JP7265092B2 - High-strength, high-elongation aluminum alloy extrusions - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high- strength, high-elongation aluminum alloy extruded material .

JIS 6000 series aluminum alloy extruded materials in which Mg and Si are added to Al are sometimes used as bumpers, bumper reinforcing materials, or frame materials for automobiles and the like. However, 6000-series aluminum alloy extruded materials are not necessarily strong enough for use as structural materials, such as bumpers and frame materials, for which further enhancement of strength is being pursued.
On the other hand, if it is a JIS 7000 series aluminum alloy extruded material to which Zn and Mg are added, it is easy to obtain high strength. It is necessary to make a composition that considers the nature of the material.

For example, in Patent Document 1 below, as an Al-Zn-Mg-Cu alloy extruded material, Zn: 5.0 to 7.5% (mass%, the same applies hereinafter), Mg: 1.6 to 3.3% , Cu: 1.1 to 2.5%, Cr: 0.30% or less (not including 0%, the same applies hereinafter), Mn: 0.60% or less, Zr: 0.30% or less and one or more of Ti: 0.06% or less and B: 0.005% or less, and Fe and Si as inevitable impurities are each limited to 0.25% or less. , the balance being Al and unavoidable impurities.

Further, in Patent Document 2 below, when the mass% of Mg is [Mg] and the mass% of Zn is [Zn], [Mg] and [Zn] satisfy the following three formulas, and 5.43 ≤ [ Zn]≤6.3, [Zn]/5.38+0.15≤[Mg]≤[Zn]/5.38+0.34, 11. 68 ≤ [Zn] + 4.7 [Mg] ≤ 14, Cu: 0.1 to 0.6 mass%, Ag: 0.01 to 0.15 mass%, and Ti: 0 .005 to 0.05% by mass, and one or two of Mn: 0.1 to 0.3% by mass, Cr: 0.05 to 0.2% by mass, and Zr: 0.05 to 0.2% by mass A high-strength aluminum alloy extruded material for bumper reinforcement is disclosed which contains at least one species and the balance is Al.

Japanese Patent No. 5083816 Japanese Patent No. 5631379

Based on the background described above, the present inventors have investigated the optimum compositional balance of 7000-series aluminum alloy extruded materials for use as bumpers and frame materials. As a result, it was found that the optimum content of Mn is important in this type of aluminum alloy extruded material.
It has been confirmed that Mn contributes to fibrous metallographic structure after extrusion in this type of aluminum alloy, increases the brass orientation density, and has the effect of improving strength.
It has also been found that when the Mn content is adjusted to 0.3% by mass or less, the fibrous structure is not sufficiently developed and the strength is lowered. They also found that when the Mn content is adjusted to more than 0.5% by mass, coarse intermetallic compounds develop and the workability deteriorates.

SUMMARY OF THE INVENTION In view of the above background, the present invention aims to provide a high-strength, high-elongation aluminum alloy extruded material having high strength and excellent elongation suitable for use as structural materials such as bumpers and frame materials.

(4) The high-strength and high-elongation aluminum alloy extruded material of the present embodiment is mass %, Zn: more than 4.0% to 7.0%, Mg: more than 0.9% to 1.3%, Zr : more than 0.1% to 0.3%, Ti: more than 0.01% to 0.1%, Cu: more than 0.2% to 0.6%, Mn: more than 0.3% to 0 .5% or less , Fe: 0.3% or less, Si: 0.2% or less, Ni: 0.1% or less, V: 0.05% or less , the balance being Al and unavoidable impurities, extrusion It is characterized by having a tensile yield strength of 350 MPa or more and an elongation of 13% or more in the extrusion direction of the subsequent molded material.

(5) The high-strength, high-elongation aluminum alloy extruded material of the present embodiment is characterized by containing more than 0.005% to 0.05% or less of V, with the balance being Al and unavoidable impurities .

(6) In the high-strength, high-elongation aluminum alloy extruded material of the present embodiment, it is preferable that the Brass orientation density in the ODF obtained from the pole figure measured by X-ray diffraction measurement is 15 or more.

The high-strength, high-elongation aluminum alloy extruded material according to the present invention has high strength and excellent elongation, and is therefore suitable as a bumper, a bumper reinforcing material, or a frame material that exhibits high strength and excellent elongation. can provide
Also, if the cross-sectional structure in the extrusion direction has a fibrous structure and the Brass orientation density in the ODF obtained from the pole figure measured by X-ray diffraction measurement is 15 or more, the aluminum alloy has high strength and excellent elongation. Extruded material can be provided.

1 is a perspective view showing an example of an aluminum alloy extruded material manufactured in Examples. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.
The aluminum alloy exhibiting high strength and high elongation according to the present embodiment has, in mass %, Zn: more than 4.0% to 7.0%, Mg: more than 0.9% to 1.3%, Zr : more than 0.1% to 0.3%, Ti: more than 0.01% to 0.1%, Cu: more than 0.2% to 0.6%, Mn: more than 0.3% to 0 .5% or less, with the balance being Al and unavoidable impurities.
In the aluminum alloy of the present embodiment, in addition to the composition described above, one or more of Fe, Si, Ni, and V are preferably controlled within the ranges shown below in terms of % by mass.
Fe: 0.3% or less, Si: 0.2% or less, Ni: 0.1% or less, V: more than 0.005% to 0.05% or less.
In addition, the aluminum alloy of the present embodiment preferably has a tensile yield strength of 350 MPa or more and an elongation of 13% or more in the extrusion direction of the molded material after extrusion.
In this specification, when the content of a component element is expressed as more than 4.0% to 7.0% or less, it contains more than 4.0% with respect to the target component element, and 7.0% It means containing:

Zn: more than 4.0% to 7.0% or less Mg: more than 0.9% to 1.3% or less The aluminum alloy according to the present embodiment contains more than 4.0% and 7.0% or less Zn is contained, and more than 0.9% and 1.3% or less of Mg is contained.
Zn and Mg form _MgZn2 in the structure and contribute to the strength improvement of the aluminum alloy. When the Mg content exceeds 1.3% and the Zn content exceeds 7.0%, the plastic workability is remarkably lowered, and the practicality of the aluminum alloy of the present embodiment is lowered. In addition, the rate of occurrence of billet cracking during casting increases, resulting in a significant decrease in yield.
The Zn content is more preferably in the range of 5.30% to 6.50%, and even more preferably in the range of 5.40% to 6.30%. The content of Mg is more preferably in the range of 1.0% to 1.30%, more preferably 1.10% to 1.26%.

Cu: more than 0.2% to 0.6% or less Cu contributes to improving the strength of the aluminum alloy according to the present embodiment. If the Cu content is 0.2% by mass or less, sufficient strength cannot be obtained in the aluminum alloy of the present embodiment. If the Cu content exceeds 0.6%, billet cracking occurs during casting, resulting in a significant decrease in yield. The Cu content is more preferably in the range of 0.30% to 0.50%, and even more preferably in the range of 0.33% to 0.41%.

Mn: more than 0.3% to 0.5% or less Mn makes it easier to obtain a fibrous structure in the structure after extrusion when an extruded material is produced from the aluminum alloy of the present embodiment. Moreover, Mn has the effect of improving the Brass orientation density in the extruded material. If the Mn content is 0.3% or less, the development of Brass orientation is insufficient and sufficient strength cannot be obtained. If the Mn content exceeds 0.5%, coarse intermetallic compounds are generated and the plastic workability is lowered.
The content of Mn is more preferably 0.31% or more and 0.45% or less, and still more preferably 0.33% or more and 0.43% or less.

Zr: more than 0.1% to 0.3% or less Ti: more than 0.01% to 0.1% or less Zr has the effect of making it easier to obtain a fibrous structure in the structure after extrusion. In addition, Zr has the effect of improving the Brass orientation density in the extruded material. If the Zr content is 0.1% or less, the Brass orientation is insufficiently developed and sufficient strength cannot be obtained. When the Zr content exceeds 0.3%, the plastic workability deteriorates. The Zr content is more preferably in the range of 0.11% to 0.20%, and even more preferably in the range of 0.15% to 0.2%.
Ti has the effect of refining the cast structure and has the effect of improving the extrusion moldability.
Ti: If it is 0.01% or less, sufficient effects cannot be obtained in terms of both the refinement effect and the extrusion moldability improvement effect. If the Ti content exceeds 0.1%, the properties are not improved, but excessive addition leads to an increase in the cost of the aluminum alloy.
More preferably, the Ti content is in the range of 0.015% to 0.055%.

Fe: 0.3% or less Si: 0.2% or less Ni: 0.1% or less Fe, Si, and Ni are elements derived from base metals. 3% or less, Si: 0.2% or less, Ni: 0.1% or less.
Fe is an element that contributes to refinement of crystal grains and improves strength by mainly forming Al—Fe-based intermetallic compounds. However, when the content exceeds the upper limit, the ductility is lowered.
Si has the effect of forming a solid solution in the aluminum base material and strengthening it, but when the content exceeds the upper limit, the ductility decreases.
As for the contents of Fe and Si, it is preferable that the sum of the Fe content and the Si content, Fe+Si, is in the range of less than 0.4%.
Ni is an element that refines crystal grains and has the effect of suppressing the formation of abnormally coarsely grown grains, and improves strength, but if it exceeds 0.1%, ductility remarkably decreases. Ni is more preferably controlled at 0.05% or less.

V: more than 0.005% to 0.05% or less V has the effect of refining the cast structure and improving the brass orientation density. If the V content is 0.005% or less, sufficient effects cannot be obtained in terms of both the refinement effect and the Brass orientation density improvement effect. If the V content exceeds 0.05%, coarse intermetallic compounds are generated and the plastic workability is lowered. The V content is more preferably 0.01% or more and 0.04% or less, and still more preferably 0.01% or more and 0.03% or less.

In the preferred ranges of the composition of the aluminum alloy of the present embodiment, the Zn content is 5.40% or more and 6.30% or less, the Mg content is 1.10% or more and 1.26% or less, and the Cu content is 0.33% or more and 0 .41% or less, Mn content of 0.33% or more and 0.43% or less, Zr content of 0.15% or more and 0.20% or less, the content of the sum of the Fe content and the Si content, Fe + Si When satisfying less than 0.4 at the same time, it is possible to provide aluminum alloys and aluminum alloy extruded materials having particularly high strength and excellent elongation.

Next, a method for producing an aluminum alloy according to the present invention and a method for producing an extruded material using the aluminum alloy will be described.
First, an ingot is cast from a molten aluminum alloy by a semi-continuous casting method so as to have the predetermined composition described above. The obtained ingot is homogenized to obtain a billet for extrusion.

The homogenization temperature is desirably 400° C. or more and 500° C. or less, the homogenization time is desirably 1 hour or more and 20 hours or less, and forced cooling by a fan is desirable after the homogenization treatment is taken out from the furnace. These processing conditions are general processing conditions applied to Al--Zn--Mg-based aluminum alloys.

Next, the billet is heated prior to extrusion, and the heating temperature is desirably 460° C. or higher and 560° C. or lower. More preferably, the temperature is 480°C or higher and 540°C or lower. An air furnace, an induction heating furnace, or the like can be used to heat the billet.
Hot extrusion can be performed to a predetermined shape using a billet heated to a predetermined temperature. By heating the billet to the above temperature range and performing hot extrusion, the main orientation of the texture can be controlled to be the Brass orientation. At that time, it is preferable that the extrusion ratio is 20 or more and that the cross-sectional thickness of the extruded shape is 10 mm or less in order to control the main orientation of the texture to be the Brass orientation. After hot extrusion, the product is cooled to room temperature (70° C. or lower) by fan air cooling, and then cut into a predetermined length to obtain an extruded material. After extrusion, the obtained extruded profile is subjected to a two-stage aging treatment. In this aging treatment, the temperature range of 90° C. to 130° C. is maintained for 1 hour to 12 hours in the first stage, and the temperature range of 130° C. to 170° C. is maintained for 1 hour to 12 hours in the second stage. .

The aluminum alloy constituting the extruded material manufactured as described above has a tensile yield strength of 350 MPa or more and an elongation of 13% or more in the extrusion direction.
Further, the extruded material made of the aluminum alloy has a fibrous structure in which crystal grains are elongated in the extrusion direction, and exhibits a Brass orientation density of 15 or more. Here, the method for measuring the Brass orientation density is to perform X-ray diffraction measurement on the surface of the extruded material by the Schulz reflection method to create an incomplete pole figure of {100}, {110}, and {111}, From the obtained incomplete pole figures of {100}, {110}, and {111}, an ODF (orientation density distribution function) is obtained by the iterative series expansion method, and the Brass orientation {110} <112> is obtained from the obtained ODF. The orientation density corresponding to is output, and the obtained orientation density is used as the Brass orientation density.

Therefore, if the extruded material is made of the aluminum alloy described above, it has good extrudability and castability, and has sufficient tensile strength and elongation. can be used for

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.
An aluminum alloy ingot having a diameter of 300 to 330 mm having the composition shown in Tables 1 and 2 was produced by a semi-continuous casting method, and the obtained ingot was subjected to a homogenization treatment at 450 to 500 ° C. for 10 to 16 hours. After that, it was taken out from the furnace and forcedly cooled by a fan. These extrusion billets are heated to 510 to 530° C. in an induction heating furnace, and a hollow extruded material having a width of 150 mm, a height of 150 mm, and a wall thickness of 4.5 mm with a square cross section (extrusion ratio of about 30) is extruded by hot extrusion. It was fabricated by cooling to room temperature with a fan air cooling immediately after processing.

Two-stage aging treatment was performed on the obtained aluminum alloy extruded material. The first stage was treated at 100-130°C for 4-6 hours, and the second stage was treated at 140-160°C for 4-6 hours.
FIG. 1 shows the shape of an aluminum alloy extruded material (hollow extruded material). In this hollow extruded material 1, a tensile test piece 2 and a disc-shaped test piece 3 for X-ray diffraction measurement were taken from the upper surface portion 1A of the square cross section shown in FIG. 1, and subjected to various measurements described below.

"Measurement of Tensile Yield Strength"
A tensile test was performed according to JISZ2241 to measure the tensile strength of each test piece. A test piece of the aluminum alloy extruded material was in the shape of a JIS No. 5 test piece, and as shown in FIG. The crosshead speed was 5 mm/min.
"Elongation measurement"
The fracture surface of each test piece after the tensile test was matched, and the change in the distance between gauge marks drawn before the tensile test was measured to obtain the elongation.
Considering the measured value of tensile yield strength and the measured value of elongation, the mechanical properties were determined according to the following criteria.
"Determination of mechanical properties"
A: yield strength of 400 MPa or more and elongation of 16% or more B: yield strength of 370 MPa or more and elongation of 14% or more C: yield strength of 370 MPa or more and elongation of 13% or more D: yield strength of 350 MPa or more and elongation of 13% or more E: yield strength of less than 350 MPa or elongation of less than 13%

"collective organization"
From the upper surface of the square cross section of each hollow extruded material, a disc test piece of φ40 mm is cut out as shown in FIG. 100}, {110}, and {111} incomplete pole figures were created.
The X-ray diffraction measurement was performed using RINT2200 manufactured by Rigaku Corporation. The conditions for X-ray diffraction measurement are as follows: Cu tube, tube voltage 40 kV, tube current 40 mA, Schulz reflection method, tilt angle α = 20 to 90 ° range, background correction. The conditions were set for standardization with a non-oriented sample. From the obtained incomplete pole figures of {100}, {110}, and {111}, ODF ( orientation density distribution function) was obtained. From the obtained ODF, the orientation density at Euler angles φ1 = 35 °, φ = 45 °, φ2 = 0 ° according to the Bunge notation method is output so as to correspond to the Brass orientation {110} <112>. The obtained orientation density was defined as the Brass orientation density.
Considering the obtained Brass orientation density, the texture was determined according to the following criteria.
A: Brass orientation density 17 or more B: Brass orientation density 15 or more to less than 17 C: Brass orientation density 14 or more to less than 15 D: Brass orientation density less than 14

"Productivity"
Samples were produced from each aluminum alloy having each composition shown in Tables 1 and 2 above, but as a result of adding various elements to the aluminum alloy, casting cracks occurred in some of the samples. Also, some of the samples had extrusion defects (shape/dimension defects, etc.). The productivity of each sample was evaluated in the following three stages of A, B, and C.
Productivity evaluation A: Good castability and extrudability, and sufficient productivity.
B: It has castability and extrudability that can be produced, but the yield is inferior due to defective dimensions and poor appearance.
C: Remarkably poor productivity due to casting cracks, excessive extrusion load, etc. (cannot be manufactured).

Table 3 summarizes the above measurement results and judgments. In addition, Table 3 shows the results of comprehensive judgment based on the following criteria, taking into consideration the determination of mechanical properties and texture and productivity.
Comprehensive judgment A: Excellent in yield strength and elongation, satisfies the texture, and has good productivity.
B: Especially excellent in yield strength, satisfies elongation and texture, and has good productivity.
C: Satisfactory yield strength, elongation and texture, and good productivity.
D: Satisfactory yield strength, elongation and texture, but slightly inferior productivity.
E: Targets for one or more of yield strength, elongation, and texture are not achieved, or productivity is significantly inferior.

As shown in the results shown in Tables 1 to 3, Zn: more than 4.0% to 7.0% or less, Mg: more than 0.9% to 1.3%, Zr: 0.0% by mass%. More than 1% to 0.3% or less, Ti: more than 0.01% to 0.1%, Cu: more than 0.2% to 0.6%, Mn: more than 0.3% to 0.5% If the extruded material of Examples 1 to 16 made of an aluminum alloy having a composition containing the following and the balance being Al and unavoidable impurities, it is possible to obtain a tensile yield strength of 350 MPa or more in the extrusion direction of the molded material after extrusion It was found to have an elongation of 13% or more.

As the results shown in Tables 1 to 3 show, Zn, Mg, Zr, Ti, Cu, and Mn are contained in the above ranges, and Fe: 0.3% or less, Si: 0.2% or less, Ni : 0.1% or less, V: more than 0.005% to 0.05% or less in Examples 1 to 8, 11 and 15 to 16, tensile yield strength of 370 MPa or more, elongation of 14% or more properties are obtained.

The sample of Comparative Example 1 shown in Table 2 has a Zn content and a Mg content that are too large, but as shown in Table 3, the elongation is small and the yield is poor due to poor appearance.
In the sample of Comparative Example 2, although the Cu content was too high in the desired range, billet cracks occurred during casting, and a billet for extrusion could not be obtained.
The sample of Comparative Example 3 was a sample in which the Mn content and the Zr content were too large in the desired range, but the elongation was small and the yield was poor due to poor appearance.

Although the sample of Comparative Example 4 had a Zn content lower than the desired range, the yield strength was small.
The sample of Comparative Example 5 is a sample in which the Mg content and the Cu content are less than the desired range, but the yield strength is small.

The samples of Comparative Examples 6 and 8 were samples in which the Mn content and the Zr content were less than the desirable range, but the Brass orientation density was inferior and the yield strength was small.
The sample of Comparative Example 7 had a Ti content lower than the more desirable range, but cracks occurred during extrusion, so an extruded material sample could not be produced.

DESCRIPTION OF SYMBOLS 1... Hollow extruded material, 1A... Upper surface part, 2... Tensile test piece, 3... Disc-shaped sample.

Claims (3)

In % by mass, Zn: more than 4.0% to 7.0%, Mg: more than 0.9% to 1.3%, Zr: more than 0.1% to 0.3%, Ti: 0 .01% to 0.1% or less, Cu: more than 0.2% to 0.6%, Mn: more than 0.3% to 0.5%, Fe: 0.3% or less, Si: 0 .2% or less, Ni: 0.1% or less, V: 0.05% or less, the balance being Al and unavoidable impurities, and the tensile yield strength in the extrusion direction of the molded material after extrusion 350 MPa or more and 13% or more A high-strength, high-elongation aluminum alloy extruded material with an elongation of The high-strength and high-elongation aluminum alloy extruded material according to claim 1 , wherein the V content is more than 0.005% to 0.05% or less, and the balance is Al and inevitable impurities. 3. The high-strength and high-elongation aluminum alloy extruded material according to claim 1 or 2 , wherein the Brass orientation density in the ODF obtained from the pole figure measured by X-ray diffraction measurement is 15 or more.

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