EP0134403A1 - Method of preparing a lithium-aluminium compound by powder metallurgy, and its use - Google Patents
Method of preparing a lithium-aluminium compound by powder metallurgy, and its use Download PDFInfo
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- 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
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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
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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
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/0408—Light metal alloys
- C22C1/0416—Aluminium-based alloys
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- 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.
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Abstract
Description
Die Erfindung betrifft einen Legierungszusatz für Aluminium-Leichtbauteile, bestehend aus Lithium und Aluminium.The invention relates to an alloy additive for aluminum lightweight components, consisting of lithium and aluminum.
Das Alkalimetall Lithium gewinnt in der Technik zunehmend an Bedeutung, z.B. als Legierungszusatz zu Aluminiumlegierungen, der die Dichte der Legierung verringert, den Elastizitätsmodul erhöht und damit die Leichtbau-Eignung verbessert.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.
Die Verarbeitung des Lithiums ist jedoch schwierig und nicht ungefährlich, denn es reagiert sehr leicht, z.B. mit Wasser, Sauerstoff, Stickstoff, Halogenen und insbesondere in flüssigem Zustand oberhalb des niedrigen Schmelzpunktes von 181°C. Daher erfordert z.B. die Herstellung von Lithium-haltigen Aluminiumlegierungen, bei der das Lithium schmelzflüssig verarbeitet wird, besondere Schutzvorkehrungen und kann nicht in normalen Schmelzanlagen ausgeführt werden.However, 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.
Es ist aus P. Assmann: Zeitschrift f. Metallkunde 18 (1926) 51 und A.P. Divecha, S.D. Karmarkar: Proc. 1st Al-Li Conference Stone Montain, Ga. 1980, Met.Soc.AIME, Warrendale, Pa. 1981, p.29 (Ref.1,2) bekannt, eine Vorlegierung schmelzmetallurgisch analog zur Lithium-haltigen Aluminiumlegierung herzustellen.It is from P. Assmann: Zeitschrift f. Metallkunde 18 (1926) 51 and A.P. Divecha, S.D. Karmarkar: Proc. 1st Al-Li Conference Stone Montain, Ga. 1980, Met.Soc.AIME, Warrendale, Pa. 1981, p.29 (Ref.1,2) known to produce a master alloy by melt metallurgy analogous to the lithium-containing aluminum alloy.
In einem anderen ungefährlicheren Verfahren gemäß R.O..Bach, A.S. Gillespie, jr.: Lithium Corporation of America, US-Patent 3,563,730 vom Februar 1971 (Ref. 3) wird das LiAl aus Aluminium- und Lithium-Pulver erzeugt, das in heißem öl gemischt und so hoch erwärmt wird, daß die Li-Pulverteilchen zu Tröpfchen geschmolzen sind, die bei vorsichtiger Bewegung des Gemisches temporär mit Al-Pulverteilchen zusammentreffen und zu LiAl reagieren. Unerwünschte oder gefährliche Nebenreaktionen mit Sauerstoff, Stickstoff, Wasserdampf usw. werden dabei durch das öl verhindert. Schwierigkeiten bereitet jedoch die Erreichung des vollständigen Umsatzes der Ausgangsstoffe. Ein weiterer Nachteil des Verfahrens ist die umständliche Abtrennung des Reaktionsproduktes LiAl vom öl, was eine technische Anwendung erschwert.In another less dangerous process according to RO.Bach, AS Gillespie, Jr.: Lithium Corporation of America, U.S. Patent 3,563,730, February 1971 (Ref. 3), the LiAl is generated from aluminum and lithium powder mixed in hot oil and is heated so high that the Li powder particles are melted into droplets, which, when the mixture is carefully agitated, temporarily meet with Al powder particles and react to form LiAl. The oil prevents undesirable or dangerous side reactions with oxygen, nitrogen, water vapor etc. However, it is difficult to achieve full conversion of the starting materials. Another disadvantage of the process is the cumbersome separation of the reaction product LiAl from the oil, which makes industrial application difficult.
Der vorliegenden Erfindung lag daher die Aufgabe zugrunde, die geschilderten Gefahren und Nachteile der bisher bekannten Methoden zur Herstellung der Verbindung LiAl zu vermeiden und einen Legierungszusatz zu entwickeln, der eine leichte, ungefährliche Herstellung von Lithium-Aluminium-Verbindungen ermöglicht, bei der keine schmelzflüssigen Ausgangs- oder Zwischenprodukte auftreten und die Endprodukte aus einer reinen Beta-Phase einer Li-Al-Legierung mit hohem E-Modul bei geringer Dichte bestehen.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.
Erfindungsgemäß geschieht das dadurch, daß der Legierungszusatz eine reine LiAl-Verbindung der Betaphase ist, mit Li-Gehalten von 44 bis 55 at.% bzw. 17 bis 25 Gew.-% und mit dem entsprechenden Aluminium-Gehalt von 56 bis 45 at.% bzw. 83 bis 75 Gew.-%.This occurs according to the invention in that 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.
Ein erfindungsgemäßes Verfahren zur Herstellung des Legierungszusatzes ist dadurch gekennzeichnet, daß elementares Lithium- pulver und elementares Aluminiumpulver im Gewichtsverhältnis 1:5 bis 1:3 unter Schutzgas (Argon oder Helium) eingewogen und gemischt werden, die Pulvermischung in eine beheizbare Preßmatrize eingeführt und bei Temperaturen, bei denen das Lithiumpulver noch nicht aufschmilzt, durch Evakuieren entgast und anschließend gepreßt wird.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.
Es ist vorteilhaft, daß die Korngrößen der Ausgangsstoffe 40 bis 200/um betragen.It is advantageous that the grain sizes of the starting materials are 40 to 200 / um.
Eine für das Erreichen des erfindungsgemäßen Zieles wesentliche Maßnahme besteht darin, daß die Pulvermischung unter Vakuum oder Schutzgas reaktionsgesintert wird.An essential measure for achieving the aim of the invention is that the powder mixture is reaction sintered under vacuum or protective gas.
Nach einem bevorzugten Verfahren gemäß der vorliegenden Erfindung wird der Preßling in der Preßmatrize ohne Druck mit einer Aufheizgeschwindigkeit von 5 bis 50°C/min. auf eine Temperatur im Bereich von 450°C bis maximal dicht unterhalb der peritektischen Temperatur von 520°C aufgeheizt.According to a preferred method according to the present invention, 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.
Es ist ferner vorteilhaft, wenn der Preßling in der Preßmatrize mit einem Druck von 50 bis 500 bar und einer Aufheizgeschwindigkeit von 5 bis 50°C/min. auf eine Temperatur im Bereich von 450°C bis maximal dicht unterhalb der peritektischen Temperatur von 520°C aufgeheizt wird.It is also advantageous if 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.
Um das Auftreten einer überhitzten, aggressiven Schmelze aus Lithium zu verhindern, die nicht rechtzeitig mit Al-Körnern reagieren kann, ist es vorteilhaft, daß die Aufheizung im Bereich von 190 bis 230°C für mindestens 15 Minuten unterbrochen wird.In order to prevent the occurrence of an overheated, aggressive lithium melt which cannot react in time with Al grains, it is advantageous that the heating in the range from 190 to 230 ° C. is interrupted for at least 15 minutes.
Wenn die Aufheizgeschwindigkeit nahe der oberen Grenze liegt, sollte der Druck auf den Preßling vorzugsweise erst bei Erreichen einer Temperatur oberhalb von 400°C aufgebracht werden.If the heating rate is close to the upper limit, the pressure should preferably be applied to the compact only when a temperature above 400 ° C. is reached.
Es ist vorteilhaft, daß die Pulvermischung unter Vakuum ohne zusätzliche Heizung mit einem Preßdruck zwischen 50 und 500 bar gepreßt wird, wobei der Preßling eine Temperatur zwischen 100 und 300°C erreicht.It is advantageous that 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.
Es ist ferner vorteilhaft, wenn nach Erreichen der Endtemperatur der Preßling bei einer Temperatur von 450°C bis maximal dicht unterhalb der peritektischen Temperatur von 520°C während einer Zeit von mindestens 4 Stunden wärmebehandelt (homogenisiert) wird.It is also advantageous if, after reaching the final temperature, 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.
Ein vorteilhaftes Verfahren zur Weiterverarbeitung des erfindungsgemäßen Preßlings ist dadurch gekennzeichnet, daß der Preßling unmittelbar vor und/oder nach der Homogenisierungsglühung unter Schutzgas aus der Matrize entnommen, in einer Aluminium-Hülse eingekapselt und im Temperaturbereich von 300 bis 500 C mit einem Verpressungsverhältnis zwischen 5 zu 1 und 100 zu 1 stranggepreßt wird.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.
Eine bevorzugte Verwendung des Legierungszusatzes zur Herstellung von Aluminiumlegierungen mit hohem E-Modul ist dadurch gekennzeichnet, daß der Legierungszusatz in fester Form in die Aluminiumlegierungsschmelze eingebracht wird, wobei die Schmelze eine Temperatur unterhalb der Schmelztemperatur der Verbindung LiAl besitzt, und ihre Oberfläche durch Schutzgas oder eine Schicht flüssigen, Lithiumchlorid-haltigen Schmelzsalzes gegen Oxidation geschützt ist.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.
Der Erfindungsgedanke beruht im wesentlichen darauf, daß das Lithium nicht in reiner Form sondern als intermetallische Verbindung LiAl verarbeitet wird. Wie das Zustandsdiagramm des Legierungssystems Aluminium-Lithium (Fig. 1) zeigt, existiert bei etwa 50% Lithium eine intermetallische Phase AlLi mit einem maximal etwa 10% breiten Existenzgebiet. Diese Beta- Phase schmilzt kongruent (ohne Zersetzung) bei 718°C, d.h. deutlich oberhalb des Aluminium-Schmelzpunktes von 660°C.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. As the state diagram of the aluminum-lithium alloy system (FIG. 1) shows, 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.
Die Ausgangsstoffe des erfindungsgemäßen Verfahrens sind elementares Aluminium- und Lithium-Pulver, deren Herstellung einschließlich der notwendigen Schutz- und Sicherheitsmaßnahmen Stand der Technik sind - z.B. wird das Li-Pulver unter Argon hergestellt, hantiert und verschickt. Das Ausgangsmaterial steht daher in ausreichenden Mengen zur Verfügung.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.
Die Ausgangspulver mit Korngrößen zwischen 10 und 1000 Mikrometer, vorzugsweise von 30 bis 200 Mikrometer, werden unter Argon als Schutzgas, z.B. in einem Handschuhkasten ("glove box"), abgewogen und in abgeschlossenen Gefäßen unter Argon ohne merkliche Erwärmung gemischt. Die Pulvermischung wird unter Argon in eine heizbare Preßform eingefüllt, die ohne Luftzutritt in eine Presse überführt wird, die sich in einem geschlossenen Gefäß befindet, das evakuiert oder mit Schutzgas (Argon) gespült werden kann.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).
Die Pulvermischung wird bei Temperaturen unterhalb des Li-Schmelzpunktes im Vakuum entgast, vorgepreßt und mit kontinuierlich ansteigender Temperatur reaktionsgesintert, wobei ein unterschiedlicher Preßdruck angewendet werden kann. Dabei geraten die Pulverteilchen in metallischen Kontakt miteinander, so daß die Bildungsreaktion der Verbindung LiAl im festen Zustand starten kann. Die Reaktionspartner - Li-und Al-Atome - werden durch Diffusion aus den Pulverteilchen nachgeliefert. Bei Aufheizgeschwindigkeiten über 5°C pro Minute können Li-Körner aufschmelzen, wodurch die Reaktion mit den Al-Körnern beschleunigt wird. Die Aufheizgeschwindigkeit sollte jedoch nicht über 50°C pro Minute liegen, um das geschmolzene, aggressive Li nicht zu überhitzen, bevor die Reaktion mit dem Al abgelaufen ist. Die Reaktionswärme der LiAl-Bildung ist merklich (ca. 54 kJ/mol) und kann z.B. durch Differential-Thermo-Analyse (DTA) nachgewiesen werden (Fig. 2).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. At heating rates above 5 ° C per minute, Li grains can melt, which accelerates the reaction with the Al grains. However, 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).
Die Aufheizung der Probe soll zweckmäßigerweise nach Erreichen einer Temperatur von 230° bis 320°C für mindestens 15 Minuten unterbrochen werden. Damit wird verhindert, daß die Probe durch das Zusammenwirken von Aufheizung und eigener Reaktionswärme zu stark überhitzt (Fig.2b).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).
Durch eine längere Homogenisierungsglühung bei der erreichten Endtemperatur, vorzugsweise unter Preßdruck, kann die chemische Homogenität der Probe - z.B. nachweisbar durch eine röntgendiffraktometrische Phasenanalyse - erhöht und die Restporosität verringert werden.By prolonged homogenization annealing at the final temperature reached, preferably under pressure, the chemical homogeneity of the sample - e.g. detectable by X-ray diffractometric phase analysis - increased and the residual porosity reduced.
Die so hergestellte Verbindung LiAl kann für die Erzeugung von Lithium-haltigen Aluminiumlegierungen verwendet werden, indem die notwendige Menge LiAl in die nicht über den Schmelzpunkt der LiAl-Verbindung erhitzte AluminiumlegierungsSchmelze eingebracht und wegen ihrer geringeren Dichte mit einer einfachen keramischen Vorrichtung in die Schmelze eingetaucht und bewegt wird, bis sie sich ohne zu schmelzen aufgelöst hat. Dabei genügt als Reaktionsschutz ein schwaches Spülen der Schmelzoberfläche mit Argon.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.
Die Wirkungsweise des erfindungsgemäßen Verfahrens soll an einem speziellen Ausführungsbeispiel näher erläutert werden. Als Ausgangsmaterial wurden ein Aluminiumpulver mit weniger als 0,8% metallischer und etwa 0,8% oxidischer Verunreinigungen mit einer mittleren Korgröße von 63 Mikrometer (ECKA AS 71/S von den ECKART-Werken, Nürnberg) sowie ein Lithium- pulver mit 99,4% Li-Gehalt und einer mittleren Korgröße von etwa 100 Mikrometer (Metallgesellschaft, Frankfurt) benutzt.The mode of operation of the method according to the invention will be explained in more detail using a special exemplary embodiment. An aluminum powder with less than 0.8% metallic and about 0.8% oxidic impurities with an average particle size of 63 micrometers (ECKA AS 71 / S from ECKART-Werke, Nuremberg) as well as a lithium powder with 99, 4% Li content and an average particle size of about 100 micrometers (Metallgesellschaft, Frankfurt) were used.
In einem Handschuhkasten mit Gas-Schleuse wurden unter reinem Argon (02-Gehalt im praktischen Betrieb unter 0,1%) 400 g Pulvermischung mit 20,5 Gew.% Li zusammen mit Kugeln aus Polyamid in ein verschließbares Glasgefäß eingefüllt und in einem Turbula-Mischer gemischt. Dabei blieb die Temperatur unter 30°C, und es setzte noch keine Reaktion ein. Nach 2 Stunden Mischzeit wurden im Handschuhkasten unter Argon etwa 40 g der Pulvermischung in die in den Handschuhkasten eingeschleuste heizbare Preßmatrize (für stabförmige Proben von 150 mm Länge und 10 mm Breite) eingefüllt. Die Matrize wurde daraufhin oben und unten mit Preß-Scheiben verschlossen, so daß sie unter Luftabschluß der eingefüllten Pulvermischung aus dem Handschuhkasten ausgeschleust und in die Presse eingesetzt werden konnte. Diese ist in ein Vakuumgehäuse eingebaut, das durch eine Turbomolekularpumpe bis auf etwa 10 (-4) mbar evakuiert oder mit Schutzgas von 0,1 bis 1000 mbar gefüllt bzw. gespült werden kann. Hierin wurde die Probe zunächst ohne Erwärmung entgast, bis der Enddruck von 10 (-4) mbar erreicht war.In a glove box with a gas lock, 400 g of powder mixture with 20.5% by weight of Li, together with polyamide balls, were filled into a closable glass vessel under pure argon (02 content in practical operation below 0.1%) and placed in a turbulent Mixer mixed. The temperature remained below 30 ° C and no reaction started. After 2 hours of mixing, about 40 g of the powder mixture were poured into the heatable press die (for rod-shaped samples 150 mm long and 10 mm wide) in the glove box under argon. The die was then closed at the top and bottom with press washers, so that it could be removed from the glove box with the air-filled powder mixture closed and inserted into the press. 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.
Die entgaste Probe wird ohne Heizung mit einem Preßdruck von 350 bar vorgepreßt. Durch die Reibungswärme des Pulvers und den eintretenden metallischen Kontakt zwischen A1 und Li wird dabei die Bildungsreaktion der Beta-Phase bereits teilweise eingeleitet, wie man an der Erwärmung der Probe feststellen und röntgendiffraktometrisch am Auftreten der LiAl-Linien nachweisen kann.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.
Nach dem Abklingen dieser Teilreaktion wird der Preßling unter Argon (500 mbar) bei einem Preßdruck von 200 bar mit einer Aufheizgeschwindigkeit von 5°C/min von Raumtemperatur bis auf 500°C aufgeheizt, wobei es ab einer Temperatur von etwa 290°C zu einer gewissen Erweichung der Probe infolge der ablaufenden restlichen Bildungsreaktion des LiAl kommt, die bei etwa 450°C ihr Maximum erreicht (Fig.2a).After this partial reaction has subsided, 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).
Nach Erreichen von 500°C wird die Probe noch mindestens 4 Stunden auf Temperatur gehalten, bis die chemische Homogenität groß genug ist und ein Röntgendiffraktogramm praktisch nur noch die Linien der Beta-Phase zeigt. Die erreichte Restporosität liegt je nach Preßdruck zwischen 2,5 und 6%.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.
Für die Herstellung einer Aluminium-Lithium-Legierung mit 4,0 Gew.-% Li wurden in einem Tiegelofen, der mit einer durchsichtigen Abdeckung versehen war und mit Argon gespült wurde, 142 g Aluminium in einem MgO-Tiegel aufgeschmolzen und auf eine Temperatur von 750°C gebracht. Eine Menge von 40 g der Verbindung LiAl wurde in Stücken in die Schmelze gegeben und mit einem Keramikstab untergetaucht und umgerührt. Durch Temperaturausgleich mit den kalten LiAl-Stücken stellte sich eine Schmelztemperatur von 700°C ein, die beibehalten wurde. Nach etwa 20 Minuten war die Verbindung aufgelöst, ohne zu schmelzen. Dabei ließ sich eine schwache Krätzebildung auf der Schmelzoberfläche nicht ganz vermeiden. Die Legierung wurde in eine kleine, flache, wassergekühlte Kupferkokille abgegossen und 4 Stunden bei 500°C homogenisierend geglüht, wobei die Probe in eine Aluminiumfolie eingewickelt war. Danach konnte das Material durch Walzen usw. weiterverarbeitet werden. Eine Kontroll-Analyse ergab einen Li-Gehalt von 3,0 Gew.-%, was auf einen infolge der geringen Probenmenge (großes Oberflächen:Volumen-Verhältnis) relativ hohen Abbrand zurückzuführen ist.For the production of an aluminum-lithium alloy with 4.0% by weight of Li, 142 g of aluminum were melted in a MgO crucible in a crucible furnace which was provided with a transparent cover and flushed with argon and brought to a temperature of Brought 750 ° C. A quantity of 40 g of the compound LiAl was added to the melt in pieces and immersed with a ceramic rod and stirred. Temperature compensation with the cold LiAl pieces resulted in a melting temperature of 700 ° C, which was maintained. After about 20 minutes, the connection was broken without melting. Weak scabies on the enamel surface could not be completely avoided. 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).
Alternativ zur Aufheizung gemäß Fig. 2a wurde der Preßling einer unterbrochenen Aufheizung gemäß Fig. 2b unterworfen. Dabei wurde bei 195°C die Aufheizung unterbrochen und erst nach 16 Minuten mit einer Aufheizgeschwindigkeit von 5°C pro Minute weiter aufgeheizt. Die Weiterbehandlung erfolgte analog zum vorherigen Beispiel, wobei die Restporosität je nach Preßdruck zwischen 1 und 2% lag.As an alternative to the heating according to FIG. 2a, 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.
Claims (12)
die Pulvermischung in eine beheizbare Preßmatrize eingefüllt und bei Temperaturen, bei denen das Lithiumpulver noch nicht aufschmilzt, durch Evakuieren entgast und anschließend gepreßt wird.2. A process for the preparation of the alloy additive according to claim 1, 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 poured into a heatable press die and degassed by evacuation at temperatures at which the lithium powder has not yet melted and then pressed.
Priority Applications (1)
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AT84105154T ATE31429T1 (en) | 1983-08-25 | 1984-05-07 | POWDER METALLURGICAL MANUFACTURE OF THE INTERMETALLIC COMPOUND LITHIUM-ALUMINUM AND ITS USE. |
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DE3330597A DE3330597C2 (en) | 1983-08-25 | 1983-08-25 | Process for the production of an alloy additive for lightweight aluminum components and its use |
DE3330597 | 1983-08-25 |
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EP0134403A1 true EP0134403A1 (en) | 1985-03-20 |
EP0134403B1 EP0134403B1 (en) | 1987-12-16 |
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EP84105154A Expired EP0134403B1 (en) | 1983-08-25 | 1984-05-07 | Method of preparing a lithium-aluminium compound by powder metallurgy, and its use |
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EP (1) | EP0134403B1 (en) |
AT (1) | ATE31429T1 (en) |
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DE3704767A1 (en) * | 1987-02-16 | 1988-08-25 | Leybold Ag | METHOD FOR PRODUCING CHARGING MATERIAL FOR MELT METALLURGICAL PROCESSES AND CHARGING MATERIAL PRODUCED BY THE METHOD |
DE19522988A1 (en) * | 1995-06-28 | 1997-01-02 | Sel Alcatel Ag | Procedure for charge information as well as service control device, subscriber exchange, terminal and communication network |
Citations (4)
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CH358238A (en) * | 1955-10-31 | 1961-11-15 | Foundry Services International | Process for manufacturing alloys or purifying a metal |
GB1484650A (en) * | 1974-06-20 | 1977-09-01 | Us Energy | Method of preparing a uniform alloy composition of lithium and aluminum |
EP0045622A1 (en) * | 1980-07-31 | 1982-02-10 | MPD Technology Corporation | Dispersion-strengthened aluminium alloys |
US4389240A (en) * | 1982-07-09 | 1983-06-21 | Novamet, Inc. | Alloying method |
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US3563730A (en) * | 1968-11-05 | 1971-02-16 | Lithium Corp | Method of preparing alkali metal-containing alloys |
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1984
- 1984-05-07 AT AT84105154T patent/ATE31429T1/en not_active IP Right Cessation
- 1984-05-07 DE DE8484105154T patent/DE3468128D1/en not_active Expired
- 1984-05-07 EP EP84105154A patent/EP0134403B1/en not_active Expired
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CH358238A (en) * | 1955-10-31 | 1961-11-15 | Foundry Services International | Process for manufacturing alloys or purifying a metal |
GB1484650A (en) * | 1974-06-20 | 1977-09-01 | Us Energy | Method of preparing a uniform alloy composition of lithium and aluminum |
EP0045622A1 (en) * | 1980-07-31 | 1982-02-10 | MPD Technology Corporation | Dispersion-strengthened aluminium alloys |
US4389240A (en) * | 1982-07-09 | 1983-06-21 | Novamet, Inc. | Alloying method |
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DE3468128D1 (en) | 1988-01-28 |
DE3330597A1 (en) | 1985-03-14 |
DE3330597C2 (en) | 1986-07-24 |
EP0134403B1 (en) | 1987-12-16 |
ATE31429T1 (en) | 1988-01-15 |
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