JPS60211034A - Alminium-lithium alloy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an aluminum-lithium alloy, and more particularly to an aluminum-lithium alloy that has both high fracture toughness and strength.

BACKGROUND OF THE INVENTION Current large commercial transport aircraft are estimated to have an annual fuel savings of 1251 to 167 f/kg (15 to 20 gallons per pound) of fuel abated during aircraft manufacture. Over the life of the aircraft, which is 20 years of service, this fuel savings per unit weight is between 2500 J and 33
404! It also becomes.

At current fuel prices, meaningful investments in reducing aircraft structural weight can improve the overall economic efficiency of aircraft.

What is needed to improve performance in various types of aircraft is:
This is accomplished through improved engines, improved airframe designs, and improved or new structural metals used in the aircraft. Improvements in engine and airframe design have generally pushed the limits of these technologies. However, the development of new and improved structural metals is now of great interest and is expected to yield further benefits in performance.

Materials have always played an important role in the mission of aircraft structural concepts. In the early part of this century, the airframe structure was made of wood, primarily pine (SprLIOe), and other fabrics. Due to the lack of pine in use in the early part of this century, lightweight metal alloys began to be used as structural materials for aircraft. At about the same time, design improvements led to the development of all-metal cantilever wings. However, it was not until the 1930s that metal-coated wings became the standard and metals, mainly aluminum alloys, became firmly established as the main structural metal of aircraft. From this time onwards, aircraft structural metals consisted of aluminum structural metals, which were mainly used for wings, fuselages and tails, and steel for landing gear and other special parts where particularly high strength materials were required. It has remained very consistent in its use as a material.

Several new materials are currently being developed for incorporation into aircraft structures. These materials include new metal materials, metal matrix composites and resin matrix composites. It is believed that improved aluminum alloys and carbon fiber composites will predominate as aircraft structural materials in the next decade. While composites will be used to an increasing extent as structural materials in aircraft, new lightweight aluminum alloys, and in particular aluminum-lithium alloys, are showing great promise in expanding the use of aluminum alloys.

Up to now, aluminum-lithium alloys have only been used sparingly in aircraft construction.

The reason why it was so sparsely used was that it was difficult to cast, which is unique to aluminum-lithium alloys, and that it had lower fracture toughness than other ordinary aluminum alloys. However, aluminum-lithium alloy has a considerably lower density than aluminum alloy (its strength to weight ratio is quite high),
This has been found to be of great importance in reducing the overall weight of structural materials used in aircraft.

Although improvements in aluminum-lithium processing technology have been made fairly rapidly, the main challenge remains in achieving a good combination of fracture toughness and high strength in aluminum-lithium alloys.

Mu'11 Momme IL The present invention has high strength and good toughness against fracture,
Moreover, the novel aluminum alloy has a composition that can be processed and heat treated to provide an aluminum-lithium alloy that has a relatively low density compared to the conventional 2000 series aluminum alloys that this invention is intended to replace. provide. The alloy prepared according to the present invention comprises: 2.
45% by weight lithium, 0.6% by weight magnesium,
It has a standard composition of 1.8% by weight copper and 0.122 weight % zirconium. By aging this alloy at low temperatures, an excellent combination of fracture toughness and high strength can be achieved.

20 DESCRIPTION OF THE INVENTION The aluminum-lithium alloy compositions of the present invention contain about 2.2 to about 2.8 weight percent lithium and 0.2 to 0.8 weight percent lithium.
It can contain 1j5 to 2.1% by weight of copper, and up to 0.15% by weight of zirconium as particle refining element.

Preferably 0.1 to 0.15% by weight of zirconium is incorporated. All percentages herein are weight percentages based on the total weight of the alloy, unless otherwise specified. Magnesium in the alloy serves to increase strength and slightly reduce density. This also increases the strength of the solid solution. Copper increases the strength of the alloy. Zirconium acts as a preferred particle refining element.

Iron and silicon may be present in amounts up to a total of 0.3% by weight. Preferably, these elements are present only as minute elements, with iron being limited to a maximum of 0.15% by weight and silicon to a maximum of 0.12% by weight, and each containing 0.1% by weight.
More preferably, it is 0% by weight and 0.10% by weight or less. The total number of microelements such as zinc is 0.
It may be present in amounts up to and not exceeding 25% by weight. 0.05 for other elements like chromium and manganese
% by weight or less.

If the maximum limits of these microelements are exceeded, the desirable properties of the aluminum-lithium alloy tend to deteriorate. Lithium and hydrogen, which are considered microelements, are also thought to be detrimental to the properties of aluminum-lithium alloys (particularly their fracture toughness); for example, for lithium,
~0.0030% by weight) and 15% for hydrogen.
In particular, it must be maintained at the lowest achievable level, such as below 111)I (0,0015% by weight), preferably below 1.0DI)l (0,0001% by weight).

Of course, the remainder of the alloy consists of aluminum.

Aluminum-lithium alloys of the composition described above are made into products by known techniques.

This alloy is brought to a molten state and cast into ingots.

This ingot is then heated to 493°C to 536°C (925'F
Homogenization treatment is carried out at a temperature in the range of ~1000K). This alloy is then formed into products for use by conventional mechanical forming techniques such as rolling or extrusion. When the product is formed in this way, the alloy is typically 4
Solution heat treated at temperatures ranging from 96°C to 538°C (below 925°F to i ooo) and 21°C to 66°C (70
It is quenched in a quenching agent, such as water, which is maintained at a temperature on the order of 150°F (below 150°F). If the alloy is rolled or extruded, it is generally stretched to about 1-3% of its original length to relieve internal stresses.

This aluminum alloy is then further processed and formed into various shapes to provide the final product. Still other heat treatments, such as solution heat treatments, can be performed if desired. For example, extruded products are cut at 524°C (97°C) to the desired length.
Solution heat treatment is performed at temperatures on the order of 5° F. for 1 to 4 hours.

The product is then quenched in a quench agent maintained at a concentration on the order of 70'F to 150'F.

Thereafter, according to the invention, the product is preferably subjected to an aging treatment, which increases the strength while maintaining the fracture toughness and other properties of the material at a relatively high level. According to the present invention, from about 93°C to about 149°C (
The product is subjected to a low temperature aging heat treatment at a temperature ranging from about 200 ℃ below to about 300 ℃ below. This alloy is approximately 121℃~13
Preferably, the heat treatment is carried out at a temperature range of 5° C. (250° C. below to 275° F.). At higher temperatures, it takes less time to achieve a suitable balance between strength and fracture toughness than at lower aging temperatures, but results in a slightly worse overall balance of properties. . For example, when aging is performed at a temperature of about 135°C to 149°C (275°C to 300°C), the aging treatment is performed for 1 to 40 hours. ! Preferably, the temperature is maintained. On the other hand, 1
When aged at temperatures around 21°C (below 250°C) or lower, aging for 2 to 80 hours or more is required to obtain a suitable balance between fracture toughness and strength. is preferred. After aging, the aluminum-lithium alloy product is cooled to room temperature.

When low-temperature aging treatment is performed according to the above explanation, the aluminum-lithium alloy becomes 45.7 to 49.2 kg/nun2 (65
70 ksi). However, the fracture toughness of this material is about 1.5 to 2 times that of a similar aluminum-lithium alloy that has undergone conventional aging treatment at temperatures above 149 degrees Celsius (below 300 degrees Celsius). . The superior strength and toughness balance achieved with the low-temperature aging technique of the present invention also makes it surprising that the class of aluminum-lithium alloys with which it is subjected to standard aging resists stress corrosion. - The goal is to do things in a way that shows improved compliance. Examples that can guarantee examples of these improved characteristics will be described in more detail.

Color, 1i1 The following examples are given to demonstrate the superior properties of aluminum-lithium alloys aged according to the present invention and to assist those skilled in the art in making and utilizing the present invention. Furthermore, they are intended to demonstrate significantly improved and also unexpected properties of aluminum-lithium alloys composed and produced according to the parameters of the present invention.

The following examples are not intended to limit the scope of this description or patent protection.

An aluminum alloy was composed containing 2.4% by weight lithium, 0.6% by weight magnesium, 1.8% by weight copper, 0.15% by weight zirconium, with the balance being aluminum. The alloy composed in this way contains 0.25% or less of microelements as a whole. Iron and silicon are each contained in an amount of less than 0.07% by weight in this alloy composition. This alloy was cast at 524℃
(975 lower) was subjected to homogenization treatment. This alloy was then tyrol milled to a thickness of 5.08 m (10.2 in). The sheet material made in this way is then heated to 524℃ (
975°F) for 1 hour.

This was followed by quenching in water maintained at approximately 21°C (70"F). The sheet material was then quenched by 1.5% of its initial length.
was stretched and cut into specimens. These test pieces were 12.7 im (0.5 in) x 6.35 in order to be subjected to a Charpy impact test with a clutch attached in advance, which is one method of measuring fracture toughness.
Cut to size mg+(2,5ii) x 5,08ve (0,2in). The test pieces used for the tensile strength test are 2
5.4si(lin)×101.611m(4in)×
5.08 am (0.2 In). The specimens were then heated at 135°C (below 275°C) for 16 hours and 40 hours.
They were then aged at 121°C (250°F) for 40 hours and 72 hours, respectively. Each aged specimen at each temperature and time was subjected to tensile strength and pre-cracked Charpy impact tests according to standard test procedures.

The maximum strength after aging at 135℃ (below 275) is 45
．． Specimens ranging from 7 to 49.2 kMu+2 (65 to 70 ksi) are 116 to 134 cm-k Mca2 (6
It had a toughness of about 50 to 750 in-1 b /in2). Maximum strength aged at 121°C (250'F) is 43.5-45.7ka/gv2 (62
~65 ksi) range of 134 to 152 c
m-ka/cs2 (750-850in-Ib/1n
It showed toughness in the range of 2). 149℃ (300”F)
The toughness of a specimen of the same material with the same maximum strength aged at a higher temperature is approximately 80.4 cm-ko/ci2
(450 in-lb/in2) or less, and is compared with this.

The invention has been described with reference to various embodiments including preferred compositions and processing parameters. After reading the foregoing description, those skilled in the art will be able to make various changes, substitutions of equivalent methods, and other modifications without departing from the broad concepts described herein. It is therefore intended that the scope of the patented invention be limited by the limitations recited in the claims appended hereto and the like.

Agent Asamura Hajime

Claims (10)

[Claims] (1) An aluminum-lithium alloy with excellent fracture toughness, with the following elements: Lithium 2.2-2.8 Magnesium 0.2-0.8 Copper 1,5-2.1 Zirconium 0 .1 to 0.15 Iron max. 0.15 Silicon max. 0.12 Other trace elements max. 0.25 Aluminum-lithium alloy with the balance being aluminum. 2. The alloy of claim 1, wherein said zirconium is present in an amount up to about 0.10 I% by weight. (3) 2.45 wt% lithium, 0.6 wt% magnesium, 1.8 wt% copper, and 0.12 wt%
2. The alloy according to claim 1, wherein the reference composition is zirconium. (4) The alloy according to claim 1, wherein the alloy has been subjected to an aging treatment at a relatively low temperature for a relatively long time. (5) The alloy has a temperature of 93°C to 149°C (below 200°C to 30°C
An alloy according to claim 1 which has been subjected to an aging treatment at a concentration in the range of 0''F). 6. The alloy of claim 5, wherein said alloy is aged for at least one hour. (7) The alloy of claim 1, wherein the alloy is aged at a temperature of 135°C (275'F) or less. 8. The alloy of claim 7, wherein said alloy is aged for at least 2 hours. (9) The alloy of claim 1, wherein the alloy is aged at a temperature of 121°C (250'F) or less. 10. The alloy of claim 9, wherein said alloy is aged for at least 4 hours.