KR102819075B1 - High strength aluminum alloy and method of manufacturing the same - Google Patents

Abstract

The present invention provides an ultra-high strength aluminum alloy plate and a method for manufacturing the same. According to one embodiment of the present invention, the ultra-high strength aluminum alloy plate contains, in wt%, zinc (Zn): 13 to 14.5%, magnesium (Mg): 2.5 to 4%, copper (Cu): 0.8 to 1.3%, scandium (Sc): 0.1 to 0.3%, zirconium (Zr): 0.1 to 0.15%, manganese (Mn): 0.05 to 0.1% and other unavoidable impurities, and satisfies a yield strength of 750 MPa or more and a tensile strength of 770 MPa or more.

Description

{High strength aluminum alloy and method of manufacturing the same}

The technical idea of the present invention relates to an aluminum alloy plate, and more specifically, to an ultra-high strength aluminum alloy plate having a yield strength of 750 MPa or more and a tensile strength of 780 MPa or more, and a method for manufacturing the same.

Recently, aluminum alloy sheets have been utilized in various industrial fields such as automobile bodies, aircraft fuselages, and UAM frames, and in particular, alloys used in the manufacture of various parts that can be utilized in the above industrial fields require very high strength and light weight due to their characteristics.

The 7000 series aluminum alloy sheets currently in use are high-strength aluminum alloys represented by Al-Zn-Mg-Cu, and have excellent mechanical properties, processing characteristics, corrosion resistance, etc. However, there is a limitation that the tensile strength can only be implemented within 700 MPa based on the current commercial alloy sheet standards, and there is a need to develop 7000 series alloy sheets with higher strength.

Meanwhile, there is a method of increasing the content of zinc, a major alloying element, and adding trace alloying elements such as zirconium and scandium to increase the strength of aluminum alloy plates. However, simply increasing the alloying elements has limitations in improving the strength. In addition, aluminum alloy plates containing the above alloying elements have a risk of being destroyed in the cold rolling stage due to rapid changes in physical properties after hot rolling.

In addition, there are casting processes such as spray casting and melt spinning for manufacturing to increase the strength of aluminum alloy plates. However, the above processes have low productivity when manufacturing bulk plates, so there are many restrictions on their application to actual bulk materials, and there are also disadvantages in terms of mass production.

Japanese Patent No. 4535731

The technical problem to be solved by the technical idea of the present invention is to provide an ultra-high strength aluminum alloy plate having a yield strength of 750 MPa or more and a tensile strength of 780 MPa or more and a method for manufacturing the same. However, this problem is exemplary, and the technical idea of the present invention is not limited thereto.

According to one aspect of the present invention, an ultra-high strength aluminum alloy plate and a method for manufacturing the same are provided.

According to one embodiment of the present invention, the ultra-high strength aluminum alloy plate contains, in wt%, zinc (Zn): 13 to 14.5%, magnesium (Mg): 2.5 to 4%, copper (Cu): 0.8 to 1.3%, scandium (Sc): 0.1 to 0.3%, zirconium (Zr): 0.1 to 0.15%, manganese (Mn): 0.05 to 0.1%, the remainder being aluminum and other unavoidable impurities, and can satisfy a yield strength of 750 MPa or more and a tensile strength of 770 MPa or more.

According to one embodiment of the present invention, the alloy contains, in wt%, zinc (Zn): 13% to 14.5%, magnesium (Mg): 2.5% to 4%, copper (Cu): 0.8% to 1.3%, scandium (Sc): 0.1% to 0.3%, zirconium (Zr): 0.1% to 0.15%, manganese (Mn): 0.05% to 0.1%, the remainder being aluminum and unavoidable impurities, and can satisfy a yield strength of 750 MPa or more and a tensile strength of 770 MPa or more.

According to one embodiment of the present invention, the content ratio of the scandium and the zirconium (weight% content of scandium/weight% content of zirconium) may be in the range of 1.0 to 3.0.

According to one embodiment of the present invention, the method may include the steps of: melting and casting an aluminum alloy including, in wt%, zinc (Zn): 13% to 14.5%, magnesium (Mg): 2.5% to 4%, copper (Cu): 0.8% to 1.3%, scandium (Sc): 0.1% to 0.3%, zirconium (Zr): 0.1% to 0.15%, manganese (Mn): 0.05% to 0.1%, and the remainder being aluminum and inevitable impurities; performing a homogenizing heat treatment on the cast aluminum alloy; hot-rolling the homogenizing heat-treated aluminum alloy to form an aluminum alloy intermediate; performing a multi-stage solution heat treatment on the aluminum alloy intermediate; cold-rolling the aluminum alloy intermediate to form an aluminum alloy plate; and aging the cold-rolled aluminum alloy plate.

According to one embodiment of the present invention, the homogenization heat treatment step can be performed at a temperature ranging from 440°C to 460°C for 3 to 24 hours.

According to one embodiment of the present invention, the hot rolling step can be performed at a temperature range of 300°C to 460°C and a reduction amount of 50% to 95%.

According to one embodiment of the present invention, the multi-stage solution heat treatment step may include a first solution heat treatment and a second solution heat treatment.

According to one embodiment of the present invention, the first solution heat treatment step can be performed at a temperature in the range of 460°C to 475°C for 1 minute to 2 hours.

According to one embodiment of the present invention, the second solution heat treatment step can be performed at a temperature in the range of 477°C to 482°C for 1 minute to 2 hours.

According to one embodiment of the present invention, after the first solution heat treatment step, the temperature increase rate for performing the second solution heat treatment step may be 0.3 to 1 °C/min.

According to one embodiment of the present invention, after the solution heat treatment step, the step of quenching the aluminum alloy intermediate material may be further included.

According to one embodiment of the present invention, the cold rolling step can be performed at a reduction of 15% to 30%.

According to one embodiment of the present invention, before the cold rolling step, the step of surface-grinding the solution-treated aluminum alloy intermediate material may be further included.

According to one embodiment of the present invention, the aging treatment step can be performed at a temperature ranging from 90°C to 110°C for 24 hours to 10 days.

According to one embodiment of the present invention, the content ratio of the scandium and the zirconium (weight% content of scandium/weight% content of zirconium) may be in the range of 1.0 to 3.0.

According to the technical idea of the present invention, the ultra-high strength aluminum alloy plate is composed of zinc, magnesium, copper, scandium, zirconium, manganese, and the remainder including aluminum and unavoidable impurities, and thus has excellent strength characteristics and can be used for automobile bodies, aircraft fuselages, UAM frames, etc.

The above ultra-high strength aluminum alloy plate can reduce the weight of the product due to the lightness unique to aluminum, and can maintain excellent strength even when continuously exposed to extreme environments, thereby increasing the lifespan of the product and significantly reducing the occurrence of defects during use. In addition, since it has superior mechanical properties compared to existing materials, it can obtain the effects of improving the lifespan and increasing productivity in corrosive environments.

The effects of the present invention described above are described as examples, and the scope of the present invention is not limited by these effects.

Figure 1 is a process flow diagram showing a method for manufacturing an ultra-high strength aluminum alloy plate according to one embodiment of the present invention.
Figure 2 is a schematic diagram showing a method for manufacturing an ultra-high strength aluminum alloy plate according to one embodiment of the present invention.
Figure 3 is a process flow diagram showing a method for manufacturing an ultra-high strength aluminum alloy plate according to another embodiment of the present invention.
Figure 4 is a schematic diagram showing a method for manufacturing an ultra-high strength aluminum alloy plate according to another embodiment of the present invention.
FIG. 5 is a transmission electron microscope photograph of an ultra-high-strength aluminum alloy plate according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those skilled in the art, and the following embodiments may be modified in various different forms, and the scope of the technical idea of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely convey the technical idea of the present invention to those skilled in the art. Like reference numerals throughout this specification denote like elements. Furthermore, various elements and areas in the drawings are schematically drawn. Therefore, the technical idea of the present invention is not limited by the relative sizes or intervals drawn in the attached drawings.

In order for aluminum alloy sheets to be used in various industrial fields such as automobile bodies, aircraft fuselages, and UAM frames, very high strength and light weight are required. Meanwhile, the tensile strength of existing commercial alloy sheets is generally implemented within 700 MPa, and as the industrial fields requiring high strength and light weight increase, their usage is limited. Therefore, a technology that can improve the yield strength and tensile strength of the existing 7xxx series aluminum alloy is required.

An ultra-high strength aluminum alloy plate according to the technical idea of the present invention can have excellent characteristics of both tensile strength and yield strength by controlling the type and range of alloy elements and performing solution treatment in multiple stages in the manufacturing process.

Therefore, the ultra-high strength Al-Zn-Mg-Cu-Sc-Zr-Mn aluminum alloy plate according to the technical idea of the present invention controls the types and contents of alloy elements as follows. In addition, by performing solution treatment in two stages after hot rolling in the manufacturing process, high strength can be achieved while limiting the amount of alloy elements added.

The above ultra-high strength aluminum alloy plate can secure high strength by adding a large amount of zinc and adding scandium, zirconium, and manganese as reinforcing elements of the above aluminum alloy plate. Automobile bodies, aircraft fuselages, and UAM frames manufactured using the above alloy have superior mechanical properties compared to existing materials, and can obtain the effects of improved service life and increased productivity in extreme environments.

Hereinafter, an ultra-high strength aluminum alloy plate, which is one aspect of the present invention, will be described.

Ultra high strength aluminum alloy sheet

The ultra-high strength aluminum alloy plate, which is one aspect of the present invention, may contain magnesium, silicon, copper, iron, manganese, chromium, zinc, titanium, vanadium, zirconium, scandium, and the remainder aluminum and other unavoidable impurities.

Specifically, the ultra-high strength aluminum alloy plate contains, in wt%, zinc (Zn): 13% to 14.5%, magnesium (Mg): 2.5% to 4%, copper (Cu): 0.8% to 1.3%, scandium (Sc): 0.1% to 0.3%, zirconium (Zr): 0.1% to 0.15%, manganese (Mn): 0.05% to 0.1%, the remainder being aluminum and unavoidable impurities, and can satisfy a yield strength of 750 MPa or more and a tensile strength of 770 MPa or more.

Regarding the above other unavoidable impurities, since unintended impurities may inevitably be mixed in from raw materials or the surrounding environment during the normal manufacturing process, this cannot be ruled out. Since these impurities can be known to anyone skilled in the normal manufacturing process, not all of the contents are specifically mentioned in this specification.

Zinc (Zn): 13 to 14.5 wt%

Zinc is an element that improves strength through solid solution strengthening and precipitation strengthening. However, in the above ultra-high strength aluminum alloy plate, if the amount of zinc added is too much, the workability of the plate may be reduced, so it is necessary to control the amount added. In particular, if the amount of zinc added exceeds 14.5 wt% of the total plate, the workability is poor, making rolling practically impossible, and the strength is reduced. On the other hand, if the amount of zinc added is less than 13 wt%, the effect of increasing the strength of the plate is minimal. For the above reasons, the amount of zinc added is limited to 13 to 14.5 wt%.

Magnesium (Mg): 2.5 to 4 wt%

Magnesium has the effect of improving strength through solid solution strengthening and precipitation strengthening.

In the above ultra-high strength aluminum alloy plate, if the magnesium addition amount is less than 2.5%, it is difficult to obtain sufficient strength. On the other hand, if the magnesium addition amount exceeds 4 wt%, the crystallites become coarse, which reduces the strength and formability. Therefore, magnesium is added in an amount of 2.5 wt% or more and 4 wt% or less.

Copper (Cu): 0.8 to 1.3 wt%

Copper can improve strength and stress corrosion cracking resistance by refining crystal grains and controlling intergranular corrosion. In the above ultra-high strength aluminum alloy plate, if the amount of copper added is less than 0.8%, the stress corrosion cracking resistance deteriorates, and the strength of the plate decreases. On the contrary, if it exceeds 1.3 wt%, the crystallites may coarsen, and the strength may decrease. Therefore, it is preferable to limit the amount of copper added to 0.8 wt% or more and 1.3 wt% or less of the entire plate.

Scandium (Sc): 0.1 to 0.3 wt%

Scandium is an element that improves the strength of aluminum alloy sheets by refining grains and strengthening precipitation. When the amount of scandium added is less than 0.1%, the amount of precipitates formed is insufficient, so the grain refinement and strengthening effects are minimal.

If scandium is added in excess of 0.3 wt%, the strength decreases due to the formation of coarse crystals, so scandium is added in an amount of 0.1 wt% or more and 0.3 wt% or less.

Zirconium (Zr): 0.1 to 0.15 wt%

Zirconium, like scandium, is an element that contributes to the strength of aluminum alloys by grain refinement and precipitation strengthening. When the amount of zirconium added is less than 0.1%, grain refinement and strengthening effects are minimal.

Meanwhile, if the amount of zirconium added exceeds 0.15%, the strength of the manufactured plate decreases due to the formation of coarse crystals, so it is preferable to add zirconium in an amount of 0.1 wt% or more and 0.15 wt% or less. In addition, the amount of zirconium added may be the same as or 1/3 or more of scandium.

Manganese (Mn): 0.05 to 0.1 wt%

Manganese is an element that acts to form fine crystal grains in aluminum alloy plates.

In the above ultra-high strength aluminum alloy plate, if the manganese content is less than 0.05 wt%, it is difficult to obtain fine grains and structures by recrystallization. On the other hand, if it exceeds 0.1 wt%, castability is drastically reduced. Therefore, in the present invention, manganese is added in an amount of 0.05 wt% or more and 0.1 wt% or less.

A high-strength aluminum alloy plate manufactured by controlling the specific components of the alloy composition described above and the content range thereof and through the manufacturing method described below can have the following characteristics.

The content ratio of the scandium and the zirconium (weight% content of scandium/weight% content of zirconium) may be in a range of 1.0 to 3.0. The weight% of the scandium may have the same content as the weight% content of the zirconium in the aluminum alloy sheet of the present invention, or may be included up to 3.0 times more.

Hereinafter, a method for manufacturing an ultra-high strength aluminum alloy plate according to the technical idea of the present invention will be described.

FIG. 1 is a process flow diagram (S100) showing a method for manufacturing an ultra-high strength aluminum alloy plate according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a method for manufacturing an ultra-high strength aluminum alloy plate according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, the method for manufacturing the ultra-high strength aluminum alloy plate (S100) includes a melt casting step (S110); a homogenization heat treatment step (S120); a hot rolling step (S130); a multi-stage solution heat treatment step (S140); a cold rolling step (S150); and an aging step (S160).

Specifically, the method for manufacturing the ultra-high-strength aluminum alloy plate (S100) comprises the steps of: melting and casting an aluminum alloy containing, in wt%, zinc (Zn): 13 to 14.5%, magnesium (Mg): 2.5 to 4%, copper (Cu): 0.8 to 1.3%, scandium (Sc): 0.1 to 0.3%, zirconium (Zr): 0.1 to 0.15%, manganese (Mn): 0.05 to 0.1%, and the remainder being aluminum and other unavoidable impurities (S110); performing a homogenization heat treatment on the cast aluminum alloy (S120); hot rolling the homogenization heat-treated aluminum alloy to form an aluminum alloy intermediate (S130); performing a multi-stage solution heat treatment on the aluminum alloy intermediate (S140); It may include a step (S150) of cold rolling the above aluminum alloy intermediate material to form an aluminum alloy plate; and a step (S160) of aging the cold-rolled aluminum alloy plate.

Melting Casting Step (S110)

The above melting and casting step (S110) may add each of the alloy elements, or may add all or part of the alloy elements in the form of a master alloy. For example, magnesium may be added to the aluminum molten metal as a pure element, or an aluminum-magnesium alloy having a high magnesium content may be added to the aluminum molten metal as a master alloy. This method may also be applied to other added elements.

The above melting and casting step (S110) can be performed at a temperature at which the aluminum alloy is completely melted. In addition, in the melting and casting step (S110), the molten aluminum alloy can be cast into a desired shape, for example, a shape such as a slab.

Homogenization heat treatment step (S120)

The above homogenizing heat treatment step (S120) can be performed at a temperature ranging from 440°C to 460°C for 3 to 24 hours. By the above homogenizing heat treatment step (S120), homogenization of alloy elements in the cast aluminum alloy can be performed.

Hot rolling stage (S130)

The hot rolling step (S130) above can be performed at a temperature range of 300°C to 460°C with a reduction of 50% to 95%. More preferably, the hot rolling step (S130) can be performed at a temperature range of 300°C to 430°C. When the temperature of the hot rolling step (S130) is less than 300°C, the processability of the aluminum alloy plate deteriorates, and when it exceeds 460°C, embrittlement occurs due to internal melting. The hot rolling step (S130) above can be performed to form an aluminum alloy intermediate material.

Multi-stage solution heat treatment step (S140)

Since the intermediate material cast within the composition range of the present invention and hot-rolled has very high strength, if the cold rolling step (S150) is performed immediately after the hot rolling step (S130), the aluminum alloy plate is broken. Therefore, the multi-stage solution heat treatment step (S140) must be performed after the hot rolling step (S130). Since the solution heat treatment step re-dissolves precipitates inside the intermediate material and lowers the strength of the intermediate material, if performed before the cold rolling step (S150), the intermediate material can be prevented from being broken.

The above multi-stage solution heat treatment step (S140) includes a first solution heat treatment and a second solution heat treatment, and the heat treatments are performed at least twice at different temperature ranges. The first solution heat treatment, which is performed first in the above multi-stage solution heat treatment step (S140), can be performed at a temperature of 460°C to 475°C for 1 minute to 2 hours. At this time, more preferably, the first solution heat treatment temperature can be performed at a temperature of 465 to 470°C for less than 1 hour. When the temperature of the first-stage solution heat treatment is less than 460°C, the solution effect is reduced, and when it exceeds 475°C, melting of internally generated phases may occur, resulting in poor characteristics.

The above second solution heat treatment is performed at a temperature range different from the temperature of the first solution heat treatment. At this time, the heating rate to reach the temperature at which the second solution heat treatment is performed is 0.3 to 1°C/min. When the heating rate is less than 0.3°C/min, internal melting is accelerated due to the increase in heating time, and when it exceeds 1°C/min, melting is accelerated due to the overheating effect, resulting in poor characteristics. More preferably, the heating temperature may be 0.5°C/min to 0.7°C/min.

After the above temperature-elevating step, the second solution heat treatment can be performed at a temperature of 470 to 482°C for 1 minute to 2 hours. When the second solution heat treatment temperature is less than 470°C, the amount of alloy elements incorporated into the matrix is insufficient, so that the strengthening effect is reduced, and when the second solution heat treatment temperature exceeds 482°C, melting of the internally generated phase occurs severely, so that the strengthening effect no longer increases.

The aluminum alloy intermediate material, for which the above multi-stage solution heat treatment has been completed, is quenched (water quenched, water cooled) to complete the solution heat treatment step (S140).

Cold rolling stage (S150)

The aluminum alloy plate can be formed by performing the cold rolling step (S150). In addition, the cold rolling step (S150) can eliminate internal defects that may occur due to partial melting in the solution heat treatment step (S140) and make the thickness of the plate uniform. The reduction amount in the cold rolling step (S150) is preferably 15 to 30%. More preferably, the reduction amount can be 20 to 28%. When the reduction amount is less than 15%, internal defects cannot be sufficiently removed during cold rolling, and when it exceeds 30%, cracks may occur during rolling.

Prescription stage (S160)

The above aging step (S160) is preferably an artificial aging maintained at 90 to 110°C for 24 hours to 10 days. If it exceeds 110°C, the strength increase effect is reduced due to over-aging, and if it is less than 90°C, the heat treatment time of the aging step (S160) increases, which is disadvantageous from a practical perspective.

In addition, FIG. 3 is a process flow diagram (S200) showing a method for manufacturing an ultra-high strength aluminum alloy plate according to another embodiment of the present invention, and FIG. 4 is a schematic diagram showing a method for manufacturing an ultra-high strength aluminum alloy plate according to another embodiment of the present invention.

In addition, FIG. 5 is a transmission electron microscope photograph of an ultra-high-strength aluminum alloy plate according to another embodiment of the present invention, in which fine precipitate phases, h'(MgZn2) and L12 (Al3(Sc,Zr)), can be observed. The presence of such precipitate phases inside can improve the strength.

Below, the same parts as the method for manufacturing an ultra-high strength aluminum alloy plate (S100) described above with reference to FIGS. 1 and 2 are omitted.

Referring to FIG. 3, the method for manufacturing the ultra-high strength aluminum alloy plate (S200) includes a melt casting step (S210); a homogenization heat treatment step (S220); a hot rolling step (S230); a multi-stage solution heat treatment step (S240); a surface grinding step (S250); a cold rolling step (S260); and an aging step (S270).

Specifically, the method for manufacturing the ultra-high strength aluminum alloy plate (S200) may further include, before the cold rolling step (S260), a step (S250) of surface-grinding the solution-treated aluminum alloy intermediate material.

Surface Grinding Step (S250)

After the solution heat treatment step (S240) is completed, the plate is maintained for less than 30 minutes to perform natural aging treatment, and then the surface grinding step (S250) of the intermediate material is performed. The reason for performing the surface grinding step (S250) is to remove a surface oxide film that may occur on the intermediate material during the solution heat treatment. If the surface grinding is not performed, an oxide film may exist on the surface of the intermediate material, which may deteriorate the mechanical properties of the final manufactured plate. The cold rolling step (S260) is performed after the surface grinding step (S250).

By performing the above-described manufacturing methods (S100 to S200), it is possible to form an ultra-high-strength aluminum alloy plate that is capable of mass production and has significantly higher strength than existing aluminum alloy rolled plates.

Experimental example

Hereinafter, preferred experimental examples are presented to help understand the present invention. However, the following experimental examples are provided only to help understand the present invention, and the present invention is not limited to the following experimental examples.

High-strength aluminum alloy plates were manufactured with the alloy compositions (unit: weight %) shown in Table 1 below. The remainder in Table 1 is aluminum (Al) and other inevitable impurities. Both the examples and comparative examples included the alloy compositions shown in Table 1.

alloy type Alloy composition (wt%) zinc magnesium copper manganese zirconium scandium Aluminum A 10.5 3.49 1.02 0.09 0.11 0.21 Bal B 11.1 3.32 0.98 0.092 0.11 0.22 Bal C 12.7 3.56 1.06 0.091 0.11 0.21 Bal D 13.3 3.72 1.04 0.058 0.11 0.22 Bal E 14.3 3.71 1.01 0.057 0.12 0.21 Bal

Referring to Table 1, it can be seen that alloy types A to C have zinc contents of less than 13%, which are outside the composition range of the present invention. Meanwhile, alloy types D and E satisfy the composition range of the present invention. Table 2 shows process condition values for forming the high-strength aluminum alloy plates of comparative examples and examples.

Referring to Table 2, it can be seen that Examples 1 and 2 of the present invention perform cold rolling after performing a two-stage solution heat treatment after hot rolling.

Meanwhile, Comparative Examples 1 to 3, Comparative Examples 6 to 8, and Comparative Examples 11 to 13 performed cold rolling immediately after hot rolling. At this time, since the aluminum alloy plate to which scandium, zirconium, and manganese are added has very high strength after hot rolling, there is a risk that the aluminum alloy plate will be destroyed if cold rolling is performed before solution heat treatment.

In addition, Comparative Examples 4 and 5 and Comparative Examples 14 and 15 do not perform cold rolling, which is different from the process for forming the aluminum alloy plate of the example of the present invention.

For Comparative Examples 16 and 17, the aging termination condition is 120°C for 24 hours, so the process conditions of the present invention are not satisfied.

Table 3 shows the mechanical properties of the ultra-high strength aluminum alloy sheets of comparative examples and examples.

division alloy type Yield strength (MPa) Tensile strength (MPa) Elongation (%) Comparative Example 1 A 677 739 8.7 Comparative Example 2 B 673 720 4.2 Comparative Example 3 C 700 742 3.4 Comparative Example 4 D 713 736 2.0 Comparative Example 5 E 721 750 2.3 Comparative Example 6 A 704 755 5.0 Comparative Example 7 B 707 739 2.9 Comparative Example 8 C 734 764 2.9 Comparative Example 9 D 738 763 2.7 Comparative Example 10 E 740 768 2.0 Comparative Example 11 A 702 749 5.5 Comparative Example 12 B 703 743 3.4 Comparative Example 13 C 713 749 2.5 Comparative Example 14 D 728 749 2.8 Comparative Example 15 E 740 767 2.1 Comparative Example 16 D 699 735 4.5 Comparative Example 17 E 715 736 4.5 Example 1 D 765 787 3.5 Example 2 E 772 788 1.7

Referring to Table 3, Examples 1 and 2 satisfying the alloy composition and process of the present invention exhibited relatively higher tensile strength and yield strength than the Comparative Examples. In addition, Examples 1 and 2 both satisfies a yield strength of 750 MPa or more and a tensile strength of 770 MPa or more. On the other hand, in cases where even one of the alloy composition and process of the present invention is not satisfied, as in Comparative Examples 1 to 17, the yield strength and tensile strength values were lower than those of the Examples. In the case of elongation, the Examples were slightly lower than the Comparative Examples.

It will be apparent to a person skilled in the art that the technical idea of the present invention described above is not limited to the above-described embodiments and the attached drawings, and that various substitutions, modifications, and changes are possible within a scope that does not depart from the technical idea of the present invention.

Claims (14)

A step of melting and casting an aluminum alloy containing, in wt%, zinc (Zn): 13% to 14.5%, magnesium (Mg): 2.5% to 4%, copper (Cu): 0.8% to 1.3%, scandium (Sc): 0.1% to 0.3%, zirconium (Zr): 0.1% to 0.15%, manganese (Mn): 0.05% to 0.1%, the remainder being aluminum and inevitable impurities;
A step of homogenizing heat treating the cast aluminum alloy;
A step of hot rolling the above homogenized heat-treated aluminum alloy to form an aluminum alloy intermediate material;
A step of performing multi-stage solution heat treatment on the above aluminum alloy intermediate material;
A step of forming an aluminum alloy plate by cold rolling the above aluminum alloy intermediate material; and
A step of aging the above cold-rolled aluminum alloy plate;
The above multi-stage solution heat treatment step is:
A first solution heat treatment step, which is maintained at a temperature ranging from 460 ^o C to 475 ^o C for 1 minute to 2 hours; and
After performing the first solution heat treatment step, a second solution heat treatment step is included, which comprises heating to a temperature in the range of 477 ^o C to 482 ^o C at a heating rate of 0.3 ^o C/min to 1 ^o C/min without cooling, maintaining the temperature in the range of 477 ^o C to 482 ^o C for 1 minute to 2 hours, and then quenching.
The above cold rolling step is performed at a reduction of 15% to 30%,
The above aging treatment step is a method for manufacturing an ultra-high strength aluminum alloy plate, which is performed at a temperature ranging from 90 ^o C to 110 ^o C for 24 hours to 10 days.
The ultra-high strength aluminum alloy plate manufactured by the above method for manufacturing the ultra-high strength aluminum alloy plate is
Satisfying a yield strength of 750 MPa or more and a tensile strength of 770 MPa or more,
Method for manufacturing ultra-high strength aluminum alloy sheet. In paragraph 1,
The content ratio of the above scandium and the above zirconium (weight% content of scandium/weight% content of zirconium) is in the range of 1.0 to 3.0.
Method for manufacturing ultra-high strength aluminum alloy sheet. In paragraph 1,
The above homogenization heat treatment step is,
Carried out at a temperature ranging from 440 ^o C to 460 ^o C for 3 to 24 hours,
Method for manufacturing ultra-high strength aluminum alloy sheet. In paragraph 1,
The above hot rolling step is,
Performed at a temperature range of 300 ^o C to 460 ^o C with a pressure reduction of 50% to 95%.
Method for manufacturing ultra-high strength aluminum alloy sheet. In paragraph 1,
Before the above cold rolling step,
A step of surface-grinding the multi-stage solution heat-treated aluminum alloy intermediate material is further included.
Method for manufacturing ultra-high strength aluminum alloy sheet. An ultra-high strength aluminum alloy plate manufactured by the method for manufacturing an ultra-high strength aluminum alloy plate according to Article 1 is
Satisfying a yield strength of 750 MPa or more and a tensile strength of 770 MPa or more,
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