WO2024105339A1

WO2024105339A1 - Injection device for amorphous metal alloy

Info

Publication number: WO2024105339A1
Application number: PCT/FR2023/051810
Authority: WO
Inventors: Sébastien GRAVIER; Xavier CERUTTI
Original assignee: Vulkam
Priority date: 2022-11-16
Filing date: 2023-11-16
Publication date: 2024-05-23
Also published as: FR3141867A1

Abstract

The invention relates to an injection device for producing at least one amorphous metal alloy moulded part, comprising: (i) a mould having at least two injection chambers connected to at least one moulding cavity; and (ii) at least one heating means capable of melting metal elements; and a multi-piston system comprising: (1) at least two injection pistons, the respective main axes of which are each aligned with that of their corresponding injection chamber and (2) a support cooperating with each of the injection pistons; and such that the support and/or the mould are able to move along an axis parallel to the main axes of the injection pistons so as to allow the loading of the metal elements and the injection of the molten metal elements into the injection chambers. The invention also relates to an injection method for producing at least one amorphous metal alloy moulded part.

Description

Title: Injection device for amorphous metal alloy

Technical area

[0001] The present invention relates to the field of production by die casting of amorphous metal alloy parts.

Prior art

[0002] “Amorphous metallic alloys” (AMAs) or “metallic glasses” have exceptional mechanical properties compared to their traditional crystalline counterparts: high yield strength and hardness, significant elastic deformation capacity, high fatigue resistance, to corrosion and abrasion.

[0003] Long limited by manufacturing processes leading to geometries that are not very inclined to industrialization, AMA parts can now be obtained industrially via, in particular, processes for molding a metal alloy capable of forming a metallic glass. Such processes consist first of all in filling an impression of a mold with a metal alloy previously molten. The alloy thus molded is then cooled quickly enough to obtain a part in the shape of the impression whose amorphous phase is the majority compared to the crystalline phase. Different types of molding have been developed for the manufacture of AMA parts such as suction molding, centrifugal molding or even die casting.

[0004] The term “pressure casting process” refers to a process during which pressure is applied to the molten alloy during the step of filling the impression. The pressure is exerted to guarantee optimum filling of the impression and “compact” the alloy in it. This pressure is generally exerted by a mechanical action, for example using a piston, and can be reinforced by the joint action of a depression or an excess pressure of the atmosphere within the mold or of other mechanical system such as, for example, a movable insert in the mold. [0005] The present invention relates more particularly to the pressure molding of AMA parts, generally considered to be the process most suited to industrialization. It is in fact known that such a process makes it possible to manufacture parts of complex shapes but it is however difficult to guarantee excellent quality of these, for example due to crystals or porosities within the parts (Lehua Liu and al. Near-Net Forming Complex Shaped Zr-Based Bulk Metallic Glasses by High Pressure Die Casting 2018, 11, 2338;

[0006] Thus, to guarantee excellent quality of the AMA parts produced, the quantity of alloy melted and then injected must be limited and the process cycle times generally exceed one minute. The limitation of injectable volume and cycle times therefore impose a limit in terms of production rate and/or volume of parts in AMA for industrial production.

Technical problem

[0007] There is therefore a need for an injection device and a pressure molding process for the manufacture of good quality AMA parts, possibly of larger volume, said process also having high productivity. The increase in productivity of the process must not, however, impact the quality of the parts compared to a process with lower productivity because it requires working at smaller volumes.

Summary of the invention

[0008] An injection device is therefore proposed for the production of at least one molded part of amorphous metal alloy, comprising:

- a mold 1 having at least two injection chambers 3 connected to at least one cavity 2; And

- at least one heating means 5 capable of melting metal elements 8; And

- a multipiston system 6 comprising: o at least two injection pistons 4 whose respective main axes are each aligned with that of their corresponding injection chamber 3 and o a support 7 cooperating with each of the injection pistons 4; and such that the support 7 and/or the mold 1 are capable of moving along an axis parallel to the main axes of the injection pistons 4 so as to allow: i. loading the metal elements 8; and he. optionally, melting said metal elements 8; and ill. the injection of molten metal elements 8 into the injection chambers 3.

[0009] According to one possibility, the invention proposes an injection device for the production of at least one molded part of amorphous metal alloy, comprising: a mold having at least two injection chambers connected to at least one cavity; and at least one heating means capable of melting metal elements; a multipiston system comprising: o at least two injection pistons whose respective main axes are each aligned with that of their corresponding injection chamber and o a support cooperating with each of the injection pistons; such that the support and/or the mold are able to move along an axis parallel to the main axes of the injection pistons so as to allow: i. loading of metal elements; and he. optionally, melting said metal elements; and ill. the injection of molten metal elements into the injection chambers, and o a single actuator configured to cooperate with the support or with the mold so as to cause the relative movement of the mold and the support along the axis parallel to the main axes of the injection pistons.

The relative translation of the mold and the different pistons mounted on the multipiston system is thus carried out by a single actuator.

This makes it possible to translate the at least two pistons concomitantly along their respective main axes thanks to the action of a single single actuator when it acts on the support. [0010] According to another aspect, an injection process is proposed for the production of at least one molded part of amorphous metal alloy, comprising the steps:

- load metal elements 8 into the device previously described, the metal elements 8 being loaded in solid form or in a molten state;

- optionally, melt the metal elements introduced in solid form;

- relatively move the support 7 and the mold 1 along an axis parallel to the main axes of the injection pistons 4 in order to inject substantially simultaneously, via the injection pistons 4, the molten metal elements into the impression 2 or the impressions 2 of the device to obtain, after cooling, at least one molded part of amorphous metal alloy.

[0011] The characteristics set out in the following paragraphs can optionally be implemented. They can be implemented independently of each other or in combination with each other.

[0012] According to one possibility, the single actuator is configured to be positioned at the level of the mold so as to allow the relative movement of the mold and the support.

[0013] According to a variant, the single actuator is configured to be positioned at the level of the support so as to allow the relative movement of the mold and the support. This allows the translation of at least two pistons concomitantly along their respective main axes thanks to the action of a single unique actuator on the support.

[0014] According to one possibility, the single actuator is a translation drive means, in particular a jack, a screw-nut system or even a ball screw system

[0015] According to one embodiment, the injection device is such that each injection piston 4 comprises a pre-stressed damping system 10 capable of exerting, when the injection piston 4 is in the injection position, a pressure on the molten metal element 8 corresponding to said injection piston 4, this effort, included in a determined force range, which may be different from that of the other injection piston(s) 4.

[0016] According to one possibility, each pre-stressed damping system is arranged between the support and the respective injection piston. This makes it possible to limit pressure peaks inside the mold, created by kinetic energy due to the speed of the injection and the pressure used when filling at least one cavity. This configuration makes it possible to reduce the mass between the metallic element and the pre-stressed damping system.

[0017] According to one arrangement, each pre-stressed damping system is arranged at the base of the respective injection piston.

[0018] According to one embodiment, the pre-stressed damping system 10 is chosen from: mechanical springs, a system using a pressurized gas and a system using a pressurized fluid.

According to one embodiment, the heating means 5 is chosen from: heating by induction, by electric arc, by laser beam, by electron beam.

[0020] According to one embodiment of the injection device, the injection direction is:

- vertical and the direction of injection from bottom to top or top to bottom,

- horizontal,

- inclined at an angle between 0 and 90 degrees relative to the vertical, preferably the direction of injection is vertical and even more preferably the direction of injection is vertical and the direction of injection is from bottom to top.

According to one possibility, each injection piston comprises an upper end face having a surface configured so that the molten metal element located on the surface does not protrude laterally from said end face. Thus, each of the molten metal elements is introduced into their own injection chamber, without touching the peripheral wall of said injection chamber. This prevents the cooling of the metal element in contact with the injection chamber and blocks the injection piston. [0021] According to one arrangement, each injection piston comprises an upper end face having a recessed shape and a peripheral rim capable of preventing the metal elements from falling from the end face of the pistons, in particular loaded metal elements. in the injection device in liquid or solid form, preferably the metal elements are loaded in solid form.

According to one embodiment, the metal elements 8 are loaded into the injection device in liquid or solid form, preferably the metal elements are loaded in solid form.

According to one embodiment, the mold 1 only includes a single imprint 2.

Technical solution

[0024] The invention and variants thereof can make it possible, in general, to propose an injection device for the simultaneous production of a large quantity of excellent quality AMA molded parts, suitable for production of industrial rate, and/or for the production of at least one large volume AMA molded part.

[0025] The simultaneous injection of small volumes of molten alloy into one or more impressions seems to be a clever solution for solving the problems of the prior art. However, such simultaneous work involves a number of technical problems to overcome. Firstly, the simultaneous management of means of translation of the different injection pistons and/or the mold is extremely complex and these different means of translation are too bulky to allow easy assembly on an industrial injection device.

[0026] The present inventors have thus developed an injection device for the industrial production of AMA molded parts making it possible to manage the injection parameters as finely as the devices of the prior art such as that disclosed for example in document WO2018/224418 A1. The device of the cited prior art allowed the production of good quality molded parts but with a lower rate and/or a limited volume. [0027] Thus, to solve these problems, the present inventors discovered that it was possible to carry out an injection of molten metal alloy using a multipiston system comprising a support on which at least two injection pistons are mounted. The relative translation of the mold and the different pistons mounted on the multipiston system is thus carried out by a single actuator.

Brief description of the drawings

Other characteristics, details and advantages of the invention will appear on reading the detailed description below, and on analyzing the appended drawings, in which:

Fig. 1

[0029] [Fig. 1] shows an injection device when the multipiston system is in the position for loading the metal elements according to one embodiment of the invention;

Fig. 2

[0030] [Fig. 2] shows an injection device when the multipiston system is in a position allowing the metal elements to melt according to one embodiment of the invention;

Fig. 3

[0031] [Fig. 3] shows an injection device when the multipiston system is in the injection position of the metal elements according to one embodiment of the invention;

Fig. 4

[0032] [Fig. 4] shows an injection device comprising a pre-stressed damping system, the multipiston system being in the position for loading the metal elements, according to one embodiment of the invention;

Fig. 5 [0033] [Fig. 5] shows an injection device comprising a pre-stressed damping system, the multipiston system being in the position of injecting the metal elements, according to one embodiment of the invention;

Fig. 6

[0034] [Fig. 6] shows an injection device comprising a unique impression according to one embodiment of the invention;

Fig. 7

[0035] [Fig. 7] shows an injection device when the multipiston system is in the position for loading the metal elements according to one embodiment of the invention;

Fig. 8

[0036] [Fig. 8] shows an injection device when the multipiston system is in the injection position, the molten metal elements being charged in the liquid state according to one embodiment of the invention.

Fig. 9

[0037] [Fig. 9] shows an injection device when the multipiston system is in the injection position and comprises a pre-stressed damping system, the molten metal elements being loaded in the liquid state according to one embodiment of the invention.

Fig. 10

[0038] [Fig. 10] represents a 3-point bending curve obtained during mechanical tests making it possible to evaluate the elastic limit, oel, and the plastic contribution to the deflection, fp, of the amorphous metal alloy samples.

Description of embodiments

[0039] The drawings and the description below contain, for the most part, elements of a certain nature. They can therefore not only be used to better understand the present invention, but also contribute to its definition, if necessary. [0040] Here, the term “metallic glass” or “amorphous metal alloy” or “AMA” means metals or metal alloys which are not crystalline, that is to say whose atomic distribution is predominantly random. However, it is difficult to obtain a one hundred percent amorphous metal alloy because there most often remains a fraction of the material which is crystalline in nature. We can therefore generalize this definition to metals or metal alloys which are partially crystalline and which, therefore, contain a fraction of crystals, as long as the amorphous fraction is the majority compared to the crystalline fraction. The metallic glasses according to the present invention have an amorphous phase fraction greater than 50%, preferably greater than 60%, even more preferably greater than 70% and even greater than 80%.

[0041] It is specified here that a metallurgical structure is said to be “totally amorphous” within the meaning of the present invention when an X-ray diffraction analysis as described below does not reveal a crystallization peak. A metallurgical structure is said to be “partially amorphous” within the meaning of the present invention when an X-ray diffraction analysis as described below highlights a few crystallization peaks. Unless otherwise specified, the term “amorphous” is used both for so-called “totally amorphous” alloys and for so-called “partially amorphous” alloys within the meaning of the invention. Such an evaluation of the amorphous character of a metallic alloy is detailed in the article Cheung et al., 2007 (Cheung et al. (2007) “Thermal and mechanical properties of Cu-Zr-AI bulk metallic glasses)” doi:10.1016 /j.jallcom.2006.08.109). It makes it possible to carry out an average analysis on a surface and to overcome the few inevitable metallurgical defects, while only analyzing crystals of significant size, that is to say greater than a few nanometers and/or in significant quantities. Figures from application W02020/128170 A1 represent an XRD analysis as described previously. These figures show the intensity of the diffracted beam as a function of the angle between the incident beam and the diffracted beam. Application W02020/128170 A1 includes an illustration of an XRD analysis of a metal alloy in the “totally amorphous” state, the amorphous fraction being very largely in the majority compared to the crystalline fraction. Application W02020/128170 A1 includes an illustration of a similar analysis carried out on an alloy in the “partially amorphous” state, the amorphous fraction being the majority compared to the crystalline fraction. In this figure, we find the characteristic bump of amorphous structures, but with the presence of peaks as well. Application W02020/128170 A1 also includes an illustration of a similar analysis carried out on a crystalline alloy, the crystalline fraction being the majority compared to the amorphous fraction. In this last figure, the characteristic bump of the AMAs is not present and the crystallinity peaks are clearly visible.

[0042] Here we mean “elastic deformation capacity, se” the maximum reversible deformation that a material can undergo. Beyond this value, the material will break or plastically deform (irreversible deformation). The elastic deformation is expressed in % and is determined during a bending test. Thus, according to the present description, the elastic limit, oel, and the plastic contribution to the deflection, fp, are evaluated as follows.

Mechanical tests are carried out on a DY34 mechanical testing machine (Adamel Lhomargy). These are 3-point bending tests in the direction of the thickness of the sample.

The test parameters are as follows:

- Length between supports L=10 mm

- Sample width b=10 mm

- Sample thickness h=0.50 mm

- Sample length 1=15 mm

- Crosshead speed v=0.005 mm/s

The 3-point bending curve presents a first linear elastic part then a plastic plate, as illustrated in Figure 10.

The elastic limit, oel, is calculated according to the following formula 1:

[Math. 1]

3 x Fe x L ael = — — ; - —

2 xbxh ² where Fe is calculated according to the following formula 2:

[Math. 2]

with

- Fmax: the maximum force value recorded at the force plate. The plastic contribution to the deflection, fp, is calculated according to the following formula 3: [Math. 3] fp = fr — fe with

-fe is the deflection reached at a stress level corresponding to the elastic limit, i.e. 2Fmax/3; And

- fr is the break arrow.

The elastic deformation capacity, £e, is calculated according to the following formula 4: [Math. 4]

(6XFe X/l) se = - - -

L ²

The injection device is specifically adapted to the production of at least one molded part made of amorphous metal alloy. It comprises a mold 1 having at least two injection chambers 3 connected to at least one cavity 2. The device thus makes it possible to produce numerous parts simultaneously and/or to produce AMA parts of large volume than was previously possible. not possible to produce until then. For the production of large volume and good quality parts, at least two injection chambers 3 can be connected to a single cavity 2. In one embodiment, the mold 1 only includes a single cavity 2, each of the chambers injection 3 therefore being connected to this single impression 2. This embodiment is illustrated in Figures 6 and 7.

[0044] The injection device comprises at least one heating means 5 capable of melting metal elements 8. The metal elements 8 are loaded into the injection device in liquid or solid form, preferably the metal elements 8 are loaded in solid form. This preferred mode is illustrated in Figures 1 and 7.

[0045] For the purposes of the present invention, the term “loading of the metal elements 8” or “loaded metal elements 8” in the device means the fact of introducing said metal elements 8 into the device so that they can then be injected, via the injection pistons 4 into the injection chambers 3 and the cavity(ies) 2 of the mold 1.

[0046] Reference is now made to Figures 1 to 3 to illustrate one embodiment of the invention. Thus, the metal elements 8 can be loaded in solid form. The metal elements 8 can thus be in the form of a grain of more or less spherical shape composed of a material capable of forming a metallic glass. In the embodiment of Figures 1 to 3, the injection device corresponds to a vertical injection device. The loading position illustrated in Figure 1 is such that the upper end faces 9 of the pistons are located below the mold 1 and the heating means 5. In this loading position, the metal elements 8 in the state solid are deposited on the upper end face 9 of the injection pistons 4.

The upper end face 9 of the injection pistons 4 comprises a central recessed shape 11 and a peripheral rim 12 capable of preventing the metal elements 8 from falling from the end face 9 of the pistons 4. For example , the central recessed shape 11 can be in the form of a spherical cap, as shown, or in the form of a cone or a bowl with a radial bottom and a frustoconical peripheral wall. The major part of each of the metal elements 8 is located above the end face 9 of an injection piston 4, outside the central recessed shape 11.

[0048] According to a variant embodiment, the loading operation, that is to say depositing each of the metal elements 8 on an end face 9 of a piston 4, can be carried out by a manipulator arm .

[0049] According to another alternative embodiment, the loading operation can be carried out in the following manner. A confinement ring is brought above and at a short distance from the end face 9 of a piston 4, the lower end of an inclined gutter is brought above the space created by the confinement ring . A metal element 8 is placed in an upper part of the gutter. The metal element 8 slides by gravity in the gutter and enters the space created by the containment ring which prevents it from falling, the metal element 8 being placed above the central hollow shape 11. After which, we remove the gutter and remove the containment ring, without hitting the metal element 8 removed.

[0050] As an indication, the volume of a metal element 8 can be approximately one tenth of a milliliter to five milliliters.

After which, the pistons 4 are moved in translation upwards to an intermediate position illustrated in Figure 2, in which the metal elements 8 are located in the interior space of the heating means 5, for example at inside the turns of an induction heating means 5.

[0052] After which, thanks to the action of the heating means 5, the metal elements 8 are heated until they pass into a molten state. Under the effect of surface tensions, the molten metal elements 8, although in the liquid state, substantially take the shape of a sphere, generally flattened, which rests and naturally takes a central position on the central shape in hollow 11. The surface of the upper end face 9 of the injection pistons 4 is such that the molten metal element 8, located on each of these surfaces, does not protrude laterally from said end face 9.

[0053] After which, the pistons 4 are moved from the intermediate position towards their respective injection chamber 3. According to an alternative embodiment possibly compatible with the previous one, the mold 1 is moved towards the pistons 4.

[0054] In doing so, as illustrated in Figure 3, each of the molten metal elements 8 is introduced into their own injection chamber 3, without it touching the peripheral wall of said injection chamber 3, the face end 9 of each of the pistons 4 engages in the injection chamber 3 which corresponds to it forming a sliding fit with little clearance between these two elements.

[0055] After which, the translational movement of each of the pistons 4 towards the mold 1 creates a pressure in each of the injection chambers 3 which causes the injection of each of the metal elements 8 in fusion into the cavity 2 or the impressions 2. One or more vents in the mold 1 are optionally provided. In the final injection position, the end face 9 of the piston 4 does not preferably reach the bottom of its injection chamber 3. [0056] It follows from the above that, until the actual phase of injection into the cavity(ies) 2, the molten metal elements 8 are only in local contact with the central recessed shape 11 of the piston 4 on which they are placed, without other contact, and remain at a distance from the wall of the injection chambers 3 as long as they do not reach the bottom of their injection chamber 3, so that the metallic material does not crystallize.

[0057] According to another embodiment illustrated in Figures 8 and 9, the metal elements 8 are loaded into the injection device in liquid form. The heating means 5 then makes it possible to melt the metal element(s) 8. The metal alloy in the liquid state is contained in one or more crucibles. According to one embodiment, gutters make it possible to connect the crucible(s) to the upper end face 9 of each of the injection pistons 4 to allow the loading of the metal elements 8. The loading can also be carried out by pouring d a given volume of alloy on the upper end face 9 of each of the injection pistons 4 or by any other equivalent means. The upper end face 9 of the pistons 4 comprises a central recessed shape 11 capable of containing the desired volume of metallic element 8 in the liquid state.

[0058] For the purposes of the present description and whatever the embodiment, the term “upper end face 9” of the injection pistons 4 means the face of the pistons 4 facing the injection chamber 3 which corresponds to them.

[0059] The device comprises at least one heating means 5 capable of melting the metal elements 8. The heating means 5 is preferably chosen from heating by induction, by electric arc, by laser beam or even by beam of electrons. By way of example, according to one embodiment of the device where the injection is a vertical injection and the metal elements 8 are charged in the solid state, the heating means 5 is preferably located below the mold 1, consisting of for example by induction turns coaxial with each of the pistons 4, wound for example in a cylinder or truncated cone. According to this embodiment, the metal elements 8 can be melted quickly and homogeneously knowing that the majority of these elements 8 can be located directly in the space heated by the heating means 5. In indeed, as indicated previously, only the lower faces of the metal elements 8 bear on the surface of the upper end face 9 of each of the pistons 4. Under the effect of surface tensions, the metal elements 8 in fusion, well that in the liquid state, take substantially the shape of a sphere, generally flattened and do not protrude laterally from said end face 9.

The device may further comprise means for heating and/or cooling at least a part of each of the pistons 4, this part being closest to their upper end face 9.

[0061] Advantageously, the mold 1 is equipped with controlled heating and/or cooling means (not shown) so that the material constituting the AMA molded part obtained in the impression(s) 2 does not crystallize and after extraction, said part has the characteristics of a metallic glass, that is to say the characteristics of an amorphous or at least partially amorphous or predominantly amorphous metal or metal alloy.

[0062] Advantageously, the injection device comprises ejectors 14 in order to be able to easily remove the molded and cooled parts at the end of the injection process. The ejectors 1' can for example be pistons and/or pressurized air nozzles.

[0063] The device comprises a multipiston system 6. The simultaneous injection of metal elements 8 in volume fusion capable of forming one or more molded parts in good quality AMA appeared until now to be an excellent technical solution for increasing the productivity of injection processes and/or to imagine producing larger volume AMA castings while maintaining excellent quality of amorphization of the alloy but also seemed unrealistic to adapt to an injection device. Indeed, piston actuators are complex and bulky systems and the present inventors have found that their simultaneous operation is difficult to achieve. This difficulty is even greater, particularly in the case where the device only includes one large-volume imprint. In addition, this involves the use of multiple actuators, generates an extremely complex actuator management system and a very high financial cost. It is therefore proposed a multipiston system 6 comprising at least two injection pistons 4 whose respective main axes are each aligned with the main axis of their corresponding injection chamber 3 and a support 7 cooperating with each of the injection pistons 4. The support 7 and/or the mold 1 are thus able to move along an axis parallel to the main axes of the injection pistons 4 using a single actuator 13 moving the support 7 or the mold 1 or two actuators 13 only capable of moving simultaneously or separately, one the support 7 and the other the mold 1 so as to allow the operation of the injection device (loading, optionally melting of the metal elements, concomitant injection of the different elements metal 8 in the injection chambers 3).

[0064] Such a multipiston system 6 makes it possible to resolve the problems of the prior art. It can in fact be actuated by a single actuator 13 thus allowing the relative movement of the support 7, and therefore of the injection pistons 4 simultaneously, and of the mold 1 along an axis parallel to the main axes of the injection pistons 4 In a variant embodiment, the actuator 13 can be positioned at the level of the mold 1 so as to allow the relative movement of the mold 1 and the support 7, and therefore of the injection pistons 4 simultaneously, along an axis. parallel to the main axes of the injection pistons 4. In yet another variant but with the same objective, an actuator 13 can be positioned at the level of the mold 1 and a second at the level of the support 7. The actuator 13 can be any means translational drive such as, in particular, a jack, a screw-nut system or even a ball screw system.

[0065] According to an advantageous embodiment, illustrated in Figures 4 and 5, each injection piston 4 of the device comprises a pre-stressed damping system 10 capable of exerting, when the injection piston 4 is in the injection position , a force on the molten metal element 8 corresponding to said injection piston 4 (Figure 5). This force, included in a determined force range, can thus be different from that of the other injection piston(s) 4.

[0066] Such a pre-stressed damping system 10 ensures that, in all cases, a minimum pressure (set by the user with the pre-stress) will be applied to the molten metal elements 14 in each of the injection chambers 3. Indeed, a difference in height, even small (dimensional tolerances) of the pistons 4 between them or of the injection chambers 3, in mass of the different metallic elements 8 and/or any other element of said device can cause an impression 2 of the mold 1 to be filled before the others. In the absence of a damping system 10, the other pistons 4, cooperating with the other indentations 2 not completely filled, can then find themselves blocked and said indentations 2 will then remain partially filled. The activation of at least one of the pre-stressed damping systems 10 then makes it possible to generate a relative movement of the piston associated with this system in relation to the others. The other pistons 4 can thus continue their stroke until their cavity is completely filled. In the same way, in the case of a cavity 2 connected to at least two injection chambers 3, the damping systems 10 make it possible to apply a minimum pressure on the alloy in each of the injection chambers 3 and to ensure homogeneous pressurization of the alloy in the cavity 2. Advantageously, the prestresses of the damping systems 10 are defined so as to generate a pressure on the alloy during injection greater than 5 MPa, preferably between 5 MPa and 300 MPa, even more preferably between 10 MPa and 250 MPa.

[0067] The pre-stressed damping system 10 is advantageously chosen from: mechanical springs (helical spring type, spring washers), a system using a gas under pressure (gas cylinder) and a system using a fluid under pressure (hydraulic cylinder ).

[0068] Although the embodiments illustrated in the present document correspond to vertical injection devices, the invention is not limited to this injection mode alone. Thus, the direction of injection can be vertical and the direction of injection from bottom to top or top to bottom, horizontal or even inclined at an angle between 0 and 90 degrees relative to the vertical. Preferably, the injection direction is vertical and, even more preferably, the injection direction is vertical and the injection direction is from bottom to top.

[0069] Reference is now made to Figure 6. Figure 6 illustrates an injection device comprising a single impression 2. Different injection chambers 3 are connected to a single cavity 2 so as to be able to produce a part in AMA large volume and excellent quality. Simultaneous injection was in fact not possible until now industrially. Indeed, the simultaneous management of means of translation of the different injection pistons 4 and/or of the mold 1 is extremely complex and these different means of translation are too bulky to allow easy assembly on an injection device industrial. The present inventors have, however, developed a multipiston system 6 comprising a support 7 on which the injection pistons 4 are mounted. The relative translation of the mold 1 and the multipiston system 6 can thus be carried out by a single actuator 13. In an alternative embodiment, several actuators 13 can be included in the device, for example one for translating the mold 1 and the other for translating the multipiston system 6. In an embodiment compatible with the previous, there can exist several multipiston systems 6, each being translated by a specific actuator 13.

[0070] Reference is now made to Figure 7. Figure 7 illustrates an injection device when the multipiston system 6 is in the loading position of the metal elements 8 according to one embodiment of the invention. The mold 1 (whatever the embodiment of the invention) is made up of at least two parts that can be dissociated from each other along a plane intersecting each of the imprints 2 so as to allow the parts to be unmolded. molded in AMA. The loading of the metal elements 8, in the solid or liquid state, can be carried out in a position where the upper end face 9 of the pistons 4 is located in a space located between the different parts of the mold 1 when the latter is in the open position, that is to say that these different parts are separated so as to allow the unmolding and/or loading of the metal elements 8. Such an embodiment makes it possible in particular to have the possibility of carrying out the removal metal elements 8 on the pistons 4 just after or at the same time as the castings are ejected and recovered. The parts recovery system can in fact be the same as that carrying out the removal of the metal elements 8 (with a robotic arm for example).

[0071] Reference is now made to Figure 8. Figure 8 illustrates an injection device in which the metal elements 8 are charged in the liquid state, therefore in fusion. The device shown corresponds to a vertical injection device but any other injection orientation can also be considered.

[0072] According to Figure 8, the metal elements 8 can be melted in a crucible using a heating means 5, both not shown. The resulting molten metal alloy can be brought into a hollow form

12 of the end face 9 of the injection pistons 4 by any suitable means, for example using chutes going from the crucible to each of the end faces 9 of the pistons 4. According to the embodiment shown , an actuator

13 allows the multipiston system 6 to be moved along a longitudinal axis parallel to the direction of the pistons 4. The multipiston system 6 can thus be translated vertically in order to inject the molten alloy into the injection chambers 3.

[0073] The embodiment of the device shown in Figures 8 and 9 comprises a pre-stressed damping system 10 at the base of each injection piston 4. The pre-stressed damping system 10 ensures a minimum pressure applied to the molten metal elements 14 in each of the injection chambers 3. Figures 8 illustrate a difference in height of the pistons 4 between them. As shown in Figure 9, the damping system 10 allows complete filling of each of the indentations 2 even in the case of a difference in height of the pistons 4 whatever the reason.

[0074] The invention also relates to an injection process for the production of at least one molded part of amorphous metal alloy, comprising the steps:

- optionally, melt the metal elements 8 introduced in solid form;

- relatively move the support 7 and the mold 1 along an axis parallel to the main axes of the injection pistons 4 in order to inject substantially simultaneously, via the injection pistons 4, the metal elements 8 in fusion in the cavity 2 or the cavity 2 of the device to obtain, after cooling, at least one molded part of amorphous metal alloy. [0075] By “substantially simultaneously” is meant the fact that the metal elements 8, due to their difference in possible volumes and/or due to the pressure differences within the injection chambers 3, in the height of the pistons 4 between them , and/or possible defects in the geometry of the pistons 4, the injection chambers 3 and/or any other element of the device, can be injected concomitantly within a few milliseconds or microseconds.

[0076] AMAs are alloys whose metallurgical quality can be difficult to control. Thus, according to a preferred embodiment of the invention, compatible with the previous modes, the device is configured so that the stages where the metal elements are in fusion, such as the actual melting, the possible transport of the molten elements, for example in chutes, their injection, are carried out under a controlled atmosphere. It may be a high vacuum, in particular a vacuum less than 1.10' ¹ mbar, preferably less than 1.10 ^-2 mbar, more preferably less than 5.10' ³ mbar and even more preferably less than 1.10' ³ mbar. It may also be an atmosphere of neutral gas, for example an atmosphere of argon or nitrogen, the pressure may then be lower or higher than atmospheric pressure.

[0077] To improve rates or manufacture larger volume parts, an approach consisting of increasing the volumes/masses of the metal element injected by the piston is conventionally used in conventional foundry/molding, that is to say in the field of crystalline materials. Unlike this classic approach, the previous device and the present method propose a multiplication and parallel operation of the injection pistons. The same volume of alloy to be injected can thus be divided into several metallic elements of smaller volume. The fusion cycle can thus be carried out on several metallic elements of small volume/small mass (for example less than 200 g, preferably less than 100 g, more preferably less than 75 g and even more preferably less than 50 g) instead of 'a bigger one. Thus, the melting temperatures are better controlled and this also ensures good homogenization of the melt. Indeed, controlling the melting quality of the alloy elements thus makes it possible to guarantee a level of quality metallurgical and to have a more homogeneous viscosity during molding, thus improving the filling and repeatability of the injection process.

[0078] Pressure injection of AMA also ideally requires management of "cold spots" which are the contact zones of the molten alloy with the different elements of the device, in particular the piston(s). At these “cold spots”, part of the heat provided to melt the AMA is dissipated. Control of the melting cycle in these areas can therefore be difficult to guarantee. Managing a small volume of alloy allows better control of these "cold spots" as well as thermal gradients in the AMA.

[0079] According to a preferred embodiment, the device is a vertical injection device. Thus, the joint use of a multipiston system making it possible to simultaneously inject small volumes of molten AMA and a vertical injection device, for example such as that described in application WO2018/224418 A1, makes it possible to limit “cold spots”, thus guaranteeing the quality of molded parts. Such an embodiment also makes it possible to avoid potential chemical interactions which could then lead to pollution of the metallic elements and/or rapid deterioration of the elements of the device (thermal is in fact more difficult to manage with volumes of alloy per cycle higher or an increased process rate).

Industrial application

[0080] The invention can be applied in particular in the field of industrial devices for manufacturing molded AMA parts. Such an invention makes it possible to produce molded AMA parts at high speed and/or with larger volumes than was previously possible using a single injection piston.

[0081] The invention is not limited to the embodiments described above, only by way of example, but it encompasses all the variants that those skilled in the art could envisage in the context of the protection sought. List of reference signs

- 1: mold

- 2: imprint

- 3: injection chamber - 4: injection piston

- 5: heating means

- 6: multi-piston system

- 7: support (injection pistons)

- 8: metallic element - 9: end face (of an injection piston)

- 10: pre-loaded damping system (of an injection piston)

- 11: hollow central shape of the end face 9

- 12: peripheral edge of end face 9

- 13: actuator (injection pistons and/or mold) - 14: ejector

- 15: main axis of a piston and its corresponding injection chamber

Claims

[Claim 1] Injection device for the production of at least one molded part of amorphous metal alloy, comprising: a mold (1) having at least two injection chambers (3) connected to at least one cavity (2) ; and at least one heating means (5) capable of melting metal elements (8); a multipiston system (6) comprising: o at least two injection pistons (4) whose respective main axes are each aligned with that of their corresponding injection chamber (3) and o a support (7) cooperating with each of the injection pistons (4); and such that the support (7) and/or the mold (1) are capable of moving along an axis parallel to the main axes of the injection pistons (4) so as to allow: i. loading the metal elements (8); and he. optionally, melting said metal elements (8); and ill. the injection of molten metal elements (8) into the injection chambers (3).

[Claim 2] Injection device according to claim 1 such that each injection piston (4) comprises a pre-stressed damping system (10) capable of exerting, when the injection piston (4) is in the position of injection, a pressure on the molten metal element (8) corresponding to said injection piston (4), this force, included in a determined force range, being able to be different from that of the other injection piston(s) ( 4).

[Claim 3] Injection device according to claim 2 such that the pre-stressed damping system (10) is chosen from: mechanical springs, a system using a gas under pressure and a system using a fluid under pressure.

[Claim 4] Injection device according to any one of the preceding claims such that the heating means (5) is chosen from: heating by induction, by electric arc, by laser beam, by electron beam.

[Claim 5] Injection device according to any one of the preceding claims such that the direction of injection is:

- vertical and the direction of injection from bottom to top or top to bottom,

- horizontal,

[Claim 6] Injection device according to any one of the preceding claims, in which each injection piston (4) comprises an upper end face (9) having a surface configured so that the metallic element (8 ) melted and located on the surface does not protrude laterally from said end face (9).

[Claim 7] Injection device according to any one of the preceding claims such that the mold (1) only comprises a single impression (2).

[Claim 8] Injection device according to any one of the preceding claims, in which the multipiston system (6) comprises a single actuator (13) configured to cooperate with the support (7) or with the mold (1) so as to to cause the relative movement of the mold (1) and the support (7) along the axis parallel to the main axes of the injection pistons (4).

[Claim 9] Injection process for the production of at least one molded part of amorphous metal alloy, comprising the steps:

- loading metal elements (8) into the device according to any one of claims 1 to 8, the metal elements (8) being loaded in solid form or in a molten state;

- optionally, melt the metal elements introduced in solid form;

- relatively move the support (7) and the mold (1) along an axis parallel to the main axes of the injection pistons (4) in order to inject substantially simultaneously, via the injection pistons (4 ), the molten metal elements in the impression (2) or impressions (2) of the device to obtain, after cooling, at least one molded part of amorphous metal alloy.