JP2018135579A - Structural aluminium alloy material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminium alloy material have high strength and excellent toughness, and method for manufacturing the same.SOLUTION: The structural aluminium alloy material contains Zn:9.1-14.0 mass%, Mg:2.0-3.0 mass%, Cu:1.0-2.0 mass% and Zr:0.080-0.20 mass%, one or more kinds of Mn:0.20-1.00 mass% and Cr:0.10-0.30 mass% and the remainder having a chemical component consisting of Al and inevitable impurities. The total amount of a Mn containing compound existing in crystal grains and having a major axis of 20-500 nm and a Cr containing compound having a major axis of 20-500 nm is 5 pieces/μmor more, and a fracture toughness value is 18.7 MPa m.SELECTED DRAWING: None

Description

  The present invention relates to a structural aluminum alloy material.

  Structural materials used for aircraft, spacecrafts, vehicles, and the like are required to be lightweight and high-strength from the viewpoints of improving motion performance and improving fuel efficiency. Since the 7000 series aluminum alloy material has a relatively high specific strength among metal materials, it is frequently used as a structural material in the above-described fields.

  In recent years, aluminum alloy materials having higher strength than conventional 7000 series aluminum alloy materials have been required. As this type of aluminum alloy material, for example, Patent Document 1 discloses that the contents of Zn and Mg are within a predetermined range, and Cu: 1.0 to 2.5 mass% and Zr: 0.08 to 0. An Al—Zn—Mg—Cu (aluminum-zinc-magnesium-copper) -based aluminum alloy material containing 20 mass% is described.

Japanese Patent No. 5343333

  However, generally, when the strength of the material is increased, the toughness tends to decrease. An aluminum alloy material having a strength higher than that of a conventional 7000 series aluminum alloy material is inferior in toughness, and is currently difficult to apply to a structural material.

  The present invention has been made in view of such a background, and intends to provide a structural aluminum alloy material having high strength and excellent toughness and a method for producing the structural aluminum alloy material.

One embodiment of the present invention is as follows: Zn (zinc): 9.1 to 14.0 mass%, Mg (magnesium): 2.0 to 3.0 mass%, Cu (copper): 1.0 to 2.0 mass% %, Zr (zirconium): 0.080 to 0.20 mass%, Mn (manganese): 0.20 to 1.00 mass% and Cr (chromium): 0.10 to 0.30 mass% Containing one or more of the above, the remainder having a chemical component consisting of Al (aluminum) and inevitable impurities,
The total of the Mn-containing compound having a major axis of 20 to 500 nm and the Cr-containing compound having a major axis of 20 to 500 nm present in the crystal grains is 5 pieces / μm ² or more,
The structural aluminum alloy material has a fracture toughness value of 18.7 MPa · m ^1/2 or more.

Other aspects of the present invention include Zn: 9.1 to 14.0% by mass, Mg: 2.0 to 3.0% by mass, Cu: 1.0 to 2.0% by mass, Zr: 0.080 to In addition to containing 0.20% by mass, one or more of Mn: 0.20 to 1.00% by mass and Cr: 0.10 to 0.30% by mass are contained, and the balance is made of Al and inevitable impurities. Making ingots with chemical components,
The time required to reach 400 ° C. after reaching 300 ° C. is 2 hours or more, and the ingot is heated and homogenized under the condition that the temperature of 450 to 490 ° C. is maintained for 5 to 20 hours. Done
A wrought material is produced by subjecting the ingot to hot working under the condition that the temperature at the end is 300 ° C. or higher,
It exists in the manufacturing method of the structural aluminum alloy material which performs a solution treatment, hardening, and artificial aging treatment to the said extending | stretching material.

  The structural aluminum alloy material (hereinafter simply referred to as “aluminum material”) has a chemical component in the specific range, and thus can achieve higher strength than the conventional 7000 series aluminum alloy material. .

Further, the total of the Mn-containing compound having a major axis of 20 to 500 nm and the Cr-containing compound having a major axis of 20 to 500 nm in the aluminum material is 5 / μm ² or more. The Mn-containing compound and the Cr-containing compound having the specific sizes have an effect of preventing the progress of cracks when cracks occur in the aluminum material. By making the total of the Mn-containing compound and the Cr-containing compound in the aluminum material 5 pieces / μm ² or more, higher strength than conventional 7000 series aluminum alloy materials is achieved and toughness is improved. be able to.

The aluminum material has at least the chemical component in the specific range, and further sets the total of the Mn-containing compound and the Cr-containing compound in the crystal grains to the specific range. A fracture toughness value of 7 MPa · m ^1/2 or more can be easily realized. As a result, an aluminum material having high strength and excellent toughness can be easily obtained.

  Moreover, according to the manufacturing method of the aluminum material of said aspect, the said aluminum material with high intensity | strength and excellent in toughness can be produced easily.

  The reasons for limiting the chemical components and the like in the aluminum material will be described below.

Zn (zinc): 9.1 to 14.0% by mass
Zn combines with Mg and Cu to form a phase such as a GP zone and a fine intermetallic compound, and has an effect of improving the strength of the aluminum material. By setting the Zn content to 9.1% by mass or more, a tensile strength of 700 MPa or more can be easily realized. When the Zn content is less than 9.1% by mass, Zn is insufficient, which may cause a decrease in strength of the aluminum material.

On the other hand, when the Zn content exceeds 14.0% by mass, the solid solubility limit of Mg and Cu is lowered, so that a coarse intermetallic compound is generated. As a result, the amount of the phase such as the GP zone and the fine intermetallic compound may be reduced, and the strength of the aluminum material may be reduced. From the viewpoint of avoiding such a problem, the Zn content is 14.0% by mass or less. From the same viewpoint, the Zn content is preferably 12.0% by mass or less, and more preferably 11.0% by mass or less.
Mg (magnesium): 2.0 to 3.0% by mass
Mg combines with Zn and Cu to form a GP zone and a fine intermetallic compound, and has the effect of improving the strength of the aluminum material. By setting the Mg content to 2.0 mass% or more, a tensile strength of 700 MPa or more can be easily realized. When the Mg content is less than 2.0% by mass, Mg is insufficient, which may cause a decrease in strength of the aluminum material. From the viewpoint of further improving the strength of the aluminum material, the Mg content is preferably 2.3% by mass or more.

  On the other hand, if the Mg content exceeds 3.0 mass%, the stress corrosion cracking resistance (hereinafter referred to as “SCC resistance”) of the aluminum material may be lowered. From the viewpoint of avoiding such a problem, the Mg content is 3.0 mass% or less. From the same viewpoint, the Mg content is preferably 2.7% by mass or less.

Cu (copper): 1.0 to 2.0% by mass
Cu combines with Zn and Mg to form a GP zone and a fine intermetallic compound, and has the effect of improving the strength of the aluminum material. By setting the Cu content to 1.0 mass% or more, a tensile strength of 700 MPa or more can be easily realized. When the Cu content is less than 1.0% by mass, Cu is insufficient, which may cause a decrease in strength of the aluminum material. From the viewpoint of further improving the strength of the aluminum material, the Cu content is preferably 1.3% by mass or more.

  On the other hand, if the Cu content exceeds 2.0% by mass, the SCC resistance of the aluminum material may be lowered. From the viewpoint of avoiding such a problem, the Cu content is set to 2.0 mass% or less. From the same viewpoint, the Cu content is preferably 1.7% by mass or less.

Zr (zirconium): 0.080 to 0.20 mass%
Zr has the effect of suppressing recrystallization during hot working and making the structure of the aluminum material a subcrystalline structure. By setting the content of Zr to 0.080% by mass or more, the structure of the aluminum material can be changed to a subcrystalline structure, and the strength and SCC resistance of the aluminum material can be improved.

  When the content of Zr is less than 0.080% by mass, recrystallization easily occurs during hot working. And when recrystallization occurs, there exists a possibility of causing the fall of the intensity | strength of an aluminum material, and SCC resistance. Therefore, from the viewpoint of suppressing recrystallization during hot working, the Zr content is set to 0.080% by mass or more. From the viewpoint of more effectively suppressing recrystallization during hot working, the Zr content is preferably 0.090% by mass or more.

  When the content of Zr exceeds 0.20% by mass, coarse crystallized products are easily formed when the aluminum material is cast. And when a coarse crystallization thing exists in an ingot, the fall of toughness will be caused. Therefore, from the viewpoint of increasing fracture toughness, the Zr content is set to 0.20 mass% or less. From the same viewpoint, the Zr content is preferably 0.16% by mass or less.

Mn (manganese): 0.20 to 1.0 mass%, Cr (chromium): 0.10 to 0.30 mass%
The aluminum material contains one or more of Mn and Cr. By setting the Mn content within the above specific range, a Mn-containing compound having a major axis of 20 to 500 nm can be precipitated inside the crystal grains of the aluminum material. Similarly, by setting the Cr content within the above specific range, a Cr-containing compound having a major axis of 20 to 500 nm can be precipitated inside the crystal grains of the aluminum material. As a result, the toughness of the aluminum material can be increased.

  When both the content of Mn and the content of Cr are less than the above specific range, the number of Mn-containing compounds and Cr-containing compounds precipitated inside the crystal grains of the aluminum material is reduced, and the fracture toughness is reduced. May be incurred. On the other hand, when at least one of the content of Mn and the content of Cr is larger than the above specific range, a coarse crystallized product is formed in the ingot during the casting of the aluminum material, and the toughness is reduced. There is a risk of inviting.

  The aluminum material may contain elements such as Ti (titanium), B (boron), Fe (iron), and Si (silicon) in addition to the above-described Zn, Mg, Cu, Zr, Mn, and Cr. .

Ti (titanium): 0 mass% to 0.15 mass% or less, B (boron): 0 mass ppm to 50 mass ppm or less Ti and B have the effect of refining the ingot structure during casting. By setting the Ti content within the above specific range, the ingot structure can be refined and the casting cracks can be more effectively suppressed. Similarly, by setting the B content in the above specific range, the ingot structure can be refined and the casting crack can be more effectively suppressed.

  When at least one of the Ti content and the B content exceeds the specific range, a coarse intermetallic compound is formed in the aluminum material, which may cause a decrease in toughness. From the viewpoint of more reliably suppressing the formation of coarse intermetallic compounds, it is preferable that the Ti content is 0.10 mass% or less and the B content is 20 mass ppm or less.

-Fe (iron): 0.40 mass% or less, Si (silicon): 0.30 mass% or less Fe and Si are contained in aluminum materials when low-purity metal or recycled materials are used as raw materials. Can be. When the content of these elements is excessively large, an Al-Fe-Si-based crystallized product is formed at the time of casting, which may cause a decrease in toughness of the aluminum material. However, if the content of these elements is to be reduced, it is necessary to use high-purity bare metal as a raw material, which may increase the raw material cost. Therefore, from the viewpoint of obtaining high toughness while suppressing an increase in raw material cost, the Fe content is preferably 0.40% by mass or less, and the Si content is preferably 0.30% by mass or less.

Total of Mn-containing compound with major axis 20-500 nm and Cr-containing compound with major axis 20-500 nm: 5 / μm ² or more Mn-containing compound with major axis 20-500 nm present inside crystal grains in the aluminum material And the total of the Cr-containing compound having a major axis of 20 to 500 nm is 5 pieces / μm ² or more. The Mn-containing compound and the Cr-containing compound having the specific sizes have an action of preventing the progress of cracks. By setting the total of these compounds to 5 / μm ² or more, a fracture toughness value of 18.7 MPa · m ^1/2 or more can be easily realized, and an aluminum material excellent in toughness can be obtained.

When the total of these compounds is less than 5 / μm ² , the effect of preventing the progress of cracks is lowered, and the toughness may be lowered. From the viewpoint of improving the toughness of the aluminum material, it is preferable that the total number of these compounds is large. However, in the range of the above specific chemical components and production conditions, the upper limit of the total of these compounds is usually 50 / μm ² . is there.

Fracture toughness value: 18.7 MPa · m ^1/2 or more The above aluminum material has the above-mentioned specific chemical components, and has a Mn-containing compound having a major axis of 20 to 500 nm and a Cr having a major axis of 20 to 500 nm inside the crystal grains. By having a total of 5 or more contained compounds / μm ² , a fracture toughness value of 18.7 MPa · m ^1/2 or more can be easily realized.

-Tensile strength: 700 MPa or more The aluminum material preferably has a tensile strength of 700 MPa or more. In this case, an aluminum material excellent in both strength and toughness can be obtained. The aluminum material having the tensile strength in the specific range can be easily obtained by setting the tempering to T6 or T77, for example.

-Porosity with equivalent circle diameter of 10 μm or more: 0.5 vol% or less In the aluminum material, porosity may be formed due to local dissolution in heat treatment, migration and accumulation of hydrogen atoms, and the like. When the volume ratio of the porosity having an equivalent circle diameter of 10 μm or more is excessively large, the porosity becomes a propagation path of cracks, which may cause a decrease in toughness. From the viewpoint of avoiding such a problem, it is preferable to set the volume ratio of porosity having a circle equivalent diameter of 10 μm or more to 0.5% by volume or less.

  As a method for producing the aluminum material, after producing an ingot having the specific chemical component, a method of sequentially performing homogenization treatment, hot working, solution treatment, quenching, and artificial aging treatment on the ingot. Can be adopted.

  For the production of the ingot, a known casting method such as a continuous casting method or a semi-continuous casting method can be employed. When producing the ingot, the amount of gas dissolved in the molten aluminum alloy is preferably 0.15 mL or less per 100 g of aluminum. Thus, the volume ratio of the porosity in the said aluminum material can be reduced by fully reducing the gas in a molten metal.

  Next, the obtained ingot is heated and homogenized. In the homogenization treatment, the ingot is heated under the condition that the time required to reach 400 ° C. after reaching 300 ° C. is 2 hours or more and the temperature of 450 to 490 ° C. is maintained for 5 to 20 hours. Do. When heating of the ingot is started and the temperature reaches 300 ° C., precipitation nuclei of Mn-containing compounds and Cr-containing compounds are formed inside the crystal grains. When the temperature of the ingot exceeds 400 ° C., the increase in the number of precipitation nuclei stops and the growth of precipitates on the precipitation nuclei starts.

When the time required for the temperature of the ingot to reach 400 ° C. after reaching the temperature of 300 ° C. is 2 hours or more, the precipitation nuclei of the Mn-containing compound and the Cr-containing compound should be formed finely and with high density. Can do. Therefore, in this case, a large number of precipitation nuclei can be uniformly dispersed in the crystal grains. As a result, a total of 5 / μm ² or more of a Mn-containing compound having a major axis of 50 to 200 nm and a Cr-containing compound having a major axis of 50 to 200 nm are precipitated in the crystal grains of the aluminum material to obtain an aluminum material having excellent toughness. Can do.

When the required time is less than 2 hours, the above-described precipitation nuclei become relatively coarse and the position of the precipitation nuclei in the crystal grains tends to be biased. As a result, it becomes difficult to precipitate a total of 5 M / μm ² or more of the Mn-containing compound and the Cr-containing compound in the crystal grains of the aluminum material, which may cause a decrease in toughness. In addition, although the upper limit of the said required time is not specifically limited, From a viewpoint of productivity, it is preferable to set it as 7 hours or less.

Moreover, by maintaining the temperature of the ingot at 450 to 490 ° C. for 5 to 20 hours, it is possible to sufficiently grow the intermetallic compound on the precipitation nuclei described above. As a result, a total of 5 M / μm ² or more of the Mn-containing compound and the Cr-containing compound are precipitated in the crystal grains of the aluminum material, and an aluminum material having excellent toughness can be obtained.

When the holding temperature is less than 450 ° C. or the holding time is less than 5 hours, the formation and growth of intermetallic compounds on the precipitation nuclei becomes insufficient, and a total of five Mn-containing compounds and Cr-containing compounds are included. / Μm ² or more may be difficult to deposit. In this case, segregation of chemical components during casting cannot be sufficiently removed, and homogenization may be insufficient. Therefore, when the holding temperature is less than 450 ° C. or the holding time is less than 5 hours, the toughness of the aluminum material may be reduced.

  When holding temperature exceeds 490 degreeC, there exists a possibility that the volume ratio of the porosity formed in an aluminum material may increase by local melt | dissolution of an ingot. As a result, the toughness of the aluminum material may be reduced. Moreover, when holding time exceeds 20 hours, the Zr type compound which exists in an aluminum material aggregates, and there exists a possibility that the quantity of a fine Zr type compound may reduce. As a result, the effect of suppressing recrystallization by Zr is lowered, and the strength of the aluminum material and the SCC resistance may be lowered.

  After performing the homogenization treatment, the ingot is hot-worked under the condition that the post-processing temperature is 300 ° C. or higher to produce a wrought material. As the hot working, for example, a known working method such as hot rolling, hot extrusion or hot forging can be employed. When the temperature after processing is less than 300 ° C., recrystallization may occur in the solution treatment to be performed later, and the strength and the SCC resistance may be lowered. The above-mentioned “temperature after processing” refers to the surface temperature of the wrought material. The temperature inside the wrought material is usually higher than the temperature on the surface of the wrought material.

  The aluminum material can be obtained by sequentially performing solution treatment, quenching, and artificial aging treatment on the wrought material after hot working. Here, after hot working, before performing solution treatment, degassing treatment may be performed as necessary. As the degassing treatment, for example, conditions for heating the wrought material at a temperature of 400 to 490 ° C. in a vacuum heating furnace can be employed. By performing degassing treatment on the wrought material, the amount of hydrogen contained in the wrought material can be further reduced, and the formation of porosity can be more effectively suppressed.

  Conditions for solution treatment, quenching, and artificial aging treatment can be appropriately selected from known conditions. In the solution treatment, it is preferable to heat the wrought material under conditions that allow Zn, Mg, and Cu in the wrought material to be dissolved. Specifically, the heating temperature in the solution treatment is preferably 400 to 490 ° C. As the quenching medium, water, warm water, oil, an aqueous solution of a glycol polymer, or the like can be used.

  The treatment conditions in the artificial aging treatment can be appropriately selected from a known condition range according to the desired quality. In order to obtain an aluminum material excellent in SCC resistance, it is preferable to perform an overaging treatment or a restoration reaging (RRA) treatment in the artificial aging treatment.

  Examples of the aluminum material and the manufacturing method thereof will be described. In addition, the specific aspect of the aluminum material which concerns on this invention, and its manufacturing method is not limited to a following example, A structure can be changed suitably in the range which does not impair the meaning of this invention.

Example 1
This example is an example of an aluminum plate produced by changing various chemical components. In this example, a dehydrogenation gas treatment with argon gas was performed on a molten aluminum alloy (alloy symbols A to V) having the chemical components shown in Table 1, and then a thickness of 150 mm, a width of 500 mm, and a length of 500 mm by DC casting. An ingot was prepared. In Table 1, “Bal.” Indicates a residual component (Balance).

  Next, the ingot was heated using an atmospheric furnace and homogenized. The temperature at the start of heating in the homogenization treatment was 300 ° C. or less, the temperature raising rate was 40 ° C./hour, and the temperature at the completion of temperature raising was 465 ° C. Further, after the temperature increase was completed, a temperature of 465 ° C. was maintained for 10 hours. That is, in this example, the time required to reach 400 ° C. after reaching 300 ° C. is 2.5 hours, and homogenization is performed under a heating condition in which the temperature is maintained at 450 to 490 ° C. for 10.4 hours. Processing was carried out.

  After holding for 10 hours, the ingot was left outside the atmospheric furnace and cooled to room temperature. Thereafter, both sides of the ingot in the thickness direction were chamfered by 15 mm.

  Next, the ingot was heated to 420 ° C. using an atmospheric furnace. This ingot was hot-rolled to obtain a wrought material having a thickness of 15 mm. For hot rolling, a hot rolling mill having a rolling roll with a built-in electric heater was used, and hot rolling was performed such that the surface temperature of the rolling roll was in the range of 330 to 370 ° C. Thereby, the surface temperature of the ingot during hot rolling became 300 ° C. or higher. Moreover, the temperature of the surface after hot rolling was 300 degreeC or more.

  The wrought material obtained using an atmospheric furnace was heated and subjected to a solution treatment. The heating conditions for the solution treatment were a heating temperature of 470 ° C. and a holding time of 1 hour. After the solution treatment, the wrought material was water quenched.

  Thereafter, the wrought material was heated using an atmospheric furnace and subjected to artificial aging treatment. In this example, RRA treatment is adopted as the artificial aging treatment. Specifically, a first step of heating the wrought material at a temperature of 120 ° C. for 24 hours, a second step of heating the wrought material at a temperature of 180 ° C. for 90 minutes, and a third step of heating the wrought material at a temperature of 120 ° C. for 24 hours; Were carried out sequentially. Thus, an aluminum alloy material (Table 2, test materials 1 to 21) having a tempering of T77 was obtained.

  About the test materials 1-21 obtained by the above, evaluation of the following each item was implemented.

-Number of Mn-containing compound and Cr-containing compound A small piece having a thickness of 0.5 to 1.0 mm, a width of 10 mm, and a length of 10 mm is sampled from the center of the plane (LT-ST plane) perpendicular to the rolling direction of the test material. did. The small piece was polished with a water-resistant abrasive paper until the thickness became 0.2 mm or less, and then electropolished by a twin jet electropolishing method to prepare a sample for TEM (transmission electron microscope) observation. The structure of this sample was observed using a TEM at a magnification of 20,000 times, and the number of Mn-containing compounds and Cr-containing compounds having a major axis of 20 to 500 nm existing in the visual field was counted. The total number (number / μm ² ) of the number of Mn-containing compounds having a major axis of 20 to 500 nm and the number of Cr-containing compounds having a major axis of 20 to 500 nm was as shown in Table 2.

-Porosity volume fraction A small piece having a thickness of 0.3 mm, a width of 0.3 mm, and a length of 15 mm is collected from the center of a plane (LT-ST plane) perpendicular to the rolling direction of the test material, and X-ray micro CT is used. A small piece of leverage was scanned. Then, based on the obtained three-dimensional image, the volume ratio of the porosity having a major axis of 10 μm or more existing inside the small piece was calculated. Table 2 shows the volume ratio (volume%) of the porosity having an equivalent circle diameter of 10 μm or more in each test material. Note that the X-ray micro CT used in this example could not detect a porosity with an equivalent circle diameter of less than 10 μm.

-Tensile strength, proof stress, elongation Each test material was subjected to a tensile test by a method in accordance with JIS Z2241. Specifically, a 14A test piece was sampled from the center of a plane (LT-ST plane) perpendicular to the rolling direction of the test material so that the longitudinal direction was parallel to the rolling direction. The diameter of the parallel part of the test piece was 6 mm, and the gauge distance was 30 mm. And the tensile test was implemented using this test piece under room temperature. Table 2 shows the values of tensile strength, yield strength and elongation calculated based on the results of the tensile test.

  Since the tempering of the test material in this example is T77, a test material having a tensile strength of 700 MPa or more can be obtained by performing homogenization treatment, solution treatment, artificial aging treatment, and the like under appropriate treatment conditions. it can. Therefore, in the evaluation of the tensile strength, when the tensile strength is 700 MPa or more, it is judged as acceptable because it has high strength, and when the tensile strength is less than 700 MPa, it is judged as unacceptable because the strength is low. .

-Fracture toughness value The fracture toughness test was implemented about each test material by the method according to the prescription | regulation of ASTM E399-12e2. Specifically, from the center of the plane perpendicular to the rolling direction of the test material (LT-ST plane), the stress load direction is the plate width direction (LT direction) of the test material, and the crack propagation direction is rolling of the plate material. CT specimens were collected in parallel with the direction (L direction). The CT specimen had a thickness of 12.7 mm, a width of 30.5 mm, and a length of 31.75 mm. And the fracture toughness test was implemented using the CT test piece at room temperature. The fracture toughness values calculated based on the results of the fracture toughness test were as shown in Table 2.

-SCC resistance The stress corrosion cracking test was implemented about each test material by the method according to the prescription | regulation of JISH8711: 2000. Specifically, a round bar shape is formed so that the stress load direction is parallel to the plate width direction (LT direction) of the test material from the center of the surface perpendicular to the rolling direction of the test material (LT-ST surface). Tensile test pieces were collected. The diameter of the parallel part of the test piece was 2.9 mm and the length was 11 mm.

  A tensile stress of 70% of the proof stress was applied to the test piece, and the stress corrosion cracking test was continued until the test piece was broken or 720 hours passed without breaking. When 720 hours have passed without breaking the test piece, the symbol “A” is entered in the “SCC resistance” column of Table 2, and when the specimen breaks before 720 hours have passed, the same The symbol “B” is described in the column. Note that a 3.5% sodium chloride aqueous solution was used as a test solution. Further, as a method for immersing the test piece in the test solution, an alternate dipping method was adopted in which the test piece was dipped in the test solution for 10 minutes, and then the test piece was pulled up from the test solution and dried for 50 minutes.

As shown in Table 1, the test materials 1 to 11 are composed of alloys A to K whose chemical components are within the specific range. In addition, in the test materials 1 to 11, the total of the Mn-containing compound having a major axis of 20 to 500 nm and the Cr-containing compound present in the crystal grains was 5 pieces / μm ² or more. Therefore, these test materials had a tensile strength of 700 MPa or more and a fracture toughness value of 18.7 MPa · m ^1/2 or more.

On the other hand, the alloy L constituting the test material 12 had a Zn content less than the specific range. Moreover, the alloy M which comprises the test material 13 had more Zn content than the said specific range. Therefore, the tensile strength of these test materials was less than 700 MPa.
The alloy N constituting the test material 14 had a Mg content less than the specific range. Therefore, the tensile strength of the test material 14 was less than 700 MPa.
The alloy O constituting the test material 15 had a Mg content higher than the specific range. Therefore, in the stress corrosion cracking test of the test material 15, the test piece broke before 720 hours passed.

The alloy P constituting the test material 16 had a Cu content less than the specific range. Therefore, the tensile strength of the test material 16 was less than 700 MPa.
The alloy Q constituting the test material 17 had a Cu content larger than the specific range. Therefore, in the stress corrosion cracking test of the test material 17, the test piece broke before 720 hours passed.

Since the alloy R constituting the test material 18 contained neither Mn nor Cr, the Mn-containing compound and the Cr-containing compound did not precipitate in the crystal grains. As a result, the fracture toughness value of the test material 18 was less than 18.7 MPa · m ^1/2 .
The alloy S constituting the test material 19 had a Zr content less than the specific range. Therefore, the tensile strength of the test material 19 was less than 700 MPa. Moreover, in the stress corrosion cracking test of the test material 19, the test piece broke before 720 hours passed.

The alloy T constituting the test material 20, the alloy U constituting the test material 21, and the alloy V constituting the test material 22 have a content of one or more of Zr, Fe, Si, Ti, and B in the specific range described above. It was more than. Therefore, the fracture toughness values of these test materials were less than 18.7 MPa · m ^1/2 .

In this way, by setting the chemical component within the above specific range and the total of the Mn-containing compound and the Cr-containing compound being 5 pieces / μm ² or more, the tensile strength of 700 MPa or more and 18 An aluminum material having a fracture toughness value of 0.7 MPa · m ^1/2 or more can be obtained. And the said aluminum material can make high intensity | strength and the outstanding toughness compatible with the conventional 7000 series aluminum alloy material.

  In addition, in the test materials 1 to 11, the test piece did not break after 720 hours in the stress corrosion cracking test, and exhibited excellent SCC resistance. Therefore, it can be understood that the aluminum material not only has both high strength and excellent toughness, but also has excellent SCC resistance and is suitable as a structural material.

(Example 2)
In this example, the production conditions of the aluminum material are variously changed. In this example, alloy B (see Table 1) was used, and the heating rate, holding temperature, holding time, and surface temperature of the wrought material at the end of hot rolling in the homogenization treatment were changed as shown in Table 3. Except for the above, aluminum materials (Tables 3 to 4, Test materials 23 to 35) were prepared in the same manner as in Example 1. In the column of “Required time” in Table 3, the time from when the ingot temperature reaches 300 ° C. until it reaches 400 ° C. under each condition is described.

  The obtained test materials 23 to 35 were evaluated in the same manner as in Example 1. The evaluation results were as shown in Table 4.

As shown in Table 3 and Table 4, since the test materials 23 to 28 were within the specific range in the heating conditions in the homogenization treatment, the Mn-containing compound having a major axis of 20 to 500 nm and the Cr content were contained in the crystal grains. A total of 5 compounds / μm ² or more could be precipitated. Further, these test materials had a tensile strength of 700 MPa or more and a fracture toughness value of 18.7 MPa · m ^1/2 or more.

On the other hand, since the time required for the test material 29 to reach 400 ° C. after reaching 300 ° C. was less than 2 hours, a total of five Mn-containing compounds and Cr-containing compounds were included in the crystal grains. / Μm ² or more could not be deposited. Therefore, the fracture toughness value of the test material 29 was less than 18.7 MPa · m ^1/2 .

Since the test material 30 had a holding temperature of less than 450 ° C. in the homogenization treatment, the Mn-containing compound and the Cr-containing compound could not be precipitated in a total of 5 particles / μm ² or more in the crystal grains. Therefore, the fracture toughness value of the test material 30 was less than 18.7 MPa · m ^1/2 .
Since the test material 31 had a higher holding temperature than the test material 30, it was possible to deposit a total of 5 M / μm ² or more of the Mn-containing compound and the Cr-containing compound in the crystal grains. However, since the holding temperature in the homogenization treatment of the test material 31 was less than 450 ° C., the homogenization became insufficient. Therefore, the fracture toughness value of the test material 31 was less than 18.7 MPa · m ^1/2 .

Since the holding temperature in the homogenization process exceeded 490 degreeC, the test material 32 generate | occur | produced local melting | dissolution of an ingot, and the volume ratio of the porosity increased. Thereby, the fracture toughness value of the test material 32 was less than 18.7 MPa · m ^1/2 .

Since the test material 33 had a retention time of less than 5 hours in the homogenization treatment, a total of 5 or more μm ^{2 of the} Mn-containing compound and the Cr-containing compound could not be precipitated in the crystal grains. Therefore, the fracture toughness value of the test material 33 was less than 18.7 MPa · m ^1/2 .
Since the holding time in the homogenization treatment exceeded 20 hours, the test material 34 was recrystallized in the solution treatment. Thereby, the tensile strength of the test material 34 became less than 700 MPa. In the stress corrosion cracking test of the test material 34, the test piece broke before 720 hours passed.

  In the test material 35, since the surface temperature of the expanded material at the end of hot rolling was less than 300 ° C., recrystallization occurred in the solution treatment. Thereby, the tensile strength of the test material 35 became less than 700 MPa. In the stress corrosion cracking test of the test material 35, the test piece broke before 720 hours passed.

(Example 3)
This example is an example of a method for producing an aluminum material by hot extrusion. In this example, the molten alloy B (see Table 1) was dehydrogenated with argon gas, and then a cylindrical ingot having a diameter of 254 mm and a length of 650 mm was produced by DC casting. The ingot was heated using an atmospheric furnace and homogenized. The temperature at the start of heating in the homogenization treatment was 300 ° C. or less, the temperature raising rate was 40 ° C./hour, and the temperature at the completion of temperature raising was 465 ° C. Further, after the temperature increase was completed, a temperature of 465 ° C. was maintained for 10 hours. After holding for 10 hours, the ingot was left outside the atmospheric furnace and cooled to room temperature.

  Next, the ingot was heated to 450 ° C. over 5 minutes using an induction heating furnace. Using a direct extruder, hot extrusion was performed under the condition that the extrusion speed on the extrusion side was 0.5 m / min, to obtain a flat plate-shaped stretched material having a thickness of 15 mm and a width of 100 mm. The surface temperature of the wrought material after hot extrusion was in the range of 425 to 443 ° C.

  Thereafter, solution treatment, water quenching and artificial aging treatment were sequentially performed in the same procedure as in Example 1 to obtain an aluminum material (Table 5, test material 36). About the obtained test material 36, evaluation similar to Example 1 was performed. The evaluation results were as shown in Table 5.

  As shown in this example, if the processing conditions of the homogenization treatment and hot working are within the specific range, known methods such as hot rolling, hot extrusion and hot forging are used as hot working. Can be adopted.

Claims (4)

Zn: 9.1-14.0 mass%, Mg: 2.0-3.0 mass%, Cu: 1.0-2.0 mass%, Zr: 0.080-0.20 mass% is contained. Along with Mn: 0.20-1.00% by mass and Cr: 0.10-0.30% by mass, containing the chemical component consisting of Al and inevitable impurities,
The total of the Mn-containing compound having a major axis of 20 to 500 nm and the Cr-containing compound having a major axis of 20 to 500 nm present in the crystal grains is 5 pieces / μm ² or more,
A structural aluminum alloy material having a fracture toughness value of 18.7 MPa · m ^1/2 or more.   The structural aluminum alloy material according to claim 1, wherein a volume ratio of porosity having an equivalent circle diameter of 10 μm or more is 0.5% by volume or less. Zn: 9.1-14.0 mass%, Mg: 2.0-3.0 mass%, Cu: 1.0-2.0 mass%, Zr: 0.080-0.20 mass% is contained. In addition, an ingot containing one or more of Mn: 0.20 to 1.00% by mass and Cr: 0.10 to 0.30% by mass, the balance being a chemical component composed of Al and inevitable impurities is produced. And
The time required to reach 400 ° C. after reaching 300 ° C. is 2 hours or more, and the ingot is heated and homogenized under the condition that the temperature of 450 to 490 ° C. is maintained for 5 to 20 hours. Done
A wrought material is produced by subjecting the ingot to hot working under the condition that the temperature at the end is 300 ° C. or higher,
A method for producing a structural aluminum alloy material, wherein the wrought material is subjected to solution treatment, quenching, and artificial aging treatment.   The manufacturing method of the structural aluminum alloy material of Claim 3 which heats the said wrought material to the temperature of 400-490 degreeC in the said solution treatment.