JPH01242750A - Production of al base alloy and al base alloy product - Google Patents

Abstract

PURPOSE: To improve strength, corrosion resistance and fracture resistant toughness by subjecting an Al-base alloy specified in Li, Mg, Cu, Zr, etc., to hot working, solution heat treatment, etc.

CONSTITUTION: The Al-base alloy consisting, by weight %, 0.2 to 5% Li, 0.05 to 6% Mg, ≥2.45% Cu, 0.01 to 0.16% Zr, 0.05 to 12% Zn, ≤0.5% Fe, ≤0.5% Si and the balance Al is smelted. This alloy is heated and hot worked at a working temp. Next, the worked products are subjected to the soln. heat treatment, rapid cooling and aging treatment. The products which have the high strength and the excellent fracture resistant toughness and corrosion resistance and are not recrystallized are thus obtd.

COPYRIGHT: (C)1989,JPO

Description

[Detailed Description of the Invention] [Industrial Application Field] Regarding the idA/based alloy of the present invention, more specifically, the improved i
The present invention relates to a lithium-containing Al-based alloy, a product manufactured from the same, and a method for manufacturing the same.

[Conventional technology]

One of the most effective ways to reduce the total weight of aircraft in the industry is to reduce the total density of aluminum alloys used in aircraft structures. It is recognized that this is the case. In order to completely reduce the density of the alloy, lithium was added to the rice, but 7
, adding lithium to aluminum alloys is not without problems. For example, adding all lithium to an aluminum alloy often results in a decrease in ductility and fracture toughness. When used in aircraft parts, lithium-containing alloys may be used in 1. A material having both fracture toughness and strength properties is absolutely necessary.

Strength and fracture toughness are both A, A, (Aluminum Association) 202, which is commonly used in aircraft.
This is quite difficult to obtain when considering common alloys such as 4-T3X and 7050-TX. For example, A
STM (American 5OC1etyforT
Properties related to fracture toughness of materials (ent, ingand material), ASTM ATP 605, J.T. Staley, 1976, pp. 71-103, in a paper entitled "Microstructure 2 and Toughness of Sieve Strength Aluminum Alloys", 1976, pp. 71-103 It is shown that the toughness of AA2024 sheets decreases as the strength increases. It is also observed in the same paper that this is true for AA7050 plates.

Further desirable alloys allow for increased strength with or without loss of toughness, or where toughness is controlled as strength is increased to obtain a more desirable combination of strength and toughness. Such a processing step f: is such as to make it possible. In a more desirable alloy,
A combination of strength and toughness is obtained with aluminum-lithium alloys that provide density reductions on the order of 5-15%. Such alloys have wide application in the aviation shell industry where low M, high strength and high toughness mean significant fuel savings. Therefore, is it possible to obtain the quality of having great strength with little or no sacrifice in toughness, or when toughness is increased? t+lJ? This makes the aluminum-lithium alloy a very unique product.

U.S. Pat. No. 4,626.409 describes
2.9 Li, 0.5-1.0 Mg, 1-6-
2-4 Cu, 0-05-O-25Zr, O
-0,5Ti, O-0,5un, 0-0-5"
Al-based alloys consisting of s O-0-5Cr and 0-2.0 Zfl and methods for producing sheets or strips therefrom are fully disclosed. Additionally, U.S. Patent No. 4,582,5
No. 44 discloses a method for superplastically deforming an aluminum alloy having a composition similar to that of U.S. Pat. No. 4,626,409. European Patent No. 210112 contains 1-3.5% Li, up to 4% Cu, up to 5% Mg, up to 3% Zn9 and M, Cr.
and/or aluminum alloy products containing Zr additives. This alloy product is recrystallized to 300μ
have a particle size smaller than m. United States/# Rod No. 4, 6
48.913, for example, the extension of the dog value (θ
An At-base alloy fabricated alloy is disclosed that has a combination of improved nine-strength and fracture toughness when subjected to a stretch.

[Problem to be solved by the invention]

An object of the present invention is to provide a lithium-containing Al-based alloy that eliminates the drawbacks of conventional lithium-containing A/based alloys and has good performance, as well as products and manufacturing methods thereof.

[Means and operations for solving the problem] The above-mentioned objects are achieved by a further A/based alloy and its products and manufacturing methods as set forth in the claims.

Thus, according to the present invention, lithium-containing A/groups can be treated to have a high overall fracture toughness and improve strength properties, and can be treated to control the toughness value to give the desired strength. An improved product of the alloy is provided.

[Example] The alloy of the present invention has a weight of 0.2-5.0 ht Li, 0
, 5-6, OM amount 96 Mg, at least 2.45 weight ii
i%cu, 0.05-121t% Zn, 0.01-0
-14fold f%Zr, i large 0.5fold f%Fe, maximum 0.
It may contain 5% by weight Si, the balance being aluminum and resistant impurities. The impurities are preferably limited to about 0.05% by weight each, for a total of 0.65% by weight.
It is desirable not to exceed %. Within these limits, it is desirable that the sum of all impurities does not exceed 0.15% by weight.

A preferred alloy according to the present invention is 1.5-3.0 wt% Li
, 2.5-2.95% by weight Cu, 0.2-2.
5-fold f% Mg, 0.2-11 side t% Zn, 0.08
-0.12 weight f% Zr, the balance can contain aluminum and the above-mentioned impurities. Typical alloy composition is 1.8-2.5w (1% LL, 2.55-2
．． 9 weight % Cu, 0.2-2.0 weight: ft% Mg, 0.
2-2.0 heavy fi% Zn, 0.1 heavy fi% Zn, large 0.
15ff% less Zr, maximum 0.1 heavy f% Fe
and Sl.

The composition of a suitable alloy is 1.9-2.4 wt% Li;2.
55-2.9% by weight Cu, 0-1-0.6% by weight Mg
, 0,5-1-OM*% Zn, 0. [] 8-0
．． 123tJt%Zr, each containing up to 0.1mm Fe and SL.

In one embodiment of the present invention, an Al-based alloy fabricated product is provided that has a combination of improved strength, fracture toughness, and corrosion resistance. This product is provided at conditions suitable for aging (kneesong) and has the ability to produce improved strength upon aging without substantially compromising fracture toughness properties and corrosion resistance. This product is 0.2-5.
0% L50.05-6.00% Mg, at least 2.45% Cu, 0.05-0.16% Zr
, skin 05-12 weight i1% Zn, maximum 0.5 weight i% Fe
% maximum 0.5% SL, the remainder containing aluminum and resistant impurities. The product can be subjected to elongation and isometric processing effects so that after aging the product has a combination of improved strength and fracture toughness. In a method of producing an Al-based alloy product having a combination of improved strength, fracture toughness and corrosion resistance,
Lithium-containing A7? A body of base alloy is provided and can be processed to produce a fabricated aluminum product. This processed product is first subjected to a heat treatment to form m-threads, and then subjected to stretching or other stretching and isometric processing. The degree of processing, such as by stretching, is usually greater than the bond used to relieve residual quench internal stresses.

The alloy of the present invention has 0.2-5.0 wt% Li, 0-5.0
Heavy weight% Mg, Cu up to 5-0 weight%, 0-1-0 weight percent Zr, 0-2.0 weight%, 0.05-12.0 weight% Zn, up to 0.5 weight %Fe, maximum 0.5% by weight
81, the balance can include aluminum and one optional impurity. Each of these impurities is approximately 0.05% by weight.
The combination of impurities is limited to 0.15
It is desirable not to exceed the multi-layered height. Within these limits, it is desirable that the sum of all impurities does not exceed 0.352 Jt t S.

Preferred alloys according to the present invention are 0.2-5.0K (ft%
Li, at least 2.45% Cu, 0, Q 5-5
．． 00 wt% Mg, 0.05-0.16 wt% Zr
, 0.05-12.0% Zn, the balance being aluminum and the impurities described above. Typical alloy composition is 1.5-3.0 wt% LL, 2.55-2
．． 90% Cu, 0.2-2.5% Mg,
0-2-11.0% by weight Zn, 0-08-0-12% by weight Zr, 0-1.0% by weight Mn and up to 0.1% by weight each of Fej? and 5ttl-contains. In a desirable typical alloy, Zn can be in the range 0.2-2.0% and Mg can be in the range 0.2-2.0%.

In the present invention, lithium is of great importance not only because it can significantly reduce the density, but also because it significantly improves the tensile and yield strength and also improves the elasticity of heavy metals. Furthermore, the presence of lithium improves fatigue resistance.

Most significantly, however, the presence of lithium, in combination with other controlled alloy components, provides aluminum alloy products that can be processed with unique strength and durability while retaining a significant reduction in density. It is possible to provide a combination of fracture toughness.

It must be understood that obtaining a unique combination of strength and fracture toughness and significant values of corrosion resistance in addition to reduced density requires careful selection of all alloy components. For example, for every 1% increase in Lt by weight, the density of the alloy decreases by about 2.4%. Therefore, if only density is considered, the Li bond is maximized. but,
If it is desired to increase toughness at a given strength value, Cu must be added. However, for every 1% by weight of 1ccu of alloy added, the density increases by 0.87.
resistance to corrosion and stress corrosion cracking is reduced. Similarly, for every 1% by weight of Mn added, the density increases by about 0.85%. Therefore, care must be taken to eliminate the benefits of lithium due to the addition of alloying elements such as Cu and Mn. Therefore,
Although lithium is the most important component to save weight, other components are also important to obtain the correct values for strength, impurity, corrosion and stress corrosion cracking resistance.

With respect to copper, the presence of copper in the above-mentioned content ranges, especially for use in the present invention, can improve the properties of the alloy product by preserving the strength values and reducing the loss of fracture toughness. be. Thus, for example, copper is capable of providing a greater combination of toughness and strength compared to lithium in the present invention. Therefore, in the present invention,
When selecting an alloy, it is important to make the choice with respect to the desired balance of both toughness and strength. This is because both of these factors work together to provide the unique toughness and strength provided by the present invention. The above-mentioned component content ranges are particularly adhered to with regard to copper limitations. For example, excessive amounts can lead to the formation of undesirable intermetallic compounds that adversely affect fracture toughness. Typically, copper should be less than 6.0% by weight. However, in less preferred embodiments, the copper can be increased in amounts less than 4.00% by weight, preferably less than 6.5% by weight.

The combination of lithium and copper includes at least one lithium
．． The lithium spear should be 5% by weight, preferably more, and should not exceed 5.5% by weight.

Therefore, according to the present invention, by adhering to the above-mentioned content range for copper, fracture toughness, strength, resistance to corrosion and stress corrosion cracking can be maximized.

Magnesium is added to aluminum alloys of this type primarily to increase strength, although this is advantageous in that it slightly reduces density. It is also important to adhere to the above-mentioned content limits for magnesium. This is because excess magnesium can adversely affect fracture toughness, for example by forming undesirable phases, especially at grain boundaries.

Although zirconium is a desirable material for grain structure control, other grain structure control materials typically have 0.
Cr, V, Hf% Mn, T in the range of 05-0.2 double f%
Hf and Mn can typically be up to 0.6% by weight. The value of Zr used depends on whether a recrystallized or non-recrystallized structure is desired. The use of zinc produces increased strength values, especially in combination with magnesium. However, excessive amounts of zinc form intermetallic phases and degrade toughness.

Zinc is important. This is because the combination with magnesium provides an alloy with improved strength and a higher value of corrosion resistance compared to alloys without zinc.

The particularly effective benefits of zinc are as mentioned above.) Magnesium is 0.
0.1-1.0 in the range of 05-0.5% by weight
``I is within the range of quantity chi.

When Mg is in the range of 0.1-1% by weight, it is important to maintain the ratio of Mg and Zn in the range of about 1 to less than 1.0, with a preferred ratio of 0.2-1. , 9, and typical ratios are in the range of approximately 3-0.8 M
The ratio of g to Zn is Mg weight ff1-% is 1-4.0
and Zn is 0.2-2.0% by weight, preferably 0.2-2.0% by weight,
When controlled at 0.9% by weight, it can be in the range of 1-6.

Processing with a Mg/Zn ratio smaller than 1 means that in this way the processed product will be less anisotropic and the properties will not be isotropic, i.e. the properties will be more uniform in all directions. It is important in that it helps i.e. 0.2-0.8
Processing with a Mg/Zn ratio in the range of 0.05 to 0.05 makes it possible to obtain a final product with significantly reduced hot-work structure caused by rolling, giving improved properties in the 45° direction, for example.

As used herein, the term toughness or fracture toughness refers to the resistance to unstable growth of cracks or other flaws in, for example, extruded products, forgings, sheets or plate bodies.

A Mg/Zn ratio of less than 1 is important for other reasons as well. In other words, the Mg/ZnO ratio is smaller than 1,
For example, holding 0.5 VC provides significantly improved strength and fracture toughness as well as significantly improved corrosion resistance. For example, Mg and Z
When the content of n is 0.5% by weight each, the resistance to corrosion is significantly reduced. However, the Mg content is about 0.6
When the content of Zn is 0.5 wt% it, the alloy will have great resistance to corrosion.

Although the inventors do not wish to adhere to a theory of invention,
is believed to increase the resistance to stripping action and crack propagation under stress. Such properties are due to Zni:J'-C
It is believed that this is due to promoting the unsaturation of Cu from the matrix solid solution by increasing the precipitation of u-rich precipitates. This action is caused by the solution potential (5olut
ion potential) to a higher electronegative value. In addition, Zn has Mg at the grain boundary.
- Zn forms in the bearing phase, which interacts with the propagating crack to blunt the crack apex, or 1fc deflects the propagating crack;
This trap is believed to improve the overall resistance to crack propagation when loaded.

The combination of improved strength and toughness is the result of the usual inverse relationship between strength and toughness, either towards higher toughness values at a given strength value, or towards higher strength values at a given toughness value. Make a move. For example, in FIG. 3, moving from point A to point A represents a decrease in toughness that normally withstands increasing strength of the alloy. Conversely, going from point A to point BIC produces an increase in strength at the same toughness value.

Therefore, Point B is a combination of improved strength and toughness. Also, going from point A to point C results in a decrease in toughness and an increase in strength, but the combination of strength and toughness is improved compared to point A. However, with respect to point C, the toughness is improved and the strength remains approximately the same, and the combination of strength and toughness is believed to be improved. (Considering the point Bt relative to the point, the toughness is improved and the strength is reduced, but the combination of strength and toughness is still considered to be improved.

As well as providing alloy products with full control of the amounts of alloying components as described above, it is desirable to prepare the alloys by special methods to obtain the most desirable properties of both strength and fracture toughness. Accordingly, the alloys described herein may be provided as ingots or billets for producing suitable wrought products by casting techniques currently utilized for cast products, preferably continuous casting. Furthermore, the alloy is 0.64 in relation to the desired final product.
cm (0,25in) -5,08αC2in)
or can be roll cast or slab cast to a thickness of 7 m (3 in) or more.

The alloy can also be prepared as a compacted billet from fine particles, such as a powdered aluminum alloy having a composition in the range described above. Powder or particulate material is atomized,
It can be manufactured by methods such as mechanical alloying and melting. Indeno) or billets are preprocessed or shaped to form suitable stock for subsequent processing operations. Prior to the main processing operation, the alloy stock is desirably subjected to homogenization and maintained at a metal temperature in the range of 482.2-565.6°G (900-1050 raw) for at least 1 hour. The soluble components such as CuSZn and Mg are dissolved to homogenize the internal structure of the metal. The preferred time is about 20 hours or more at homogenization temperature. Typically, the heat homogenization treatment should not be extended for more than 40 hours, although longer times are usually not harmful. A time of 20-40 hours at the homogenization temperature has been found to be quite adequate.

This homogenization process, in addition to total dissolution of the components to improve processability, is important in that it is believed to deposit a Mn- and Zr-supported dispersion that helps control the final grain structure. .

After homogenization, the metal can be subjected to rolling or extrusion or other processing operations to produce stock suitable for shaping into sheets, plates or extrusions or other finished products. In order to manufacture sheet casings or plate products, the alloy body must be 2.54-6.35 to the sheet.
Tomo (0,1-0,251n), 6.35- for the board
It is preferably hot rolled to a thickness in the range of 152.4 #11 (0.25-6.0 in). For hot rolling purposes, the temperature must range from 537.8°C (1000"F) to a lower 398.9°C (750'P). The initial temperature is 454. 4-523
．． A range of 9°0 (850-975'P) is desirable.

If the intended use of the sheet product is in shoulder girders where thick sections are used, no conventional operations other than hot rolling are necessary. If the intended use is a wing or body panel requiring thin gauge dimensions, further thickness reduction operations, such as by cold rolling, are performed. Such a thickness reduction is, for example, 0.254-6.32n+(0,010-0,2
491n), usually 7.62-2.5411 (0.03
Sheet thicknesses ranging from 0 to 0,101 n) can be carried out.

After processing the alloy body to the desired thickness, the sheet or plate or other fabricated product is subjected to a solution treatment to melt the soluble components. This melting treatment is 482.
Preferably, the process is carried out at a temperature in the range of 2-565.6°C (900-1050°E?), and preferably produces grain sets ta, t- that are not recrystallized.

The solution treatment can be carried out one set at a time or continuously, and the treatment time can vary from a few hours for one set at a time to a few seconds for a continuous operation.

Basically, the solution of the alloy into a single phase region is
ionizing) is -degree metal is approximately 482.2-5
65.6°C! Reaching a solution temperature of (900-1050"F') can occur fairly quickly, e.g. in a short period of 30-60 seconds. However, heating the metal to such temperatures is Depending on the type of operation involved, this can be substantially time consuming.In the processing of each set of sheet products in a production plant, the sheets are processed in a furnace loading, bringing the entire furnace loading to the solution temperature. Therefore, solution heat treatment takes an hour or more, e.g. 1 or 2 hours for each batch of solution heat treatment.In continuous processing, the sheet It is passed continuously through an elongated furnace as a single strip, which significantly increases the heating rate.This continuous process is especially advantageous for carrying out the invention on sheet products.Why? This is because relatively rapid heating and short residence times at the solution temperature are obtained.

Therefore, the inventors of the present invention fully intended to carry out the solution treatment in a short time such as 1.0 minutes. As a further aid in obtaining short heat times, furnace or furnace zone temperatures significantly higher than the desired metal temperature provide a large temperature head that is effective in reducing the overall heat time.

In order to provide the desired strength and fracture toughness and corrosion resistance required for the final product and the operations that make the product, the product must be rapidly cooled to prevent or minimize uncontrolled precipitation of reinforcing phases as described below.

After the alloy product of the present invention is solution treated and quenched,
It can be artificially aged to obtain the combination of fracture toughness and strength that is highly desired in aircraft parts. This means that the sheet or board or any shaped product can be heated at 65.6-204.4°O (150-400°
This can be achieved by applying a temperature in the range of F') to further increase the total yield strength. 6,758 products with some composition
Artificial aging treatment can be performed up to a high yield strength of 1i/cm2 (95k81). However, the useful strength is 3.520-5.984/Cg/(m” (50-
85 ksi) and the corresponding fracture toughness for plate products is in the range of 25-75 ksi f positive.

Artificial aging treatment is applied to alloy products at least 135 minutes for at least 60 minutes.
This is done by providing a temperature in the range of -190.66°C (275-375°F'). A suitable method of carrying out the aging treatment is at a temperature of about 325°F (162.8°C) for about 8-24 hours. Additionally, it is noted that alloy articles according to the present invention may undergo any typical underaging treatments known in the art, including natural aging and multi-step aging treatments. Also, although a single aging treatment is shown here, multi-step aging treatments such as two- or three-step aging treatments can also be performed; It can be done before or even after part of the aging process.

After the solution treatment and quenching described above, the improved sheets, plates or extrusions and other processed products of about 1
,760-3,520 to 9/Cm"(25-50k'
sL ) yield strength range and approximately 5O-150ksi
It can have fracture toughness values in the range of JT. However, when artificial aging treatment is performed to improve strength,
Fracture resistance may be significantly reduced. In the past, alloy products, particularly sheets, plates or extrusions, which have been solution annealed and quenched to minimize the loss of such fracture toughness withstand improved strength, have been used at room temperature, e.g. Stretching to a value greater than 1, such as about 2-6 factors of the length of the product, or a processing effect equivalent to such stretching of more than 1 factor of the original length. It has been found that processing other than elongation 19 must be performed by deformation. The processing effects indicated herein are meant to include rolling and forging and other processing operations. For example, the strength of sheets or plates of the alloys of the present invention may be substantially increased by subjecting them to a substantial drawing process prior to artificial aging, and such drawing may only slightly reduce the fracture toughness. It has been found that it does not increase or reduce fracture toughness. It is understood that in relatively high strength alloys, stretching can significantly reduce fracture toughness. When AA7050e is expanded, the previously mentioned G.T.
This reduces both toughness and strength as shown in the paper by Starley. 2 for AA2024
Stretching of a steel increases the combination of toughness and strength over one that is not fully stretched. However, greater stretching does not provide a substantial increase in toughness. Therefore, considering the relationship between toughness and strength, it is larger than 2-chi (AA2024'
! ! - Stretching offers little advantage and A
Stretching A7050 is harmful. Conversely, when drawing or equivalent processing is combined with an artificial aging treatment, alloy products according to the invention are obtained which have a significantly increased combination of fracture toughness and strength.

Although the inventors do not necessarily wish to adhere to a theory of the invention, it is believed that deformation or processing, such as stretching imparted after solution treatment and quenching, may result in metastable precipitates containing lytecum after artificial aging treatment. It is believed that this results in a more uniform distribution of matter. Such metastable precipitates arise as a result of the introduction of a high density of defects (intracrystalline dislocations, intracrystalline vacancies, vacancy populations, etc.), which pre-drive these precipitated phases (At2CuLi phase) throughout each grain. rr which is a substance 1
It is thought that it can act as a preferential nucleation site for (such as /). Furthermore, such a method can reduce At3Li, AtLi, A at grain boundaries and subboundaries.
It is believed to inhibit the nucleation of metastable equilibrium phases such as A2CuLi and kL5cuLi3. The combination of improved uniform precipitation throughout the grains and reduced grain boundary precipitation can also be achieved by processing or deforming, e.g. by stretching, before the final aging treatment. It is believed that the combination of the observed and further increased specific strength and fracture toughness of the nine aluminum-lithium alloys is as follows.

For example, in the case of a sheet or plate, the stretching or equivalent processing is preferably 1 inch, for example about υIfc, which is greater than this and less than 14 inches. Furthermore, the extension is about 2
-10% range, e.g. 5.7-9% over the original length, although a typical increase is 5-8%.
An increase in is desirable.

If the alloy input is a roll or slab casting, the casting material has no intermediate processing or
Alternatively, the strength and fracture toughness according to the present invention can be obtained by undergoing processing equivalent to elongation or rolling with only a slight intermediate treatment.

After the alloy products of the present invention have been processed, they can be subjected to an artificial aging treatment to provide the combination of increased fracture toughness and strength that is highly desired in aircraft components.

The specific strength used here is the tensile yield strength divided by the density of the alloy. For example, plate products made of the alloy according to the invention have a weight of at least 1.907 Xl 0' kg/
Cm” 2”/9 (0,75X 106 ksi
in”/lb), preferably at least 2.03X
106Icy/an2cm”/lcg (0,80x 1
Roofing has a specific strength of 0.06 ksi in3/lb). These alloys are 2.543 x 106klj/Cm”
cm'/lie' (1,00X 106 ksi in'/
It has the ability to exhibit high specific strength such as lb).

The processed product according to the invention is characterized by the mechanical treatment used (t
hermo-mchanical process
ng) is recrystallized in relation to the form of the nen particle, 1iua
It can be provided either in the form of a grain or in a non-recrystallized grain structure. If a sheet product with a non-recrystallized grain structure is desired, the alloy is spot rolled and solution treated as described above. If it is desired to obtain a recrystallized plate product, zr is kept at a very low value, e.g. less than 0.05 g/w, and the thermomechanical treatment is carried out at about 426.7-454°C ( 800-850ff
), and the above-mentioned solution treatment is performed. For grain structures that are not recrystallized, zr is 0
．． 10 weight upwind shall be carried out, and the thermomechanical treatment shall be greater than 2.78°C/min (5 乍/min), preferably 0.56°C/min (1 乍/min).
used for solution heat treatment except for heating rates below.

If a recrystallized sheet having low Zr, e.g. less than 0.1% by weight, typically in the range of 0.05-0.08% by weight, is desired, the in-it first Approximately 5.08-12.7cm (approximately 2-5cm)
hot rolled with a slab size 21 in the range of in). After that, 371.1-454.4℃ (700-850ff
) and then hot rolled to sheet size.

After this, 260-454.4°C (500-850ff
) for 1-12 hours. The material is then cold rolled to reduce the thickness by at least 25 degrees to form a sheet product. The sheet is then solution treated as described above, rapidly cooled, stretched and aged. Zr content is approximately 0.1
In the case of large numbers, such as double fl, a recrystallized grain structure is obtained if desired. Here the impit is 42
Hot rolled at a temperature of 6.7-537.8°C (800-1000°F1) and then about 426.7-454.4°C
(800-850'F) for about 4-16 hours.

It is then cold rolled to reduce dimensions by at least 25c6. The sheet is then heated to approximately 5.56°C/min (106F/min).
If the heating rate is faster, a finer recrystallized grain structure can be obtained.
) at a fast heating rate of 510-548.9°C (
The solution annealed metal is applied at a temperature in the range of 950 to 1020 degrees. The sheet can then be quenched, stretched, and aged.

Fabricated products such as sheets, plates and forgings according to the invention, for example, produce solid precipitates along the (100) plane group. The precipitate is plate-shaped and has a diameter in the range of 50-10 angstroms and a thickness of 4-20 angstroms. This precipitate is commonly referred to as the 0P zone and is incorporated herein by reference, as published by R. J. Lloja and D. G. Rollin, Metallurgical Society Bulletin A, August 1977, Vol. 8A, No. 1257- 61, in a paper titled "Early Stages of GP Band Formation in Naturally Aged AI-4wtpct Steel Alloy".

This GP band precipitate is thought to be caused by the addition of Mg and Zn, which are thought to reduce the total solubility of Cu in the At matrix. Additionally, Mg and Zn are believed to enhance the overall nucleation of this metastable reinforcing precipitate. (100) 1 crn of precipitates on plane
The numerical density per 3 is in the range I x 10'' - 1 x 1017, with the preferred range being greater than l An aging time of 15 hours at .7°C (350 years) helps obtain great strength values without any loss in fracture toughness.

The alloys of the present invention are also useful in extrusions and forgings and have improved mechanical properties, such as those shown in FIG. Extrusions and forgings typically have some desired properties and micro ft@5
Manufactured by hot working at temperatures of 600-1000'F.

The following examples illustrate the complete history of the invention.

Example 1 The alloy of the invention in this example (Table 1) was cast into a suitable in-kit for rolling. Alloy A corresponds to AA2090, Alloy B corresponds to AA2090 plus 0.3 wt Mg, Alloy C corresponds to AA2090 plus 0.6 wt-n%
Corresponds to Mg. Alloys A, B and C were provided for comparison purposes. These inbits were then 51 for 8 hours.
537.8 for the next 24 hours at 0°C (950 Ya)
Homogenized at 1000'F, 2.54crn (
11n) to a thickness of 548.9°O (10
20'l? ) was subjected to solution treatment for 1 hour. These samples were quenched and aged. Other samples were stretched to original lengths of 2 and 6 inches at room temperature and then artificially aged. The sample that was not stretched was heated to 176.7°C (
650°F). Samples subjected to 2% and 6% stretching were aged at 162.8°C (325↑). Table 2 shows the maximum specific intensities obtained. Stretched and unstretched samples were also aged to determine corrosion performance.

EXCO (A8TM C) 34) has high strength 2 xx
This is a full immersion test designed to determine the exfoliation corrosion resistance of x and 7 XXX aluminum alloys. Table 3 shows Z
Alloys J in which the ratio of Mg to n is less than 1. Alloys J F' and G are Zn f-containing alloys (alloys A1B and C).
'E or alloy with a ratio of Mg to Zn of 1 (Alloy D
) alloys AXB, C and D have also been shown to perform well in the 4 day accelerated test. Alloy A, B
, C and D received many ratings of EC (severe exfoliation corrosion) or FD (extremely severe exfoliation). Alloy C suffered particularly severe corrosion, with all four samples receiving a gD rating after 4 days of EXCO exposure.

Conversely, alloys E5F and G were rated as more predominant lli:A (mild exfoliation) or EB (mild exfoliation).

Only one sample from these three alloys had a poor EB rating. This was a 25-hour aging treatment of Alloy E with 2-inch elongation, and was rated as ED.

This data indicates that At
-Cu-Li alloys have improved resistance to exfoliation corrosion.

Tables 5.6 and 7 list the pressed specific strength and toughness for these alloys subjected to 0.2 and 6 degrees of elongation, respectively. Figure 1 shows the properties of alloys E, F and G, which have a combination of improved corrosion resistance, strength and toughness.

Example 2 The alloy of the invention in this example
2.54 before undergoing solution treatment for 1 hour at 20'F)
cm (11n) instead of 3-81 cm (1,5in)
) was the same as that of Example 1 except that it was hot rolled into a sheet of thickness. The sample was rapidly cooled to 176.7°C (350°C).
'E? ) for 20-30 hours. (Alloys E, F and G with Mg to Zn ratios less than
None contain Zn t- (alloys A and B).

C) having a Zn to Mg ratio of 1 or 1 (Alloy D)
It had even better stress corrosion cracking resistance (8CC) than alloys A, B, C and D. The results of the stress corrosion cracking tests are listed in Table 4, which also includes a description of the test procedure.

3.5 wt% NaCt solution (ASTM G 44
) Another immersion test is commonly used to fully evaluate the stress corrosion cracking performance of high strength aluminum alloys to ASTM ( ) 47. In this table, it can be seen that alloys E, F and G have better SCC resistance than the other four alloys. This is because samples from alloys gSF and G were all 2,800 tc9/C for 30 days! It”(4
This is because they all remained in another immersion test at 0,000 pSi). One difference between these groups was the ratio of Mg to ZnK, which was less than 1 (by weight), giving greater resistance to stress corrosion.

Example 3 This sample shows that forgings made from the alloys of the present invention have an improved combination of corrosion resistance, strength and fracture toughness. An ingot was also prepared as in Example 1, identical to that of Gold Side 1 of this example. Samples were prepared from these ingots by hot extrusion and forging, and the forged samples were solution treated for 1 hour at 548.9°C (1020'P) and then heated to 176.7°C for 20-4 hours. (350'F
) Alloy E with an Mg to Zn ratio less than 1 is artificially aged.

and G are alloys that do not contain Zn (alloy A % B % '
Alloys with a Mg to Zn ratio of 1 have better resistance to stress corrosion (SCC) than alloys A, B, C and D, and alloys E, Fj? and G.
All of them were inspected alternately at 2,800 Yu/2 (40,000 psi) and found to be in good condition. The results of stress corrosion cracking are listed in. Strength and fracture toughness are shown in box 9.

Q mouth country country person four Φ Φ salt difficulty (a) Although the present invention has been described in terms of preferred embodiments, it is intended that the scope of the claims broadly encompass other embodiments that fall within the spirit of the invention. It is something.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to solve the drawbacks of conventional lithium-containing AE-based alloys by appropriately selecting constituent components and appropriately performing aging treatment in addition to acetylation treatment, cracking, and elongation treatment. This provides an excellent effect of providing a F A1-based alloy, particularly for use in aircraft, which can improve both strength and fracture toughness by eliminating this, as well as processed products and manufacturing methods thereof.

[Brief explanation of the drawing]

Figure 1 is a diagram plotting the strength and fracture toughness of the alloy according to the present invention. FIG. 2 is a diagram showing the strength plotted against the aging period of the alloy according to the present invention (in the figure, L and ST indicate the direction in which the test piece is taken; see JIS). FIG. 3 is a diagram illustrating various toughness-yield strength relationships such that moving upward and to the right indicates an improved combination of toughness-yield strengths;

Claims (10)

[Claims] (1) An Al-based alloy suitable for forming fabricated products having a combination of improved strength, corrosion resistance and fracture toughness, wherein said alloy contains 0.2-5.0 wt% Li, 0.2-5.0 wt.
05-6.00 wt% Mg, at least 2.45 wt%
Cu, 0.01-0.16 wt% Zr, 0.05-12
wt% Zn up to 0.5 wt% Fe, up to 0.5 wt%
An Al-based alloy consisting of Si, the balance being aluminum and incidental impurities. (2) The composition of the alloy meets the following limiting conditions, that is, Li is 1
．． 5-3.0 or 1.8-2.5% by weight, Mg 0.
2-2.5 or 0.2-2.0 wt%, Zn 0.2
-11 or 0.2-2.0% by weight, Zr is 0.05-
0.12% by weight, Cu is 2.55-2.90% by weight, Claim 1 having one or more of the following limiting conditions.
Alloys listed. (3) The alloy of claim 1 or 2, wherein the alloy product has a combination of improved corrosion resistance, strength and fracture strength, wherein the alloy has more than 2.45% by weight Cu; Mg-Z from 0.1 to less than 1.0 when Mg is in the range 0.1-1.0% by weight
An alloy with n ratio. (4) the product has in-plane solid plate-like precipitates;
The alloy product has a precipitate numerical density per cm^3 of at least 1.0 x 10^1^5 in the unstretched state before aging, and 1.9 x 10^9 kg/cm^2 cm^
3/kg (0.75×10^6ksi in^3/Ib
4. The product of claim 3 having a specific strength greater than ). (5) The alloy according to any one of claims 1 to 4, wherein the alloy product has solid plate-like precipitates in the plane of 1, 0, 0 groups. 6×10^1^
It has a precipitate numerical density per cm^3 in the range of 0.
An alloy having a specific tensile yield strength greater than 8 x 10^6 ksi in^3/Ib. (6) 0.2-0.9 or 0.3-0.8 Mg-Z
4. An alloy according to claim 3, having a n ratio. (7) Claim 1 in which Zr is 0.05-0.16% by weight
7. The alloy according to any one of claims 1 to 6, wherein the product is capable of producing an improved combination of strength and toughness upon aging, and the product is subjected to a working action equivalent to elongation prior to the aging step. an alloy so that after aging treatment said product has an improved combination of strength and toughness. (8) The amount is 1-14%, 1-10% or 1-8%
The alloy according to claim 7, wherein the alloy is selected from the group consisting of: (9) A method for producing an unrecrystallized aluminum-lithium fabricated product having improved values of strength, fracture toughness and corrosion resistance, comprising: (a) an Al group according to any one of claims 1 to 6; providing a lithium body containing an alloy; (b) heating said body to a processing temperature; (c) hot working said body to provide a processed product; and (d) solution-treating said product and quenching. and aging to provide a substantially unrecrystallized product having improved values of strength and fracture toughness. (10) A method of manufacturing an Al-based alloy product having a combination of improved strength, corrosion resistance and fracture toughness, comprising: (a) substantially 0.2-5.0% by weight Li, 0.05-
6.0 wt% Mg, 2.45-2.95 wt% Cu, 0
．． 05-0.12 wt% Zr, 0.05-12 wt% Z
n, a lithium-containing Al-based alloy product consisting of up to 0.5 wt% Fe, up to 0.5 wt% Si, the balance aluminum and incidental impurities is prepared, and the product is equivalent to elongation before aging treatment. (b) subjecting said product to an equivalent stretching action at room temperature before aging so that said product has an improved combination of strength and toughness after aging; A method comprising the steps of imparting a working effect so that after aging the product may have improved strength and fracture toughness in addition to corrosion resistance.