EP0200079A1 - Method of manufacturing a metallic article from an amorphous alloy - Google Patents

Abstract

The method is used to produce a metallic body from an amorphous alloy, in particular from a metallic glass, an intermediate product being formed from at least two mostly crystalline, powdery components of the alloy by performing a compacting step in such a way that the alloy components in the intermediate product are each in at least one dimension of at most 1 µm, and the intermediate product is converted into the metallic body with an amorphous alloy state by means of a diffusion reaction at a predetermined elevated temperature. The process is said to be able to produce bodies of larger dimensions on an industrial scale. For this purpose, it is provided according to the invention that a mixed powder with particles is produced from the powdery alloy components by means of a grinding process to be terminated at a predetermined point in time in such a way that they each have at least largely a layer-like structure made of the alloy components, and that this mixed powder then forms the intermediate product of the desired Shape and dimension is compacted and deformed if necessary.

Description

• -ein Zwischenprodukt aus mindestens zwei pulverförmigen Komponenten der Legierung unter Vornahme eines Kompaktierungsschrittes so ausgebildet wird, daß die Legierungskomponenten in dem Zwischenprodukt jeweils in mindestens einer Dimension höchstens 1 um ausgedehnt sind, und
• -das Zwischenprodukt in den metallischen Körper mit amorphem Legierungszustand mittels einer Diffusionsreaktion bei vorbestimmter erhöhter Temperatur umgewandelt wird.

The invention relates to a method for producing a metallic body from an amorphous alloy, in particular from a metallic glass, in which

• an intermediate product is formed from at least two powdery components of the alloy by performing a compacting step in such a way that the alloy components in the intermediate product are each expanded by at most 1 µm in at least one dimension, and
• the intermediate product is converted into the metallic body with an amorphous alloy state by means of a diffusion reaction at a predetermined elevated temperature.

Such a method is e.g. in the "Frankfurter Zeitung: Blick durch die Wirtschhaft" - (publisher: "Frankfurter Allgemeine Zeitung"), 27th year, No. 23, 12.1984, page 5 and in "Machine Design", vol. 55, no. 25, 10.10.1983, page 8 indicated

Amorphous materials referred to as "metallic glasses" are generally known (cf., for example, "Zeitschrift für Metallkunde", volume 69, 1978, number 4, pages 212 to 220 or "Elektrotechnik und Maschinenbau", 97th year, September 1980, number 9, Pages 378 to 385). These materials are generally special alloys which are to be produced from at least two predetermined starting elements or compounds, also referred to as alloy components, by means of special processes. These special alloys have a glass-like, amorphous structure instead of a crystalline one and have a number of extraordinary properties or combinations of properties such as high wear and corrosion resistance great hardness and tensile strength with good ductility as well as special magnetic properties. In addition, by detouring the amorphous state, microcrystalline materials with interesting properties can be produced (see e.g. DE-PS 28 34 425).

Up to now, metallic glasses have generally been produced by rapid quenching from the melt (cf. also DE-OS 31 35 374 or 31 28 063). However, this method results in at least one dimension of the material produced being less than about 0.1 mm. For various applications, on the other hand, it would be desirable if metallic glasses of any shape and size were available.

Furthermore, it has been proposed to produce metallic glasses instead of by rapid quenching by means of a special solid-state reaction. Here, one of the alloy components must diffuse nicely below the crystallization temperature of the metallic glass to be produced, the other component remaining practically immobile. Such a diffusion reaction is generally referred to as anomalous, rapid diffusion. Certain energetic prerequisites must be met (see, for example, "Physical Review Letters", vol. 51, Ne 5, August 1983, pages 415 to 418 or "Joum of Non-Crystalline Solids", vol. 61 and 62, 19 & pages 817 to 822). The alloy components must react exothermically with one another. A specific microstructure is also required, in that the alloying alloys involved are closely adjacent and each have very small dimensions of less than 1 μm in at least one dimension. Accordingly, layer structures are particularly suitable which can be produced, for example, by vapor deposition (cf., for example, the cited reference from "Phys.Rev. Letters", Vol.51). In addition, layering of thin metal foil is also possible (see, for example, "Proc. MRS Europe Meeting o Amorphous Metals and Non-Equilibrium Processes", ed. M. von Allen, Strasbourg, 1984, pages 135 to 140). In addition, a corresponding layer-like structure can also be obtained by the process, which can be found in the publication "Blick durch die Wirtschaft" mentioned at the beginning. According to this process, metal alloys of the desired composition are first mixed as alloy components and then compacted to form an intermediate product. This intermediate product, in which the alloy components in each case in at least one dimension, are expanded by at most 1 µm from _E , is subsequently converted into the desired metallic body with an amorphous structure by anomalous rapid diffusion at a predetermined increased temperature.

While only very thin structures can be obtained in the aforementioned vapor deposition process, the two deformation processes mentioned presuppose good ductility of the alloy components involved. In addition, it is assumed in the approximate components of powdered LEGIE occurs when bekar n-th process, the more difficult rigkeit to that which then on the surface d _f metal powder located coatings by di deformation must be removed and that the structure resulting from the compacting and deformation is very irregular. If you also consider technically interesting alloys, you will find that often one of the alloy components is practically not deformable, such as boron for FeNiB or cobalt for CoZr. Also, some components are not available as a film, or only at a high price, such as rare earth metals for amorphous transition metal / rare earth compounds.

The object of the present invention is to design the method mentioned at the outset in such a way that metallic bodies with a relatively extensive shape and dimension can be produced on an industrial scale from amorphous alloys, and in particular difficult to deform or brittle alloy components should be used.

This object is achieved with the measures specified in the main claim.

In the method according to the invention, a mixed powder is thus first produced using a grinding process known per se from the mostly crystalline powders of the starting elements or compounds constituting the alloy components, the individual particles of which are built up in layers from the starting elements or compounds. The point in time at the end of the grinding process at which this structure of the mixed powder particles is present can be e.g. by experimental investigation of the particles, easily determine and thus determine. This mixed powder produced in this way is then compacted and / or deformed in a further working step to form a compact intermediate product with the desired shape and size adapted to the body. This compact intermediate product still consists of crystalline parts of the starting elements or compounds, the respective dimensions of which in at least one dimension are less than 1 μm. In a subsequent diffusion annealing, the intermediate product is then converted into the desired metallic body with the amorphous alloy in a manner known per se. Since there are practically no restrictions with regard to the expansion of the intermediate product to be produced when compacting the mixed powder, the advantages associated with the method according to the invention can be seen in particular in the fact that metallic bodies made of amorphous alloys with larger expansions can be produced on a large industrial scale in a relatively simple manner have it made.

Advantageous refinements of the method according to the invention emerge from the subclaims.

The invention is further explained below on the basis of the production of a body from a metallic glass. The at least two powdery alloy components do not necessarily all have to be metallic, but in some cases can also be metalloids. Generally these components will be crystalline; however, amorphous powders can also be provided in the special cases of using metalloids.

The metallic glass of the body to be manufactured should have an average composition A _x By, where A, B are the metallic starting elements or

Alloy components and x, y mean percentages (with x + y = 100). First, powder of the two alloy components A and B together with hardened steel balls are placed in a suitable grinding jar, which is sealed under protective gas, eg argon. The size of the powder can be any; however, a similar size distribution of both components involved is advantageous. The resulting atomic concentration of the body to be produced from this powder is determined by the quantitative ratio of the two types of powder. During the subsequent grinding process in a powder mill, the powders are flattened, welded and also divided again. A predetermined temperature level below the crystallization temperature of the amorphous material to be formed can advantageously be maintained. If necessary, several temperature levels can also be provided or a corresponding temperature program can be expedient. As the grinding time progresses, larger powder particles are formed which at least largely have a layer-like structure, ie consist of a multiplicity of alternating layer-like regions of the alloy components involved. This is therefore a microstructure of the type that also arises, for example, in the initial phase of a known method for mechanical alloying (cf., for example, "Scientific American", vol. 234, 1976, pages 40 to 48). This known method can also be used to produce amorphous alloys per se (see, for example, "Applied Physics Letters", Vol. 43, No. 11, Dec. 1, 1983, pages 1017 to 1019). However, while grinding in the known method of mechanical alloying until the aforementioned layer-like structure dissolves again and a real alloy is formed, demge compared with the process according to the invention, the grinding process is terminated when the - layer-like structure mentioned has been reached, in which the - layer-like regions are generally about 0.01 to 0.9 μm, preferably between 0.05 and 0.5 μm thick. The size of the powder particles themselves is approximately 10 to 200 μm in diameter. The predetermined point in time at which this desired structure of the powder particles is present can be determined, for example, by cutting the particles. At the end of the grinding process to be terminated at this point in time, there is a mixed powder, the particles of which consist of alternating thin, crystalline, layer-like areas, and which therefore still has sufficient ductility for subsequent compacting at sufficiently low temperatures below the respective crystallization temperature. This mixed powder is now compacted, for which, for example, hammering in a jacket or extrusion with an extrusion press is carried out without substantial heating. At the end of a possibly further shaping step, there is then an intermediate product of the body to be produced with the desired shape and dimension. This is followed by a heat treatment in which the interdiffusion of the alloy components involved, which is responsible for the amorphization, takes place as a solid-state reaction. This reaction can, if appropriate, take place as an anomalous, rapid diffusion in a known manner, one alloy component diffusing into the other. However, other diffusion reactions with, for example, mutual diffusion of the components are also possible. In all of these reactions, it should be noted that the finer the structure, the lower the temperatures or the shorter the annealing times are sufficient for the complete conversion of the intermediate into the desired body. For this solid-state diffusion reaction, the annealing temperature must in any case be below the crystallization temperature of the metallic glass in a known manner. The metallic body present as the end product at the end of this process thus consists of an amorphous alloy with a thickness and shape which is predetermined by the compacting process and can therefore be chosen as desired.

In a departure from the method described, the compaction and the diffusion treatment can also be carried out in one step, for example by hot extrusion. It is important to ensure that the powder is only warmed up immediately before shaping, since otherwise the amorphous phase would form before extrusion and would thus hinder good compaction.

• -Ni, Co, Fe, Cu, Ag oder Au in Ti, Zr, Hf, Nb, Y, La Ta, Pb, Sn oder Ge sowie in Lanthaniden ode Actiniden;
• -B, C, P, Si in Fe, Ni, Co.

The process according to the invention can be used to produce amorphous alloy in all systems in which the amorphous phase can be produced by a solid-state reaction. The corresponding systems are generally characterized by the occurrence of abnormally rapid diffusion. Corresponding combinations of elements as alloy components of these systems are known (see, for example, "Journal o Nuclear Materials", Vol. 69 and 70, 1978, pages 7 (to 96). In particular, the following are to be mentioned as alloy components:

• -Ni, Co, Fe, Cu, Ag or Au in Ti, Zr, Hf, Nb, Y, La Ta, Pb, Sn or Ge as well as in lanthanides or actinides;
• -B, C, P, Si in Fe, Ni, Co.

In addition to these element combinations, one or both alloy components can themselves consist of an alloy or a combination of several elements. One example of this is B ir FeNi. Alloys with more than two starting components are also possible. Manufacture alloys of the FeSEB type (SE = rare earths).

If one of the alloy components consists of a non-deformable powder such as Boron for a mixture of Fe and B powders, so the B powder particles are installed between the Fe layers. To have a sufficiently fine structure. obtained, it is advantageous to start with Sehs fine B powder as the one alloy component, the B particles should be smaller than 1 µm. It is thermodynamic. reasons advantageous to use B powder in the amorphous state.

• Zur Herstellung eines metallischer bandförmigen Körpers aus amorphem NiZr werder zunächst Ni-Pulver und Zr-Pulver mit Pulverpartiv kelgrößen von jeweils z.B. durchschnittlich etwa 40um in eine Pulvermühle (z.B. Marke Fritsch, Type "Pulverisette-5") gegeben und mit Hilfe derer Stahlkugeln, die jeweils einen Durchmesser von 1
  
  mm aufweisen, zermahlen. Dabei ist ir Abhängigkeit von der Mahldauer zu beobachten daß zunächst die anfängliche Partikelgröße der Pulver abnimmt und sich später jedoch wiede größere Teilchen bilden. Diese Teilchen wachser mit zunehmender Mahldauer bis zu einer maximalen Teilchengröße von etwa 20 bis 100 um Durchmesser an. Betrachtet man diese Teilchen im Schnitt, so ist festzustellen, daß sie dann einen etwa schichtförmigen Aufbau aus den beiden Materialien Ni und Zr aufweisen, wobei die jeweiligen Schichtdicken unter 1 um liegen. Diese Teilchen bilden somit das gewünschte Mischpulver, so daß der Mahlvorgang zu diesem Zeitpunkt beendet wird. Bei Fortsetzung des Mahlens würden nämlich diese Mischpulverteilchen wieder zermahlen, d.h. der für das erfindungsgemäße Verfahren erforderliche schichtförmige Aufbau aus den beiden Legierungskomponenten zerstört. Daran anschließend werden Stahlrohre mit einem Innendurchmesser von 15mm und einer Wanddicke von 2,5 mm mit dem so erhaltenen Mischpulver unter Kompaktierung des Pulvers gefüllt und verschlossen. Durch Hämmern werden dann die Stahlrohre mit ihren Kemen aus dem Mischpulver der beiden Legierungskomponenten auf die gewünschten Maße des herzustellenden Bandes verformt. Beispielsweise wird der Kern auf eine Dicke von 1 mm gebracht. Die so verformten, nunmehr bandförmigen Gebilde werden anschließend einer Diffusionsglühung unterhalb der Kristallisationstemperatur des gewünschten amorphen Materials, beispielsweise bei 300°C etwa 24 Stunden lang geglüht. ImFalle der Verwendung von Co statt Ni läge die zu wählende Temperatur bei etwa 240°C. Nach Entfernen des noch vorhandenen Stahlmantels, z.B. durch Abätzen mit verdünnter Salzsäure, liegt dann das gewünschte Band aus der amorphen Legierung NiZr mit der verhältnismäßig großen Dicke von etwa 1 mm vor und kann schließlich noch in bekannter Weise weiterverarbeitet werden.

The method according to the invention is explained below using an exemplary embodiment:

• To produce a metallic band-shaped body made of amorphous NiZr, Ni powder and Zr powder with partial particle sizes of, for example, an average of about 40 μm each are first placed in a powder mill (for example the Fritsch brand, type "Pulverisette-5") and with the aid of the steel balls which each with a diameter of 1
  
  mm, grind. Irrespective of the grinding time, it can be observed that the initial particle size of the powders initially decreases, but later that larger particles form again. These particles grow with increasing grinding time up to a maximum particle size of about 20 to 100 µm in diameter. If one looks at these particles in section, it can be seen that they then have an approximately layered structure made of the two materials Ni and Zr, the respective layer thicknesses being less than 1 μm. These particles thus form the desired mixed powder, so that the grinding process is ended at this time. If grinding continued, these mixed powder particles would be ground again, ie the layered structure of the two alloy components required for the process according to the invention would be destroyed. Subsequently, steel tubes with an inner diameter of 15 mm and a wall thickness of 2.5 mm are filled with the mixed powder thus obtained, and the powder is compacted, and sealed. The steel pipes with their cores are then deformed from the mixed powder of the two alloy components to the desired dimensions of the strip to be produced by hammering. For example, the core is brought to a thickness of 1 mm. The thus shaped, now band-shaped structures are then subjected to diffusion annealing below the crystallization temperature of the desired amorphous material, for example at 300 ° C. for about 24 hours. If Co instead of Ni were used, the temperature to be selected would be around 240 ° C. After removing the steel sheath that is still present, for example by etching with dilute hydrochloric acid, the desired band made of the amorphous NiZr alloy with a relatively large thickness of about 1 mm is present and can finally be processed further in a known manner.

According to the exemplary embodiment, it was assumed that the metallic body to be created is an amorphous, i.e. non-crystalline structure, in particular that of a metallic glass. However, the method according to the invention can also be provided in a particularly advantageous manner for the production of microcrystalline materials by way of the amorphous state. For example, accordingly, intermediate products from Nd-Fe-B alloys are first produced in amorphous form according to the invention. This alloy is then crystallized in a subsequent annealing treatment. The resulting microcrystalline structure has excellent hard magnetic properties (see, for example, "Applied Physics Letters", Vol. 44, No. 1, January 1984, pages 148 and 149).

Claims (14)

1. A method for producing a metallic body from an amorphous alloy, in particular from a metallic glass, in which method an intermediate product is formed from at least two powdery components of the alloy by performing a compacting step in such a way that the alloy components in the intermediate product are each expanded by at most 1 µm in at least one dimension, and the intermediate product is converted into the metallic body with an amorphous alloy state by means of a diffusion reaction at a predetermined elevated temperature,
characterized in that a mixed powder with particles is produced from the powdery alloy components by means of a grinding process to be terminated at a predetermined point in time such that these each have at least largely a layer-like structure from the alloy components, and that this mixed powder then forms the intermediate product of the desired shape and Dimension is compacted and deformed if necessary. 2. The method according to claim 1, characterized in that the termination of the grinding process is determined experimentally by examining the mixed powder particles. 3. The method according to claim 1 or 2, characterized in that the powdery alloy components are ground under protective gas to the mixed powder. 4. The method according to any one of claims 1 to 3, characterized in that the alloy components are ground to the mixed powder at at least one predetermined temperature. 5. The method according to any one of claims 1 to 4, characterized in that the powdery alloy components are milled until the mixed powder particles with thicknesses between 0.01 µm and 0.9 µm, preferably between 0.05 nm and 0.5 µm. 6. The method according to any one of claims 1 to 5, characterized in that the powdery Alloy components to be mixed to mixed powder particles with particle diameters between about 10 and 200 microns, preferably about 20 and 100 microns. 7. The method according to any one of claims 1 to 6, characterized in that the mixed powder is deformed by hammering or extrusion to the intermediate product. 8. The method according to any one of claims 1 to 7, characterized in that the diffusion reaction after the last Kompaktierungsbzw. Deformation step is made. 9. The method according to any one of claims 1 to 7, characterized in that the diffusion reaction simultaneously with the last compacting or. Deformation step is carried out. 10. The method according to any one of claims 1 to 9, characterized in that the non-crystalline structure of the intermediate is converted into a microcrystalline structure by a predetermined annealing treatment. 1. The method according to any one of claims 1 to 1C, characterized in that the intermediate product is formed from at least two crystalline alloy components. 12. The method according to any one of claims 1 to 1C, characterized in that in addition to at least: a metallic starting element or a metallic starting compound as the one alloy component, at least one further starting element or a further starting compound is provided as a further alloy component which is a metalloid. 13. The method according to claim 12, characterized in that an amorphous powder is provided as the metalloid. 14. The method according to any one of claims 1 to 13, characterized in that a compound or alloy of several elements is provided as at least one starting component.