EP0151301B1 - Aluminium-Lithium-Legierung - Google Patents

Aluminium-Lithium-Legierung Download PDF

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Publication number
EP0151301B1
EP0151301B1 EP84115927A EP84115927A EP0151301B1 EP 0151301 B1 EP0151301 B1 EP 0151301B1 EP 84115927 A EP84115927 A EP 84115927A EP 84115927 A EP84115927 A EP 84115927A EP 0151301 B1 EP0151301 B1 EP 0151301B1
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EP
European Patent Office
Prior art keywords
alloy
aluminium
article
lithium
zirconium
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EP84115927A
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English (en)
French (fr)
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EP0151301A1 (de
Inventor
William E. Quist
R. Eugene Curtis
G. Hari Narayanan
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Boeing Co
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Boeing Co
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Publication of EP0151301A1 publication Critical patent/EP0151301A1/de
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    • 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 a process of manufacturing products from an aluminium alloy having lithium together with magnesium and copper as main alloying elements. Its object is particularly to provide products of high fracture toughness and high strength that may be used in the aircraft industry.
  • aluminium-lithium alloys have been used only sparsely in aircraft structure. Their relatively low use has been caused by casting difficulties associated with aluminium-lithium alloys and by their relatively low fracture toughness compared to other more conventional aluminium alloys. Aluminium-lithium alloys, however, provide a substantial lowering of the density of aluminium 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 aluminium-lithium processing technology, a major challenge is still to obtain a good blend of fracture toughness and high strength in an aluminium-lithium alloy.
  • the invention thus provides a process of manufacturing products from an aluminium alloy having lithium together with magnesium and copper as main alloying elements, which process comprises the steps of:
  • EP-A-0 124 286 (GB-A-2 137 227).
  • Some alloy compositions exemplified therein are falling within the compositional ranges of the alloy of the present invention but, on the other hand, all articles formed from the exemplified alloys in EP-A-0 124 286 are subjected to an aging step at a conventional temperature of about 170°C or 190°C.
  • An aluminium-lithium alloy formulated in accordance with the present invention will contain 2.2 to 2.8% lithium, 0.2 to 0.8% magnesium, 1.5 to 2.1% copper and max 0.15% zirconium. All percentages herein are by weight based on the total weight of the alloy unless otherwise indicated.
  • the magnesium in the alloy functions to increase strength and slightly decreases density. It also provides solid solution strengthening.
  • the copper adds strength to the alloy.
  • Zirconium functions as a grain refiner.
  • Iron and silicon can be present only in trace amounts, limiting the iron to a maximum of 0.15% and the silicon to a maximum of 0.12%, and preferably limiting them to less than 0.10% and 0.10%, respectively.
  • Certain trace elements such as zinc, may be present in amounts up to, but not exceeding 0.25% of the total.
  • Other elements such as chrominium and manganese must be held to levels of 0.05% or below. If the maximums of these trace elements are exceeded, the desired properties of the aluminium-lithium alloy will tend to deteriorate.
  • the trace elements sodium and hydrogen are also thought to be harmful to the properties (fracture toughness in particular) of aluminium-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 aluminium.
  • An aluminium-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 496°C to 538°C.
  • the alloy is converted into a usable article by conventional mechanical formation techniques such a rolling, extrusion or the like.
  • the alloy is normally subjected to a solution treatment at temperatures ranging from 510°C to 538°C, quenched in a quenching medium such as water that is maintained at a temperature on the order of 21°C to 67°C. If the alloy has been rolled or extruded, it is generally stretched on the order of 1 to 3% of its original length to relieve internal stresses.
  • the aluminium 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.
  • additional heat treatments such as solution heat treatment can be employed if desired.
  • an extruded product after being cut to desired length is generally solution heat-treated at temperatures on the order of 524°C for 1 to 4 hours.
  • the product is then quenched in a quenching medium held at temperatures ranging from about 21°C to 67°C.
  • the article is 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 93°C to about 149°C. It is preferred that the alloy be heat treated in the range of from about 121°C to 135°C. 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 properties mix will be slightly less desireable.
  • the aging when the aging is conducted attemperatures on the order of 135°C to 149°C, it is preferred that the product be subjected to the aging temperature for periods of from 1 to 40 hours.
  • aging when aging is conducted at temperatures on the order of 121°C or below, aging times from 2 to 80 hours or more are preferred to bring about the proper balance between fracture toughness and strength.
  • the aluminium-lithium articles are cooled to room temperature.
  • the treatment will result in an aluminium-lithium alloy having an ultimate strength on the order of 448 to 483 MPa.
  • the fracture toughness of the material will be on the order of 1.5 to 2 times greater than that of similar aluminium-lithium alloys subjected to conventional aging treatments, which are normally conducted at temperatures greater than 149°C.
  • the superior strength and toughness combination achieved by the low temperature underaging techniques in accordance with the present invention also surprisingly causes some aluminium-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 aluminium alloy containing 2.4% lithium, 0.6% magnesium, 1.8% copper, 0.15% zirconium with the balance being aluminium was formulated.
  • the trace elements present in the formulation constituted less than 0.25% of the total.
  • the iron and silicon present in the formulation each constituted less than 0.07% of the formulation.
  • the alloy was cast and homogenized at about 524°C. Thereafter, the alloy was hot rolled to a thickness of 0.5 cm. The resulting sheet was then solution treated at about 524°C for about 1 hour. It was then quenched in water maintained at about 21°C. Thereafter, the sheet was subjected to a stretch of 1.5% of its initial length and then cut into specimens.
  • the specimens were cut to a size of 1.27 cm by 6.35 cm by 0.5 cm for the precrack Charpy impact tests, one method of measuring fracture toughness.
  • the specimens prepared for the tensile strength tests were 2.5 cm by 10.2 cm by 0.5 cm.
  • a plurality of specimens were then aged for 16 and 40 hours at 135°C and 121°C 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 Sharpy impact tests in accordance with standard testing procedures.
  • the specimens underaged at 135°C had ultimate strengths ranging from about 448 MPa to about 483 MPa with a toughness on the order of 0.114to 0.131 J/mm 2 .
  • the specimens at 121°C exhibit an ultimate strength ranging from 427 to 448 MPa ksi, while their toughness was in the range of 0.131 to 0.149 J/mm 2 . These values compare with toughness values less than about 0.079 J/mm 2 for similar materials aged attemperatures over 149°C, yet having similar ultimate strengths.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Forging (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)

Claims (10)

1. Verfahren zur Herstellung von Produkten aus einer Aluminiumlegierung, die zusammen mit Magnesium und Kupfer Lithium als Hauptlegierungselemente aufweist, gekennzeichnet durch die Stufen
a) Herstellung eines Barrens einer Legierung mit folgender Zusammensetzung:
Figure imgb0004
b) Homogenisierung des Barrens;
c) Formung eines Gegenstands;
d) Unterwerfung des Gegenstands einer Lösungsglühungsbehandlung;
e) Abschrecken des Gegenstands in einem Abschreckungsmedium;
f) Alterung des Gegenstands bei einer Temperatur im Bereich von etwa 93°C (200°F) bis etwa 149°C (300°F).
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß Zirkonium in einer Menge von 0,1 bis 0,15 Gew.-% vorhanden ist.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Legierung eine nominale Zusammensetzung von 2,45 Gew.-% Lithium, 0,6 Gew.-% Magnesium, 1,8 Gew.-% Kupfer und 0,12 Gew.-% Zirconium, Rest Aluminium und Spurenelemente aufweist.
4. Verfahren nach den Ansprüchen 1 bis 3, dadurch gekennzeichnet, daß die Legierung bei einer Temperatur im Bereich von etwa 121°C (250°F) bis etwa 135°C (275°F) gealtert wird.
5. Verfahren nach den Ansprüchen 1 bis 4, dadurch gekennzeichnet, daß die Legierung über einen Zeitraum von 1 bis 80 Stunden gealtert wird.
6. Gegenstand aus einer Aluminiumlegierung, gekennzeichnet durch eine Legierung der folgenden Zusammensetzung:
Figure imgb0005
hat und eine Zerreißfestigkeit von etwa 427 bis etwa 483 MPa (62 bis 70 ksi) in Kombination mit einer Bruchzähigkeit von etwa 114 bis etwa 149x103 J/m2 (650 bis 850 in-lbslin2) hat.
7. Gegenstand aus einer Aluminiumlegierung nach Anspruch 6, dadurch gekennzeichnet, daß' Zirkonium in einer Menge von 0,1 bis 0,15 Gew.- % vorhanden ist.
8. Gegenstand aus einer Aluminiumlegierung nach Anspruch 6 oder 7, dadurch gekennzeichnet, daß die Legierung eine Nominalzusammensetzung von 2,45 Gew.-% Lithium, 0,6 Gew.-% Magnesium, 1,8 Gew.-% Kupfer und 0,12 Gew.-% Zirconium, Rest Aluminium und Spurenelemente hat.
9. Gegenstand aus einer Aluminiumlegierung nach den Ansprüchen 6 bis 8, dadurch gekennzeichnet, daß er eine Zerreißfestigkeit von etwa 448 bis etwa 483 MPa (65 bis 70 ksi) in Kombination mit einer Bruchzähigkeit von etwa 114 bis etwa 131 x103 J/m2 (650 bis 750 in-lbs/in2) hat.
10. Gegenstand aus einer Aluminiumlegierung nach den Ansprüchen 6 bis 8, dadurch gekennzeichnet, daß er eine Zerreißfestigkeit von etwa 472 bis etwa 448 MPa (62 bis 65 ksi) in Kombination mit einer Bruchzähigkeit von etwa 131 bis etwa 149x103 J/m2 (750 bis 850 in-lbs/in2) hat.
EP84115927A 1983-12-30 1984-12-20 Aluminium-Lithium-Legierung Expired EP0151301B1 (de)

Applications Claiming Priority (2)

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

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EP0151301A1 EP0151301A1 (de) 1985-08-14
EP0151301B1 true EP0151301B1 (de) 1989-06-07

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JP (1) JPS60211034A (de)
DE (1) DE3478616D1 (de)

Families Citing this family (4)

* 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
JPS62175935A (ja) * 1986-01-30 1987-08-01 Canon Inc 光学系駆動装置
EP0250656A1 (de) * 1986-07-03 1988-01-07 The Boeing Company Unvollständige Aushärtung von lithiumhaltigen Legierungen bei niedriger Temperatur
JP2017110266A (ja) * 2015-12-17 2017-06-22 株式会社神戸製鋼所 ろう付け後の強度に優れたアルミニウム合金製ブレージングシート

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0090583A2 (de) * 1982-03-31 1983-10-05 Alcan International Limited Wärmebehandlung von Aluminiumlegierungen
EP0124286A1 (de) * 1983-03-31 1984-11-07 Alcan International Limited Aluminiumlegierungen

Family Cites Families (5)

* 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
ZA83954B (en) * 1982-02-26 1984-01-25 Secr Defence Brit Aluminium alloys
GB2137227B (en) * 1983-03-31 1986-04-09 Alcan Int Ltd Aluminium-lithium alloys
ZA842381B (en) * 1983-03-31 1984-11-28 Alcan Int Ltd Aluminium alloys
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
EP0090583A2 (de) * 1982-03-31 1983-10-05 Alcan International Limited Wärmebehandlung von Aluminiumlegierungen
EP0124286A1 (de) * 1983-03-31 1984-11-07 Alcan International Limited Aluminiumlegierungen

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
1982 National Powder Metallurgy Conference Proceedings, Progress in Powder Metallurgy Vol. 38 D.J. Chellman, G.G. Wald, p. 361-381 *
4th International Aluminium-Lithium Conference "Alcar" Paris 10-12. June 1987 Contribution of Miller, White and Lloyd and of White and Miller. *

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Publication number Publication date
JPS60211034A (ja) 1985-10-23
EP0151301A1 (de) 1985-08-14
DE3478616D1 (en) 1989-07-13

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