KR100904503B1 - High-strength wrought aluminum alloy - Google Patents

Abstract

The present invention relates to an aluminum alloy having high strength by adding zinc, magnesium, nickel, iron, zirconium and silicon to an aluminum base. The aluminum alloy according to the present invention comprises about 5.5-8.5 wt% Zn, about 2-4% wt Mg, about 0.8-3% Ni, about 0.1-0.8 wt% Fe, about 0.05-0.3 wt% Zr, about 0.05-0.3 Si, and 0.1% or less of impurities. The aluminum alloy having such a composition has a structure including a matrix including the precipitated phase of the second phase formed from the aluminum solid solution and uniformly precipitated, and an aluminide dispersed phase containing nickel and iron and uniformly dispersed. The aluminum alloy according to the present invention has advantages of excellent castability and workability while showing high strength characteristics.

Aluminum alloy, nickel, zirconium, iron, matrix, aluminide

Description

High-strength wrought aluminum alloy

In general, pure aluminum has low strength properties and its use range is very limited. Therefore, various types of aluminum alloys have been developed to use aluminum as a material having high demand strength. Such aluminum alloys include i) Al-Zn-Mg-based heat treatment alloys for processing and ii) Al-Zn-Mg-Cu with nickel added thereto.

First, the heat treatment alloy for processing based on the Al-Zn-Mg structure exhibits excellent characteristics in corrosion resistance, fatigue strength, ductility, and the like. At this time, the tensile strength typically has a value of about 300 ~ 450MPa (Zn + Mg content 7 ~ 8%). However, as the concentration of Zn and Mg increases, the strength increases, but the grain boundary is easily broken, which causes a bad effect on ductility, fatigue properties, fracture toughness, and corrosion resistance.

In addition, in the alloy based on the Al-Zn-Mg structure, hot cracking occurs during solidification, and this hot cracking causes a problem that the alloy is difficult to apply to a complex casting. Therefore, due to the low casting characteristics of the alloy, the alloy is difficult to use as a casting alloy of a complicated form.

On the other hand, Al-Zn-Mg-Cu alloys are excellent in strength but cannot be used as casting alloys due to their low castability.

 The alloy added Ni to Al-Zn-Mg-Cu can improve the castability, but in the case of the alloy is limited to improve the castability due to the expansion of the solid-liquid coexistence zone according to the addition of Cu, and is used only in the production of small castings, Deformation is accompanied by ductility reduction due to the influence of Cu.

In addition, according to the recent Russian technology, a high-strength aluminum alloy excellent in workability and castability has been developed by adding Ni to the Al-Zn-Mg system.

However, the alloy in which Ni is added to the Al-Zn-Mg has a high production cost due to a large amount of expensive metal nickel (3 to 5% by weight), ii) a tensile strength of 570 MPa in a semi-processed state, casting In the state, the tensile strength is about 510 MPa.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, an object of the present invention is to provide a low-cost aluminum alloy excellent in combination with high strength properties, workability and castability.

Here, the mechanical properties of the alloy to be obtained by the present invention are expressed as follows.

-Down-

a) Vickers hardness of 180 HV or more

b) In the casting state, the ultimate tensile strength is at least 550 MPa, the yield strength is at least 480 MPa, and the elongation is at least 3%.

c) In semi-processed state, ultimate tensile strength of 620 MPa or more, yield strength of 530 MPa or more, elongation 4% or more

According to a feature of the present invention for achieving the above object, the present invention is based on aluminum, the aluminum contains zinc, magnesium, nickel, iron, zirconium and silicon.

In this case, the zinc is 5.5 to 8.5% by weight, the magnesium is 2 to 4% by weight, the nickel is 0.8 to 3% by weight, the iron is 0.1 to 0.8% by weight, the zirconium is 0.05 to 0.3% by weight The silicon is from 0.05 to 0.3% by weight; 0.1 wt% or less of impurities may be further included.

In addition, the aluminum may make up 83.1 to 91.5 wt%.

The aluminum alloy thus formed may have a structure including a matrix including precipitates of a second phase formed from an aluminum solid solution and uniformly dispersed, and aluminide particles uniformly dispersed including nickel and iron.

At this time, the aluminide particles may be 3 to 8% by volume.

In addition, the average size of the aluminide is 6 μm or less.

On the other hand, the precipitate may include Al 2 Mg 3 Zn 3 and MgZn 2 phases containing zinc and magnesium and being quasi-stable against phase changes, and Al3Zr phases containing zirconium and quasi-stable against phase changes.

Here, the precipitate is an average size of the phase containing the zinc and magnesium, and the zirconium phase is less than 40nm.

And the solidus temperature of the alloy is 540 ℃ or more.

The aluminum alloy having such a configuration may be manufactured in the form of a rolled plate, an extrusion rod, or may be manufactured by forging.

According to the present invention having the configuration as described above, there is an advantage that can produce an aluminum alloy excellent in castability while showing high-strength characteristics.

The present invention includes zinc, magnesium, nickel, iron, zirconium and silicon in aluminum as described above.

The phase containing zinc and magnesium is limited in amount to obtain tensile strength. That is, if the amount of the phase including Mg- and Zn- is below a certain value, the desired strength cannot be obtained after the heat treatment at the temperature of T6. Conversely, if it is above a certain value, the ductility of the material is reduced and the castability is lowered. Here, T6 heat treatment refers to a general artificial aging treatment used for heat treatment of metals. The solution precipitated by heating above a predetermined temperature through solution treatment is dissolved in a matrix to be described later, cooled by water, and then finely precipitated by heating for a long time at low temperature. Refers to the heat treatment that precipitates the phase in the matrix.

On the other hand, a phase containing nickel or iron is present in the form of a circle or ellipse by the heat treatment.

In addition, zirconium exists in the form of Al3Zr, and is a part that supplies a structure that is not recrystallized in a semi-processed state after heat treatment at a temperature of T6. At this time, the Al 3 Zr is a quasi-stable state in the form of a cube.

Hereinafter, the reason why the composition ratio of the constituent materials added in the present invention is limited and the characteristics of each constituent material will be described.

The alloy base of the present invention is based on a 7000-based high-strength alloy component containing 4-8% zinc and 1-4% magnesium and containing Fe, Si, and Zr as trace additive elements.

At this time, each of the alloying elements are required to combine with aluminum to form reinforcement phases such as MgZn2, AlFeSi, Al3Zr.

For example, when the nickel added in the present invention is added to 0.8 to 3% by weight, it can be seen from the experiment that the reinforcement phases are produced in the appropriate size and the appropriate amount.

That is, the difference in the amount of the additive determines the type and size of secondary reinforcing elements formed through reaction with other elements, and excellent high strength properties are exhibited by the new reinforcing elements produced through such component control.

Strength and Ductility [a] Vickers hardness of the present invention is 180HV or more, b) tensile strength of 550 MPa or more, yield strength of 480 MPa or more, elongation of 3% or more in a cast state, and c) tensile strength of 620 MPa or more in a semi-processed state. , Yield strength 530 MPa or more, elongation of 4% or more], the reinforcing phases acting on the present invention are aluminide phases (Al3Ni, Al9FeNi phase) containing nickel and iron of less than 6㎛ size, and average size less than 40nm Precipitation phases (Al2Mg3Zn3, MgZn2, Al3Zr phases) containing zinc and magnesium should be formed. At this time, the volume fraction of the aluminide in the alloy is maintained at 3 to 8%.

If the size and volume fraction cannot be maintained, it is difficult to obtain desired physical properties, and examples thereof can be found in the embodiments of the present invention (see Tables 1 and 2).

Therefore, in order to satisfy the above conditions, the amount of the additive should be limited to the amount defined in the present invention.

As described above, in the present invention, the amount of additives is important, and even if the elements are already included in pure aluminum, such as iron and silicon (the amount of iron and silicon contained in pure aluminum is typically 0.1 to 0.15% Fe). , Si 0.03% or less) Adding more than the usual content (Fe 0.1 ~ 0.8%, Si 0.05 ~ 0.3%) to obtain the physical properties targeted in the present invention.

Therefore, even if similar additives are added, the physical properties of the resulting material may be completely different.

Hereinafter, the present invention will be described through various embodiments of the present invention as described above.

The first embodiment of the present invention represents a forged product using the above-described aluminum alloy.

Table 1 shows six experimental examples. These experimental alloys are made of 99.9% pure aluminum, magnesium, zinc, silicon and master alloys in the furnace, including Al-Ni, Al-Fe and Al-Zr. The alloy is cast in a steel mold having an interior of 15 * 30 * 180mm.

Test pieces for testing the properties of these test alloys are measured from specimens cut from castings heat treated with T6. The solidus temperature is measured by differential thermal analysis (DTA), and the structural characteristics are determined by optical microscope, scanning microscope (SEM), transmission electron microscope (TEM), electron micro probe analysis, and X-ray analysis.

Composition and Characteristics of Test Alloy No. Content of Constituents (% by weight) Q1 (vol.%) Ts (℃) Zn Mg Ni Fe Si Zr Al One 5 1.5 0.5 0.03 0.02 0.01 balance ~ 3 602 2 5.5 4 3 0.1 0.05 0.3 balance To 7 585 3 7 3 0.8 0.8 0.3 0.2 balance To 4 570 4 8.5 2 2.3 0.4 0.2 0.05 balance To 7 545 5 9 4.5 5 1.5 0.5 0.5 balance To 9 482 6 7 2.1 3.7 <0.01 <0.001 <0.01 balance - -

here,

Q1 is the volume fraction of the aluminide particles (phases Al3Ni and Al9FeNi),

Ts represents the temperature of the equilibrium solidus line.

The mechanical (strength, ductility, and hardness) characteristics of the six test specimens tested by the method described above are shown in Table 2.

Characteristics of Test Alloys in Casting State after Complete Heat Treatment No. Tensile Strength (MPa) Yield strength (MPa) Elongation (%) Vickers Hardness (HV) One 325 220 15 150 2 600 520 4 185 3 620 510 6 190 4 610 500 5 187 5 340 340 0 205 6 560 485 6 -

Looking at these, only the second to fourth test alloys satisfy the level of Q1 and Ts required by the present invention. This is because the amount of phase containing Ni- and Fe- is smaller than that of the other specimens in alloy No. 1, and conversely, that of alloy No. 5 is higher than that of other specimens. Moreover, alloy 5 has a low level of Ts.

The average size of the precipitates of the second to fourth alloys does not exceed 40 nm. And the average size of the aluminide including nickel and iron does not exceed 6㎛. In addition, the phase form containing Ni- and Fe- is spherical or elliptical.

Figure 2 shows the appearance of alloy No. 2 after the heat treatment using the scanning microscope and the transmission microscope.

Pic 1

<Alloy 2 Heat-treated after Casting by Scanning Electron Microscope>

<Alloy 2 Heat-treated after Casting by Transmission Electron Microscope>

In addition, a photograph of the third alloy extruded after the heat treatment was observed with a scanning electron microscope and a projection electron microscope.

Picture 2

<Alloy 3 viewed by scanning electron microscope>

<The appearance of the third alloy seen by a projection microscope>

Mechanical properties were determined following a standardized process using cylindrical standard specimens of 4 mm diameter.

Alloys 2 to 4 exhibit significantly higher strengths than Alloys 1 and 6, and have superior ductility compared to Alloy 5.

A second embodiment of the invention is a rod extruded from the test alloy described above. At this time, the test rod for the experiment of the extrusion rod is formed to have a diameter of 14mm.

In the manufacture of such a test rod, a cylindrical rod having a diameter of 60 mm is first obtained, and after homogenizing and heat treatment, the rod is extruded to obtain a test rod. And finally, reinforcing heat treatment. Reinforced heat treatment refers to solution heat treatment, water cooling, artificial aging and the like.

The strength characteristics of such test rods are shown in Table 3.

Strength Characteristics of Extruded Rods After Complete Heat Treatment No. Tensile Strength (MPa) Yield strength (MPa) % Elongation Vickers Hardness (HV) One 410 300 18 135 2 640 560 7 195 3 650 550 8 200 4 640 540 7 190 5 Crack generation during extrusion process

The mechanical properties of the test rods were determined from cylindrical specimens (4 mm diameter) cut longitudinally by standard test methods. Table 3 shows that alloys 2 to 4 exhibit higher strength than alloy 1. Alloy 5 does not obtain strength characteristics because cracking occurs during the extrusion process. Recrystallized particles cannot be found in the structure of test rods 2 to 4 after heat treatment.

The third embodiment of the present invention takes a rolled plate using the aluminum alloy described above as an example. At this time, the test plate for the test is produced by rolling to a thickness of 1.5mm.

The test plate first obtains a flat plate of 20 mm thickness, and then rolls again after a homogeneous heat treatment process to obtain a rolled plate. Finally, heat treatment is performed. In this case, the reinforcement heat treatment refers to solution treatment, water cooling, artificial aging, and the like.

The strength characteristics of such a test rolled sheet are shown in Table 4.

Strength Characteristics of Rolled Test Plates No. Tensile Strength (MPa) % Elongation Vickers Hardness (HV) One 380 14 130 2 630 5 185 3 640 6 190 4 620 6 185 5 Crack occurrence during rolling process

The mechanical properties of the rolled sheet are measured from test pieces cut in the longitudinal axis direction by the standard test method. Table 4 shows that alloys 2 to 4 exhibit higher strength than alloy 1. In addition, the alloy No. 5 does not obtain strength characteristics because cracking occurs during the rolling process.

On the other hand, the recrystallized particles were not seen in the structures of the second to fourth plates after the heat treatment.

Hereinafter, a method for manufacturing and testing an aluminum alloy of a specific embodiment of the present invention will be described in detail so that those skilled in the art can easily practice the embodiment of the present invention.

1) Production and testing of aluminum alloy in casting state

First, 99.9% pure aluminum, magnesium, zinc, silicon and Al-Ni, Al-Fe, Al-Zr mother alloy are charged into the crucible and completely melted in an electric furnace.

Then, the crucible is taken out and poured into the molten molten metal in a steel casting (15x30x180 mm) mold to cool.

After the homogenization heat treatment (450 ℃ x 3h ⇒ 500 ℃ x 3h) and T6 heat treatment (450 ℃ x 1h solution treatment / aging 120 ℃ x 6h) to produce the cast aluminum alloy.

Then, as shown in Table 1 and Table 2, a tensile test is performed to calculate physical properties.

2) Production and testing of aluminum alloy in extruded state

First, 99.9% pure aluminum, magnesium, zinc, silicon and Al-Ni, Al-Fe, Al-Zr mother alloy are charged into the crucible and completely melted in an electric furnace.

Then, the molten molten metal is poured into a 60 mm diameter cylindrical casting to obtain a casting rod.

Thereafter, the casting rod is extruded to a diameter of 14 mm after homogenization heat treatment (450 ° C. x 3h → 500 ° C. × 3h).

After that, it is subjected to a T6 heat treatment (450 ° C x 1h solution treatment / aging treatment 120 ° C x 6h).

Then, as shown in Table 3, a tensile test is performed to calculate physical properties.

On the other hand, the tensile test piece is obtained by cutting the extrusion rod in the longitudinal axis to produce a cylindrical test piece with a diameter of 4mm.

3) Production and testing of rolled aluminum alloy

First, 99.9% pure aluminum, magnesium, zinc, silicon and Al-Ni, Al-Fe, Al-Zr mother alloy are charged into the crucible and completely melted in an electric furnace.

Thereafter, a flat plate having a thickness of 20 mm is cast using the molten molten metal.

After the homogeneous heat treatment (450 ° C. × 3h → 500 ° C. × 3h) of the cast plate, a rolling process is performed to produce a 1.5 mm thick rolled plate.

Thereafter, the mixture is subjected to a T6 heat treatment (450 ° C. × 1 h solution treatment / aging treatment 120 ° C. × 6 h).

Next, a tensile test as shown in Table 4 is carried out to obtain physical properties.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and those skilled in the art can make various modifications and adaptations within the scope of the claims. It is self-evident.

In the high strength aluminum according to the present invention as described in detail above, the following effects can be expected.

That is, an aluminum alloy which exhibits high strength and is excellent in ductility and excellent in castability is produced. Therefore, there is an advantage that can produce a product having a complex form or structure using high strength aluminum.

On the other hand, the aluminum alloy according to the present invention has a) Vickers hardness of 180 HV or more, b) tensile strength of 550 MPa or more, yield strength of 480 MPa or more, elongation 3% or more, and c) semi-processed state, tensile strength of 620 MPa or more The yield strength is higher than 530MPa and the elongation is higher than 4%.

And the present invention has the advantage that can be used as a material of products that are subjected to high stress, for example, automotive parts or leisure equipment at a temperature from room temperature to about 150 ℃.

In addition, in the present invention, while having the mechanical advantages as described above, there is an advantage that the production cost is reduced due to the low nickel content.

Claims (11)

delete delete delete delete In an aluminum alloy containing aluminum as a base material and containing zinc, magnesium, nickel, iron, zirconium and silicon in the aluminum, The aluminum is 83.1 to 91.5 weight%, The zinc is 5.5 to 8.5% by weight, The magnesium is 2 to 4% by weight, The nickel is 0.8 to 3% by weight, The iron is 0.1 to 0.8% by weight, The zirconium is 0.05 to 0.3% by weight, The silicon is 0.05 to 0.3% by weight: The aluminum alloy, A matrix formed from an aluminum solid solution and containing uniformly dispersed second phase precipitates; It has a structure comprising nickel and iron and comprising uniformly dispersed aluminide particles: The aluminide particles are 3 to 8% by volume, the aluminum alloy, characterized in that the average size of the aluminide is 6μm or less. The method of claim 5, wherein The precipitate is, Al2Mg3Zn3 and MgZn2 phases containing zinc and magnesium, which are metastable against phase change; An aluminum alloy comprising zirconium and comprising an Al 3 Zr phase that is quasi-stable against phase changes. The method of claim 6, The aluminum alloy, characterized in that the average size of the phase containing the zinc and magnesium, and the zirconium phase of the precipitate is 40nm or less. The method of claim 7, wherein The solidus temperature of the alloy is an aluminum alloy, characterized in that more than 540 ℃. The method according to any one of claims 5 to 8, The aluminum alloy, An aluminum alloy, which is cast in the form of a rolled sheet. The method according to any one of claims 5 to 8, The aluminum alloy, Aluminum alloy, which is cast in the form of an extrusion rod. The method according to any one of claims 5 to 8, The aluminum alloy, Aluminum alloy, characterized in that formed by forging.