EP0134403A1 - Fabrication par métallurgie des poudres d'un composé intermétallique lithium-aluminium et son utilisation - Google Patents

Fabrication par métallurgie des poudres d'un composé intermétallique lithium-aluminium et son utilisation Download PDF

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Publication number
EP0134403A1
EP0134403A1 EP84105154A EP84105154A EP0134403A1 EP 0134403 A1 EP0134403 A1 EP 0134403A1 EP 84105154 A EP84105154 A EP 84105154A EP 84105154 A EP84105154 A EP 84105154A EP 0134403 A1 EP0134403 A1 EP 0134403A1
Authority
EP
European Patent Office
Prior art keywords
temperature
lithium
aluminum
compact
powder
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
EP84105154A
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German (de)
English (en)
Other versions
EP0134403B1 (fr
Inventor
Gerhard Dr. Ibe
Josef Dipl.-Ing. Penkava
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.)
Vereinigte Aluminium Werke AG
Original Assignee
Vereinigte Aluminium Werke AG
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 Vereinigte Aluminium Werke AG filed Critical Vereinigte Aluminium Werke AG
Priority to AT84105154T priority Critical patent/ATE31429T1/de
Publication of EP0134403A1 publication Critical patent/EP0134403A1/fr
Application granted granted Critical
Publication of EP0134403B1 publication Critical patent/EP0134403B1/fr
Expired legal-status Critical Current

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    • 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
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/03—Making non-ferrous alloys by melting using master 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

Definitions

  • the invention relates to an alloy additive for aluminum lightweight components, consisting of lithium and aluminum.
  • the alkali metal lithium is becoming increasingly important in technology, e.g. as an alloy additive to aluminum alloys, which reduces the density of the alloy, increases the modulus of elasticity and thus improves suitability for lightweight construction.
  • processing the lithium is difficult and not harmless because it reacts very easily, e.g. with water, oxygen, nitrogen, halogens and especially in the liquid state above the low melting point of 181 ° C. Therefore, e.g. the production of lithium-containing aluminum alloys, in which the lithium is processed in a molten state, special protective measures and cannot be carried out in normal smelting plants.
  • the present invention was therefore based on the object of avoiding the described dangers and disadvantages of the previously known methods for the preparation of the compound LiAl and to develop an alloy additive which enables easy, harmless production of lithium aluminum compounds with no molten starting material - Or intermediate products occur and the end products consist of a pure beta phase of a Li-Al alloy with a high modulus of elasticity and low density.
  • the alloy additive is a pure LiAl compound of the beta phase, with Li contents of 44 to 55 at.% Or 17 to 25 wt.% And with the corresponding aluminum content of 56 to 45 at. % or 83 to 75% by weight.
  • a method according to the invention for producing the alloy additive is characterized in that elemental lithium powder and elemental aluminum powder are weighed and mixed in a weight ratio of 1: 5 to 1: 3 under protective gas (argon or helium), the powder mixture is introduced into a heatable press die and at temperatures , in which the lithium powder has not yet melted, degassed by evacuation and then pressed.
  • protective gas argon or helium
  • the grain sizes of the starting materials are 40 to 200 / um.
  • An essential measure for achieving the aim of the invention is that the powder mixture is reaction sintered under vacuum or protective gas.
  • the compact is pressed in the die without pressure with a heating rate of 5 to 50 ° C / min. heated to a temperature in the range from 450 ° C to a maximum of just below the peritectic temperature of 520 ° C.
  • the compact in the press die with a pressure of 50 to 500 bar and a heating rate of 5 to 50 ° C / min. is heated to a temperature in the range of 450 ° C to a maximum of just below the peritectic temperature of 520 ° C.
  • the heating in the range from 190 to 230 ° C. is interrupted for at least 15 minutes.
  • the pressure should preferably be applied to the compact only when a temperature above 400 ° C. is reached.
  • the powder mixture is pressed under vacuum without additional heating with a pressing pressure between 50 and 500 bar, the compact reaching a temperature between 100 and 300 ° C.
  • the compact is heat-treated (homogenized) at a temperature of 450 ° C. to a maximum of just below the peritectic temperature of 520 ° C. for at least 4 hours.
  • An advantageous process for the further processing of the compact according to the invention is characterized in that the compact is removed from the die immediately before and / or after the homogenization annealing under protective gas, encapsulated in an aluminum sleeve and in the temperature range from 300 to 500 C with a compression ratio between 5 to 1 and 100 to 1 is extruded.
  • a preferred use of the alloy additive for the production of aluminum alloys with a high modulus of elasticity is characterized in that the alloy additive is introduced into the aluminum alloy melt in solid form, the melt having a temperature below the melting temperature of the compound LiAl, and its surface by means of protective gas or Layer of liquid, lithium chloride-containing molten salt is protected against oxidation.
  • the idea of the invention is essentially based on the fact that the lithium is not processed in pure form but as an intermetallic compound LiAl.
  • an intermetallic phase AlLi exists with approximately 50% lithium with a maximum area of existence of approximately 10%.
  • This beta phase melts congruently (without decomposition) at 718 ° C, i.e. well above the aluminum melting point of 660 ° C.
  • the starting materials of the process according to the invention are elementary aluminum and lithium powder, the production of which, including the necessary protective and safety measures, is state of the art - e.g. the Li powder is produced under argon, handled and sent. The starting material is therefore available in sufficient quantities.
  • the starting powders with grain sizes between 10 and 1000 micrometers, preferably from 30 to 200 micrometers, are weighed out under argon as a protective gas, for example in a glove box, and in sealed vessels under argon mixed without noticeable warming.
  • the powder mixture is filled under argon into a heatable mold, which is transferred without air into a press which is located in a closed vessel which can be evacuated or flushed with protective gas (argon).
  • the powder mixture is degassed at temperatures below the Li melting point in a vacuum, pre-pressed and reaction sintered with a continuously increasing temperature, it being possible to use a different pressing pressure.
  • the powder particles come into metallic contact with one another so that the formation reaction of the compound LiAl can start in the solid state.
  • the reactants - Li and Al atoms - are supplied by diffusion from the powder particles.
  • Li grains can melt, which accelerates the reaction with the Al grains.
  • the heating rate should not exceed 50 ° C per minute so as not to overheat the molten, aggressive Li before the reaction with the Al has ended.
  • the heat of reaction of LiAl formation is noticeable (approx. 54 kJ / mol) and can e.g. can be detected by differential thermal analysis (DTA) (Fig. 2).
  • the heating of the sample should expediently be interrupted for at least 15 minutes after a temperature of 230 ° to 320 ° C. has been reached. This prevents the sample from overheating due to the interaction of heating and its own reaction heat (Fig. 2b).
  • the chemical homogeneity of the sample - e.g. detectable by X-ray diffractometric phase analysis - increased and the residual porosity reduced.
  • the LiAl compound produced in this way can be used for the production of lithium-containing aluminum alloys by introducing the necessary amount of LiAl into the aluminum alloy melt which is not heated above the melting point of the LiAl compound and, owing to its lower density, being immersed in the melt with a simple ceramic device and is moved until it has dissolved without melting. A weak purging of the enamel surface with argon is sufficient to protect against the reaction.
  • This is built into a vacuum housing that can be evacuated to about 10 (-4) mbar by a turbomolecular pump or filled or flushed with protective gas from 0.1 to 1000 mbar.
  • the sample was first degassed without heating until the final pressure of 10 (-4) mbar was reached.
  • the degassed sample is pre-pressed without heating at a pressure of 350 bar. Due to the frictional heat of the powder and the metallic contact between A1 and Li, the formation reaction of the beta phase is already partially initiated, as can be seen from the warming of the sample and can be demonstrated by X-ray diffraction at the occurrence of the LiAl lines.
  • the compact is heated under argon (500 mbar) at a pressure of 200 bar with a heating rate of 5 ° C / min from room temperature to 500 ° C, starting at a temperature of about 290 ° C to a certain softening of the sample occurs due to the ongoing formation reaction of the LiAl, which reaches its maximum at about 450 ° C (Fig.2a).
  • the sample After reaching 500 ° C the sample is kept at temperature for at least 4 hours until the chemical homogeneity is large enough and an X-ray diffractogram shows practically only the lines of the beta phase.
  • the residual porosity achieved is between 2.5 and 6% depending on the pressure.
  • the alloy was poured into a small, flat, water-cooled copper mold and homogenized for 4 hours at 500 ° C., the sample being wrapped in an aluminum foil. Then the material could be further processed by rolling etc.
  • a control analysis showed a Li content of 3.0% by weight, which can be attributed to a relatively high burn-up due to the small amount of sample (large surface area: volume ratio).
  • the compact was subjected to an interrupted heating according to FIG. 2b.
  • the heating was interrupted at 195 ° C and only continued after 16 minutes at a heating rate of 5 ° C per minute.
  • the further treatment was carried out analogously to the previous example, the residual porosity being between 1 and 2% depending on the pressure.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Manufacture And Refinement Of Metals (AREA)
EP84105154A 1983-08-25 1984-05-07 Fabrication par métallurgie des poudres d'un composé intermétallique lithium-aluminium et son utilisation Expired EP0134403B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84105154T ATE31429T1 (de) 1983-08-25 1984-05-07 Pulvermetallurgische herstellung der intermetallischen verbindung lithium-aluminium und ihre verwendung.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3330597 1983-08-25
DE3330597A DE3330597C2 (de) 1983-08-25 1983-08-25 Verfahren zur Herstellung eines Legierungszusatzes für Aluminium-Leichtbauteile und dessen Verwendung

Publications (2)

Publication Number Publication Date
EP0134403A1 true EP0134403A1 (fr) 1985-03-20
EP0134403B1 EP0134403B1 (fr) 1987-12-16

Family

ID=6207366

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84105154A Expired EP0134403B1 (fr) 1983-08-25 1984-05-07 Fabrication par métallurgie des poudres d'un composé intermétallique lithium-aluminium et son utilisation

Country Status (3)

Country Link
EP (1) EP0134403B1 (fr)
AT (1) ATE31429T1 (fr)
DE (2) DE3330597C2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3704767A1 (de) * 1987-02-16 1988-08-25 Leybold Ag Verfahren zum herstellen von chargiermaterial fuer schmelzmetallurgische prozesse und durch das verfahren hergestelltes chargiermaterial
DE19522988A1 (de) * 1995-06-28 1997-01-02 Sel Alcatel Ag Verfahren zur Gebühreninformation sowie Dienststeuereinrichtung, Teilnehmervermittlungsstelle, Endgerät und Kommunikationsnetz

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH358238A (fr) * 1955-10-31 1961-11-15 Foundry Services International Procédé de fabrication d'alliages ou de purification d'un métal
GB1484650A (en) * 1974-06-20 1977-09-01 Us Energy Method of preparing a uniform alloy composition of lithium and aluminum
EP0045622A1 (fr) * 1980-07-31 1982-02-10 MPD Technology Corporation Alliages en aluminium durci par vieillissement
US4389240A (en) * 1982-07-09 1983-06-21 Novamet, Inc. Alloying method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3563730A (en) * 1968-11-05 1971-02-16 Lithium Corp Method of preparing alkali metal-containing alloys

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH358238A (fr) * 1955-10-31 1961-11-15 Foundry Services International Procédé de fabrication d'alliages ou de purification d'un métal
GB1484650A (en) * 1974-06-20 1977-09-01 Us Energy Method of preparing a uniform alloy composition of lithium and aluminum
EP0045622A1 (fr) * 1980-07-31 1982-02-10 MPD Technology Corporation Alliages en aluminium durci par vieillissement
US4389240A (en) * 1982-07-09 1983-06-21 Novamet, Inc. Alloying method

Also Published As

Publication number Publication date
DE3468128D1 (en) 1988-01-28
EP0134403B1 (fr) 1987-12-16
DE3330597A1 (de) 1985-03-14
DE3330597C2 (de) 1986-07-24
ATE31429T1 (de) 1988-01-15

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