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
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
  • C22C21/04—Modified aluminium-silicon alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0408—Light metal alloys
  • C22C1/0416—Aluminium-based alloys
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
  • Y10T29/49988—Metal casting

Definitions

• the field of the invention relates to Al-based alloys relating to high contents of Li and Si and having a high to medium mechanical strength, a very low density and a high Young modulus; a process for obtaining it uses rapid solidification (atomization, hyper quenching on a metal substrate, etc.) densification and hot shaping.
• metallurgists have proposed additions of a few% of hardening elements such as Cu, Mg, Zn and other minor elements controlling the recrystallization or the grain size of the alloy, such as Mn, Cr, Ti, etc ...
• These alloys also contain very low Fe and Si contents (less than 0.1% by weight).
• Swiss patent CH-216 204 discloses AI-Li-Si alloys containing from 1 to 10% (by weight) of Li and Si (in undetermined amount); the example given relates to an alloy containing: 3.5% Li; 5% If; 1 ° / o Cu; 1% Ni; remains AI. However, this alloy, most probably obtained by conventional casting, probably has a low heat stability, unlike the alloys according to the invention.
• the Applicant has found that it is possible to obtain gains in specific modulus much greater than 25 ° / o on AI-Li-Si alloys containing large amounts of Si and Li, while retaining acceptable mechanical characteristics, satisfactory spontaneous corrosion resistance, and good formability.
• This objective is achieved by the choice of a specific composition, the use of rapid solidification and techniques of powder metallurgy, and finally a shaping at controlled temperature.
• the Li content is preferably kept between 4 and 7%.
• the total content of secondary elements is preferably kept below 2% .
• the properties of the products obtained are only satisfactory if the alloys are produced by rapid solidification at cooling rates from the liquid state above 1000 ° C / sec. by any known means (solidification on a wheel, atomization, etc.).
• This operation preferably takes place under an inert atmosphere, for example argon or helium.
• the alloys thus obtained are then consolidated by known techniques of powder metallurgy, for example according to the range: possible grinding, cold compaction, degassing under possible vacuum, hot compression and drawing by spinning, forging, stamping or any other technique. , with a rate of wrought (section initial cross-section / final cross-section) generally greater than 8.
• the product temperature must remain below 400 ° C, and preferably 350 ° C, to obtain acceptable mechanical characteristics.
• the products are generally used, as indicated, in the raw state of hot transformation, or after a slight additional deformation at a lower temperature, which makes it possible to improve both the flatness, the straightness or the dimensional tolerances and the mechanical resistance characteristics.
• the products thus obtained have a large volume fraction, between 15 and 60%, preferably between 20 and 50%, of particles essentially consisting of a phase of cubic structure, with a parameter close to 0 , 59 at 0.60 nm, identified as phase T - AI2 Li 3 Si 2 or AI Li Si, according to the authors.
• This phase distributed homogeneously, has a size of between 0.01 to 10 ⁇ m, more generally between 0.01 and 5 ⁇ m: it is believed that this phase contributes to cold hardening and to the average temperatures of the alloy, its fine and homogeneous precipitation being accentuated by an income between room temperature and 350 ° C, preferably between 150 and 250 ° C.
• the microstructure may optionally include a very fine globular precipitation of phase 8 '(AI 3 Li) whose diameter is less than 50 nm and also a slight precipitation of free Si or phase 8 AI Li.
• phase 8 represents less than 10% (by volume).
• the products thus obtained are characterized by an extremely fine grain whose size is less than 20 ⁇ m, and generally less than 10 ⁇ m.
• phase 8 AI Li which is spontaneously corrodible and also of phase phase 'AI 3 Li weakening is favored.
• the Applicant has on the other hand, found that for an equal composition, the hardness of the products is all the higher the smaller the size of the T phase particles (AI, Li, Si); in particular the very rapid solidification of the thin ribbons (20 to 30 ⁇ m thick) on a metallic substrate ("melt spinning") leads, on the substrate side, to T-phase particle sizes of 0.01 to 0.5 ⁇ m.
• microhardness is then approximately 40% greater than that obtained on the external face of the thicker ribbons or on powders obtained by atomization, for which the size of particles of phase T is of the order of 0.5 to 5 ⁇ m.
• Alloys the composition of which is given in Table 1, were obtained in the form of powder, by centrifugal spraying with helium, the latter being sieved to 200 ⁇ m maximum.
• These powders were made from cast ingots, made with a pure base having an Fe content ⁇ 0.05%.
• the bars obtained were air-cooled, and characterized by density measurement, Young's modulus, tensile tests (long sense) and micrographic examinations.
• Table I brings together the targeted chemical compositions determined by atomic absorption and the results obtained (average of 5 tests).
• the oxygen content is around 0.5%.
• phase T present was coarse (average size 2 ⁇ m, maximum size 5 ⁇ m), but homogeneously dispersed except for a few large particles of phase T (100 to 200 ⁇ m) whose presence explains the low elongations observed (primers premature rupture).
• Alloys AI, Li, Si including the compositions given in Example 1 were cast in strips of 10 mm x 40 ⁇ m approximately, of cross section, on a copper wheel 0 480 mm rotating at 1000 rpm, since 730 to 830 ° C; they were characterized by Vickers microhardness under 10 g micrographic examination by optical microscopy, electron and X-ray diffraction in the raw casting state, and after heat treatment of tempering from 1 to 10 h between 200 and 350 ° C, to evaluate hot stability and structural evolution.
• the external part of the ribbons B, C, D and the entire thickness of the ribbons (E, F) had a coarse structure of the order of 1 ⁇ m on average (maximum size of 4 ⁇ m) in the raw state of casting and after income.
• the volume fraction of the precipitates did not vary significantly during the incomes.
• the hardness increases with the contents of Li and Si, and the volume fraction of phase T, at least as long as the latter remains in the form of fine particles.
• the fine structures give the alloys according to the invention a very high level of hardness after tempering at 200 ° C, and this remains high even after tempering at 350 ° C, unlike the alloys outside the invention.
• phase T very coarse particles of phase T (AI, Li, Si, of very heterogeneous sizes, rather coarse, of several ⁇ m to several hundreds of ⁇ m, and clearly higher than 10 ⁇ m on average, associated with a small amount of phase 8 AI Li.
• This example shows the need to use a method involving rapid solidification for the alloys according to the invention.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Silicon Compounds (AREA)
• Conductive Materials (AREA)
• Powder Metallurgy (AREA)
• Ceramic Products (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Materials For Medical Uses (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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• 1985
  • 1985-06-28 FR FR8510375A patent/FR2584095A1/fr not_active Withdrawn
• 1986
  • 1986-06-23 IL IL79198A patent/IL79198A0/xx unknown
  • 1986-06-23 CA CA000512207A patent/CA1274107A/fr not_active Expired - Fee Related
  • 1986-06-24 JP JP61148019A patent/JPS627828A/ja active Granted
  • 1986-06-25 EP EP86420166A patent/EP0208631B1/fr not_active Expired
  • 1986-06-25 DE DE8686420166T patent/DE3664789D1/de not_active Expired
  • 1986-06-25 AT AT86420166T patent/ATE45189T1/de active
  • 1986-06-27 US US06/879,347 patent/US4804423A/en not_active Expired - Fee Related
  • 1986-06-27 BR BR8602980A patent/BR8602980A/pt unknown
  • 1986-06-27 ES ES8600019A patent/ES2000175A6/es not_active Expired

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