KR20170077886A - High-strength and low-density aluminum-lithium alloy and Preparation method of alloy wrought products using the same - Google Patents

Abstract

The present invention relates to a high-strength and low-density aluminum-lithium alloy and a method for manufacturing an aluminum-lithium alloy processed product using the same. In detail, a high-strength low-density aluminum-lithium alloy containing 7 to 9 wt% of magnesium and 1.5 to 2.5 wt% of lithium relative to the total alloy weight and a step (step 1) of dissolving and casting the aluminum-lithium alloy; Preparing an aluminum-lithium alloy ingot from the molten and cast aluminum-lithium alloy melt (step 2); A step (step 3) of subjecting the aluminum-lithium alloy ingot to homogenization heat treatment; And a step (step 4) of producing a work piece from the homogenized heat-treated aluminum-lithium alloy ingot. The present invention also relates to a method of manufacturing a high-strength low-density aluminum-lithium alloy workpiece.
The present invention also relates to a high-strength and low-density aluminum-lithium alloy manufactured by the above-described method and having a tensile strength of 550 MPa to 580 MPa and a density of 2.46 to 2.40 g / cm ³ . The weight of the product can be significantly reduced when the aluminum-lithium alloy processed product is used in automobiles, airplanes, trains, ships, mobile phones, notebooks, etc. since the strength of the lithium alloy is maintained or improved. There is an advantage.

Description

[0001] The present invention relates to a high-strength and low-density aluminum-lithium alloy and a method for manufacturing an aluminum-

The present invention relates to a high-strength and low-density aluminum-lithium alloy and a method for manufacturing an aluminum-lithium alloy processed product using the same.

Recently, there is an increasing demand for high-strength materials in accordance with the tendency to reduce fuel through lightening of transportation device parts. In particular, the aircraft has a very high fuel saving effect due to the weight reduction, so there has been a constant demand for high strength materials. The weight reduction of an aircraft can be made by reducing the weight of a structure such as a fuselage and a wing, so weight reduction of the material used in the structure is essential. Aluminum alloys have been used extensively as structural materials for aircraft due to their low density and excellent mechanical properties. Recently, however, new alloys with improved non-strength have been developed to further reduce aircraft weight.

Aluminum (Al), magnesium (Mg), titanium (Ti), and the like are mainly used for lightweight metal materials which have recently attracted attention. Lightweight metals and their alloys whose density is only a fraction of that of steel are new materials for aircraft and land transportation equipment that require high strength (tensile strength / density).

Aluminum has a high specific strength in spite of its low density, and it has a wide variety of alloying possibilities. Some alloys can be used at a rather high temperature, and they have good plastic workability and excellent electrical conductivity. It is a representative non-ferrous material. Accordingly, efforts have been made to manufacture an alloy having a high non-strength value by reducing the weight of aluminum as a base material and adding other elements thereto.

Among them, aluminum-lithium alloy is a typical structural material for aircraft, and has excellent strength and fatigue life, and has a lower density than other aluminum alloys. The addition of about 1% by weight of lithium relative to the total weight of the aluminum-lithium alloy reduces the density by about 3%. This low density is characteristic of aluminum-lithium alloys that do not have other aluminum alloys. Therefore, considering that material density reduction is most effective for lighter aircraft, aluminum-lithium alloy is the best material for aircraft. In addition, an aluminum-lithium alloy can obtain excellent strength by adding alloying elements such as copper and magnesium together with lithium.

A number of aluminum-lithium alloys have been developed and aluminum-lithium alloys currently used in aircraft have a tensile strength of about 500 MPa and a density of about 2.6 g / cm ³ .

In this connection, as an example of manufacturing a high-strength low-density aluminum-lithium alloy, Korean Patent Laid-Open No. 10-2003-7001508 discloses an aluminum-copper-lithium alloy having a high strength and a low density. And at least one selected from the group consisting of silicon, beryllium, magnesium, manganese, zinc, germanium, yttrium, cerium and titanium is added to an aluminum alloy containing elements selected from the group consisting of copper, lithium, zirconium, scandium, iron, magnesium and manganese. JOURNAL OF MATERIALS SCIENCE, Vol. 29, 5826-5832 (1994) discloses an alloy having a density of about 543 MPa and a tensile strength of about 2.51 g / cm ³ < / RTI >

However, as mentioned above, reducing the density while maintaining high strength is the most effective way to lighten the aircraft. Therefore, it is possible to further reduce the weight of the aircraft when ultra-low density aluminum-lithium alloy is developed. Therefore, it is necessary to develop a new alloy having a reduced density and improved strength in order to satisfy the trend of light weight of aircraft in recent years.

The present inventors have found that the aluminum containing aluminum, magnesium, lithium, manganese, zirconium and beryllium having a tensile strength of 550 to 580 MPa and a density of 2.4 to 2.46 g / cm ³ - High-strength low-density alloy with a lithium alloy and the produced alloy The present inventors have developed a method for manufacturing a processed product and completed the present invention.

Korea Patent Publication No. 10-2003-7001508

JOURNAL OF MATERIALS SCIENCE, Vol.29, 5826-5832 (1994)

It is an object of the present invention to provide a high-strength and low-density aluminum-lithium alloy and a method of manufacturing an aluminum-lithium alloy processed product using the same.

In order to achieve the above object,

A high-strength low-density aluminum-lithium alloy including 7 to 9 wt% of magnesium and 1.5 to 2.5 wt% of lithium based on the total alloy weight.

In addition,

Melting and casting the aluminum-lithium alloy (step 1);

Preparing an aluminum-lithium alloy ingot from the molten and cast aluminum-lithium alloy melt (step 2);

A step (step 3) of subjecting the aluminum-lithium alloy ingot to homogenization heat treatment; And

And a step (step 4) of producing a work piece from the homogenized heat-treated aluminum-lithium alloy ingot. The present invention also provides a method of manufacturing a high-strength low-density aluminum-lithium alloy workpiece.

Further,

A high-strength, low-density aluminum-lithium alloy manufactured by the above-described method has a tensile strength of 550 MPa to 580 MPa and a density of 2.46 to 2.40 g / cm ³ .

Further,

And a high-strength and low-density aluminum-lithium alloy processed product.

The aluminum-lithium alloy of the present invention exhibits a very light weight feature as the strength of the aluminum-lithium alloy is maintained or improved as compared with the conventional aluminum-lithium alloy. Therefore, the aluminum-lithium alloy of the present invention can be used for automobiles, aircraft, trains, ships, When used, there is an advantage that the weight of the product can be drastically reduced.

1 is a graph showing magnesium and lithium contents of Example 1, Comparative Examples 1 to 3 and a conventional aluminum-lithium alloy extrusion rod according to the present invention,
FIG. 2 is a graph showing the density and tensile strength of Example 1, Comparative Examples 1 to 3 and conventional aluminum-lithium alloy extruded rods according to the present invention,
3 is a microstructure photograph of an aluminum-lithium alloy extrusion rod according to Example 1 of the present invention.

According to the present invention,

A high-strength low-density aluminum-lithium alloy including 7 to 9 wt% of magnesium and 1.5 to 2.5 wt% of lithium based on the total alloy weight.

Hereinafter, the aluminum-lithium alloy of the present invention will be described in detail.

The aluminum-lithium alloy preferably contains magnesium in an amount of 7 to 9 wt% based on the total weight of the alloy.

The magnesium can continuously increase the strength of the material as the added amount increases. On the other hand, in order to obtain excellent strength, it is necessary to improve strength by solid solution strengthening and precipitation strengthening. However, when magnesium is added in an amount of less than 7% by weight, solid solution strengthening may occur but precipitation strengthening may not occur. On the other hand, when the magnesium content is more than 9% by weight, segregation may easily occur and hot workability may be deteriorated in the process of dissolving and casting the alloy, and magnesium is preferably contained in an amount of 7 to 9% by weight .

The aluminum-lithium alloy preferably contains 1.5 to 2.5% by weight of lithium relative to the total weight of the alloy.

The lithium may lower the density of the alloy and increase the modulus of elasticity. However, when the lithium content is less than 1% by weight, the effect of reducing the density and improving the physical properties may be insignificant. When the lithium content exceeds 2.5% by weight, dissolution and casting may be difficult due to the reactivity of lithium. Therefore, lithium is preferably contained in an amount of 1.0 to 2.5% by weight.

The aluminum-lithium alloy may further contain 0.2 to 0.35 wt% of manganese based on the total weight of the alloy.

The manganese can increase the strength of the alloy and control the grain structure. In particular, when manganese is added to the aluminum-lithium alloy containing magnesium, the strength of the alloy can be further improved. By adding the manganese to the aluminum-lithium alloy, the grain size of the alloy can be controlled and the strength can be improved. However, when the content of manganese is less than 0.2 wt%, the effect may be insignificant. When the content of manganese exceeds 0.35 wt%, the moldability may be deteriorated. It is preferable that the manganese is contained in an amount of 0.2 to 0.35% by weight.

The aluminum-lithium alloy may further include 0.05 to 0.15% by weight of zirconium based on the total weight of the alloy.

The zirconium can control the grain structure. When the zirconium is added to the aluminum-lithium alloy, an Al-Zr intermetallic compound may be generated, and the resulting Al-Zr intermetallic compound may inhibit recrystallization and interfere with the growth of the crystal grains, Can play a role. However, when zirconium is added in an amount of less than 0.05% by weight, the effect of controlling the grain structure may be insignificant. When the content of zirconium exceeds 0.15% by weight, grain refinement may not be further increased. It is preferable that zirconium is contained in an amount of 0.05 to 0.15% by weight.

The aluminum-lithium alloy may further include 0.002 to 0.005% by weight of beryllium based on the total weight of the alloy.

When beryllium dissolves an aluminum-magnesium-lithium alloy containing a large amount of reactive magnesium and a large amount of lithium element, oxidation of the alloy element can be prevented and generation of bubbles on the casting surface caused by hydrogen absorption can be suppressed. Further, there may be an effect of suppressing high temperature oxidation and high temperature brittleness of the alloy. However, if the content of beryllium is less than 0.002%, the effect of the binding element may be insignificant, and if the content of beryllium exceeds 0.005% by weight, it may be harmful to the human body. Accordingly, it is preferable that the beryllium is contained in an amount of 0.002 to 0.005% by weight.

The produced aluminum-lithium alloy includes magnesium and lithium, and contains at least one element selected from the group consisting of manganese, zirconium, and beryllium. Thus, the strength of the aluminum-lithium alloy is improved and the weight is very light It is advantageous in that the weight of the product can be drastically reduced when the above-described aluminum-lithium alloy is used in automobiles, airplanes, trains, ships, mobile phones, notebooks and the like requiring high strength and low density simultaneously .

On the other hand,

Melting and casting the aluminum-lithium alloy (step 1);

Preparing an aluminum-lithium alloy ingot from the molten and cast aluminum-lithium alloy melt (step 2);

A step (step 3) of subjecting the aluminum-lithium alloy ingot to homogenization heat treatment; And

And a step (step 4) of producing a work piece from the homogenized heat-treated aluminum-lithium alloy ingot. The present invention also provides a method of manufacturing a high-strength low-density aluminum-lithium alloy workpiece.

Hereinafter, the method for producing a high-strength and low-density aluminum-lithium alloy processed product of the present invention will be described in detail for each step.

In the method for producing a high-strength and low-density aluminum-lithium alloy processed product of the present invention, step 1 is a step of dissolving and casting the aluminum-lithium alloy.

At this time, the dissolving and casting of the step 1 may be performed in a vacuum or an inert atmosphere. Therefore, a strong oxidation reaction by lithium contained in the aluminum-lithium alloy can be suppressed.

Due to the very strong reactivity of lithium, lithium may contact with oxygen and water during dissolution and casting to cause a strong oxidation reaction. Accordingly, by dissolving and casting the aluminum-lithium alloy in a vacuum or inert gas atmosphere, the contact with oxygen and water can be restricted, and a strong oxidation reaction caused thereby can be suppressed. Also, in the case of dissolving and casting in the vacuum or inert gas atmosphere, oxidation of magnesium contained in the aluminum-lithium alloy can be prevented.

However, the atmosphere during the dissolving and casting in step 1 is not limited thereto, and may be carried out by appropriate methods and conditions to prevent the oxidation of lithium and magnesium.

In the method for producing a high-strength low-density aluminum-lithium alloy processed product of the present invention, step 2 is a step of producing an aluminum-lithium alloy ingot from the melted and casted aluminum-lithium alloy melt.

In step 2, the aluminum-lithium alloy ingot is produced from the alloy melt of step 1. The ingot of step 2 is prepared by maintaining the alloy melt at a temperature of 680 to 740 캜 and injecting it into a metal mold at 150 to 250 캜 .

If the temperature of the molten metal is lower than 680 ° C., the flowability of the molten metal is low and the ingot is difficult to manufacture. If the temperature of the molten metal exceeds 740 ° C., the molten metal is oxidized, Not only can not be produced, but also the resulting oxide can be incorporated into the ingot.

If the temperature of the mold is lower than 150 ° C., it is difficult to effectively remove moisture from the inside of the mold. If the temperature of the mold is higher than 250 ° C. The energy and time required for preheating and casting may be long, resulting in a loss in economy.

However, the production of the ingot in the step 2 is not limited to this, and can be carried out with appropriate methods and conditions to produce ingots of the desired composition from the molten metal.

In the method for producing a high-strength and low-density aluminum-lithium alloy processed product of the present invention, step 3 is a step of subjecting the aluminum-lithium alloy ingot to homogenization heat treatment.

The homogenization treatment in step 3 may be for improving inhomogeneous structure due to segregation of the alloying element occurring in the production of the ingot, and improving the extrudability and mechanical properties of the alloy.

At this time, the homogenization heat treatment may be performed at a temperature of 430 to 450 ° C. for 0.5 to 30 hours.

If the homogenization treatment is carried out at a temperature of less than 430 ° C., the content of magnesium and lithium dissolved in the matrix in the homogenization process may be low, so that the segregation may not be sufficiently removed, . Further, when the homogenization treatment is performed at a temperature exceeding 450 캜, the heat treatment temperature is higher than the solidus temperature of the aluminum-lithium alloy, so that a part of the ingot may be dissolved.

When the homogenization heat treatment is performed for less than 0.5 hour, the effect of the homogenization heat treatment may not be sufficient due to a low content of dissolved magnesium and lithium. When the homogenization heat treatment is performed for more than 30 hours, the crystal grains are greatly grown to inhibit hot workability In addition, it may be undesirable from the economic point of view as compared with the effect.

In the method for producing a high-strength low-density aluminum-lithium alloy processed product of the present invention, step 4 is a step of manufacturing a work piece from the homogenized heat-treated aluminum-lithium alloy ingot.

At this time, the workpiece can be manufactured through a rolling process.

The rolling process may be performed by hot rolling or cold rolling. For example, the hot rolling and cold rolling may be performed in parallel, but the present invention is not limited thereto, and an appropriate rolling process can be selected and used.

For example, the workpiece may be a plate, and the plate may be manufactured by subjecting the ingot after completion of the homogenization treatment to hot rolling at 300 to 400 캜, followed by cold rolling. If the temperature of the hot rolling is less than 300 ° C, the rolling load is increased to shorten the lifetime of the rolling roll and cause defects of the rolled plate. If the temperature of the hot rolling exceeds 400 ° C, The phases inside the alloy may melt and cracks may occur.

In addition, the processed product can be produced through an extrusion process.

The extrusion may be carried out by using an extruding process such as an indicative extrusion process, a direct extrusion process, a hydrostatic extrusion process, a lateral or side extrusion process, an impact extrusion process, etc. And may be performed by, for example, indirect extrusion. However, the present invention is not limited thereto and may be performed by selecting an appropriate extrusion process.

At this time, the workpiece manufactured through the extrusion process may be, for example, in the form of a rod. After the homogenized ingot is preheated at 300 to 400 ° C, extrusion is carried out at an outlet speed of 300 to 3000 mm / min . At this time, if the preheating temperature for the extrusion is less than 300 ° C, the extrusion load is increased to shorten the life of the extrusion die, and furthermore, defects may occur in the workpieces. If the preheating temperature is higher than 400 ° C, the phases in the alloy may melt during the extrusion and cracks may occur.

If the outlet speed is less than 300 mm / min, the productivity may be significantly lowered. If the outlet speed exceeds 3000 mm / min, the extrusion may not be performed smoothly due to excessive extrusion load and machining heat generation. And the surface quality of the extruded product may be deteriorated.

On the other hand, in the method for manufacturing a high-strength and low-density aluminum-lithium alloy processed product of the present invention, after the step of manufacturing the processed product of step 4, the process may further include a solution heat treatment and an aging heat treatment.

When the solution heat treatment and the aging heat treatment are performed, a fine precipitate phase in the form of Al-Mg-Li can be produced and the strength of the workpiece can be improved due to the precipitated phase.

At this time, it is preferable that the solution heat treatment is performed at a temperature of 430 to 450 ° C. If the solution heat treatment is carried out at a temperature of less than 430 캜, magnesium or lithium may not sufficiently dissolve in the matrix, and if carried out at a temperature exceeding 450 캜, Cracking of the material may occur due to melting phenomenon on the melting point.

The aging heat treatment is preferably performed at a temperature of 120 to 170 ° C. If the aging heat treatment is carried out at a temperature of less than 120 ° C, the formation of precipitate phase may not be sufficient to improve the strength of the workpiece, and if carried out at a temperature in excess of 170 ° C, The strengthening effect can be reduced.

On the other hand,

A high strength, low density aluminum-lithium alloy manufactured by the above method and having a tensile strength of 550 MPa to 580 MPa and a density of 2.46 to 2.40 g / cm ³ is provided.

As mentioned above, a lightweight material such as an aluminum-lithium alloy has been attracting attention in order to improve the fuel efficiency by reducing the weight of the transportation device parts. As shown in Table 1, in the commercial aluminum-lithium alloy developed to date, the lowest density alloy 1420 has a density of about 2.47 g / cm < 2 > ³ , and the tensile strength is somewhat lower than 450 MPa.

Kinds

Composition (% by weight)
density
(g / cm ³⁾
The tensile strength
(MPa)
Nasal cavity
(Tensile strength / density)
Mg
Li
Cu
Mn
Zr
Zn 1420 4.5
~ 6.0 1.8
~ 2.2 0.08
~ 0.15
2.47
450
182.2 8090 0.6
~ 1.3 2.2
~ 2.7 1.0
~ 1.6 ≪ 0.1 0.04
~ 0.16
<0.15
2.54
510
300.8 2090

<0.25
1.9 ~
2.4
&Lt; 0.05
0.08 ~
&Lt; 0.1
2.59
550
212.4 2099
0.1
~ 0.5 1.6
~ 2.0 2.4
~ 3.0 0.1
~ 0.5 0.05
~ 0.12 0.4
~ 1.0
2.63
545
207.2

However, it is the most effective way to reduce the density while maintaining high strength for the light weight of the aircraft. Therefore, when the ultra-low density aluminum-lithium alloy is developed, it is possible to further reduce the weight of the aircraft. Accordingly, in the present invention, a high-strength and low-density aluminum-lithium alloy for improving the density and tensile strength characteristics of the conventional aluminum-lithium was prepared. The aluminum-lithium alloy processed product of the present invention manufactured using the alloy had 550 MPa A tensile strength of 580 MPa and a density of 2.46 to 2.40 g / cm &lt; ³ &gt; and can be used in place of a material for airplane weight reduction.

In addition,

And a high-strength and low-density aluminum-lithium alloy processed product.

As described above, although the mechanical characteristics of high strength are required for the parts of transportation equipment, for example, parts for automobiles, it is necessary to improve the fuel efficiency by weight reduction. In addition to high mechanical strength, Is increasing significantly.

At this time, the aluminum-lithium alloy processed product of the present invention can exhibit characteristics of high strength and low density as a lightweight material, and the transportation equipment parts of the present invention including the same also have an advantage of meeting the recent lightweight atmosphere while exhibiting high strength characteristics .

At this time, the transportation device parts include a car frame, a railway car body, and the like, but the transportation device parts of the present invention are not limited thereto.

Hereinafter, the present invention will be described in detail by way of examples. However, the following examples are illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

&Lt; Example 1 > Preparation of aluminum-lithium alloy processed product (1)

In order to produce the aluminum-lithium alloy processed product of the present invention, an aluminum-alloy extruded material was produced through the following steps.

Step 1: Dissolve and dissolve pure aluminum (99.8%), pure magnesium (99.8%), pure lithium (99.95%), aluminum-15 wt.% Manganese alloy, aluminum-10 wt.% Zirconium alloy, Casting. At this time, argon (Ar) gas was applied to the top of the molten metal in order to prevent oxidation and melting of the molten and cast molten metal.

Step 2: The molten and cast molten metal was maintained at a temperature of 700 캜, and an aluminum-magnesium-lithium-manganese-zirconium-beryllium alloy ingot was prepared using a steel mold preheated to 200 캜.

Step 3: The ingot was homogenized at 440 캜 for 24 hours and then air-cooled.

Step 4: The homogenized heat-treated aluminum-lithium alloy ingot was extruded using an indirect extruder having a maximum pressure output of 500 tonf. The extrusion conditions were an initial ingot temperature of 350 ° C, an extrusion ratio of 16: 1, and a ram speed of 1.0 mm / sec, and extruded into a rod having a diameter of 20 mm.

Step 5: The extruded extruded material was subjected to solution heat treatment at 440 ° C for 1 hour, then cooled, and aged heat treatment was performed at 150 ° C for 8 hours.

Example 2 Preparation of Aluminum-Lithium Alloy Finished Product (2)

In order to produce the aluminum-lithium alloy processed product according to the present invention, the aluminum-lithium alloy extruded material was produced by the same method except that the step 5 was not carried out in the above-mentioned Example 1.

&Lt; Comparative Example 1 > Manufacture of aluminum-lithium alloy processed product

In order to manufacture an aluminum-lithium alloy having different magnesium contents according to the present invention, aluminum-lithium alloy was produced by using pure aluminum (99.8%), pure magnesium (99.8%), pure lithium (99.95% After the lithium alloy was produced, an extruded material was produced in the same manner as in Example 1.

&Lt; Comparative Example 2 > Manufacture of aluminum-magnesium alloy processed product

In order to produce an aluminum-magnesium alloy having the same magnesium content and no other components, pure aluminum (99.8%) and pure magnesium (99.8%) were used, and aluminum containing 7.8% magnesium -Magnesium alloy, an extruded material was prepared in the same manner as in Example 1. [

&Lt; Comparative Example 3 > Manufacture of aluminum-copper-lithium alloy processed product

(99.8%), pure magnesium (99.8%), pure lithium (99.95%), aluminum-39.5 wt% copper alloy, pure silver (99%), aluminum- After the aluminum-copper-lithium-magnesium-silver-zirconium alloy was prepared using a 10 wt% zirconium alloy, an extruded material was prepared in the same manner as in Example 1.

<Experimental Example 1>

In order to confirm the composition of the aluminum-lithium alloy produced in accordance with the present invention and the aluminum alloy prepared for comparison, the aluminum-lithium alloy extruded material produced in Example 1 and the aluminum alloy extruded material prepared in Comparative Examples 1 to 3 , The following experiment was conducted.

The composition of the extruded material prepared in Example 1 and Comparative Examples 1 to 3 was analyzed using an inductively coupled plasma mass spectrometer (ICP, Inductively Coupled Plasma). The results are shown in Table 2 and FIG.

Furtherance
(weight%) density
(g / cm ³⁾ The tensile strength
(MPa) (The tensile strength
/density) Mg Li Cu Mn Zr Ag Be
Example 1

8.12
2.20
0.005
0.25
0.12
-
0.003
2.440
568
232.8
Comparative Example 1

5.01
1.61
0.03
0.002
0.13
-
-
2.514
350
139.2
Comparative Example 2

7.8
-
-
-
-
-
-
2.601
335
128.8
Comparative Example 3

0.42
0.98
3.8
0.002
0.13
0.41
-
2.712
512
188.8

As shown in Table 2 and FIG. 1, it can be seen that the aluminum-lithium alloy extruded material produced by Example 1 had a magnesium content of 8.12 wt% and a lithium content of 2.2 wt% based on the total alloy weight , And in the case of Comparative Example 1, the magnesium content was 5.01% by weight and the lithium content was 1.61% by weight, which is outside the magnesium content and lithium content range of the present invention. In the case of Comparative Example 2, it is understood that the aluminum-magnesium alloy contains 7.8% by weight of magnesium, and in Comparative Example 3, the aluminum-copper-lithium alloy contains 3.8% by weight of copper.

<Experimental Example 2>

In order to confirm the microstructure of the aluminum-lithium alloy produced according to the present invention, the following experiment was conducted on the aluminum-lithium alloy extruded material produced by Example 1.

The microstructure of the extruded material prepared in Example 1 was observed by scanning electron microscopy and the results are shown in FIG.

As shown in FIG. 3, the surface of the aluminum-lithium alloy extruded material produced according to Example 1 of the present invention was observed to be fine and the crystal grains were miniaturized and no anisotropy was observed. As a result, it can be expected that the strength of the aluminum-lithium alloy extruded material produced according to Example 1 is high.

<Experimental Example 3>

In order to compare the density of the aluminum-lithium alloy manufactured according to the present invention with that of the conventional aluminum alloy, the aluminum-lithium alloy extruded material produced in Example 1 and the aluminum alloy extruded material produced in Comparative Examples 1 to 3 The following experiment was carried out.

The density of the extruded material prepared in Example 1 and Comparative Examples 1 to 3 was measured using the Archimedes method. The results are shown in Table 2 above.

As shown in Table 2, the aluminum-lithium alloy prepared according to Example 1 of the present invention has a very low density of 2.440 g / cm &lt; ³ &gt;. It can be seen that this shows a lower density value than the conventional aluminum-lithium alloy.

<Experimental Example 4>

In order to compare the tensile strengths of the aluminum-lithium alloy produced in accordance with the present invention and the conventional aluminum alloy, the aluminum-lithium alloy extruded material produced in Example 1 and the aluminum alloy extruded material produced in Comparative Examples 1 to 3 , The following experiment was conducted.

In order to measure the tensile strength of the extruded material produced in Example 1 and Comparative Examples 1 to 3, a rod-like tensile specimen having a gauge length of 25 mm and a gauge diameter of 6 mm was prepared and subjected to a tensile test at a crosshead speed of 1.5 mm / The test was performed. At this time, three tensile tests were performed on each alloy, and the results are shown in Table 2 and FIG.

As shown in Table 2, the aluminum-lithium alloy produced according to Example 1 of the present invention had a very high tensile strength of 568 MPa and a non-strength (tensile strength / density) of 232.8 MPa. It is understood that the value is high. It can be seen that this shows relatively excellent strength characteristics as compared with Comparative Examples 1 to 3.

2, the aluminum-lithium alloy extruded material produced according to Example 1 of the present invention had a very high tensile strength / density value as compared with the conventional aluminum-lithium alloy and Comparative Examples 1 to 3 . As a result, the strength of the aluminum-lithium alloy of the present invention is improved compared with that of the conventional aluminum-lithium alloy, so that the weight of the aluminum-lithium alloy is remarkably light. The weight of the product can be drastically reduced.

Claims (15)

A high strength, low density aluminum-lithium alloy comprising 7 to 9 wt% magnesium and 1.5 to 2.5 wt% lithium relative to the total alloy weight.
The aluminum-lithium alloy according to claim 1, wherein the aluminum-lithium alloy further comprises 0.2 to 0.35% by weight of manganese.
The aluminum-lithium alloy according to claim 1, wherein the aluminum-lithium alloy further comprises 0.05 to 0.15% by weight of zirconium.
The aluminum-lithium alloy according to claim 1, wherein the aluminum-lithium alloy further comprises 0.002 to 0.005% by weight of beryllium.
Dissolving and casting the aluminum-lithium alloy of claim 1 (step 1);
Preparing an aluminum-lithium alloy ingot from the molten and cast aluminum-lithium alloy melt (step 2);
A step (step 3) of subjecting the aluminum-lithium alloy ingot to homogenization heat treatment; And
And a step (step 4) of producing a work piece from the homogenized heat-treated aluminum-lithium alloy ingot.
6. The method of claim 5, wherein the dissolving and casting of step 1 is performed in a vacuum or inert atmosphere.
6. The method of claim 5, wherein the homogenizing heat treatment in step 3 is performed at 430 to 450 DEG C for 0.5 to 30 hours.
6. The method of claim 5, wherein the workpiece of step 4 is manufactured by a rolling or extrusion process.
9. The method of claim 8, wherein the rolling is performed by cold rolling after hot rolling at 300 to 400 占 폚.
9. The method of claim 8, wherein the extrusion is performed at an outlet speed of 300 to 3000 mm / min after preheating at 300 to 400 &lt; 0 &gt; C.
6. The method of claim 5, further comprising the step of performing a solution heat treatment and an aging heat treatment on the workpiece after step (4).
12. The method of claim 11, wherein the solution heat treatment is performed at a temperature of 430 to 450 &lt; 0 &gt; C.
12. The method of claim 11, wherein the aging heat treatment is performed at a temperature of 120-170 &lt; 0 &gt; C.
5. A high strength, low density aluminum-lithium alloy article produced by the method of claim 5 and having a tensile strength of 550 MPa to 580 MPa and a density of 2.46 to 2.40 g / cm &lt; ³ &gt;.
A transport device part comprising the high strength, low density aluminum-lithium alloy article of claim 14.

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