Such a method of producing an amorphous alloy has been discussed e.g. in Frankfurter Zeitung: Blick durch die Wirtschaft (published by "Frankfurter Allgemeine Zeitung"), Vol. 27, No. 23, Feb. 1, 1984, page 5, and in Machine Design, Vol. 55, No. 25, Oct. 10, 1983, page 8.
Amorphous metals sometimes called "metallic glasses" are generally known. See, e.g., Zeitschrift Fur Metallkunde, Vol. 69, 1978, No. 4, pages 212 to 220 or Elektrotechnik und Maschinenbau, Vol. 97, September 1980, No. 9, pages 378 to 385. These materials generally involve specific alloys which can be produced by special methods from at least two predetermined starting elements or compounds called alloying components. Often, the material of at least one of the starting elements or compounds is magnetic. Instead of a crystalline structure, these special alloys have a glasslike amorphous structure. Amorphous metal alloys have a number of extraordinary properties or combinations of characteristics such as great wear and corrosion resistance, great hardness and tensile strength and at the same time are ductile as well as having special magnetic properties. In addition, microcrystalline materials with interesting properties can be produced via the detour of the amorphous state. See, e.g., DE-PS No. 28 34 425.
To date, metallic glasses are generally produced by rapid quenching from the molten state. See also DE-OS Nos. 31 35 374 or 31 28 063. However, this method leads to at least one dimension of the material produced being smaller than about 0.1 mm. It would be desirable for various applications, however, if metallic glasses were available in any shape or size.
It has also been suggested to produce metallic glasses by a special solid state reaction instead of by rapid quenching. This requires the rapid diffusion of one of the alloy components into the other below the crystallization temperature of the metallic glass to be produced, while the other component remains practically immobile. Such a diffusion reaction is generally called an anomalous, rapid diffusion. Certain thermodynamic conditions must be met. See, e.g., Physical Review Letters, Vol. 51, No. 5, August 1983, pages 415 to 418 or Journal of Non-Crystalline Solids, Vol. 61 and 62, 1984, pages 817 to 822. For instance, the mutual reaction of the alloy components must be exothermal. Furthermore, a certain microstructure is required because the alloy components involved are closely adjacent and have, in at least one dimension, very small dimensions extending less than 1 .mu.m. Accordingly, layered structures are especially suitable which can be produced, e.g. by vapor deposition. See, e.g., the previously cited literature in Phys. Rev. Letters, Vol. 51. In addition, a lamination of thin metal foils is also possible. See, e.g., Proc. MRS Europe Meeting on Amorphous Metals and Non-Equilibrium Processing, published by M. von Allmen, Strasbourg, 1984, pages 135 to 140.
In addition, a similar layer-like (statified) structure can also be obtained by the method described in the previously cited publication Blick durch die Wirtschaft. According to this method, appropriate metal powders of the desired composition are first mixed as alloy components and are then compacted to form an intermediate product. This intermediate product, in which the alloy components each extend a maximum of 1 um in at least one dimension, is subsequently transformed into the desired metallic part having an amorphous structure by anomalous, rapid diffusion at a predetermined elevated temperature.
Whereas only very thin structures can be obtained by the vapor deposition method, the two deformation methods mentioned require good ductility of the alloy components involved. In addition, in the known method using powdery alloy components there is the difficulty of having to remove, by the deformation, oxide films on the surface of the metal powders and the structure resulting from the compaction and deformation is very irregular. Furthermore, when studying technically interesting alloys, it will be often found that one of the alloy components is difficult to deform or is virtually undeformable, such as boron of FeNiB or cobalt of CoZr. Also, some components are not available in foil form, or if so, only at a high price, such as rare-earth metals for amorphous transition metal/rare-earth compounds.
For the mass production of metallic parts having a relatively extended shape and size, also using in particular hard to deform or brittle alloy components, a method may be used which is disclosed by unpublished German Patent Application No. P 35 15 167.6 (U.S. patent application Ser. No. 848,984 now U.S. Pat. No. 4,710,236). According to this method, there is first produced, in a powder mill by means of a milling operation known per se, from the usually crystalline powders of the starting elements or compounds representing the alloy components, a mix powder whose individual particles are structured roughly in layers of the starting elements or compounds. The time to conclude the milling process, at which this structure of the particles of the mix, powder is present, can be determined without difficulty by experimental investigations and can thus be specified. The mix powder mix thus produced is then compacted and/or deformed in another operation to form a compact intermediate product of the shape and size matching the desired part. This compact intermediate product still comprises the crystalline particles of the starting elements or compounds with their respective dimensions being less than 1 .mu.m or even less than 0.2 .mu.m, at least in one dimension. A diffusion annealing step follows in which the intermediate product is transformed, in a manner known per se, into the desired metallic part of the amorphous alloy or metallic glass.
In this method, the powder is preferably compacted either by extrusion or by other deforming methods such as hammering. This deformation causes a reduction of the individual layer thicknesses, if the layers are parallel to the deformation direction. While the milling operation produces powder particles with layers largely arranged parallel, the compaction provides no particle alignment so that the arrangement of the individual layers is statistically distributed as to the deformation direction. For layers oriented perpendicular to the deformation direction, there may even result a greater layer thickness during the deformation. Layers predominantly parallel to the deformation direction become thinner while being deformed. The statistically oriented alignment of the layers prior to the compaction thus possibly leads to an increase in the band width of the layer thicknesses after deformation; i.e., the deformation during the compaction is not being utilized.
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