JPS60211035A - Aluminum-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 The present invention relates to an aluminum-lithium alloy, and more particularly to an aluminum-lithium alloy having both high fracture toughness and high strength.

Current large commercial transport aircraft are expected to save 1251-167J1 (15-20 gallons per bond) of fuel per year for each kilogram of weight saved in the aircraft's manufacture. ing. Over the life of the aircraft, which is 20 years of use, this fuel savings per unit weight is 250,041~
It also becomes 334ON.

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 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, airframe structures were made of wood, primarily spruce, and other fabrics.Due to the lack of pine in use in the early part of this century, lightweight metal alloys were used as structural materials for aircraft. At about the same time, design improvements led to the development of all-metal cantilevers. However,
It was after 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 composite materials 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, the aluminum-lithium alloy has a much lower density than the 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 unresolved challenge remains in achieving a good combination of fracture toughness and high strength in aluminum-lithium alloys.

8-”11 sides JLL The present invention has high strength and good toughness against fracture,
Moreover, the present invention provides a novel aluminum alloy of composition that can be processed and heat treated to provide an aluminum-lithium alloy having a relatively low density compared to the conventional aluminum alloys that the present invention is intended to replace. The alloy prepared according to the invention has a base composition of 2.2% by weight lithium, 0.7% by weight magnesium, 2.5% by weight copper, and 0.12% by weight zirconium. By aging this alloy at low temperatures, an excellent combination of fracture toughness and high strength can be achieved.

21 Description of the Invention Aluminum-lithium alloys composed in accordance with the present invention contain about 2.2 to about 2.4 weight percent lithium, O to 0.9 weight percent magnesium, and 2.3 to 2.7 weight percent It can contain copper and up to 0.15% by weight of zirconium as a particle refining element.

Preferably o,io to 15% by weight of zirconium is incorporated. All percentages herein are weight percentages based on the total weight of the alloy, unless otherwise specified. Although the alloy need not contain magnesium, it is preferred to include magnesium to increase strength without increasing density. Magnesium also increases the strength of the solid solution. The preferred amount of magnesium is 0.5-0.9
% by weight, and 0.7% by weight is more preferable. Copper increases the strength of the alloy.

Iron and silicon may be present in amounts up to a total of 0.3 weight percent. 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 having a maximum of 0.
．． More preferred are 10% and 0.10% by weight. 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.

Sodium and hydrogen, which are considered microelements, are also thought to be detrimental to the properties of aluminum-lithium alloys (particularly their fracture toughness);
5-3oppi (0,0015-0.0030% by weight
) and 15 ppm (0,001
5% by weight) or less, preferably 1.0f) pH (0,00
01% by weight) must be maintained at the lowest achievable level, such as: Of course, the rest of the alloy is made 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 493°C~536'C (925'C)
The homogenization process is carried out at temperatures ranging from below to 1000'F. This alloy is then formed into products for use by conventional mechanical forming techniques such as rolling or extrusion. Once the product is thus formed, the alloy is typically solution annealed at temperatures in the range of 496°C to 538°C (below 925°C to below 1000°C) and 21°C to 66°C (70°C).
It is rapidly cooled in a quenching agent such as water that is maintained at a temperature of about 150°F to 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 a temperature of about 5 below) for 1 to 4 hours.

The product is then quenched in a quenching agent maintained at a temperature on the order of 70"F to 150F. Thereafter, according to the present invention, the product is cooled to a temperature between 93C and 149C. (200°
Preferably, the aging treatment is performed at a relatively low temperature in the range of 300'F to 300'FW).

Since this alloy is intended to replace the conventional 7XXX series alloys, it is preferred that the alloy be aged for a time to allow it to reach at least 95% of its peak strength. This alloy has a peak strength of 9
Preferably, it is aged for a time that can reach between 5% and 97%.

The preferred aging temperature range is 121°C to 135°C (250°C
275°F). Within these temperature ranges approximately 4~
Aging of 95% to 97% of the peak intensity can be achieved by aging for 120 hours.

E. EXAMPLES The following examples are provided 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-lamb-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 the scope of patent protection.

An aluminum alloy was prepared containing 2.2% by weight lithium, 0.5% by weight magnesium, 2.5% by weight copper, 0.1% by weight zirconium, with the balance being aluminum. The alloy composed in this way has an overall value of 0.
．． Contains 25% by weight or less of microelements. Iron and silicon are present in this compositional alloy at less than 0.07% by weight.

This alloy was cast and homogenized at 524°C (below 975°C). This model alloy is 5.08rl1m (
It was rolled to a thickness of 0.21 rl). The sheet material thus produced was then subjected to a solution treatment at 524° C. (below 975° C.) for 1 hour. After this, about 21℃
quenched in water held at (70°F). The sheet material was then stretched to 1.5% of its initial length and cut into specimens. 12.711 (
0,5in)X6.35mN2.5in)X5,081
It was cut to a size of 111 (0.2 in). The test piece used for the tensile strength test was 25.4 mm (Iin) Xl 0
1.61N4in) x 5.08m10.2in). The specimens were then heated to 120°C at 135°C (below 275°C).
It has been aged for many hours.

Each aged specimen at each temperature and time was subjected to tensile strength and pre-cracked Charpy impact tests according to standard ASTM test procedures.

The maximum strength of the test piece aged at 135℃ (below 275℃) is 45.7~66, 8ko/mi2 (65~95k
si) in the range of 39.3 to 50011-kQ/C12
(220 to 280 in-lb/in2).

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: Akira AsamuraContinued from page 1@Inventor: Gee, Hari Narayana Amen 70 Inventor: William E., R. Ameist Tourika, Seattle, Washington, United States, 39th Avenue, N.E., 10309

Claims (7)

[Claims] (1) An aluminum-lithium alloy with excellent fracture toughness, with the following elements: Lithium 2.0-2.4 Magnesium O-0.9 Copper 2.3-2.7 Zirconium Maximum 0. 15 Iron Maximum 0.15 Silicon Maximum 0. ．． 12. An aluminum-lithium alloy characterized in that it consists of at most 0.25 other trace elements and the remainder aluminum. 2. The alloy of claim 1, wherein said zirconium is present in an amount up to about 0.12% by weight. (3) The alloy according to claim 1, having a base composition of 2.2% by weight of lithium, 0.5% by weight of δ magnesium, 2.5% by weight of copper, and 0.12% by weight of zirconium. . (4) The alloy according to claim 1, wherein the alloy is aged at a relatively low temperature to near its peak strength. (5) The alloy has a temperature of 9.3°C to 149°C (below 200°C to 3°C
2. The alloy of claim 1 which has been aged at a temperature in the range of 0.00" F. 6. The alloy of claim 5, wherein said alloy is aged for at least 4 hours. (7) The alloy according to claim 1, wherein magnesium is contained in an amount ranging from 0.5 to 0.9% by weight.