Electrical discharge machining (EDM) process for an amorphous metallic alloy sample

Abstract

The invention relates to a method for cutting a sample of amorphous metal alloy, comprising at least two wire electrical discharge machining (EDM) steps producing electrical discharges on a sample to remove material from the sample so as to obtain a sample cut along a reference path and maintained in an amorphous state, wherein the amorphous metal alloy (AMA) has a critical diameter Dc of less than 8 millimeters and / or a difference ΔTx between the crystallization temperature Tx and the glass transition temperature Tg of less than 80°C, and / or a quotient ΔTx / (TI-Tg) of the difference ΔTx between the crystallization temperature Tx and the glass transition temperature Tg and the difference between the liquidus temperature TI and the glass transition temperature Tg of less than 0.16. The method comprises at least one roughing EDM step and at least one finishing EDM step.The invention also relates to a method for manufacturing an AMA component and such a component. Abstract figure: Figure 5.

Description

Title of the invention: Electro-erosion process for an amorphous metallic alloy sample technical field

[0001] The present invention relates to the field of machining methods for metallic microcomponents, in particular parts made of amorphous metal alloy (AMA). Indeed, amorphous alloys exhibit mechanical characteristics that are particularly advantageous for technical fields involving very small parts. Previous technique

[0002] It is known to obtain preforms of amorphous metal by injection into molds of specific shape. By cooling the injected metal sufficiently rapidly, crystallization of the alloy can be avoided and an amorphous structure can be obtained. This type of amorphous alloy structure is also called metallic glass.

[0003] In order to obtain a mechanical part ready to be integrated for example into a watch mechanism, it is sometimes necessary to machine the molded preform.

[0004] In the general field of alloys, particularly crystalline alloys, numerous machining and / or forming techniques have been developed (stamping, micro-milling, etc.). However, these techniques cannot be easily transposed to AMAs, which have specific chemical compositions and mechanical properties that are generally much higher than those of crystalline alloys. Machining is therefore more complex to master (achieving the desired precision and surface finish, perpendicularity of the flanges, tool life, production speed compatible with industrial constraints, etc.).

[0005] On the other hand, many of these techniques cause thermal heating in the machined areas, leading to local recrystallization of the alloy and the loss of the amorphous structure of the AMA in the machined areas. This is especially true for AMAs with low thermal stability. Indeed, some AMAs exhibit lower thermal stability than others. This low thermal stability reflects the ease / speed with which the alloy structure can be affected by a temperature variation (temperature increase above the glass transition temperature Tg, excessively slow cooling, etc.). AMAs with lower thermal stability therefore exhibit a greater capacity to evolve towards a crystalline state more rapidly above the glass transition temperature Tg.

[0006] Electrical discharge machining (EDM) processes are suitable for manufacturing components, particularly microcomponents made of crystalline metal alloys. Electrical discharge machining By overcoming the limitations imposed by the mechanical properties of materials, machining hard materials becomes possible, achieving machining precision on the order of a few micrometers. However, its thermal nature, the high temperatures involved, and the long machining times make electrical discharge machining (EDM) a poor candidate for machining amorphous metallic alloys. As mentioned earlier, these alloys, and especially those with low thermal stability, are indeed much more sensitive to temperature than crystalline alloys.

[0007] Thus, the challenge lies in successfully performing these machining operations on AMOs while preserving their amorphous structure, ensuring a high-quality surface finish on the machined part, and maintaining a high cycle time suitable for industrial production. Indeed, a machining operation that leads to excessive heating of the material would cause crystallization of the heat-affected zone and thus result in the loss of the advantageous properties conferred by the amorphous structure of the material.

[0008] There is therefore a need for a machining process that preserves an amorphous microstructure while allowing for an industrial-level production rate. Another requirement is the ability to obtain a surface finish with very low roughness and / or excellent perpendicularity of the flanks in the cutting zone, in order to fully exploit the intrinsic qualities of AMA. Summary

[0009] To this end, the invention proposes a method for cutting a sample 1 made of an amorphous metal alloy, comprising at least two wire electrical discharge machining (EDM) steps 2 producing electrical discharges on a sample 1 to remove material from the sample 1 so as to obtain a sample 1 cut along a reference trajectory TRef and maintained in an amorphous state, wherein: The amorphous metallic alloy possesses: - a critical diameter of less than 8 millimeters, preferably less than 6 millimeters, and even more preferably less than 4 mm, and / or - a difference ATx between the crystallization temperature Tx and the glass transition temperature Tg of less than 80°C, preferably less than 70°C, and even more preferably less than 60°C, and / or - a quotient ATx / (TI-Tg) of the difference ATx between the crystallization temperature Tx and the glass transition temperature Tg and of the difference between the liquidus temperature TI and the glass transition temperature Tg less than 0.16, preferably less than 0.14 and even more preferably less than 0.12; and in which the successive electro-erosion stages are such that they include: - at least one electrical discharge machining (EDM) step, known as a "roughing" step, of sample 1 along a reference trajectory TRef+n to perform a roughing 5 or 51 along a trajectory TRef+n, n being the total number of EDM steps, known as "roughing" steps, the discharge energy E per roughing step being less than 5000 pJ per millimeter of thickness of sample 1 to be cut; and - at least one electrical discharge machining (EDM) step, known as the "finishing" step, of sample 1 along a reference path TRef to remove material from sample 1 along the reference path TRef, the discharge energy E per finishing step being less than 200 pJ per millimeter of thickness of sample 1 to be cut; and - the reference trajectory(ies) TRef+n being translated by a given distance gn from the reference trajectory TRef+(nl) which is directly adjacent to it and which is closest to the final part 4, in the opposite direction to that of the cut final part 4; and - the given distances gn between two directly adjacent reference trajectories, identical or different, are such that the electrical discharges removing material from the sample 1 to be cut on the reference trajectory TRef+n, also remove, at least partially, material from the sample 1 to be cut on the reference trajectory TRef+(nl) which is directly adjacent to it.

[0010] According to another aspect, a method for manufacturing a part 4 made of an amorphous metallic alloy is proposed, comprising the steps: - melt a mixture of metals to obtain a piece of alloy, and - inject the resulting pellet into a mold and cool the molded alloy at a rate exceeding the critical crystallization rate of the alloy, to obtain a sample 1 of amorphous alloy, and - cut at least one surface of sample 1 according to the cutting process as described above to obtain a part 4 in amorphous alloy with a predetermined geometry, and - optionally perform a finishing step on at least the surface of the machined sample 1, preferably a tribofinishing step or a chemical treatment.

[0011] Also proposed is an amorphous metal alloy component comprising at least one surface cut according to the cutting process described above or manufactured according to the manufacturing process above.

[0012] The features described in the following paragraphs may optionally be implemented. They may be implemented independently of each other or in combination with each other.

[0013] According to one embodiment, the cutting process comprises at least two electrical discharge machining (EDM) stages referred to as "roughing" stages, the successive energy levels E of which are de growing, the first roughing step(s) being carried out with electrical discharges whose discharge energy E is between 2000 pJ and 5000 pJ per millimeter of sample 1; and the last roughing step(s) being carried out with electrical discharges whose energy level (E) is between 200 pJ and 2000 pJ per millimeter of sample 1.

[0014] According to one embodiment of the cutting process, the diameter of the wire 2 is less than 200pm, preferably less than 100pm and even more preferably less than 75pm.

[0015] According to one embodiment of the cutting process, sample 1 is a stack of samples.

[0016] Advantageously, the current of each electrical discharge across the terminals of wire 2 is less than 200 amperes.

[0017] Preferably, the voltage across wire 2 is less than 200V.

[0018] Advantageously, the pulse duration during which sample 1 is subjected to an electrical discharge is less than 1000 ps, ​​preferably less than 400 ps or even more preferably less than 100 ps.

[0019] The flank obtained by electro-erosion of the cut sample 1 advantageously has a surface whose roughness Ra is less than 800 nm, preferably less than 600 nm, more preferably less than 400 nm and even more preferably less than 300 nm.

[0020] Cutting by electro-erosion of a first surface PI of the sample 1 results in obtaining a second surface P2 of the cut sample (1) and, at each point of intersection between the first remaining surface PI and the created surface P2, said surfaces PI and P2 advantageously form between them an angle Ad of 90° ± 1.5°, preferably 90° ± 1° and even more preferably 90° ± 0.5°. Brief description of the drawings

[0021] Other features, details and advantages will become apparent from reading the detailed description below and analyzing the accompanying drawings, on which:

[0022] [Fig. 1] represents an X-ray diffraction analysis of an amorphous metallic alloy.

[0023] [Fig.2] represents an X-ray diffraction analysis of a partially metallic alloy amorphous.

[0024] [Fig.3] represents an X-ray diffraction analysis of a crystalline metallic alloy.

[0025] [Fig.4] is a schematic top view illustrating one embodiment of putting implementation of the cutting process,

[0026] [Fig. 5] is a schematic, side view detailing a cutting method for an em stacking of samples,

[0027] [Fig.6] is a schematic top view illustrating the cutting process including roughing electrical discharge machining (EDM) stages and a finishing EDM stage,

[0028] [Fig.7] is a schematic side view illustrating a cutting process for obtaining a part exhibiting excellent perpendicularity of flanks,

[0029] [Fig.8] is a diagram representing the results of the bending tests of the example 1. Description of the implementation methods

[0030] To facilitate reading the figures, the various elements are not necessarily drawn to scale. In these figures, identical elements bear the same reference numerals. Certain elements or parameters may be indexed, that is, designated, for example, as first element or second element, or first parameter and second parameter, etc. This indexing aims to differentiate similar, but not identical, elements or parameters. This indexing does not imply any priority of one element or parameter over another, and it is possible to interchange the designations.

[0031] For the purposes of this description, the following definitions should be specified.

[0032] The terms "amorphous metallic alloy" or "AMA" or "metallic glass" are understood to mean Metals or metallic alloys that are not crystalline, meaning their atomic distribution is predominantly random. However, it is difficult to obtain a 100% amorphous metallic glass because a fraction of the material usually remains crystalline. This definition can therefore be generalized to metals or metallic alloys that are partially crystalline and thus contain a fraction of crystals, as long as the amorphous fraction is predominant. Generally, the fraction of the amorphous phase is greater than 50%. Therefore, "amorphous metallic alloy" or "AMA" or "metallic glass" refers to metals or metallic alloys in which the fraction of the amorphous phase is greater than 50%, preferably greater than 65%, more preferably greater than 75%, and even more preferably greater than 80%.

[0033] It is specified here that a metallurgical structure is said to be amorphous or totally amorphous when an X-ray diffraction analysis as described below does not reveal crystallization peaks.

[0034] The term "critical diameter" (De) of a specific metal alloy means the maximum limiting thickness below which the metal alloy exhibits a completely amorphous metallurgical structure, or above which it is no longer possible to obtain a completely amorphous metallurgical structure, when the metal alloy is cast from a liquid state and subjected to rapid cooling such that heat transfer within the metal alloy is optimal. More specifically Specifically, the critical diameter is determined by successive molding of cylindrical bars (generally longer than 50mm) of different diameters, molded from the liquid state under the following conditions: The alloy is melted at a temperature of Tl + 150°C with Tl, the liquidus temperature of the alloy (in °C). It is cast in a CuCl type copper mold and is cooled to a maximum temperature of about twenty degrees Celsius (20°C). The alloy is developed and molded under an inert and high-purity atmosphere (e.g., under argon of grade 6.0) or under secondary vacuum (pressure < 10-4mbar). The alloy is molded using a system that applies a pressure differential to facilitate molding and ensure close contact between the alloy and the mold walls, thus ensuring rapid cooling. The molding process can be carried out under a pressure of 20 MPa. This system can be mechanical (e.g., piston) or gaseous (application of overpressure). After casting, the bars are cut to obtain a slice (a cross-section of the cylinder preferably located near the middle of the bar, with a thickness between 1 and 10 mm) and analyzed by X-ray diffraction (XRD) to determine whether the slices exhibit an amorphous or partially crystalline structure. The critical diameter is then determined as the maximum diameter for which the structure is amorphous (the presence of characteristic AMA bumps is then highlighted by X-ray diffraction). Given that defects are most often present in metallurgical structures, a 100% amorphous alloy is virtually impossible to obtain, and the critical diameter can be defined as the diameter above which X-ray diffraction analysis clearly reveals peaks of crystallinity. Such an assessment of the amorphous character of a metallic alloy is detailed in the article by Cheung et al., 2007 (Cheung et al. (2007) “Thermal and mechanical properties of Cu-Zr-Al bulk metallic glasses)” doi:10.1016 / j.jallcom.2006.08.109). It allows for an average analysis over a surface and eliminates the few inevitable metallurgical defects while analyzing only crystals of significant size (greater than a few nanometers) and / or in significant quantity. Figures 1, 2 and 3 represent an XRD analysis as described above of a metallic alloy in the amorphous state ([Fig. 1]), partially amorphous state (the characteristic hump of AMAs is present but with peaks - [Fig. 2]) and crystalline state ([Fig. 3]) respectively.

[0035] The term “low thermal stability AMA” means a metallic alloy having: - a critical diameter (De) of less than 8 millimeters, preferably less than 6 millimeters, and even more preferably less than 4 mm, and / or - a difference (ATx) between the crystallization temperature (Tx) and the temperature of glass transition temperature (Tg) below 80°C, preferably below 70°C, and even more preferably below 60°C, and / or - a ratio (ATx / (TLTg)) of the difference (ATx) between the crystallization temperature (Tx) and the glass transition temperature (Tg) and the difference between the liquidus temperature (T1) and the glass transition temperature (Tg) less than 0.16, preferably less than 0.14, and even more preferably less than 0.12.

[0036] The critical diameter De, the difference ATx = Tx - Tg between the crystallization temperature Tx and the glass transition temperature Tg, and the ratio ATx / (T1 - Tg) are quantities that all define a thermal stability criterion for the metallic alloy. The lower the value of each of these three parameters, the more unstable the alloy; in other words, the more difficult it is to maintain the metallic alloy in an amorphous state during any machining that induces heating.

[0037] The term "microcomponent" means a small component, for example, a component where at least one dimension does not exceed 2 mm or even 1 mm, preferably 100 µm, more preferably 60 or even 25 µm. The term "mechanical microcomponent" means a microcomponent capable of cooperating with one or more other microcomponents.

[0038] Electro-erosion (“electrical discharge machining” in English, also indicated by the acronym “EDM”) is a machining process which consists of removing material from a workpiece by using an electrode that produces electrical discharges.

[0039] Electrical discharge machining takes place in different phases: 1 / Application of a voltage between the workpiece and the electrode; 2 / Under the action of the electric field, the dielectric is ionized, thus creating a conductive channel between the electrode and the part; 3 / The passage of current through this channel allows the formation of a spark which will generate a plasma bubble and a significant increase in temperature (spark breakdown). It is this electrical discharge, which occurs from the electrode to the workpiece, that will cause the melting and vaporization of material on the workpiece, but also on the electrode; 4 / When the current is interrupted, the gas bubble implodes and ejects the molten material. This material then finds itself in the dielectric in the form of microparticles and is thus rapidly cooled and removed. Following this discharge, a crater is left on the workpiece and the electrode (material removal). The material that melted during the discharge but was not ejected during the implosion of the gas bubble resolidifies on the workpiece and the electrode.

[0040] EDM is recommended for machining very hard (but necessarily conductive) materials, hardened steels, or in cases where the complexity of The play demands it.

[0041] Contrary to expectations, the present inventors have demonstrated that EDM, in particular wire electro-erosion, could be used for industrial-scale machining and, more specifically, for cutting samples in AMA, particularly in AMA with low thermal stability, while maintaining the amorphous structure of the alloy and its associated mechanical characteristics.

[0042] An electrical discharge machining (EDM) system generally comprises a chamber in which a sample is placed, immersed in a dielectric fluid. An electrode, positioned opposite the sample, emits electrical discharges. The part of the sample to be machined is positioned opposite the point(s) of emission of the electrode. The sample can thus be machined by the electrical discharges, which can reach the surface of the sample to be machined and interact with the sample material. The electrode and / or the sample are relatively mobile along a defined machining path, indicated in particular in this description as the reference path TRef.

[0043] The interaction between the electrical discharges and the sample enables material removal. A relative displacement of the electrode with respect to the sample enables material removal along the reference trajectory TRef.

[0044] An electronic control unit allows for the control of the triggering and interruption times of the electrical discharges, as well as the movement of the electrode relative to the sample. The reference trajectory TRef can thus be controlled in real time.

[0045] Alternatively, the sample to be machined can be mobile so as to move relative to the electrode. For this purpose, the sample to be machined is fixed to a movable platform along at least 2 axes.

[0046] Alternatively, the electrode and the sample to be machined can both be mobile, successively or simultaneously, in particular to facilitate the machining of complex parts.

[0047] The sample 1 to be cut can have any shape and the portion of sample 1 to be machined can also be of any shape.

[0048] By way of example, in one embodiment, the sample 1 to be cut is flat. In other words, the sample 1 to be cut is a plate of amorphous metal alloy. The thickness of the sample 1 is preferably between 5 µm and 6 mm, preferably between 100 µm and 4 mm.

[0049] Sample 1 can be a single sample or a stack of several samples 1. In an advantageous embodiment, it is a stack of several samples, preferably a stack of more than three, and even more preferably of more than eight samples. This embodiment allows, in particular, to reduce cutting time.

[0050] The amorphous metal alloy of the sample 1 to be cut may, for example, contain, as an atomic percentage, more than 40% of Ni, Zr, Cu, Ti, Fe or Co, preferably more than 50% of Ni, Zr, Cu, Ti, Fe or Co. According to another embodiment, the amorphous metal alloy of the sample 1 to be machined contains, as an atomic percentage, more than 50% of the elements Ni and Nb, preferably more than 60% of the elements Ni and Nb, more preferably more than 70% of the elements Ni and Nb.

[0051] Alloys with low thermal stability, such as those described above, are particularly difficult to shape while retaining their amorphous character. The process described here is therefore particularly advantageous for cutting such alloys at an industrial rate.

[0052] The present invention proposes a method for machining a sample 1 made of an amorphous metal alloy with low thermal stability using a femtosecond laser, comprising at least two wire electrical discharge machining (EDM) steps 2 producing electrical discharges on a sample 1 to remove material from the sample 1 so as to obtain a sample 1 cut along a reference path TRef and maintained in an amorphous state. Thus, in this particular case, the electrode is a wire 2.

[0053] Figure 4 illustrates the concept of sample 1, cut sample 1, and / or part 4. Sample 1 constitutes the raw material or preform to be cut. Following the cutting process, a cut sample 1 or a part 4, which can also be called a microcomponent, is obtained. Part 4 can therefore be a detached portion of sample 1. Reference numeral 9 schematically represents the perimeter 9 of part 4. The shape of part 4 can be arbitrary. In the example of Figure 4, part 4 is entirely contained within the perimeter of sample 1. According to an example not shown, a portion of the perimeter 10 of sample 1 can form part of part 4.

[0054] The reference trajectory TRef can define a portion of the perimeter 9 of the part 4. In other words, the cutting process can be implemented to form only a portion of the perimeter 9 of the part 4. The remainder of the perimeter 9 of the part 4 can be obtained by other machining methods or processes. A portion of the perimeter 9 of the microcomponent 4 can also be formed by a portion of the periphery 10 of the sample 1, which can then remain unworked in this area.

[0055] According to the claimed process, electrical discharge machining is a cutting process, more particularly wire electrical discharge machining. As illustrated in [Fig. 5], the electrode 2 is therefore a wire 2 which is applied along one side of the sample 1 or, as illustrated in [Fig. 5], along the sides of at least two stacked samples 1. The wire 2, through which successive electrical discharges pass, removes material from the samples 1 along a reference path TRef or TRef+n depending on the step of the process.

[0056] The cutting process comprises at least two wire electrical discharge machining (EDM) steps, including: - at least one roughing step of sample 1 along a reference trajectory TRef+n to create a rough cut 5 or 51 along a trajectory TRef+n, where n is the total number of roughing EDM steps and the discharge energy E per roughing step is less than 5000 pJ per millimeter of thickness of sample 1 to be cut; and - at least one electro-erosion step, called "finishing", of the sample 1 along a reference path TRef to remove material from the sample 1 along the reference path TRef, the discharge energy E per finishing step being less than 200 pJ per millimeter of thickness of sample 1 to be cut.

[0057] Such a process comprising at least two electro-erosion steps as described below makes it possible to cut, at an industrial rate, samples in low stability AM A while preserving the amorphous state of said samples despite a high cutting rate.

[0058] As illustrated in [Fig. 6], the reference trajectory(s) TRef+n are translated by a given distance gn from the reference trajectory TRef+(nl) that is directly adjacent to it and closest to the final part 4, in the opposite direction to that of the cut final part 4. The distances gn between two directly adjacent reference trajectories may be identical or different. These distances gn are such that the electrical discharges removing material from the sample 1 to be cut on the reference trajectory TRef+n also remove, at least partially, material from the sample 1 to be cut on the directly adjacent reference trajectory TRef+(nl).

[0059] Figure 6 illustrates an embodiment comprising two roughing steps along reference trajectories TRef1 and TRef2 and a finishing step along the reference trajectory TRef. The first roughing step produces the rough part 51. The second roughing step along the reference trajectory TRefl produces the rough part 5. The finishing step along the reference trajectory TRef produces the final part 4. The reference trajectory TRef2 is a given distance g2 from the reference trajectory TRefl, while the reference trajectory TRefl is a given distance gl from the reference trajectory TRef. The distances gl and g2 may be the same or different. Such a cutting process makes it possible to obtain cuts with complex trajectories and excellent surface finishes at the cut points.

[0060] The process includes at least one finishing electrical discharge machining (EDM) step. When there are multiple EDM steps, their reference trajectories TRef may coincide and / or be translated by a distance gn' relative to each other. The same number of finishing steps applies as to the roughing steps, with n' being the number of finishing steps. For example, the process may include four finishing steps, the first two being translated by a distance gl' and g2' respectively from the reference path of the next finishing step, which is directly adjacent to it, according to the order of the process steps. The last two finishing steps may, in this case, have a reference path TRef, the paths of these last two steps thus coinciding and both corresponding to the final contour of the desired cut.

[0061] In an advantageous embodiment, the process comprises at least two roughing electro-erosion steps with successive decreasing energy levels E, the first roughing step(s) being carried out with electrical discharges with a discharge energy E between 2000 pJ and 5000 pJ per millimeter of sample 1; and the last roughing step(s) being carried out with electrical discharges with an energy level E of each of these finishing steps between 200 pJ and 2000 pJ per millimeter of sample 1.

[0062] Advantageously, the diameter of wire 2 is less than 200 µm, preferably less than 100 µm, and even more preferably less than 75 µm. Such a diameter can indeed make it possible to obtain an optimized cutting surface quality.

[0063] The current of each electrical discharge across the terminals of electrode 2 is preferably less than 200 amperes.

[0064] The voltage across electrode 2 is advantageously less than 200V.

[0065] Advantageously, the pulse duration during which sample 1 is subjected to an electrical discharge is less than 1000 ps, ​​preferably less than 400 ps, ​​or even more preferably less than 100 ps. Such a pulse duration is adapted to the AMA of sample 1 in order to avoid any recrystallization of the AMA during the cutting process.

[0066] The cutting process advantageously allows a first surface PI of the sample 1 to be cut, resulting in a second surface P2 of the cut sample 1, and at each point of intersection between the remaining first surface PI and the created surface P2, said surfaces PI and P2 form an angle Ad of 90° ± 1.5°, preferably 90° ± 1°, and even more preferably 90° ± 0.5° between them. According to an embodiment illustrated in [Fig. 7].

[0067] Advantageously, the cutting process is such that the blank obtained by electro-erosion of the cut sample 1 has a surface roughness Ra of less than 800 nm, preferably less than 600 nm, more preferably less than 400 nm, and even more preferably less than 300 nm. Such a roughness makes it possible, in particular, to obtain microcomponents with excellent surface finishes, suitable especially for the watchmaking and / or implantology, particularly dental implantology.

[0068] The invention also relates to a method for manufacturing a part 4 made of an amorphous metal alloy, comprising the steps: - melt a mixture of metals to obtain a piece of alloy, and - inject the resulting pellet into a mold and cool the molded alloy at a rate exceeding the critical crystallization rate of the alloy, to obtain a sample 1 of amorphous alloy, and - machine at least one surface of sample 1 according to the cutting process described above to obtain a part 4 in amorphous alloy with a predetermined geometry, and - optionally perform a finishing step on at least the surface of the machined sample 1, preferably a tribofinishing step or a chemical treatment, in particular a surface deoxidation treatment.

[0069] The invention finally relates to a mechanical component, in particular a mechanical microcomponent in AMA comprising at least one surface cut according to the previous processes.

[0070] The mechanical component could, for example, be an element of a clockwork mechanism for a mechanical watch, such as a date hand, a gear wheel, or a shaft. The combination of the intrinsic mechanical properties of amorphous alloys and the precision of the cutting achieved by the process makes it possible to supply components, particularly micromechanical components, that are especially suited to this application. It could also be a component for medical use, such as an implant. List of reference signs

[0071] 1. Sample to be machined 2. Wire electrode 3. Dielectric 4. Machined part 5, 51. Draft. Control Unit 7. Enclosure 8. Irradiated portion 9. Outline of the room 10. Periphery of sample 1 Examples Example 1 - Conservation of amorphous structure

[0072] Samples of Ni(57-67)Nb(28-38)Zr(0-10) alloy (atomic %) were The samples were cut with different sets of parameters detailed in Table 1 to validate the maintenance of the amorphous structure of the alloy in samples machined according to the process of the invention. The Ni(57-67)Nb(28-38)Zr(0-10) alloy exhibits low thermal stability within the meaning of the invention. Indeed, its critical diameter De is only 3 mm, its stability coefficient, i.e., its quotient (ATx / (TI-Tg)), is 0.07, and its ATx is equal to 40.

[0073] The samples were cut by wire electrical discharge machining (EDM) from 500 µm thick preforms and two setups were carried out: - Assembly 1: Cutting of a single sample, - Assembly 2: Cutting a stack of 9 samples.

[0074] The machining process comprises two cutting phases. The first phase, called roughing, allows the material to be cut and defines the initial reference geometry; therefore, the intensity of the parameters for this phase is the most critical. The second phase, called finishing, is less energy-intensive and improves the surface finish created by the roughing phase.

[0075] Several steps per phase may be necessary to cut a part. Furthermore, different energy levels are used for each of these phases and / or steps. The energy level depends on the process step, the material thickness, and the desired surface finish.

[0076] Table 1 below summarizes the successive phases of the process implemented in this example and the corresponding parameters:

[0077] [Tables 1] Assembly Phase 1: Thickness Parameters = 0.5 mm Energy per mm of sample thickness Assembly Phase 2: Thickness Parameters = 4.5 mm Energy per mm of sample thickness Roughing Phase Level 1 2000 pJ / mm < E < 5000 pJ / mm 2000 pJ / mm < E < 5000 pJ / mm Roughing Phase Level 2 200 pJ / mm < E < 2000 pJ / mm 200 pJ / mm < E < 2000 pJ / mm Finishing Phase E < 200 pJ / mm E < 200 pJ / mm

[0078] Assembly 1 corresponds to a sample with a thickness of 0.5 mm. Assembly 2 corresponds to a stack of 9 samples, each 0.5 mm thick, for a total thickness of 4.5 mm.

[0079] Two sequences of steps were tested using the phases defined in Table 1 above. Table 2 below summarizes the parameter sets defined for the cutting tests.

[0080] [Tables2] Pass Type: Play 1, Level 1 Draft, Level 2 Draft, Level 2 Draft, Level 2 Draft, Finish - - Play 2, Level 1 Draft, Level 2 Draft, Level 2 Draft, Finish, Finish, Finish

[0081] Table 3 below summarizes the structural state of the samples after cutting.

[0082] [Tables3] Game 1 Montage 1 Game 1 Montage 2 Game 2 Montage 1 Game 2 Montage 2 Amorphous Amorphous Amorphous Amorphous

[0083] Microstructural analyses as well as XRD analyses have clearly shown a conservation of the amorphous microstructure for all the sets tested.

[0084] In addition to microstructural analyses, mechanical tests were carried out with the aim of quantifying the influence of electro-erosion on the material properties. Bars with a width of 500 µm made of Ni(57-67)Nb(28-38)Zr(0-10) (atomic %) alloy were therefore machined by EDM cutting and by micro-cutting (a controlled cutting method that does not affect the material, equivalent to the same sample from the casting stage or so-called "as-cast" sample).

[0085] The mechanical tests performed are 3-point bending tests. The machine used is the Shimadzu MMT-101NV-10 in bending mode. The parameters for Fessais were as follows: - Length between supports L0=5mm - Traverse speed v=0.005mm / s - Total sample length 1 = 10mm - Sample width L=500pm - Sample thickness e=500pm

[0086] The dimensions of the samples are presented in Table 4.

[0087] [Tables4] Samples Width b (mm) Height h (mm) LO / b 1: Set 1 - Assembly 1 0.5 0.5 10 2: Set 1 - Assembly 2 0.5 0.5 10 3: Set 2 - Assembly 1 0.5 0.5 10 4: Set 2 - Assembly 2 0.5 0.5 10 5: As cast cut 0.5 0.5 10

[0088] The results are presented in [Fig.8].

[0089] By comparison, the properties of the AMA are clearly preserved before and after EDM cutting for all samples tested in bending. There is no dispersion in the results, and the elastic limit value in bending is indeed equal to that obtained for the as-cast sample.

[0090] Similarly, the properties are conserved in the plastic zone. The elastic limit and plastic deformation values ​​are consistent with the values ​​observed on directly molded parts for which no cutting or other processing steps have been carried out.

[0091] Example 2 - Achieving the desired quality (dimensional and geometric) and its influence on production rates

[0092] This example aims to evaluate the surface and edge conditions, as well as the roughness and condition of the flanks after cutting. Indeed, for the type of application targeted, for example watch movement parts, a low Ra and good perpendicularity are essential to control tribological contacts and obtain low coefficients of friction and wear rates, which optimize the efficiency of mechanical systems (energy conservation) and their lifespan.

[0093] The quality criteria therefore include the roughness of the cut surfaces, the achievement of straight edges (perpendicularity between the cut area and the upper and lower surfaces), and the production of parts that are not oxidized and free of particle redeposition (burrs) directly after cutting or after cutting followed by surface treatment. The post-cut surface treatment consists of an organic acid-based treatment, marketed by NGL Cleaning Technology SA, applied to the cut sample for 5 minutes at 60°C.

[0094] The quality analyses were therefore carried out in Table 5.

[0095] [Tables5] Quality Criteria Level 1: (Compliant) Level 2: (Acceptable) Level 3: (Non-compliant) Taper <0.5° Between 0.5° and 1° >1° Roughness<N5 = N5 > N5 Surface quality after cutting (qualitative analysis) No particle redeposition and no oxidation Little particle redeposition and little oxidation Particle redeposition and / or excessive oxidation Surface quality after surface treatment (qualitative analysis) No particle redeposition and no oxidation Little particle redeposition and little oxidation Particle redeposition and / or excessive oxidation

[0096] Table 6 below summarizes the results obtained after implementation of the test plan

[0097] [Tableauxô] Samples: Taper, Roughness, Surface Quality after Cutting, Surface Quality after Surface Treatment. 1: Set 1 - Assembly 1, Level 1, Level 1, Level 1, Level 1. 2: Set 1 - Assembly 2, Level 1, Level 1, Level 2, Level 1. 3: Set 2 - Assembly 1, Level 1, Level 1, Level 3, Level 1. 4: Set 2 - Assembly 2, Level 1, Level 1, Level 3, Level 1.

[0098] All tests resulted in post-machining surface roughness below N5, and overall the surface finish is homogeneous. The addition of finishing steps (Set 2) produces a more homogeneous surface but slightly oxidizes it. This oxidation, which does not affect the properties, can be easily removed by surface treatment.

Claims

Demands

1. A method for cutting a sample (1) of an amorphous metal alloy, comprising at least two wire electrical discharge (ED) steps (2) producing electrical discharges on a sample (1) to remove material from the sample (1) so as to obtain a sample (1) cut along a reference path (TRef) and maintained in an amorphous state, wherein: The amorphous metallic alloy possesses: - a critical diameter (De) of less than 8 millimeters, preferably less than 6 millimeters, and even more preferably less than 4 mm, and / or - a difference (ATx) between the crystallization temperature (Tx) and the glass transition temperature (Tg) of less than 80°C, preferably less than 70°C, and even more preferably less than 60°C, and / or - a ratio (ATx / (TI-Tg)) of the difference (ATx) between the crystallization temperature (Tx) and the glass transition temperature (Tg) and the difference between the liquidus temperature (TI) and the glass transition temperature (Tg) less than 0.16, preferably less than 0.14 and even more preferably less than 0.12; and wherein the successive electro-erosion steps are such that they include: - at least one roughing step of the sample (1) along a reference path (TRef+n) to create a rough cut (5; 51) along a path (TRef+n), where n is the total number of roughing steps, the discharge energy (E) per roughing step being less than 5000 pJ per millimeter of sample (1) thickness to be cut; and - at least one finishing step of the sample (1) along a reference path (TRef) to remove material from the sample (1) along the reference path (TRef), the discharge energy (E) per finishing step being less than 200 pJ per millimeter of sample (1) thickness to be cut; and - the reference trajectory(s) (TRef+n) being translated by a given distance (gn) from the reference trajectory (TRef+(nl)) which is directly adjacent and which is closest to the final part (4), in the opposite direction to that of the final part (4) cut; and - the given distances (gn) between two directly adjacent reference trajectories, identical or different, are such that the electrical discharges removing material from the sample (1) to be cut on the reference trajectory (TRef+n, also remove, at least partially, material from the sample (1) to be cut on the reference trajectory TRef+(nl) which is directly adjacent to it.

2. A method according to claim 1 comprising at least two "roughing" electro-erosion steps, the successive energy levels (E) of which are decreasing, the first roughing step(s) being carried out with electrical discharges having a discharge energy (E) between 2000 pJ and 5000 pJ per millimeter of sample (1); and the last roughing step(s) being carried out with electrical discharges having an energy level (E) between 200 pJ and 2000 pJ per millimeter of sample (1).

3. A method according to any one of the preceding claims, characterized in that the diameter of the wire (2) is less than 200pm, preferably less than 100pm and even more preferably less than 75pm.

4. A method according to any one of the preceding claims, characterized in that the sample (1) is a stack of samples.

5. A method according to any one of the preceding claims, characterized in that the current of each electrical discharge is less than 200 amperes.

6. A method according to any one of the preceding claims characterized in that the voltage is less than 200V.

7. A method according to any one of the preceding claims, characterized in that the pulse duration during which the sample (1) is subjected to an electrical discharge is less than 1000 ps, ​​preferably less than 400 ps or even more preferably less than 100 ps.

8. A method according to any one of the preceding claims wherein the flank obtained by electro-erosion of the cut sample (1) has a surface whose roughness Ra is less than 800 nm, preferably less than 600 nm, more preferably less than 400 nm and even more preferably less than 300 nm.

9. A method according to any one of the preceding claims such that the cutting by electro-erosion of a first surface PI of the sample (1) results in obtaining a second surface P2 of the cut sample (1) and that, at each point of intersection between the first remaining surface PI and the created surface P2, said surfaces PI and P2 form between them an angle Ad of 90° ± 1.5°, preferably 90° ± 1° and even more preferably 90° ± 0.5° between them.

10. A method for manufacturing a part (4) of an amorphous metal alloy, comprising the steps: - melting a mixture of metals to obtain a billet of alloy, and - injecting the billet obtained into a mold and cooling the molded alloy with a cooling rate greater than a critical crystallization rate of the alloy, to obtain a sample (1) of amorphous alloy, and - to cut at least one surface of the sample (1) according to the cutting process of any one of claims 1 to 11 to obtain a part (4) made of amorphous alloy with a predetermined geometry, and - optionally perform a finishing step on at least the surface of the machined sample (1), preferably a tribofinishing step or a chemical treatment.

11. A component made of an amorphous metal alloy comprising at least one surface cut according to the cutting process of any one of claims 1 to 9 or according to the manufacturing process of claim 10, from the sample (1) made of an amorphous metal alloy, the amorphous metal alloy having a critical diameter (De) of less than 8 millimeters, preferably less than 6 millimeters, and even more preferably less than 4 mm, and / or - a difference (ATx) between the crystallization temperature (Tx) and the glass transition temperature (Tg) of less than 80°C, preferably less than 70°C, and even more preferably less than 60°C, and / or - a quotient (ATx / (TI-Tg)) of the difference (ATx) between the crystallization temperature (Tx) and the glass transition temperature (Tg) and of the difference between the liquidus temperature (TI) and the glass transition temperature (Tg) less than 0.16, preferably less than 0.14 and even more preferably less than 0.12.

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