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
  • 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

• the present invention relates to alloys based on AI essentially containing Cu, Li and Mg, having a very high specific mechanical resistance and usable in particular, for obtaining heat-treated parts of complex shape.
• metallurgists have proposed a new experimental alloy with nominal composition AI-3% Li-2% Cu-0.2% Zr (with high strength, low density and low ductility), as well as new alloys of the Aluminum-Lithium system. -Copper-Magnesium with medium resistance, low density and improved ductility. This is in particular the alloy of average composition AI-2.4% Li-1.25% Cu-0.75% Mg (- Cr-Mn-Zr-Ni) which has been the subject of the European Patent Application No. 0088511 to the Secretary for Defense of the United Kingdom.
• the alloy AI-2.0-2.4% Li-2.3-2.7% Cu up to 0.9% Mg up to 0.15% Zr and Fe up to 0 are also known. 12% Si, which was the subject of European patent application No. EP-A-0 156 995 not yet published on the date of filing of this application.
• the invention described below makes it possible to have new lithium alloys which do not have these limitations.
• These alloys give products of any configuration very high mechanical properties in the T6 state (equivalent to those of alloys 7075-T 6 and 7010-T 736) combined with a density reduced by 6 to 9% compared to that of alloys conventional of the 2000 or 7000 series.
• the alloy products according to the invention have a specific mechanical resistance further improved by work hardening between quenching and tempering (states T-651, T-652 or T-8) but this deformation operation plastic can be limited, for example, to the sole holding or leveling of hardened products.
• the alloys according to the invention have the following weight compositions:
• compositions taken individually or in combinations are as follows:
• the alloys according to the invention have their optimum level of resistance and ductility after homogenization treatments of the cast products and dissolving of the processed products comprising at least one bearing at a temperature O H of between 520 and 545 ° C for a sufficient time either to completely dissolve the intermetallic compounds of the phases rich in Cu and Li and either to obtain a size less than 5 ⁇ m.
• the optimal durations of heat treatment for homogenization at O H temperature were 0.5 to 8 hours for alloys produced by rapid solidification (atomization-splat cooling) and 12 hours to 72 hours for products molded or produced in semi casting -continuous, for which it is preferable to carry out, during the homogenization or the dissolution, one or two intermediate stages of a few hours at 500 ° C, 515 ° C or 528 ° C approximately so as to avoid the beginning melting of the alloy when it is kept at the temperature On.
• tempering kinetics tests have shown that these alloys have their optimal mechanical properties after tempering lasting 8 hours to 48 hours at temperatures between 170 and 220 ° C (preferably between 190 and 200 ° C), and that it was preferable to subject the products of adequate shape (sheets, bars, widgets) to work hardening giving rise to a plastic deformation of 1.5 to 5% (preferably 2 to 4%) between quenching and tempering, which further improves the compromise between mechanical strength and ductility of these alloys.
• the alloys according to the invention have in the T-6 (51) state a mechanical resistance equivalent to that of the 7075 or 7010 T-6 (51) alloys.
• These high levels of elastic limit and breaking load are moreover combined with densities reduced by 6 to 8% compared to those of conventional aeronautical aluminum alloys. (without lithium) and with satisfactory levels of ductility or elongation, which shows the advantage of the alloys according to the invention for the production of wrought or molded structural parts with very high specific mechanical strength and good dynamic properties (toughness, resistance fatigue), whether these are products produced by semi-continuous casting, atomization or splat-cooling.
• Ingots the analysis of which is given in Table 1a, were produced from refined aluminum (AI 99.99%), refined by adding 0.15% AT5B, then cast into molds with a structure similar to that obtained by semi-continuous industrial casting.
• All these alloys contain less than 0.02% (by weight) of Fe and less than 0.02% of Si.
• alloys were homogenized under the conditions making it possible to obtain an almost complete dissolution of the intermetallic compounds rich in lithium and copper, and quenched with water at 20 ° C. they have matured for at least 5 days and 24 hour treatments at temperatures of 150, 170, 190 and 210 ° C.
• Table Ib gives the heat treatments and the average Vickers hardnesses after tempering, as well as the maximum specific hardness of each of these alloys (Vickers hardness / density ratio).
• the alloys were poured semi-continuously in the form of ⁇ 200 mm billets.
• the billets were homogenized at 515 ° C for 16 h + 24 h at 535 ° C, peeled and spun into strips 50 x 20 mm at 430 ° C (i.e. with a spinning ratio of 12).
• the largets were dissolved in 539 ° C and soaked in water and underwent various incomes.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Physical Vapour Deposition (AREA)
• Forging (AREA)
• Conductive Materials (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Sealing Battery Cases Or Jackets (AREA)
• Continuous Casting (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 1984
  • 1984-03-15 FR FR8404483A patent/FR2561260B1/fr not_active Expired - Fee Related
• 1985
  • 1985-03-11 ES ES541151A patent/ES541151A0/es active Granted
  • 1985-03-12 CA CA000476314A patent/CA1287508C/fr not_active Expired - Fee Related
  • 1985-03-13 DE DE8585420043T patent/DE3560729D1/de not_active Expired
  • 1985-03-13 JP JP60050241A patent/JPS60215734A/ja active Granted
  • 1985-03-13 EP EP85420043A patent/EP0158571B1/fr not_active Expired
  • 1985-03-14 IL IL74604A patent/IL74604A/xx unknown
  • 1985-03-14 BR BR8501144A patent/BR8501144A/pt unknown
• 1988
  • 1988-02-16 US US07/158,048 patent/US4840683A/en not_active Expired - Fee Related
  • 1988-04-27 JP JP63105375A patent/JPS63286557A/ja active Pending

Non-Patent Citations (1)

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