addition, by water cooling at a water temperature of 80 ° C. or less after the solution treatment, precipitation of intermetallic compounds is suppressed, and the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the base material is reduced. It can be 0.1% or less.

Furthermore, the present invention also provides a method for producing an aluminum alloy forged material, characterized by subjecting the aluminum alloy extruded material of the present invention to forging.

As described above, the composition of the aluminum alloy extruded material of the present invention is adjusted so that the flow stress is low, so that it can be easily forged. In addition, since the flow stress is low, an aluminum alloy member having a complicated shape can be efficiently manufactured.

According to the present invention, an aluminum alloy extruded material with low flow stress that can efficiently produce an aluminum alloy forged member having a complicated shape, has a higher strength than a 2000 series aluminum alloy, and forms an anodized film. It is possible to provide an aluminum alloy extruded material that can maintain a good surface gloss even after the process. Further, according to the present invention, there is provided an aluminum alloy forged material having a complicated shape, having higher strength than a 2000 series aluminum alloy, and capable of maintaining a good surface gloss even after the anodized film is formed. We can also provide materials. Furthermore, according to the present invention, it is also possible to provide a simple and efficient method for producing these aluminum alloy extruded materials and aluminum alloy forged materials.

1 is a schematic diagram of a structure of an aluminum alloy extruded material of the present invention; FIG. FIG. 4 is a schematic diagram of the structure of an aluminum alloy extruded material when the cooling rate after solution treatment is slow. 1 is a schematic diagram of a structure of an aluminum alloy forged material of the present invention; FIG. 1 is a scanning electron micrograph of a cross section of an example aluminum alloy extruded material 1. FIG. 4 is a scanning electron micrograph of a cross section of a comparative aluminum alloy extruded material.

Hereinafter, representative embodiments of the aluminum alloy extruded material, the aluminum alloy forged material, and the manufacturing method thereof according to the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. . In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description may be omitted. Also, since the drawings are for the purpose of conceptually explaining the present invention, the dimensions and ratios of the depicted components may differ from the actual ones.

1. Aluminum Alloy Extruded Material (1) Structure A schematic diagram of the structure of the aluminum alloy extruded material of the present invention obtained by water cooling after solution treatment is shown in FIG. FIG. 2 shows a schematic diagram of the structure of the aluminum alloy extruded material when it is air-cooled after the solution treatment.

When air cooling is performed after the solution treatment, precipitates 4 are precipitated mainly along the grain boundaries of the base material crystal grains 2, and precipitates 4 having an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains 2. occupied area ratio is higher than 0.1%. As a result, the glossiness of the surface is lowered, and the glossiness is greatly lowered due to the formation of the anodized film. More specifically, when an anodized film having a thickness of 5 μm is formed by an anodized film treatment in a sulfuric acid bath, the glossiness is less than 45% of that before the treatment. The composition of the sulfuric acid bath, the conditions for the anodized film treatment, and the like are not particularly limited, and conventionally known various sulfuric acid baths and conditions for the anodized film treatment may be used.

On the other hand, in the aluminum alloy extruded material of the present invention, almost no precipitates 4 are precipitated at the grain boundaries of the base material crystal grains 2, and an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains 2 The occupied area ratio of the precipitates 4 having As a result, the glossiness of the surface is increased, and the decrease in glossiness due to the formation of the anodized film is suppressed. More specifically, when an anodized film having a thickness of 5 μm is formed by an anodized film treatment in a sulfuric acid bath, the glossiness is 45% or more of that before the treatment.

The method for determining the occupied area ratio of the precipitates 4 is not particularly limited, and may be measured by various conventionally known methods. For example, by cutting an aluminum alloy extruded material at an arbitrary cross section and observing the obtained cross-sectional sample with an optical microscope or a scanning electron microscope, the deposit 4 having an area of 0.05 μm ² or more with respect to the entire observation area Area ratio can be calculated. Here, in order to prevent the evaluation of the area ratio from being limited to a local area, the observation area is preferably at least 2000 μm ² or more. The cross-sectional sample may be subjected to mechanical polishing, buffing, electrolytic polishing, etching, or the like depending on the observation method.

The aluminum alloy extruded material of the present invention preferably has tensile strength of 500 MPa or more, 0.2% proof stress of 460 MPa or more, and elongation of 10% or more in terms of tensile properties in the extrusion direction (L direction). Here, the more preferable tensile strength is 525 MPa or more, and the most preferable tensile strength is 550 MPa or more. Moreover, the more preferable 0.2% yield strength is 480 MPa or more, and the most preferable 0.2% yield strength is 500 MPa or more. Furthermore, the more preferred elongation is 12% or more, and the most preferred elongation is 15% or more.

(2) Composition The aluminum alloy extruded material of the present invention contains Zn: 6.0 to 7.0 mass%, Mg: 1.2 to 1.6 mass%, Mn: 0.1 to 0.4 mass%, Cu : 0.1 to 0.3% by mass, Fe: 0.05 to 0.2% by mass, Zr: 0.05 to 0.2% by mass, Si: 0 to 0.2% by mass, Cr: 0 to 0 .2% by mass, Ti: 0 to 0.15% by mass, and the balance is Al and unavoidable impurities. Each component will be described in detail below.

Zn: 6.0 to 7.0% by mass
Zn and Mg precipitate as a Zn-Mg phase and contribute to increasing the strength of the aluminum alloy. When the Zn content is 6.0% by mass or more, sufficient strength can be obtained, and when the Zn content is 7.0% by mass or less, good corrosion resistance can be obtained. The aluminum alloy extruded material according to the present embodiment has a Zn content of 6.0% by mass or more and 7.0% by mass or less, more preferably 6.2% by mass or more and 6.6% by mass or less.

Mg: 1.2 to 1.6% by mass
If the Mg content is 1.2% by mass or more, sufficient strength can be obtained, and if the Mg content is 1.6% by mass or less, good extrusion workability can be obtained.

Mn: 0.1 to 0.4% by mass
By setting the Mn content to 0.1% by mass or more, the corrosion resistance of the aluminum alloy extruded material can be improved, and by setting the Mn content to 0.4% by mass or less, the aluminum alloy extruded material can be fiber-structured and crystallized. Grain growth and coarsening of crystallized substances can be suppressed.

Cu: 0.1 to 0.3% by mass
By setting the Cu content to 0.1% by mass or more, the strength and stress corrosion cracking resistance of the aluminum alloy extruded material can be improved. Yellowing and deterioration of corrosion resistance can be suppressed.

Fe: 0.05 to 0.2% by mass
When the Fe content is 0.05% by mass or more, coarse recrystallization of the cast structure can be suppressed during homogenization. If there is a coarse crystal structure in the ingot, uneven deformation tends to occur during extrusion, making it difficult to fit the extruded material into a predetermined size. Furthermore, if a billet contains a coarse crystal structure, recrystallized grain structures of different sizes are likely to coexist even in an equiaxed recrystallized structure during recrystallization after extrusion. Arrangement of such structures in layers causes streak-like color tone differences. When the Fe content is 0.2% by mass or less, it is possible to suppress the formation of excessive crystallized substances due to the formation of compounds with other elements.

Zr: 0.05 to 0.2% by mass
Zr has the same effect as Mn, and by making the Zr content 0.05% by mass or more, it is possible to improve the corrosion resistance of the aluminum alloy extruded material, and by making it 0.2% by mass or less, , the fiber structure of the aluminum alloy extruded material, grain growth and coarsening of crystallized substances can be suppressed.

Si: 0 to 0.2% by mass
The addition of Si increases the precipitation density of Al ₂ CuMg and contributes to the strength. On the other hand, Si forms an Mg—Si compound with Mg and impairs the appearance of the surface after the formation of the anodized film. You don't have to.

Cr: 0 to 0.2% by mass
Cr has the same effects as Zr and Mn, and the addition of Cr can improve the corrosion resistance of the aluminum alloy extruded material. On the other hand, if more than 0.2% by mass of Cr is added, fiber organization, grain growth, and coarsening of crystallized substances occur in the aluminum alloy extruded material, so it is necessary to limit it to 0.2% by mass or less. Preferably, it may not be added when emphasizing the aesthetic appearance of the surface.

Ti: 0 to 0.15% by mass
If the crystals in the cast structure of the aluminum alloy are coarse, uneven deformation is likely to occur during extrusion molding, and in addition, concentration segregation and uneven grain size in the recrystallized structure are likely to occur. In some cases, it is added as a grain refiner. On the other hand, when Ti is added excessively, it is excessively crystallized as a compound and impairs the appearance of the surface.

2. Aluminum Alloy Forged Material (1) Structure A schematic diagram of the structure of the aluminum alloy forged material of the present invention is shown in FIG. The aluminum alloy forged material of the present invention can be easily obtained by forging the aluminum alloy extruded material of the present invention, but the production method is not particularly limited, and other aluminum alloy materials can be forged. may

In the aluminum alloy forging material of the present invention, almost no precipitates 4 are precipitated at the grain boundaries of the base material crystal grains 2, and precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains 2 The occupied area ratio of 4 is 0.1% or less of the whole. As a result, the glossiness of the surface is increased, and the decrease in glossiness due to the formation of the anodized film is suppressed. More specifically, when an anodized film having a thickness of 5 μm is formed by an anodized film treatment in a sulfuric acid bath, the glossiness is 45% or more of that before the treatment.

When an aluminum alloy forged material is obtained by forging an aluminum alloy extruded material, the forging causes refinement of the base material crystal grains 2, refinement of the precipitates 4, and homogenization of the distribution. It is more preferable from the viewpoint of the strength, reliability and surface appearance of the alloy member.

(2) Composition The aluminum alloy forged material of the present invention contains Zn: 6.0 to 7.0 mass%, Mg: 1.2 to 1.6 mass%, Mn: 0.1 to 0.4 mass%, and Cu. : 0.1 to 0.3% by mass, Fe: 0.05 to 0.2% by mass, Zr: 0.05 to 0.2% by mass, Si: 0 to 0.2% by mass, Cr: 0 to 0 .2% by mass, Ti: 0 to 0.15% by mass, and the balance is Al and unavoidable impurities.

The effect and amount of addition of each component are the same as those of the aluminum alloy extruded material of the present invention described above. can do.

3. Method for producing aluminum alloy extruded material The method for producing an aluminum alloy extruded material of the present invention provides an effective and efficient method for producing the aluminum alloy extruded material of the present invention. It is characterized by cooling with water at a water temperature of 80° C. or less after the heat treatment. In addition, you may perform a tension|stretch straightening and an aging process as needed. One aspect of the manufacturing method will be described in detail below.

The method for producing an aluminum alloy extruded material of the present invention is a method for producing an aluminum alloy extruded material by extruding an aluminum alloy billet, wherein Zn: 6.0 to 7.0% by mass, Mg: 1.2 ~1.6% by mass, Mn: 0.1-0.4% by mass, Cu: 0.1-0.3% by mass, Fe: 0.05-0.2% by mass, Zr: 0.05-0 .2% by mass, Si: 0 to 0.2% by mass, Cr: 0 to 0.2% by mass, Ti: 0 to 0.15% by mass, and the balance is Al and unavoidable impurities. . The role of each component is as described above.

(homogenization treatment)
A billet having the above composition is subjected to a homogenization treatment. The homogenization treatment eliminates concentration segregation of elements and reduces crystallized substances.

The homogenization treatment temperature is preferably 400 to 560° C., and the homogenization treatment is preferably carried out for 1 hour or more and 24 hours or less. If the homogenization treatment conditions are within this range, the homogenization will be sufficiently performed. If the 24-hour homogenization treatment temperature exceeds 560°C, the crystals of the ingot grow, the extrusion workability is lowered, the crystal grains of the extruded material are coarsened, and at the same time the recrystallized structure is locally coarsened. The grain size difference in the recrystallized structure becomes large, which causes patterns to occur when the anodized film is formed.

The homogenization treatment temperature is more preferably 540° C. or lower. Even if the homogenization treatment is performed for more than 24 hours, no further effect can be expected, and only the manufacturing cost is increased.

In order to eliminate concentration segregation and promote solid solution of crystallized substances, it is preferable to perform the homogenization treatment at 470°C or higher, and more preferably to perform the homogenization treatment at about 500°C. If the cooling rate after homogenization is slow, dissolved elements tend to precipitate, so the average cooling rate from the homogenization temperature to 150°C is preferably 100°C/h or more.

(extrusion processing)
Then, the obtained billet is subjected to extrusion processing. The extrusion conditions are preferably an extrusion ratio of 4 or more, a product extrusion speed of 3 to 20 m/min, and an extrusion temperature of 350 to 500°C. The structure formed by extrusion is greatly affected by extrusion temperature and extrusion speed. Here, a fiber structure can be formed by setting the extrusion ratio, product extrusion speed and extrusion temperature within these ranges.

(Solution treatment)
Next, the obtained aluminum alloy extruded material is subjected to solution treatment. The temperature of the solution treatment is preferably 400-520°C. By setting the temperature of the solution treatment to 400° C. or higher, the solid-solution element can be sufficiently dissolved in the aluminum. Further, by setting the temperature to 520° C. or less, it is possible to suppress deterioration in the strength and ductility of the extruded material due to local eutectic melting.

The aluminum alloy extruded material after the solution treatment is water-cooled at a water temperature of 80° C. or less. By water cooling at a water temperature of 80 ° C. or less, precipitation of intermetallic compounds is suppressed, and the occupied area ratio of the precipitates 4 having an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains 2 is reduced to the entire area. It can be 0.1% or less.

In order to effectively suppress precipitation of intermetallic compounds, it is preferable to set the cooling rate after the solution treatment to 1000° C./min or more. Here, when the aluminum alloy extruded material after the solution treatment is air-cooled, the cooling rate is 100°C/min. can be done.

(Aging treatment)
Then, if necessary, aging treatment is applied. The holding temperature in the aging treatment is preferably 100 to 180° C., and the treatment time is preferably 1 to 30 hours. By performing the aging treatment under the treatment conditions, in addition to being able to efficiently develop precipitation strengthening, the occupancy of the precipitates 4 having an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains 2 The area ratio can be maintained at 0.1% or less of the whole. In order to obtain higher strength and stress corrosion cracking resistance, two-step aging treatment may be performed.

As a pretreatment for aging treatment, it is preferable to apply 1 to 3% tension straightening to the aluminum alloy extruded material. The quenching distortion can be reduced by increasing the solid solubility of solid solution elements by quenching after the solution treatment, and applying 1 to 3% tensile straightening.

4. Method for producing aluminum alloy forgings The method for producing aluminum alloy forgings of the present invention provides an effective and efficient method for producing the aluminum alloy forgings of the present invention. Forging is performed on an aluminum alloy extruded material.

As described above, the aluminum alloy extruded material of the present invention has low flow stress and can be forged relatively easily. Moreover, even when the desired aluminum alloy member has a complicated shape, the shape can be efficiently and accurately realized.

The forging method is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known forging methods can be used. Tensile properties such as a strength of 500 MPa or more, a 0.2% yield strength of 460 MPa or more, and an elongation of 10% or more can be obtained. In addition, fine equiaxed recrystallized grains can be obtained by cold forging, and the appearance quality after the anodized film can be further improved. In this case, it is preferable that the average crystal grain size is 200 μm or less and the maximum base material crystal grain size is 1 mm or less.

Although representative embodiments of the present invention have been described above, the present invention is not limited to these, and various design changes are possible, and all such design changes are included in the technical scope of the present invention. be

<<Example 1, Example 2, Example 3>>
An aluminum alloy billet having the components shown in Table 1 and the balance being Al and unavoidable impurities was extruded. In addition, the components in Table 1 are shown in mass %. The extrusion conditions were an extrusion ratio of 55, a billet temperature of 400° C., and an extrusion speed of 5 m/min to obtain an aluminum alloy extruded material having a width of 150 mm and a thickness of 10 mm.

After subjecting the obtained aluminum alloy extruded material to solution treatment at 450° C. for 1 hour, it was cooled to room temperature using water at 35° C. Further, artificial aging treatment was performed at 105° C. for 8 hours and at 150° C. for 8 hours to obtain aluminum alloy extruded materials 1, 2 and 3.

The aluminum alloy extruded materials 1, 2 and 3 were cut, mirror-polished and etched to prepare cross-sectional observation samples, and their structures were observed with a scanning electron microscope. From the observed image obtained at a magnification of 2000 (observation area: 56 μm×43 μm), the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains was determined. Table 2 shows the results obtained.

Next, a tensile test was performed at room temperature on the test piece obtained from the aluminum alloy extruded material 1, and the 0.2% proof stress, tensile strength, and elongation were measured. A No. 14 A test piece according to JIS Z 2241 was used as the tensile test piece, and the parallel portion was made parallel to the extrusion direction. The tensile speed was 2 mm/min up to 0.2% proof stress and 5 mm/min after 0.2% proof stress in accordance with JIS Z 2241. The values obtained are shown in Table 2.

Next, aluminum alloy extruded materials 1, 2 and 3 were subjected to an anodization film treatment using a sulfuric acid bath to form an anodization film having a thickness of 5 μm. The glossiness was measured before and after the anodized film treatment, and the glossiness retention rate was obtained. Table 2 shows each glossiness and glossiness retention rate.

Here, a sulfuric acid bath of 180 g/L was used for the anodized film treatment, bath temperature: 18 to 20° C., current density: 1.5 A/dm ² , and an anodized film with a thickness of 5 μm was formed. Before the anodizing film treatment, 1 mm of the surface of the extruded shape was chamfered and then buffed with a magnesium oxide abrasive having a particle size of 1 μm, and the glossiness was measured.

FIG. 4 shows a scanning electron micrograph of Example Aluminum Alloy Extruded Material 1 as a representative example of the results of structure observation by a scanning electron microscope. Precipitation of intermetallic compounds on grain boundaries of the base material is hardly observed.

In order to evaluate the flow stress of the aluminum alloy extruded material 1, a test piece of φ8.5 mm × 10.5 mm was taken and subjected to high temperature conditions of compression temperatures of 360 ° C. and 410 ° C. and strain rates of 1, 5 and 20 s ^-1 . A deformation resistance measurement test was performed. Table 3 shows the deformation resistance obtained under each condition. For comparison, a similar test was also conducted on an A7075 aluminum alloy extruded material.

Under all measurement conditions, the deformation resistance of the aluminum alloy extruded material 1 is lower than that of the A7075 aluminum alloy extruded material, indicating that the aluminum alloy extruded material 1 has excellent forgeability.

<<Example 4>>
An aluminum alloy billet having the components shown in Table 1 and the balance being Al and unavoidable impurities was extruded. The extrusion conditions were an extrusion ratio of 55, a billet temperature of 400°C, and an extrusion speed of 5 m/min.

The obtained forged material was subjected to solution treatment at 450°C for 1 hour, and then cooled to room temperature using water at 35°C. Next, an artificial aging treatment was performed at 120° C. for 24 hours to obtain a practical aluminum alloy forging 4. Occupied area ratio, tensile properties, glossiness, and glossiness retention of precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains of the aluminum alloy forging material 4 in the same manner as in Example 1 evaluated. Table 2 shows the results obtained.

<<Example 5>>
An aluminum alloy billet having the components shown in Table 1 and the balance being Al and unavoidable impurities was extruded in the same manner as in Example 4. Subsequently, after soaking at 350 ° C. for 1 hour, after furnace cooling treatment, cold forging to a thickness of 15 mm, solution treatment and artificial aging treatment were performed under the same conditions as in Example 4, and the aluminum alloy forging was performed. Material 5 was obtained.

In the same manner as in Example 1, the occupied area ratio, tensile properties, glossiness, and glossiness retention rate of precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the crystal grains of the aluminum alloy forging material 5 were evaluated. did. Table 2 shows the results obtained.

<<Comparative Example 1>>
An aluminum alloy billet having the components shown in Table 1 and the balance being Al and unavoidable impurities was extruded. A comparative aluminum alloy extruded material was obtained in the same manner as in Example 1, except that the composition was different and the cooling after the solution treatment was air cooling.

In the same manner as in Example 1, the occupied area ratio, tensile properties, glossiness, and glossiness retention of precipitates having an area of 0.05 μm ² or more existing at the grain boundaries of the base material crystal grains of the comparative aluminum alloy extruded material were measured. evaluated. Table 2 shows the results obtained.

A scanning electron micrograph of a comparative aluminum alloy extruded material is shown in FIG. 5 as a representative example of the results of structure observation by a scanning electron microscope. Remarkable precipitation of intermetallic compounds on grain boundaries of the base material is observed.

From the results in Table 2, the aluminum alloy extruded material and the aluminum alloy forged material of the present invention have an extremely small occupied area ratio of grain boundary precipitates (≦0.1%) and have a glossiness retention rate of 45% or more. ing. In addition, all of the aluminum alloy extruded materials 1 to 3 and the aluminum alloy forged materials 4 and 5 have excellent tensile properties such as a tensile strength of 500 MPa or more, a 0.2% yield strength of 460 MPa or more, and an elongation of 10% or more. ing.

On the other hand, the comparative aluminum alloy extruded material obtained by air cooling from the solution treatment satisfies the criteria for tensile properties (tensile strength of 500 MPa or more, 0.2% proof stress of 460 MPa or more, elongation of 10% or more), but grain size The occupied area ratio of interfacial precipitates is 2.3%, and the glossiness retention rate is low (31%).

2 ... base material crystal grains,
4... Precipitate.

Claims (8)

Zn: 6.0 to 7.0% by mass,
Mg: 1.2 to 1.6% by mass,
Mn: 0.1 to 0.4% by mass,
Cu: 0.1 to 0.3% by mass,
Fe: 0.05 to 0.2% by mass,
Zr: 0.05 to 0.2% by mass,
Si: 0 to 0.2% by mass,
Cr: 0 to 0.2% by mass,
Ti: 0 to 0.15% by mass,
An aluminum alloy with the balance being Al and inevitable impurities,
An aluminum alloy extruded material, characterized in that the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing in the grain boundaries of the base material is 0.1% or less when observing the cross-sectional structure of an arbitrary cross section. . In terms of tensile properties in the extrusion direction (L direction), the tensile strength is 500 MPa or more, the 0.2% proof stress is 460 MPa or more, and the elongation is 10% or more;
The aluminum alloy extruded material according to claim 1, characterized by: 3. The aluminum alloy extruded material according to claim 1 or 2, wherein a glossiness retention rate determined by the following relational expression (1) is 45% or more.
Gloss retention rate = (Using a sulfuric acid bath of 180 g/L , bath temperature: 18 to 20 ° C., current density: 1.5 A / dm ² An anodized film with a thickness of about 5 μm was formed by anodized film treatment. Post-glossiness/glossiness after mirror polishing)×100 (1) Zn: 6.0 to 7.0% by mass,
Mg: 1.2 to 1.6% by mass,
Mn: 0.1 to 0.4% by mass,
Cu: 0.1 to 0.3% by mass,
Fe: 0.05 to 0.2% by mass,
Zr: 0.05 to 0.2% by mass,
Si: 0 to 0.2% by mass,
Cr: 0 to 0.2% by mass,
Ti: 0 to 0.15% by mass,
An aluminum alloy with the balance being Al and inevitable impurities,
An aluminum alloy forged material, characterized in that the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing in the grain boundaries of the base material is 0.1% or less when observing the cross-sectional structure of an arbitrary cross section. . The aluminum alloy forged material according to claim 4, having a tensile strength of 500 MPa or more, a 0.2% yield strength of 460 MPa or more, and an elongation of 10% or more. The glossiness retention rate determined by the following relational expression (1) is 45% or more,
The aluminum alloy forged material according to claim 4 or 5, characterized by:
Gloss retention rate = (Using a sulfuric acid bath of 180 g/L , bath temperature: 18 to 20 ° C., current density: 1.5 A / dm ² An anodized film with a thickness of about 5 μm was formed by anodized film treatment. Post-glossiness/glossiness after mirror polishing)×100 (1) A method for producing an aluminum alloy extruded material by extruding an aluminum alloy billet,
The aluminum alloy is
Zn: 6.0 to 7.0% by mass,
Mg: 1.2 to 1.6% by mass,
Mn: 0.1 to 0.4% by mass,
Cu: 0.1 to 0.3% by mass,
Fe: 0.05 to 0.2% by mass,
Zr: 0.05 to 0.2% by mass,
Si: 0 to 0.2% by mass,
Cr: 0 to 0.2% by mass,
Ti: 0 to 0.15% by mass,
An aluminum alloy with the balance being Al and inevitable impurities,
After subjecting the extruded billet to solution treatment, water cooling at a water temperature of 80 ° C. or less,
In observation of the cross-sectional structure of an arbitrary cross section , the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing in the grain boundaries of the base material is 0.1% or less,
A method for producing an aluminum alloy extruded material, characterized by: A method for producing an aluminum alloy forged material by hot forging an aluminum alloy extruded material,
The aluminum alloy extruded material is
Zn: 6.0 to 7.0% by mass,
Mg: 1.2 to 1.6% by mass,
Mn: 0.1 to 0.4% by mass,
Cu: 0.1 to 0.3% by mass,
Fe: 0.05 to 0.2% by mass,
Zr: 0.05 to 0.2% by mass,
Si: 0 to 0.2% by mass,
Cr: 0 to 0.2% by mass,
Ti: 0 to 0.15% by mass,
Made of an aluminum alloy with the balance being Al and inevitable impurities,
After subjecting the aluminum alloy forged material in which a recrystallized structure is formed by the hot forging process to solution treatment, water cooling at a water temperature of 80 ° C. or less,
In observation of the cross-sectional structure of an arbitrary cross section , the occupied area ratio of precipitates having an area of 0.05 μm ² or more existing in the grain boundaries of the base material is 0.1% or less,
A method for producing an aluminum alloy forging characterized by:

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