EP0250811A2 - Process for manufacturing articles from at least partially amorphous alloys - Google Patents

Process for manufacturing articles from at least partially amorphous alloys Download PDF

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Publication number
EP0250811A2
EP0250811A2 EP87107060A EP87107060A EP0250811A2 EP 0250811 A2 EP0250811 A2 EP 0250811A2 EP 87107060 A EP87107060 A EP 87107060A EP 87107060 A EP87107060 A EP 87107060A EP 0250811 A2 EP0250811 A2 EP 0250811A2
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Prior art keywords
alloy
metastable
crystal modification
metastable crystal
amorphous
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German (de)
French (fr)
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EP0250811A3 (en
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Martin Von Allmen
Andreas Blatter
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Cendres and Metaux SA
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Cendres and Metaux SA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/006—Amorphous articles
    • B22F3/007—Amorphous articles by diffusion starting from non-amorphous articles prepared by powder metallurgy
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C45/00—Amorphous alloys
    • C22C45/10—Amorphous alloys with molybdenum, tungsten, niobium, tantalum, titanium, or zirconium or Hf as the major constituent

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  • the invention relates to a method for producing an at least partially amorphous alloy piece.
  • Amorphous (non-crystalline, glazed or glass-like) alloy pieces are produced according to the current state of the art (eg Basler Science, 4 Dec. 1985, p. 46) by extremely rapid quenching of a suitable metallic melt. Cooling rates of the order of 1000 ° C / ms are required so that glazing does not crystallize when quenching takes place. In order to achieve such high cooling rates, the melt is usually sprayed through nozzles onto a rapidly rotating cooling roller. This process is known under the name "melt spinning". The products of this and similar known processes are films or tapes with a thickness of a few tens of micrometers. Because of the fundamentally inverse relationship between thickness and cooling rate, the former cannot be increased, or at least not significantly, in the melt quenching process.
  • the object of the present invention is to specify how large, hard and non-porous alloy pieces can be produced in a simple manner.
  • the invention is based on the surprising finding that suitable alloys are put into a metastable crystal modification and spontaneously tempered (without any additional measures) and without ma microscopic diffusion (ie diffusion over many atomic diameters) can be glazed.
  • a metastable crystal modification is understood to mean a crystal structure which, although permanently suitable under suitable conditions, does not correspond to the thermodynamic equilibrium.
  • the method according to the invention enables the production of (completely) amorphous alloy pieces with thicknesses in the cm range. In this way, workpieces can be produced in practically usable dimensions instead of just thin foils as before.
  • the reason for this is that the glazing is not achieved by rapid melt quenching, which is only possible with thin layers, but by (long) annealing as a solid-state reaction. Since the method according to the invention is based on the annealing of a homogeneous metastable crystal modification instead of an inhomogeneous laminate, the vitrification takes place without macroscopic diffusion, so that the resulting amorphous product is pore-free.
  • the alloy or the part of the alloy to be glazed according to the invention must first be brought into the special state of a matastable crystal modification.
  • a matastable crystal modification can consist of a mixed or compound crystal which is stable at high temperatures and which is supercooled at low temperatures and is therefore metastable.
  • the metastable crystal modification can be produced by a quenching process, but the cooling rates required for this are typically many orders of magnitude smaller than those required in the known vitrification by melt quenching.
  • a starting product for the process according to the invention one can use conventional metallurgical techniques, e.g. homogeneous alloy produced by melting or casting can be used.
  • a binary alloy can be used, the composition being selected so that a metastable crystalline solution or compound of the selected composition exists in the binary alloy system, which has a higher free energy than the glass phase at temperatures below the glass temperature, but is still present Room temperature.
  • Systems with stable high-temperature or high-pressure solutions or connections (of which there are dozens to hundreds) as well as systems with solutions or connections that are metastable at all temperatures, but can be produced by melt quenching, are suitable for this.
  • Solution crystals with high lattice strain (stress energy), such as occur with combinations of elements with noticeably different atomic radii, are particularly favorable.
  • Supercooled high-temperature phases can be produced by heating them above a characteristic transition temperature and then quenching them, for example in water.
  • Other options for producing metastable crystal modifications are the use of high pressure or chemical deposition processes.
  • An exemplary embodiment of the method according to the invention for producing amorphous Cr-Ti alloy pieces comprises three steps: in a first step, chemically pure Cr and Ti powders are weighed out in an atomic ratio of 40:60 and melted together. The crystal structure of the resulting alloy corresponds to the thermodynamic equilibrium (Cr2Ti + Alpha, see Fig. 1). Next, a few mm pieces of the alloy are heated in an arc or by a laser beam under protective gas at 1200 ° C for a few seconds and then quenched in water. This forms a high-temperature solution crystal (beta-Cr40Ti met) that is metastable at room temperature.
  • the pieces are annealed at 600 ° C (below the glass transition temperature of approx. 650 ° C) in a vacuum for about 48 hours, during which they spontaneously and completely glaze.
  • the glazing is expressed, among other things. due to an increase in electrical resistance, elasticity and hardness (the latter from approx. 6 to approx. 10 GPa Meyer-Ritz hardness).
  • One advantage of the method is that the workpiece can not be mechanically processed in the hard glass state, but in the much softer beta state.
  • the metastable crystal modification can also be produced directly from an alloy melt, e.g. B. a melt of Cr-Ti in an atomic ratio of 40:60 slowly with a cooling rate of 10 ° C / s to 1200 ° C. cooled and then rapidly quenched to a cooling rate of a few 100 ° C / s to 600 ° C, whereupon the tempering takes place at the final temperature of the quenching process of 600 ° C.
  • an alloy melt e.g. B. a melt of Cr-Ti in an atomic ratio of 40:60 slowly with a cooling rate of 10 ° C / s to 1200 ° C. cooled and then rapidly quenched to a cooling rate of a few 100 ° C / s to 600 ° C, whereupon the tempering takes place at the final temperature of the quenching process of 600 ° C.
  • pieces can also be produced from only partially amorphous and partially crystalline material.
  • Pieces that are crystalline on the inside and have an amorphous surface layer can be produced by placing only the surface layer of an alloy piece in the metastable crystal modification and then tempering the whole piece. The process can be carried out in the same way as explained above, but with slower quenching (possibly without water). Only a surface layer of the alloy piece heated to 1200 ° C then cools down quickly enough that the metastable beta modification remains, while inside the workpiece the crystal structure (Cr2Ti + Alpha-Ti) corresponding to the thermodynamic equilibrium is formed. During the subsequent tempering, only the surface layer is glazed and the inside remains crystalline.
  • the process according to the invention can also be carried out in the Cr-Ti system with a composition other than 40:60.
  • a composition of Cr and Ti in an atomic ratio of 30:70 can be selected.
  • the glazing process is slower (longer annealing required), but is reversible by heating the amorphous Cr-Ti alloy obtained by the described process to a temperature above the glass transition temperature of, for example, 800 ° C (and if necessary temper at this higher temperature) the metastable beta crystal can be produced again.
  • FIG. 2 shows the free energy of the phases involved as a function of the composition at 600 and 800 ° C., arrows indicating different possible conversions.
  • the method according to the invention can also be carried out with alloys other than Cr-Ti.
  • alloys other than Cr-Ti can be binary, ternary or even more complex.
  • binary and ternary systems which are suitable for the process according to the invention are cobalt-niobium, copper-titanium, iron-titanium, manganese-titanium, iob-nickel and iron-chromium-titanium.
  • alloys are preferably used which contain at least one of the elements Si, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Pd, Ag, Hf, Ta, W, Pt or Au contain.

Abstract

Eine z.B. aus Chrom und Titan im Atom-Verhältnis 40:60 bestehende Legierung wird in eine metastabile Kristallmodifikation versetzt, indem die Legierung z.B. im Lichtbogen erhitzt und in Wasser abgeschreckt wird. Die metastabile Kristallmodifikation wird unterhalb der Glastemperatur so lange getempert, z.B. bei 600°C während 48 Stunden, bis sie vollständig verglast ist. Das erfindungsgemässe Verfahren ermöglicht die Herstellung grosser, amorpher, harter und porenfreier Legierungsstücke mit Dicken im cm-Bereich.A e.g. Alloy consisting of chromium and titanium in an atomic ratio of 40:60 is put into a metastable crystal modification by e.g. heated in an arc and quenched in water. The metastable crystal modification is annealed below the glass temperature, e.g. at 600 ° C for 48 hours until completely glazed. The method according to the invention enables the production of large, amorphous, hard and non-porous alloy pieces with thicknesses in the cm range.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung eines wenigstens teilweise amorphen Legierungsstücks.The invention relates to a method for producing an at least partially amorphous alloy piece.

Amorphe (nichtkristalline, verglaste oder glasartige) Legierungsstücke werden nach dem gegenwärtigen Stand der Technik (z.B. Basler Zeitung 4. Dez. 1985, S. 46) durch ausserordentlich rasches Abschrecken einer geeig­neten, metallischen Schmelze erzeugt. Damit beim Ab­schrecken nicht Kristallisation, sondern Verglasung er­folgt, sind Abkühlraten in der Grössenordnung von 1000°C/ms erforderlich. Um derart hohe Abkühlraten zu erreichen, wird die Schmelze üblicherweise durch Düsen auf eine rasch rotierende Kühlwalze gespritzt. Dieses Verfahren ist bekannt unter dem Namen "melt spinning". Die Produkte dieses und ähnlicher bekannter Verfahren sind Folien oder Bänder mit einer Dicke von einigen 10 Mikrometern. Wegen des grundsätzlich inversen Zusammen­hangs zwischen Dicke und Abkühlrate lässt sich erstere bei den Schmelzabschreckverfahren nicht oder zumindest nicht wesentlich vergrössern.Amorphous (non-crystalline, glazed or glass-like) alloy pieces are produced according to the current state of the art (eg Basler Zeitung, 4 Dec. 1985, p. 46) by extremely rapid quenching of a suitable metallic melt. Cooling rates of the order of 1000 ° C / ms are required so that glazing does not crystallize when quenching takes place. In order to achieve such high cooling rates, the melt is usually sprayed through nozzles onto a rapidly rotating cooling roller. This process is known under the name "melt spinning". The products of this and similar known processes are films or tapes with a thickness of a few tens of micrometers. Because of the fundamentally inverse relationship between thickness and cooling rate, the former cannot be increased, or at least not significantly, in the melt quenching process.

Als Alternativverfahren zur Herstellung amorpher Legie­rungsdrähte in mm-Stärke ist vorgeschlagen worden (L. Schultz in "Amorphous Metals and Nonequilibrium Proces­sing", ed. by M. von Allmen, Editions de Physique, Les Ulis 1984), sehr dünne Folien aus reinem kristallinem Nickel (Ni) und aus reinem kristallinem Zirkon (Zr) ab­wechselnd als Laminat aufeinanderzuschichten, spiral­förmig zu wickeln, dann wie bei der üblichen Drahther­stellung durch ein Ziehwerkzeug zu ziehen und an­schliessend bei niedriger Temperatur zu tempern. Beim Kaltziehen und Tempern durchmischen sich die Elemente Ni und Zr, wobei Verglasung durch eine Festkörperreak­tion eintritt. Das Verfahren ist jedoch kompliziert und nur für Mischungen unterschiedlich rasch diffundieren­der Elemente mit stark negativer Mischwärme anwendbar. Die durch Diffusion entstehende amorphe Legierung ist meist porös und daher mechanisch schwach. Dies gilt mindestens teilweise auch für ein verwandtes Verfahren, bei dem eine Mischung elementarer kristalliner Pulver durch intensives Mahlen und Kaltverformen in einer Ku­gelmühle zur Durchmischung und Verglasung gebracht wird.As an alternative method for producing amorphous alloy wires with a thickness of mm, it has been proposed (L. Schultz in "Amorphous Metals and Nonequilibrium Processing", ed. By M. von Allmen, Editions de Physique, Les Ulis 1984), very thin foils made of pure crystalline nickel (Ni) and from pure crystalline zircon (Zr) alternately layered on top of each other as a laminate, wound spirally, then pulled through a drawing tool like in the usual wire production and then tempered at low temperature. The elements Ni and Zr mix during cold drawing and tempering, with glazing occurring as a result of a solid-state reaction. However, the process is complicated and can only be used for mixtures of elements diffusing at different speeds with strongly negative mixed heat. The amorphous alloy created by diffusion is usually porous and therefore mechanically weak. This also applies at least in part to a related process in which a mixture of elementary crystalline powders is mixed and vitrified by intensive grinding and cold working in a ball mill.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, anzugeben, wie man in einfacher Weise grosse sowie har­te und porenfreie Legierungsstücke erzeugen kann.The object of the present invention is to specify how large, hard and non-porous alloy pieces can be produced in a simple manner.

Die erfindungsgemässe Lösung dieser Aufgabe ist Gegen­stand des Patentanspruchs 1. Bevorzugte Ausführungsar­ten sind in den Ansprüchen 2 bis 10 umschrieben.The achievement of this object according to the invention is the subject of claim 1. Preferred embodiments are described in claims 2 to 10.

Die Erfindung beruht auf der überraschenden Erkenntnis, dass geeignete Legierungen in eine metastabile Kri­stallmodifikation versetzt und durch Tempern spontan (ohne irgendwelche zusätzliche Massnahmen) und ohne ma­ kroskopische Diffusion (d.h. Diffusion über viele Atom­durchmesser) verglast werden können. Unter einer meta­stabilen Kristallmodifikation versteht man eine zwar unter geeigneten Bedingungen beliebig langlebige, aber nicht dem thermodynamischen Gleichgewicht entsprechende Kristallstruktur.The invention is based on the surprising finding that suitable alloys are put into a metastable crystal modification and spontaneously tempered (without any additional measures) and without ma microscopic diffusion (ie diffusion over many atomic diameters) can be glazed. A metastable crystal modification is understood to mean a crystal structure which, although permanently suitable under suitable conditions, does not correspond to the thermodynamic equilibrium.

Das erfindungsgemässe Verfahren ermöglicht die Herstel­lung durchgehend (vollständig) amorpher Legierungs­stücke mit Dicken im cm Bereich. Es lassen sich so Werkstücke in praktisch verwertbaren Dimensionen, an­statt wie bisher nur dünne Folien, erzeugen. Der Grund liegt darin, dass die Verglasung nicht durch das nur bei dünnen Schichten mögliche rasche Schmelzab­schrecken, sondern durch (langes) Tempern als Festkör­perreaktion erreicht wird. Da das erfindungsgemässe Verfahren auf dem Tempern einer homogenen metastabilen Kristallmodifikation anstatt eines inhomogenen Lamina­tes beruht, erfolgt das Verglasen ohne makroskopische Diffusion, so dass das entstehende amorphe Produkt po­renfrei ist.The method according to the invention enables the production of (completely) amorphous alloy pieces with thicknesses in the cm range. In this way, workpieces can be produced in practically usable dimensions instead of just thin foils as before. The reason for this is that the glazing is not achieved by rapid melt quenching, which is only possible with thin layers, but by (long) annealing as a solid-state reaction. Since the method according to the invention is based on the annealing of a homogeneous metastable crystal modification instead of an inhomogeneous laminate, the vitrification takes place without macroscopic diffusion, so that the resulting amorphous product is pore-free.

Um durch blosses Tempern eine Verglasung zu erreichen, muss die Legierung bzw. der zu verglasende Teil der Le­gierung gemäss der Erfindung zunächst in den speziellen Zustand einer matastabilen Kristallmodifikation ge­bracht werden. Diese kann aus einem bei hohen Tempera­turen stabilen Misch- oder Verbindungskristall beste­hen, welcher bei niedrigen Temperaturen unterkühlt und somit metastabil ist. Die Herstellung der metastabilen Kristallmodifikation kann durch einen Abschreckvorgang erfolgen, wobei die dafür erforderlichen Abkühlraten jedoch typischerweise viele Grössenordnungen kleiner sind, als diejenigen, die beim bekannten Verglasen durch Schmelzabschrecken erforderlich sind.In order to achieve glazing by mere annealing, the alloy or the part of the alloy to be glazed according to the invention must first be brought into the special state of a matastable crystal modification. This can consist of a mixed or compound crystal which is stable at high temperatures and which is supercooled at low temperatures and is therefore metastable. The metastable crystal modification can be produced by a quenching process, but the cooling rates required for this are typically many orders of magnitude smaller than those required in the known vitrification by melt quenching.

Als Ausgangsprodukt kann für das erfindungsgemässe Ver­fahren eine durch konventionelle metallurgische Techni­ken, z.B. durch Zusammenschmelzen oder Giessen herge­stellte, homogene Legierung verwendet werden. Bei­spielsweise kann eine binäre Legierung verwendet wer­den, wobei die Zusammensetzung so zu wählen ist, dass im binären Legierungssystem eine metastabile kristalli­ne Lösung oder Verbindung der gewählten Zusammensetzung existiert, welche bei Temperaturen unterhalb der Glas­temperatur eine höhere Freie Energie aufweist als die Glasphase, sich aber trotzdem bei Raumtemperatur dar­stellen lässt. Dafür in Frage kommen Systeme mit stabi­len Hochtemperatur- oder Hochdruck-Lösungen oder -ver­bindungen, (wovon es Dutzende bis Hunderte gibt), sowie Systeme mit Lösungen oder Verbindungen, die bei allen Temperaturen metastabil sind, sich jedoch durch Schmelzabschrecken herstellen lassen. Besonders günstig sind Lösungskristalle mit hoher Gitterverspannung (Spannungsenergie), wie sie bei Kombinationen von Ele­menten mit merklich unterschiedlichen Atomradien auf­treten. Unterkühlte Hochtemperaturphasen lassen sich durch Aufheizen über eine charakteristische Uebergangs­temperatur und anschliessendes Abschrecken, etwa in Wasser, herstellen. Andere Möglichkeiten der Herstel­lung metastabiler Kristallmodifikationen liegen in der Anwendung hohen Druckes oder chemischer Abscheidever­fahren.As a starting product for the process according to the invention, one can use conventional metallurgical techniques, e.g. homogeneous alloy produced by melting or casting can be used. For example, a binary alloy can be used, the composition being selected so that a metastable crystalline solution or compound of the selected composition exists in the binary alloy system, which has a higher free energy than the glass phase at temperatures below the glass temperature, but is still present Room temperature. Systems with stable high-temperature or high-pressure solutions or connections (of which there are dozens to hundreds) as well as systems with solutions or connections that are metastable at all temperatures, but can be produced by melt quenching, are suitable for this. Solution crystals with high lattice strain (stress energy), such as occur with combinations of elements with noticeably different atomic radii, are particularly favorable. Supercooled high-temperature phases can be produced by heating them above a characteristic transition temperature and then quenching them, for example in water. Other options for producing metastable crystal modifications are the use of high pressure or chemical deposition processes.

Im folgenden werden Ausführungsbeispiele des erfin­dungsgemässen Verfahrens anhand der Zeichnungen er­läutert. Es zeigen:

  • Fig. 1 das Phasendiagramm des Systems Cr-Ti (Chrom­-Titan), worin Cr₂Ti und Alpha bei Raumtempe­ratur stabile Phasen, und Beta ein (bei nie­driger Temperatur metastabiler) Hochtemperatur - Lösungsristall ist,
  • Fig. 2 die Freie Enthalpie (auch Gibbs'sche Freie Energie genannt) als Funktion der Zusammenset­zung im System Cr-Ti bei 600 und 800°C, worin a die amorphe und ce die Gleichgewichtskonfi­guration bezeichnen, und senkrechte Pfeile mö­gliche Umwandlungen andeuten.
Exemplary embodiments of the method according to the invention are explained below with reference to the drawings. Show it:
  • 1 is the phase diagram of the system Cr-Ti (chromium-titanium), in which Cr₂Ti and alpha phases stable at room temperature, and beta is a (at low temperature metastable) high-temperature solution crystal,
  • Fig. 2 shows the free enthalpy (also called Gibbs free energy) as a function of the composition in the system Cr-Ti at 600 and 800 ° C, where a denotes the amorphous and c e the equilibrium configuration, and vertical arrows indicate possible conversions.

Ein Ausführungsbeispiel des erfindungsgemässen Verfah­rens zur Herstellung amorpher Cr-Ti Legierungsstücke umfasst drei Schritte: In einem ersten Schritt werden chemisch reine Cr und Ti Pulver im Atom-Verhältnis 40:60 abgewogen und zusammengeschmolzen. Die Kristall­struktur der entstehenden Legierung entspricht dem thermodynamischen Gleichgewicht (Cr₂Ti + Alpha, vgl. Fig. 1). Als nächstes werden einige mm grosse Stücke der Legierung im Lichtbogen oder durch einen Laser­strahl unter Schutzgas für einige Sekunden auf 1200°C erhitzt und dann in Wasser abgeschreckt. Dabei bildet sich ein bei Raumtemperatur metastabiler Hochtempera­tur- Lösungskristall (Beta-Cr₄₀Ti₆₀). Im letzten Schritt werden die Stücke bei 600°C (unterhalb der Glastemperatur von ca. 650°C) im Vakuum während etwa 48 Stunden getempert, wobei sie spontan und vollständig verglasen. Die Verglasung äussert sich u.a. durch ein Ansteigen des elektrischen Widerstandes, der Elastizi­tät sowie der Härte, (letztere von ca. 6 auf ca. 10 GPa Meyer-Ritzhärte). Ein Vorteil des Verfahrens ist, dass eine mechanische Bearbeitung des Werkstücks nicht im harten Glaszustand, sondern bereits im wesentlich wei­cheren Beta-Zustand erfolgen kann.An exemplary embodiment of the method according to the invention for producing amorphous Cr-Ti alloy pieces comprises three steps: in a first step, chemically pure Cr and Ti powders are weighed out in an atomic ratio of 40:60 and melted together. The crystal structure of the resulting alloy corresponds to the thermodynamic equilibrium (Cr₂Ti + Alpha, see Fig. 1). Next, a few mm pieces of the alloy are heated in an arc or by a laser beam under protective gas at 1200 ° C for a few seconds and then quenched in water. This forms a high-temperature solution crystal (beta-Cr₄₀Ti met) that is metastable at room temperature. In the last step, the pieces are annealed at 600 ° C (below the glass transition temperature of approx. 650 ° C) in a vacuum for about 48 hours, during which they spontaneously and completely glaze. The glazing is expressed, among other things. due to an increase in electrical resistance, elasticity and hardness (the latter from approx. 6 to approx. 10 GPa Meyer-Ritz hardness). One advantage of the method is that the workpiece can not be mechanically processed in the hard glass state, but in the much softer beta state.

Die metastabile Kristallmodifikation kann auch direkt aus einer Legierungsschmelze hergestellt werden, indem z. B. eine Schmelze aus Cr-Ti im Atom-Verhältnis 40:60 langsam mit einer Abkühlrate von 10°C/s auf 1200°C ab­ gekühlt und dann rasch mit einer Abkühlrate von einigen 100°C/s auf 600°C abgeschreckt wird, worauf die Tem­perung bei der Endtemperatur des Abschreckvorgangs von 600°C erfolgt.The metastable crystal modification can also be produced directly from an alloy melt, e.g. B. a melt of Cr-Ti in an atomic ratio of 40:60 slowly with a cooling rate of 10 ° C / s to 1200 ° C. cooled and then rapidly quenched to a cooling rate of a few 100 ° C / s to 600 ° C, whereupon the tempering takes place at the final temperature of the quenching process of 600 ° C.

Um die vorteilhaften Eigenschaften sowohl der amorphen wie der kristallinen Beschaffenheit für bestimmte An­wendungen zu kombinieren, können auch Stücke aus nur teilweise amorphem und teilweise kristallinem Material hergestellt werden. Stücke, die im Innern kristallin sind und eine amorphe Oberflächenschicht haben, lassen sich dadurch herstellen, dass man nur die Oberflächen­schicht eines Legierungsstücks in die metastabile Kri­stallmodifikation versetzt und das ganze Stück dann tempert. Das Verfahren kann dabei gleich wie oben er­läutert, jedoch mit langsamerem Abschrecken (ggf. ohne Wasser) durchgeführt werden. Von dem auf 1200°C erhitz­ten Legierungsstück kühlt dann nur eine Oberflächen­schicht rasch genug ab, dass die metastabile Beta-Modi­fikation bestehen bleibt, während sich im Innern des Werkstückes die dem thermodynamischen Gleichgewicht entsprechende Kristallstruktur (Cr₂Ti + Alpha-Ti) bil­det. Beim anschliessenden Tempern wird demzufolge nur die Oberflächenschicht verglast und das Innere bleibt kristallin.In order to combine the advantageous properties of both the amorphous and the crystalline nature for certain applications, pieces can also be produced from only partially amorphous and partially crystalline material. Pieces that are crystalline on the inside and have an amorphous surface layer can be produced by placing only the surface layer of an alloy piece in the metastable crystal modification and then tempering the whole piece. The process can be carried out in the same way as explained above, but with slower quenching (possibly without water). Only a surface layer of the alloy piece heated to 1200 ° C then cools down quickly enough that the metastable beta modification remains, while inside the workpiece the crystal structure (Cr₂Ti + Alpha-Ti) corresponding to the thermodynamic equilibrium is formed. During the subsequent tempering, only the surface layer is glazed and the inside remains crystalline.

Das erfindungsgemässe Verfahren kann im Cr-Ti System auch mit anderer Zusammensetzung als 40:60 durchgeführt werden. Beispielsweise kann eine Zusammensetzung von Cr und Ti im Atomverhältnis 30:70 gewählt werden. Der Ver­glasungsvorgang ist dabei zwar langsamer (längeres Tem­pern erforderlich), dafür aber reversibel, indem sich durch Erhitzen der durch das beschriebene Verfahren er­haltenen amorphen Cr-Ti-Legierung auf eine über der Glastemperatur liegende Temperatur von z.B. 800°C (und ggf. tempern bei dieser höheren Temperatur) wieder der metastabile Beta-Kristall erzeugen lässt. Zur Veran­schaulichung zeigt Figur 2 die Freie Energie der betei­ligten Phasen als Funktion der Zusammensetzung bei 600 und 800°C, wobei Pfeile verschiedene mögliche Umwand­lungen symbolisieren.The process according to the invention can also be carried out in the Cr-Ti system with a composition other than 40:60. For example, a composition of Cr and Ti in an atomic ratio of 30:70 can be selected. The glazing process is slower (longer annealing required), but is reversible by heating the amorphous Cr-Ti alloy obtained by the described process to a temperature above the glass transition temperature of, for example, 800 ° C (and if necessary temper at this higher temperature) the metastable beta crystal can be produced again. For illustration, FIG. 2 shows the free energy of the phases involved as a function of the composition at 600 and 800 ° C., arrows indicating different possible conversions.

Das erfindungsgemässe Verfahren kann auch mit anderen Legierungen als Cr-Ti durchgeführt werden. Diese können binär, ternär oder auch komplexer sein. Beispiele von binären und ternären Systemen, die sich für das erfin­dungsgemässe Verfahren eignen sind Kobalt-Niob, Kupfer­-Titan, Eisen-Titan, Mangan-Titan, iob-Nickel sowie Eisen-Chrom-Titan. Allgemein werden vorzugsweise Legie­rungen verwendet, die mindestens eines der Elemente Si, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Pd, Ag, Hf, Ta, W, Pt oder Au enthalten.The method according to the invention can also be carried out with alloys other than Cr-Ti. These can be binary, ternary or even more complex. Examples of binary and ternary systems which are suitable for the process according to the invention are cobalt-niobium, copper-titanium, iron-titanium, manganese-titanium, iob-nickel and iron-chromium-titanium. In general, alloys are preferably used which contain at least one of the elements Si, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Pd, Ag, Hf, Ta, W, Pt or Au contain.

Claims (10)

1. Verfahren zur Herstellung eines wenigstens teilweise amorphen Legierungsstücks, dadurch gekennzeichnet, dass wenigstens ein Teil einer Legierung zunächst in eine metastabile Kristallmodifikation versetzt, und diese anschliessend so getempert wird, dass sie verglast.1. A method for producing an at least partially amorphous alloy piece, characterized in that at least part of an alloy is first set in a metastable crystal modification, and this is then annealed so that it is glazed. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die metastabile Modifikation aus einem nur bei ho­hen Temperaturen stabilen Misch- oder Verbindungskri­stall besteht.2. The method according to claim 1, characterized in that the metastable modification consists of a mixed or connecting crystal stable only at high temperatures. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekenn­zeichnet, dass die Legierung mindestens zwei Elemente mit merklich unterschiedlichen Atomradien enthält.3. The method according to claim 1 or 2, characterized in that the alloy contains at least two elements with markedly different atomic radii. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die Legierung mindestens eines der Elemente Si, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Pd, Ag, Hf, Ta, W, Pt, Au enthält.4. The method according to any one of claims 1 to 3, characterized in that the alloy at least one of the elements Si, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Pd , Ag, Hf, Ta, W, Pt, Au contains. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Legierungszusammensetzung so gewählt wird, dass die durch das Verglasen erhaltene amorphe Legierung bzw. der amorphe Legierungsteil durch Erhitzen über die Glastemperatur wieder in die metasta­bile Kristallmodifikation zurückversetzbar ist.5. The method according to any one of claims 1 to 4, characterized in that the alloy composition is selected so that the amorphous alloy or the amorphous alloy part obtained by vitrification can be reset to the metastable crystal modification by heating above the glass transition temperature. 6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass die metastabile Kristallmodifi­kation bei einer unter der Glastemperatur liegenden Temperatur getempert wird.6. The method according to any one of claims 1 to 5, characterized in that the metastable crystal modification is annealed at a temperature below the glass transition temperature. 7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, dass die Temperatur, bei der die metastabile Kristall­modifikation getempert wird, um eine Toleranz von vor­zugsweise mindestens einigen °C unter der Glastempera­tur liegt.7. The method according to claim 6, characterized in that the temperature at which the metastable crystal modification is annealed is a tolerance of preferably at least a few ° C below the glass transition temperature. 8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die Legierung bzw. der Teil der Legierung durch Erhitzen und anschliessendes Ab­schrecken in die metastabile Kristallmodifikation ver­setzt wird.8. The method according to any one of claims 1 to 7, characterized in that the alloy or the part of the alloy is added to the metastable crystal modification by heating and subsequent quenching. 9. Verfahren nach Anspruch 8, dadurch gekennzeichnet, dass das Erhitzen der Legierung in einem Lichtbogen oder einem Laserstrahl, vorzugsweise unter Schutzgas, erfolgt.9. The method according to claim 8, characterized in that the heating of the alloy takes place in an arc or a laser beam, preferably under a protective gas. 10. Verfahren nach Anspruch 8 oder 9, dadurch gekenn­zeichnet, dass das Abschrecken der Legierung mittels einer Flüssigkeit, z.B. Wasser, erfolgt.Method according to claim 8 or 9, characterized in that the quenching of the alloy by means of a liquid, e.g. Water.
EP87107060A 1986-05-29 1987-05-15 Process for manufacturing articles from at least partially amorphous alloys Withdrawn EP0250811A3 (en)

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WO2000008217A1 (en) * 1998-08-04 2000-02-17 National University Of Singapore Metastable aluminium-titanium materials

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DE4216150A1 (en) * 1991-05-15 1992-11-19 Koji Hashimoto Highly corrosion-resistant amorphous alloy contg. chromium@ and titanium@ and/or zirconium@
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US6623571B1 (en) 1998-08-04 2003-09-23 National University Of Singapore Metastable aluminum-titanium materials

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