EP0151301A1 - Alliage aluminium-lithium - Google Patents

Alliage aluminium-lithium Download PDF

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Publication number
EP0151301A1
EP0151301A1 EP84115927A EP84115927A EP0151301A1 EP 0151301 A1 EP0151301 A1 EP 0151301A1 EP 84115927 A EP84115927 A EP 84115927A EP 84115927 A EP84115927 A EP 84115927A EP 0151301 A1 EP0151301 A1 EP 0151301A1
Authority
EP
European Patent Office
Prior art keywords
alloy
percent
aluminum
lithium
aged
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP84115927A
Other languages
German (de)
English (en)
Other versions
EP0151301B1 (fr
Inventor
William E. Quist
R. Eugene Curtis
G. Hari Narayanan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Boeing Co
Original Assignee
Boeing Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Boeing Co filed Critical Boeing Co
Publication of EP0151301A1 publication Critical patent/EP0151301A1/fr
Application granted granted Critical
Publication of EP0151301B1 publication Critical patent/EP0151301B1/fr
Expired legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium

Definitions

  • the present invention relates to aluminum-lithium alloys and more particularly to an aluminum-lithium alloy composition with high fracture toughness and high strength.
  • aluminum-lithium alloys have been used only sparsely in aircraft structure.
  • the relatively low use has been caused by casting difficulties associated with aluminum-lithium alloys and by their relatively low fracture toughness compared to other more conventional aluminum alloys.
  • Aluminum-lithium alloys provide a substantial lowering of the density of aluminum alloys (as well as a relatively high strength to weight ratio), which has been found to be very important in decreasing the overall weight of structural materials used in an aircraft. While substantial strides have been made in improving the aluminum-lithium processing technology, a major challenge is still to obtain a good blend of fracture toughness and high strength in an aluminum-lithium alloy.
  • the present invention provides a novel aluminum alloy composition that can be worked and heat treated so as to provide an aluminum-lithium alloy with high strength, good fracture toughness, and relatively low density compared to conventional 2000 Series aluminum alloys that it is intended to replace.
  • An alloy prepared in accordance with the present invention has a nominal composition on the order of 2.45 weight percent lithium, 0.6 percent magnesium, 1.8 percent copper and 0.12 percent zirconium. By underaging the alloy at a low temperature, an excellent blend of fracture toughness and high strength results.
  • An aluminum-lithium alloy formulated in accordance with the present invention can contain from about 2.2 to about 2.8 percent lithium, 0.2 to 0.8 percent magnesium, 1.5 to 2.1 percent copper and a maximum of 0.15 percent zirconium as a grain refiner. Preferably from 0.1 to 0.15 percent zirconium is incorporated. All percentages herein are by weight percent based on the total weight of the alloy unless otherwise indicated.
  • the magnesium in the alloy functions to increase strength and slightly decrease density. It also provides solid solution strengthening.
  • the copper adds strength to the alloy. Zirconium functions as a preferred grain refiner.
  • Iron and silicon can each be present in maximums up to a total of 0.3 percent. It is preferred that these elements be present only in trace amounts, limiting the iron to a maximum of 0.15 percent and the silicon to a maximum of 0.12 percent, and most preferably to less than 0.10 percent and 0.10 percent, respectively. Certain trace elements such as zinc, may be present in the amounts up to, but not to exceed, 0.25 percent of the totaL Other elements usch as chromium and manganese must be held to levels of 0.05 percent or below.
  • the trace elements sodium and hydrogen are also thought to be harmful to the properties (fracture toughness in particular) of aluminum-lithium alloys and should be held to the lowest levels practically attainable, for example on the order of 15 to 30 ppm (0.0015-0.0030 wt. %) for the sodium and less than 15 ppm (0.0015 wt. %) and preferably less than 1.0 ppm (0.0001 wt. %) for the hydrogen.
  • the balance of the alloy comprises aluminum.
  • An aluminum-lithium alloy formulated in the proportions set forth in the foregoing paragraph is processed into an article utilizing known techniques.
  • the alloy is formulated in molten form and cast into an ingot.
  • the ingot is then homogenized at temperatures ranging from 925" F to 1000° F.
  • the alloy is converted into a usable article by conventional mechanical formation techniques such as rolling, extrusion or the like.
  • the alloy is normally subjected to a solution treatment at temperatures ranging from 950° F to 1000° F, quenched in a quenching medium such as water that is maintained at a temperature on the order of 70 0 F to 150° F. If the alloy has-been rolled or extruded, it is generally stretched on the order of 1 to 3 percent of its original length to relieve internal stresses.
  • the alumium alloy can then be further worked and formed into the various shapes for its final application. Additional heat treatments such as solution heat treatment can be employed if desired. For example, an extruded product after being cut to desired length are generally solution heat treated at temperatures on the order of 975° F for 1 to 4 hours. The product is then quenched in a quenching medium held at temperatures ranging from about 70° F to 1 50 0 F.
  • the article is preferably subjected to an aging treatment that will increase the strength of the material, while maintaining its fracture toughness and other engineering properties at relatively high levels.
  • the articles are subjected to a low temperature underage heat treatment at temperatures ranging from about 200 0 F to about 300° F. It is preferred that the alloy be heat treated in the range of from about 250° F to 27 5° F. At the higher temperatures, less time is needed to bring about the proper balance between strength and fracture toughness than at lower aging temperatures, but the overall property mix will be slightly less desireable.
  • the aging when the aging is conducted at temperatures on the order of 275° F to 300° F, it is preferred that the product be subjected to the aging temperature for periods of from 1 to 40 hours. On the other hand, when aging is conducted at temperatures on the order of 250° F or below, aging times from 2 to 80 hours or more are preferred to bring about the proper balance between fracture toughness and strength. After the aging treatment, the aluminum-lithium articles are cooled to room temperature.
  • the treatment will result in an aluminum-lithium alloy having an ultimate strength on the order of 65 to 70 ksi.
  • the fracture toughness of the material will be on the order of 1 1/2 to 2 times greater than that of similar aluminum-lithium alloys subjected to conventional aging treatments, which are normally conducted at temperatures greater than 300 0 F.
  • the superior strength and toughness combination achieved by the low temperature underaging techniques in accordance with the present invention also surprisingly causes some aluminum-lithium alloys to exhibit an improvement in stress corrosion resistance when contrasted with the same alloy aged with standard aging practices. Examples of these improved characteristics will be set forth in more detail in conjunction with the ensuing example.
  • An aluminum alloy containing 2.4 percent lithium, 0.6 percent magnesium, 1.8 percent copper, 0.15 percent zirconium with the balance being aluminum was formulated.
  • the trace elements present in the formulation constituted less than about 0.25 percent of the total.
  • the iron and silicon present in the formulation constituted less than 0.07 each percent of the formulation.
  • the alloy was cast and homogenized at about 975° F. Thereafter, the alloy was hot rolled to a thickness of 0.2 inches. The resulting sheet was then solution treated at about 975° F for about 1 hour. It was then quenched in water maintained at about 70° F. Thereafter, the sheet was subjected to a stretch of 1 1/2 percent of its initial length and then cut into specimens.
  • the specimens were cut to a size of 0.5 inch by 2 1/2 inch by 0.2 inch for the precrack Charpy impact tests, one method of measuring fracture toughness.
  • the specimens prepared for the tensile strength tests were 1 inch by 4 inches by 0.2 inches.
  • a plurality of specimens were then aged for 16 and 40 hours at 275° F, and at 250° F for 40 and 72 hours.
  • Each of the specimens aged at each of the temperatures and times were then subjected to the tensile strength and precrack Charpy impact tests in accordance with standard testing procedures.
  • These values compare with toughness values less than about 450 in-lbs/in 2 for similar materials aged at temperatures over 300° F, yet having similar ultimate strengths.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Forging (AREA)
EP84115927A 1983-12-30 1984-12-20 Alliage aluminium-lithium Expired EP0151301B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US56709783A 1983-12-30 1983-12-30
US567097 1983-12-30

Publications (2)

Publication Number Publication Date
EP0151301A1 true EP0151301A1 (fr) 1985-08-14
EP0151301B1 EP0151301B1 (fr) 1989-06-07

Family

ID=24265702

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84115927A Expired EP0151301B1 (fr) 1983-12-30 1984-12-20 Alliage aluminium-lithium

Country Status (3)

Country Link
EP (1) EP0151301B1 (fr)
JP (1) JPS60211034A (fr)
DE (1) DE3478616D1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3613224A1 (de) * 1985-08-20 1987-02-26 Boeing Co Aluminium-lithium-legierung
EP0250656A1 (fr) * 1986-07-03 1988-01-07 The Boeing Company Sous-vieillissement à basse température d'alliages contenant du lithium
CN106906383A (zh) * 2015-12-17 2017-06-30 株式会社神户制钢所 钎焊后的强度优异的铝合金制钎焊板

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62175935A (ja) * 1986-01-30 1987-08-01 Canon Inc 光学系駆動装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB787665A (en) * 1955-04-05 1957-12-11 Stone & Company Charlton Ltd J Improvements relating to aluminium-base alloys
GB2137227A (en) * 1983-03-31 1984-10-03 Alcan Int Ltd Aluminium-Lithium Alloys

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ZA83954B (en) * 1982-02-26 1984-01-25 Secr Defence Brit Aluminium alloys
GB2121822B (en) * 1982-03-31 1985-07-31 Alcan Int Ltd Al-li-cu-mg alloys
JPS602644A (ja) * 1983-03-31 1985-01-08 アルカン・インタ−ナシヨナル・リミテイド アルミニウム合金
US4624717A (en) * 1983-03-31 1986-11-25 Alcan International Limited Aluminum alloy heat treatment
DE3483607D1 (de) * 1983-12-30 1990-12-20 Boeing Co Alterung bei relativ niedrigen temperaturen von lithium enthaltenden aluminiumlegierungen.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB787665A (en) * 1955-04-05 1957-12-11 Stone & Company Charlton Ltd J Improvements relating to aluminium-base alloys
GB2137227A (en) * 1983-03-31 1984-10-03 Alcan Int Ltd Aluminium-Lithium Alloys

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3613224A1 (de) * 1985-08-20 1987-02-26 Boeing Co Aluminium-lithium-legierung
EP0250656A1 (fr) * 1986-07-03 1988-01-07 The Boeing Company Sous-vieillissement à basse température d'alliages contenant du lithium
CN106906383A (zh) * 2015-12-17 2017-06-30 株式会社神户制钢所 钎焊后的强度优异的铝合金制钎焊板

Also Published As

Publication number Publication date
JPS60211034A (ja) 1985-10-23
DE3478616D1 (en) 1989-07-13
EP0151301B1 (fr) 1989-06-07

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