EP0325937B1 - Alliages aluminium-lithium - Google Patents

Alliages aluminium-lithium Download PDF

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Publication number
EP0325937B1
EP0325937B1 EP19890100355 EP89100355A EP0325937B1 EP 0325937 B1 EP0325937 B1 EP 0325937B1 EP 19890100355 EP19890100355 EP 19890100355 EP 89100355 A EP89100355 A EP 89100355A EP 0325937 B1 EP0325937 B1 EP 0325937B1
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Prior art keywords
alloy
product
strength
accordance
toughness
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EP19890100355
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German (de)
English (en)
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EP0325937A1 (fr
Inventor
Roberto J. Rioja
Alex Cho
Edward L. Colvin
Asuri Vasudevan
Philip E. Bertz
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Howmet Aerospace Inc
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Aluminum Company of America
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Priority claimed from US07/149,802 external-priority patent/US5137686A/en
Priority claimed from US07/172,506 external-priority patent/US4961792A/en
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Publication of EP0325937A1 publication Critical patent/EP0325937A1/fr
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/057—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with copper as the next major constituent
    • 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
    • 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
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon

Definitions

  • This invention relates to aluminum base alloys, and more particularly, it relates to improved lithium containing aluminum base alloys, products made therefrom and methods of producing the same.
  • More desirable alloys would permit increased strength with only minimal or no decrease in toughness or would permit processing steps wherein the toughness was controlled as the strength was increased in order to provide a more desirable combination of strength and toughness. Additionally, in more desirable alloys, the combination of strength and toughness would be attainable in an aluminum-lithium alloy having density reductions in the order of 5 to 15%. Such alloys would find widespread use in the aerospace industry where low weight and high strength and toughness translate to high fuel savings. Thus, it will be appreciated that obtaining qualities such as high strength at little or no sacrifice in toughness, or where toughness can be controlled as the strength is increased would result in a remarkably unique aluminum-lithium alloy product.
  • U.S. Patent 4,626,409 discloses aluminum base alloy consisting of, by wt.%, 2.3 to 2.9 Li, 0.5 to 1.0 Mg, 1.6 to 2.4 Cu, 0.05 to 0.25 Zr, 0 to 0.5 Ti, 0 to 0.5 Mn, 0 to 0.5 Ni, 0 to 0.5 Cr and 0 to 2.0 Zn and a method of producing sheet or strip therefrom.
  • U.S. Patent 4,582,544 discloses a method of superplastically deforming an aluminum alloy having a composition similar to that of U.S. Patent 4,626,409.
  • European Patent Application 210112 discloses an aluminum alloy product containing 1 to 3.5 wt.% Li, up to 4 wt.% Cu, up to 5 wt.% Mg, up to 3 wt.% Zn and Mn, Cr and/or Zr additions.
  • the alloy product is recrystallized and has a grain size less than 300 micrometers.
  • U.S. Patent 4,648,913 discloses aluminum base alloy wrought product having improved strength and fracture toughness combinations when stretched, for example, an amount greater than 3%.
  • the present invention provides as improved lithium containing aluminum base alloys which permit products having improved strength characteristics while retaining high toughness properties.
  • the present invention provides an improved lithium containing aluminum base alloy product which can be processed to improve strength characteristics while retaining high toughness properties or which can be processed to provide a desired strength at a controlled level of toughness.
  • Figure 1 shows a strength and fracture toughness plot of alloys in accordance with the invention.
  • Figure 2 shows strength plotted against aging time of an alloy in accordance with the invention.
  • Figure 3 illustrates different toughness yield strength relationships where shifts in the upward direction and to the right represent improved combinations of these properties.
  • an aluminum base alloy suitable for forming into a wrought product having improved combinations of strength, corrosion resistance and fracture toughness the alloy comprised of 0.2 to 5.0 wt.% Li, 0.05 to 6.0 wt.% Mg, 2.45 to less than 4.0 wt.% Cu, 0.05 to 2.0 wt.% Zn, 0.01 to 0.16 wt.% Zr, 0.5 wt.% max. Fe, 0.5 wt.% max.
  • Si and optional components consisting of 0 to 1.0 wt.% Mn, 0.05 to 0.2 wt.% Cr, V, Hf, Ti; the balance aluminum and incidental impurities, and having an Mg-Zn ratio of 0.1 to less than 1.0 when Mg is in the range of 0.1 to 1.0 Wt.%.
  • the impurities are preferably limited to about 0.05 wt.% each, and the combination of impurities preferably should not exceed 0.35 wt.%. Within these limits, it is preferred that the sum total of all impurities does not exceed 0.15 wt.%.
  • a preferred alloy in accordance with the present invention can contain 1.5 to 3.0 wt.% Li, 2.5 to 2.95 wt.% Cu, 0.2 to 2.5 wt.% Mg, 0.2 to 2.0 wt.% Zn, 0.05 to 0.12 wt.% Zr, the balance aluminum and impurities as specified above.
  • a typical alloy composition would contain 1.8 to 2.5 wt.% Li, 2.55 to 2.9 wt.% Cu, 0.2 to 2.0 wt.% Mg, 0.2 to 2.0 wt.% Zn, greater than 0.1 to less than 0.16 wt.% Zr, and max. 0.1 wt.% of each of Fe and Si.
  • a suitable alloy composition would contain 1.9 to 2.4 wt.% Li, 2.55 to 2.9 wt.% Cu, 0.1 to 0.6 wt.% Mg, 0.5 to 1.0 wt.% Zn, 0.08 to 0.12 wt.% Zr, max. 0.1 wt.% of each of Fe and Si, the remainder aluminum.
  • an aluminum base alloy wrought product having improved combinations of strength, fracture toughness and corrosion resistance is provided.
  • the product can be provided in a condition suitable for aging and has the ability to develop improved strength in response to aging treatments without substantially impairing fracture toughness properties or corrosion resistance.
  • the product comprises 0.2 to 5.0 wt.% Li, 0.05 to 6.0 wt.% Mg, 2.45 to 2.95 wt.% Cu, 0.05 to 0.16 wt.% Zr, 0.2 to 2.0 wt.% Zn, 0.5 wt.% max. Fe, 0.5 wt.% max. Si, the balance aluminum and incidental impurities.
  • the product is capable of having imparted thereto a working effect equivalent to stretching so that the product has combinations of improved strength and fracture toughness after aging.
  • a body of a lithium containing aluminum base alloy is provided and may be worked to produce a wrought aluminum product.
  • the wrought product may be first solution heat treated and then stretched or otherwise worked amount equivalent to stretching.
  • the degree of working as by stretching is normally greater than that used for relief of residual internal quenching stresses.
  • a preferred alloy in accordance with the present invention can contain 0.2 to 5.0 wt.% Li, 2.45 to less than 4.0 wt.% Cu, 0.05 to 5.0 wt.% Mg, 0.05 to 0.16 wt.% Zr, 0.2 to 2.0 wt.% Zn, the balance aluminum and impurities as specified above.
  • a typical alloy composition would contain 1.5 to 3.0 wt.% Li, 2.55 to 2.90 wt.% Cu, 0.2 to 2.5 wt.% Mg, 0.2 to 2.0 wt.% Zn, 0.08 to 0.12 wt.% Zr, 0 to 1.0 wt.% Mn and max. 0.1 wt.% of each of Fe and Si.
  • Mg may be in the range of 0.2 to 2.0 wt.%.
  • lithium is very important not only because it permits a significant decrease in density but also because it improves tensile and yield strengths markedly as well as improving elastic modulus. Additionally, the presence of lithium improves fatigue resistance. Most significantly though, the presence of lithium in combination with other controlled amounts of alloying elements permits aluminum alloy products which can be worked to provide unique combinations of strength and fracture toughness while maintaining meaningful reductions in density.
  • alloying elements such as Cu and Mn, for example. Accordingly, while lithium is the most important element for saving weight, the other elements are important in order to provide the proper levels of strength, fracture toughness, corrosion and stress corrosion cracking resistance.
  • copper should be less than 3.0 wt.%; however, in a less preferred embodiment, copper can be increased to less than 4.0 wt.% and preferably less than 3.5 wt.%.
  • the combination of lithium and copper should not exceed 5.5 wt.% with lithium being at least 1.5 wt.% with greater amounts of lithium being preferred.
  • Magnesium is added or provided in this class of aluminium alloys mainly for purposes of increasing strength although it does decrease density slightly and is advantageous from that standpoint. It is important to adhere to the limits set forth for magnesium because excess magnesium, for example, can also lead to interference with fracture toughness, particularly through the formation of undesirable phases at grain boundaries.
  • Zirconium is the preferred material for grain structure control; however, other grain structure control materials can include Cr, V, Hf, Mn, Ti, typically in the range of 0.05 to 0.2 wt.% with Hf and Mn up to typically 0.6 wt.%.
  • the level of Zr used depends on whether a recrystallized or unrecrystallized structure is desired.
  • the use of zinc results in increased levels of strength, particularly in combination with magnesium. However, excessive amounts of zinc can impair toughness through the formation of intermetallic phases.
  • Zinc is important because, in this combination with magnesium, it results in an improved level of strength which is accompanied by high levels of corrosion resistance when compared to alloys which are zinc free.
  • Particularly effective amounts of Zn are in the range of 0.1 to 1.0 wt.% when the magnesium is in the range of 0.05 to 0.5 wt.%, as presently understood. It is important to keep the Mg and Zn in a ratio in the range of about 0.1 to less than 1.0 when Mg is in the range of 0.1 to 1 wt.% with a preferred ratio being in the range of 0.2 to 0.9 and a typical ratio being in the range of about 0.3 to 0.8.
  • the ratio of Mg to Zn can range from 1 to 6 when the wt.% of Mg is 1 to 4.0 and Zn is controlled to 0.2 to 2.0 wt.%, preferably in the range of 0.2 to 0.9 wt.%.
  • Mg/Zn ratio of less than one is important in that it aids in the worked product being less anisotropic or being more isotropic in nature, i.e., properties more uniform in all directions. That is, working with the Mg/Zn ratio in the range of 0.2 to 0.8 can result in the end product having greatly reduced hot worked texture, resulting from rolling, for example, to provide improved properties, for example in the 45° direction.
  • Toughness or fracture toughness as used herein refers to the resistance of a body, e.g. extrusions, forgings, sheet or plate, to the unstable growth of cracks or other flaws.
  • the Mg/Zn ratio less than one is important for another reason. That is, keeping the Mg/Zn ratio less than one, e.g., 0.5, results not only in greatly improved strength and fracture toughness but in greatly improved corrosion resistance. For example, when the Mg and Zn content is 0.5 wt.% each, the resistance to corrosion is greatly lowered. However, when the Mg content is about 0.3 wt.% and the Zn is 0.5 wt.%, the alloys have a high level of resistance to corrosion.
  • Improved combinations of strength and toughness is a shift in the normal inverse relationship between strength and toughness towards higher toughness values at given levels of strength or towards higher strength values at given levels of toughness.
  • going from point A to point D represents the loss in toughness usually associated with increasing the strength of an alloy.
  • going from point A to point B results in an increase in strength at the same toughness level.
  • point B is an improved combination of strength and toughness.
  • going from point A to point C results in an increase in strength while toughness is decreased, but the combination of strength and toughness is improved relative to point A.
  • point C at point C, toughness is improved and strength remains about the same, and the combination of strength and toughness is considered to be improved.
  • toughness is improved and strength has decreased yet the combination of strength and toughness are again considered to be improved.
  • the alloy be prepared according to specific method steps in order to provide the most desirable characteristics of both strength and fracture toughness.
  • the alloy as described herein can be provided as an ingot or billet for fabrication into a suitable wrought product by casting techniques currently employed in the art for cast products, with continuous casting being preferred.
  • the alloy may be roll cast or slab cast to thicknesses from 6.3 to 50 or 75 mm (0.25 to 2 or 3 inches) or more depending on the end product desired.
  • the alloy may also be provided in billet form consolidated from fine particulate such as powdered aluminum alloy having the compositions in the ranges set forth hereinabove.
  • the powder or particulate material can be produced by processes such as atomization, mechanical alloying and melt spinning.
  • the ingot or billet may be preliminarily worked or shaped to provide suitable stock for subsequent working operations.
  • the alloy stock Prior to the principal working operation, the alloy stock is preferably subjected to homogenization, and preferably at metal temperatures in the range of 482 to 566°C (900 to 1050°F) for a period of time of at least one hour to dissolve soluble elements such as Li, Cu, Zn and Mg and to homogenize the internal structure of the metal.
  • a preferred time period is about 20 hours or more in the homogenization temperature range. Normally, the heat up and homogenizing treatment does not have to extend for more than 40 hours; however, longer times are not normally detrimental.
  • a time of 20 to 40 hours at the homogenization temperature has been found quite suitable.
  • this homogenization treatment is important in that it is believed to precipitate the Mn and Zr-bearing dispersoids which help to control final grain structure.
  • the metal can be rolled or extruded or otherwise subjected to working operations to produce stock such as sheet, plate or extrusions or other stock suitable for shaping into the end product.
  • a body of the alloy is preferably hot rolled to a thickness ranging from 2.5 to 6.3 mm (0.1 to 0.25 inch) for sheet and 6.3 to 150 mm (0.25 to 6.0 inches) for plate.
  • the temperature should be in the range of 538°C (1000°F) down to 399°C (750°F).
  • the metal temperature initially is in the range of 454 to 524°C (850 to 975°F).
  • Such reductions can be to a sheet thickness ranging, for example, from 0.25 to 6.33 mm (0.010 to 0.249 inch) and usually from 0.76 to 2.5 mm (0.030 to 0.10 inch).
  • the sheet or plate or other worked article is subjected to a solution heat treatment to dissolve soluble elements.
  • the solution heat treatment is preferably accomplished at a temperature in the range of 482 to 566°C (900 to 1050°F) and preferably produces an unrecrystallized grain structure.
  • Solution heat treatment can be performed in batches or continuously, and the time for treatment can vary from hours for batch operations down to as little as a few seconds for continuous operations. Basically, solutionizing of the alloy into a single phase field can occur fairly rapidly, for instance in as little as 30 to 60 seconds, once the metal has reached a solution temperature of about 538 to 566°C (1000 to 1050°F). However, heating the metal to that temperature can involve substantial amounts of time depending on the type of operation involved. In batch treating a sheet product in a production plant, the sheet is treated in a furnace load and an amount of time can be required to bring the entire load to solution temperature, and accordingly, solution heat treating can consume one or more hours, for instance one or two hours or more in batch solution treating.
  • the sheet is passed continuously as a single web through an elongated furnace which greatly increases the heat-up rate.
  • the continuous approach is favored in practicing the invention, especially for sheet products, since a relatively rapid heat up and short dwell time at solution temperature is obtained. Accordingly, the inventors contemplate solution heat treating in as little as about 1.0 minute.
  • a furnace temperature or a furnace zone temperature significantly above the desired metal temperature provides a greater temperature head useful in reducing heat-up times.
  • the product should be quenched to prevent or minimize uncontrolled precipitation of strengthening phases referred to herein later.
  • the alloy product of the present invention may be artificially aged to provide the combination of fracture toughness and strength which are so highly desired in aircraft members.
  • This can be accomplished by subjecting the sheet or plate or shaped product to a temperature in the range of 65 to 204°C (150 to 400°F) for a sufficient period of time to further increase the yield strength.
  • Some compositions of the product are capable of being artificially aged to a yield strength as high as 655 MPa (95 ksi).
  • the useful strengths are in the range of 345 to 586 MPa (50 to 85 ksi) and corresponding fracture toughnesses for plate products are in the range of 28 to 83 MPa ⁇ m (25 to 75 ksi ⁇ in ).
  • artificial aging is accomplished by subjecting the alloy product to a temperature in the range of 135 to 190°C (275 to 375°F) for a period of at least 30 minutes.
  • a suitable aging practice contemplate a treatment of about 8 to 24 hours at a temperature of about 163°C (325°F).
  • the alloy product in accordance with the present invention may be subjected to any of the typical underaging treatments well known in the art, including natural aging and multi-step agings.
  • multiple aging steps such as two or three aging steps, are contemplated and stretching or its equivalent working may be used prior to or even after part of such multiple aging steps.
  • the improved sheet, plate or extrusion and other wrought products can have a range of yield strength from about 172.5 to 345 MPa (25 to 50 ksi) and a level of fracture toughness in the range of about 55 to 165 MPa ⁇ m (50 to 150 ksi ⁇ in ).
  • fracture toughness can drop considerably.
  • the solution heat treated and quenched alloy product, particularly sheet, plate or extrusion must be stretched, preferably at room temperature, an amount greater than 1%, e.g.
  • stretching or equivalent working is greater than 1%, e.g. about 2% or greater, and less than 14%. Further, it is preferred that stretching be in the range of about 2 to 10%, e.g., 3.7 to 9% increase over the original length with typical increases being in the range of 5 to 8%.
  • the cast material may be subjected to stretching or the equivalent thereof without the intermediate steps or with only some of the intermediate steps to obtain strength and fracture toughness in accordance with the invention.
  • the alloy product of the present invention After the alloy product of the present invention has been worked, it may be artificially aged to provide the combination of fracture toughness and strength which are so highly desired in aircraft members.
  • Specific strength is the tensile yield strength divided by the density of the alloy.
  • Plate products for example, made from alloys in accordance with the invention, have a specific strength of at least 0.75 x 106 ksi in3/lb and preferably at least 0.80 x 106 ksi in3/lb.
  • the alloys have the capability of producing specific strengths as high as 1.00 x 106 ksi in3/lb. 1 ksi in3/lb ⁇ 110,9 MPa kg/m3
  • the wrought product in accordance with the invention can be provided either in a recrystallized grain structure form or an unrecrystallized grain structure form, depending on the type of thermomechanical processing used.
  • the alloy is hot rolled and solution heat treated, as mentioned earlier.
  • the Zr is kept to a very low level, e.g., less than 0.05 wt.%, and the thermomechanical processing is carried out at rolling temperatures of about 426-454°C (800 to 850°F) with the solution heat treatment as noted above.
  • Zr should be above 0.10 wt.% and the thermomechanical processing is as above except a heat-up rate of not greater than 5°F/min and preferably less than 1°F/min is used in solution heat treatment.
  • the ingot is first hot rolled to slab gauge of about 2 to 5 inches as above. Thereafter, it is reheated to between 371-454°C (700 to 850°F) then hot rolled to sheet gauge. This is followed by an anneal at between 260-454°C (500 to 850°F) for 1 to 12 hours. The material is then cold rolled to provide at least a 25% reduction in thickness to provide a sheet product. The sheet is then solution heat treated, quenched stretched and aged as noted earlier.
  • the ingot is hot rolled at a temperature in the range of 426-538°C (800 to 1000°F) and then annealed at a temperature of about 426-454°C (800 to 850°F) for about 4 to 16 hours. Thereafter, it is cold rolled to achieve a reduction of at least 25% in gauge.
  • the sheet is then solution heat treated at a temperature in the range of 510-549°C (950 to 1020°F) using heat-up rates of not slower than about 5,6°C/min (10°F/min) with typical heat-up rates being as fast as 200°F/min with faster heat-up rates giving finer recrystallized grain structure.
  • the sheet may then be quenched, stretched and aged.
  • Wrought products e.g., sheet, plate and forgings, in accordance with the present invention develop a solid state precipitate along the (100) family of planes.
  • the precipitate is plate like and has a diameter in the range of about 50 to 100 Angstroms and a thickness of 4 to 20 Angstroms.
  • the precipitate is primarily copper or copper-magnesium containing; that is, it is copper or copper-magnesium rich. These precipitates are generally referred to as GP zones and are referred to in a paper entitled "The Early Stages of GP Zone Formation in Naturally Aged Al-4 Wt Pct Cu Alloys" by R. J. Rioja and D. E. Laughlin, Metallurgical Transactions A , Vol.
  • the number density of precipitates on the (1 0 0) planes per cubic centimeter ranges from 1 x 1015 to 1 x 1017 with a preferred range being higher than 1 x 1015 and typically as high as 5 x 1016. These precipitates aid in producing a high level of strength without losing fracture toughness, particularly if short aging times, e.g., 15 hours at 350°F, are used for unstretched products.
  • the alloy of the present invention is useful also for extrusions and forgings with improved levels of mechanical properties, as shown in Figure 2, for example.
  • Extrusions and forgings are typically prepared by hot working at temperatures in the range of 315-538°C (600 to 1000°F), depending to some extent on the properties and microstructures desired.
  • alloys of the invention (Table 1) in this Example were cast into ingot suitable 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.% Mg.
  • Alloys A, B and C were provided for comparative purposes.
  • the ingots were then homogenized at 950°F for 8 hours followed by 24 hours at 1000°F, hot rolled to 1 inch thick plate and solution heat treated for one hour at 1020F.
  • the specimens were quenched and aged. Other specimens were stretched 2% and 6% of their original length at room temperature and then artificially aged. Unstretched samples were aged at 350°F.
  • Alloys A, B, C and D received many ratings of EC (severe exfoliation corrosion) or ED (very severe exfoliation). Alloy C suffered especially severe attack; all four samples received ED ratings after four days exposure to EXCO. Conversely, Alloys E, F and G received ratings that were predominantly EA (mild exfoliation) or EB (moderated exfoliation). Only one specimen from these three alloys was rated worse than EB. This was the 2% stretch 25 hour aging of Alloy E which was rated ED. This data indicates that Al-Cu-Li alloys with Mg to Zn ratios of less than 1 have improved resistance to exfoliation corrosion.
  • Tables 5, 6 and 7 list the strength and toughness exhibited by these alloys at 0, 2 and 6% stretch, respectively.
  • Figure 1 shows the properties of alloys E, F and G which exhibit improved combinations of corrosion resistance, strength and toughness.
  • Table 1 Composition of the Seven Alloys in Weight Percent Alloy Cu Li Mg Zn Zr Si Fe Al A 2.5 2.2 0 0 0.12 0.04 0.07 Balance B 2.5 2.2 0.3 0 0.12 0.04 0.07 Balance C 2.5 2.1 0.6 0 0.12 0.04 0.07 Balance D 2.6 2.2 0.6 0.6 0.12 0.04 0.07 Balance E 2.5 2.2 0.5 1 0.12 0.04 0.07 Balance F 2.6 2.1 0.3 0.5 0.12 0.04 0.07 Balance G 2.6 2.2 0.3 0.9 0.12 0.04 0.07 Balance Table 2 Specific Tensile Yield Strengths (x106 KSI in3/lb) Alloy 0% Stretch 2% Stretch 6% Stretch Calculated Density A 0.71 0.81 0.82 0.0909 B 0.80 0.82 0.88 0.0908 C 0.
  • the alloys of the invention in this example are the same as those from Example 1 except they were hot rolled to 1.5 inch thick plate rather than to 1 inch plate before they were solution heat treated for one hour at 1020F.
  • the specimens were quenched and artificially aged at 350°F for 20 and 30 hours.
  • Alloys E, F and G which had ratios of Mg to Zn of less than 1, had better resistance to stress corrosion cracking (SCC) than Alloys A, B, C and D which either contained no Zn (A, B, C) or had a Zn to Mg ratio of 1 (Alloy D).
  • SCC stress corrosion cracking
  • Alloys A, B, C and D which either contained no Zn (A, B, C) or had a Zn to Mg ratio of 1 (Alloy D).
  • the stress corrosion cracking test results are listed in Table 4 which also contains a description of the test procedures.
  • Example 1 This sample illustrates that forgings made from alloys of the present invention have improved combinations of corrosion resistance, strength and fracture toughness.
  • the alloys in this Example are the same as those in Example 1 and the ingots were prepared also as in Example 1. Specimens were prepared from these ingots by hot extruding and forging.
  • the forged specimens were solution heat treated from one hour at 1020°F then artificially aged at 350°F for 20 and 40 hours. Alloys E, F and G, which had ratios of Mg to Zn of less than 1, had better resistance to stress corrosion cracking (SCC) than Alloys A, B, C and D which either contained no Zn (A, B, C) or had an Mg to Zn ratio of 1 (Alloy D). Alloys E, F and G all survived 20 days in alternate immersion at 40,000 psi. The stress corrosion cracking results are listed in Table 8. The strength and fracture toughness are shown in Table 9.

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Claims (11)

  1. Alliage à base d'aluminium pouvant être mis sous forme d'un produit façonné ayant des combinaisons améliorées de résistance mécanique, de résistance à la corrosion et de ténacité à la rupture, l'alliage étant constitué par 0,2 à 5,0 % en poids de Li, 0,05 à 6,0 % en poids de Mg, 2,45 à moins de 4,0 % en poids de Cu, 0,01 à 0,16 % en poids de Zr, 0,05 à 2,0 % en poids de Zn, 0,5 % en poids au maximum de Fe, 0,5 % en poids au maximum de Si et des constituants éventuels consistant en 0 à 1,0 % en poids de Mn, 0,05 à 0,2 % en poids de Cr, V, Hf, Ti, le complément étant constitué par de l'aluminium et des impuretés éventuelles, et ayant un rapport Mg-Zn de 0,1 à moins de 1,0 lorsque Mg représente 0,1 à 1,0 % en poids.
  2. Alliage selon la revendication 1, dans lequel la combinaison de Li et Cu ne dépasse pas 5,5 % en poids, Li représentant au moins 1,5 % en poids.
  3. Alliage selon la revendication 1 ou 2, dans lequel :
       Li représente 1,5 à 3,0 % en poids ;
       Mg représente 0,2 à 2,5 % en poids ;
       Zr représente 0,05 à 0,12 % en poids ;
       Cu représente 2,55 à 2,90 % en poids ; et
       Zn représente 0,2 à 2,0 % en poids.
  4. Alliage selon la revendication 1, 2 ou 3, dans lequel :
       Li représente 1,8 à 2,5 % en poids ; et
       Mg représente 0,2 à 2,0 % en poids.
  5. Produit selon l'une quelconque des revendications 1 à 4, dans lequel le produit a un précipité solide en forme de plaque dans les plans, le produit à base d'alliage développant un nombre volumique de précipités par cm³ d'au moins 1,0 x 10¹⁵ dans un état non étiré avant le vieillissement et ayant une résistance mécanique spécifique telle qu'elle est définie ici supérieure à 83,2 x 10⁶ MPa kg/m³ (0,75 x 10⁶ ksi in³/lb).
  6. Alliage selon l'une quelconque des revendications 1 à 5, ayant un précipité solide en forme de plaque dans la famille des plans 1,0,0, le produit à base d'alliage ayant un nombre volumique de précipités par cm³ situé dans la plage de 1 x 10¹⁶ à 5,6 x 10¹⁶ et ayant une limite apparente d'élasticité spécifique telle qu'elle est définie ici supérieure à 88,0 x 10⁶ MPa kg/m³ (0,8 x 10⁶ ksi in³/lb).
  7. Alliage selon l'une quelconque des revendications 1 à 6, ayant un rapport Mg-Zn de 0,2 à 0,9 ou de 0,3 à 0,8.
  8. Alliage selon l'une quelconque des revendications 1 à 7, dans lequel Zr représente 0,05 à 0,12 % en poids, un effet de façonnage équivalent à un étirage étant communiqué au produit, avant une étape de vieillissement, de sorte que, après une étape de vieillissement, le produit présente des combinaisons améliorées de résistance mécanique et de ténacité.
  9. Alliage selon la revendication 8, dans lequel ledit effet de façonnage est équivalent à un étirage dudit produit en une quantité supérieure à sa longueur initiale, ladite quantité étant choisie entre 1 et 14 %, 1 et 10 % ou 1 et 8 %.
  10. Procédé de production d'un produit façonné à base d'aluminium-lithium non recristallisé ayant des niveaux améliorés de résistance mécanique, de ténacité à la rupture et de résistance à la corrosion, le procédé comprenant les étapes consistant à :
    (a) fournir un corps en un alliage à base d'aluminium contenant du lithium tel qu'il est défini dans l'une quelconque des revendications 1 à 6,
    (b) chauffer le corps à une température de façonnage à chaud ;
    (c) façonner à chaud le corps pour fournir un produit façonné ; et
    (d) soumettre ledit produit à un traitement thermique de mise en solution, à une trempe et à un vieillissement pour fournir un produit sensiblement non recristallisé ayant des niveaux améliorés de résistance mécanique et de ténacité à la rupture.
  11. Procédé de production de produits en alliage à base d'aluminium ayant des combinaisons de résistance mécanique, de résistance à la corrosion et de ténacité à la rupture améliorées, le procédé comprenant les étapes consistant à :
    (a) fournir un produit en alliage à base d'aluminium contenant du lithium consistant essentiellement en 0,2 à 5,0 % en poids de Li, 0,05 à 6,0 % en poids de Mg, 2,45 à 2,95 % en poids de Cu, 0,05 à 0,12 % en poids de Zr, 0,2 à 2,0 % en poids de Zn, 0,5 % en poids au maximum de Fe, 0,5 % en poids au maximum de Si, le complément étant constitué par de l'aluminium et des impuretés éventuelles, et ayant un rapport Mg-Zn de 0,1 à moins de 1,0 lorsque Mg représente 0,1 à 1,0 % en poids ; et
    (b) communiquer audit produit, avant une étape de vieillissement, un effet de façonnage équivalent à un étirage dudit produit à la température ambiante afin que, après une étape de vieillissement, ledit produit puisse avoir des combinaisons améliorées de résistance mécanique et de ténacité à la rupture en plus d'une résistance à la corrosion.
EP19890100355 1988-01-28 1989-01-10 Alliages aluminium-lithium Expired - Lifetime EP0325937B1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US07/149,802 US5137686A (en) 1988-01-28 1988-01-28 Aluminum-lithium alloys
US07/172,506 US4961792A (en) 1984-12-24 1988-03-24 Aluminum-lithium alloys having improved corrosion resistance containing Mg and Zn
US172506 1988-03-24
US149802 1988-03-24

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EP0325937B1 true EP0325937B1 (fr) 1994-03-09

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EP0325937B1 (fr) * 1988-01-28 1994-03-09 Aluminum Company Of America Alliages aluminium-lithium
US5455003A (en) * 1988-08-18 1995-10-03 Martin Marietta Corporation Al-Cu-Li alloys with improved cryogenic fracture toughness
US5211910A (en) * 1990-01-26 1993-05-18 Martin Marietta Corporation Ultra high strength aluminum-base alloys
US5151136A (en) * 1990-12-27 1992-09-29 Aluminum Company Of America Low aspect ratio lithium-containing aluminum extrusions
US5198045A (en) * 1991-05-14 1993-03-30 Reynolds Metals Company Low density high strength al-li alloy
KR940008071B1 (ko) * 1991-12-26 1994-09-01 한국과학기술연구원 Al-Li합금의 초소성화 가공열처리 방법
GB9308171D0 (en) * 1993-04-21 1993-06-02 Alcan Int Ltd Improvements in or related to the production of extruded aluminium-lithium alloys
US6562154B1 (en) 2000-06-12 2003-05-13 Aloca Inc. Aluminum sheet products having improved fatigue crack growth resistance and methods of making same
JP2013542320A (ja) * 2010-09-08 2013-11-21 アルコア インコーポレイテッド 改良された６ｘｘｘアルミニウム合金及びその製造方法
CN104152753B (zh) * 2014-07-08 2016-06-15 蚌埠市英路光电有限公司 一种led用含改性树木灰的铝基复合散热材料
CN104164597B (zh) * 2014-07-22 2016-03-30 安徽冠宇光电科技有限公司 一种重利用电镀废水的led用铝基复合散热材料
BR112017006131A2 (pt) * 2014-09-29 2017-12-19 Constellium Issoire produto corroído em liga de alumínio - magnésio - lítio
US10724127B2 (en) 2017-01-31 2020-07-28 Universal Alloy Corporation Low density aluminum-copper-lithium alloy extrusions
CN106893897B (zh) * 2017-02-27 2018-04-10 广东省材料与加工研究所 一种耐热稀土铝合金导线及其制造方法
CN108754358B (zh) * 2018-05-29 2020-03-17 江苏理工学院 一种耐低温铝合金复合材料及其制备方法
CN110484792B (zh) * 2019-09-27 2021-02-26 福建省闽发铝业股份有限公司 一种提高铝型材抗压强度的熔铸生产工艺
CN111500901A (zh) * 2020-05-29 2020-08-07 中南大学 一种高锂铝锂合金及其制备方法

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GB2137227B (en) * 1983-03-31 1986-04-09 Alcan Int Ltd Aluminium-lithium alloys
FR2561260B1 (fr) * 1984-03-15 1992-07-17 Cegedur Alliages al-cu-li-mg a tres haute resistance mecanique specifique
US4806174A (en) * 1984-03-29 1989-02-21 Aluminum Company Of America Aluminum-lithium alloys and method of making the same
US4648913A (en) * 1984-03-29 1987-03-10 Aluminum Company Of America Aluminum-lithium alloys and method
DE3613224A1 (de) * 1985-08-20 1987-02-26 Boeing Co Aluminium-lithium-legierung
EP0325937B1 (fr) * 1988-01-28 1994-03-09 Aluminum Company Of America Alliages aluminium-lithium

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JPH01242750A (ja) 1989-09-27
DE68913561T2 (de) 1994-10-20
CA1338007C (fr) 1996-01-30
DE4123560B4 (de) 2006-03-09
EP0325937A1 (fr) 1989-08-02
JP3101280B2 (ja) 2000-10-23
DE68913561D1 (de) 1994-04-14

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