Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D29/00—Removing castings from moulds, not restricted to casting processes covered by a single main group; Removing cores; Handling ingots
  • B22D29/001—Removing cores
  • B22D29/002—Removing cores by leaching, washing or dissolving
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/003—Making ferrous alloys making amorphous alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
  • B22D17/08—Cold chamber machines, i.e. with unheated press chamber into which molten metal is ladled
  • B22D17/10—Cold chamber machines, i.e. with unheated press chamber into which molten metal is ladled with horizontal press motion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
  • B22D17/20—Accessories: Details
  • B22D17/22—Dies; Die plates; Die supports; Cooling equipment for dies; Accessories for loosening and ejecting castings from dies
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/11—Making amorphous alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C45/00—Amorphous alloys

Definitions

• TITLE Injection molding device and process for the production of metal glass parts Technical area
• the present disclosure relates to the field of production by injection of parts in metallic glasses, also called amorphous metals or amorphous metallic alloys (AMA).
• the invention relates to an injection molding device intended for the manufacture of at least one part made of amorphous metal alloy, a method of manufacturing at least one part made of amorphous metal alloy and a part capable of being obtained. according to said method.
• a metallic glass is conventionally obtained by specific manufacturing processes including in particular rapid cooling of a molten metal alloy whose chemical formulation is specifically appropriate so that the amorphous character is at least partially maintained after solidification.
• amorphous metal alloys or “metallic glasses” applies to metals or metal alloys which are not crystalline, that is to say which have a predominantly random atomic distribution.
• the amorphous structure of metallic glasses gives them particularly interesting properties: a very high mechanical resistance, a large capacity for elastic deformation, which is generally greater than 1.5%, a high resistance to corrosion and abrasion.
• AMAs in particular based on zirconium (Zr), magnesium (Mg), iron (Fe), copper (Cu), aluminum (Al), palladium (Pd), platinum ( Pt), titanium (Ti), cobalt (Co), nickel (Ni), hafnium (Hf).
• Zr zirconium
• Mg magnesium
• Fe iron
• Cu aluminum
• Al palladium
• Pd platinum
• Pt titanium
• Co cobalt
• Ni nickel
• Hf hafnium
• One method of manufacturing metal glass parts consists of injecting the liquid material into the imprint of a mold and solidifying the material under specific suitable conditions of injection speed and cooling.
• the manufacture with extreme precision, for example an accuracy of less than 5 ⁇ m or even less than or equal to 1 ⁇ m, of AMA parts of very small dimensions (in particular of length between 0.1 mm and 25 mm, preferably 0.5 mm and 10 mm in the largest dimension of the part) and having a high height / thickness ratio generally requires complex manufacturing processes involving a casting step, a thermoforming step of a preform and a removal finishing step of material to lead to the final AMA part.
• the material removal step is generally carried out by machining or by "hot-scraping" (Schroers et. Al (2007) "Thermoplastic forming of bulk metallic glass— Applications for MEMS and microstructure fabrication", accessible via the internet link https : // doi: 10. 1016 / d. msea.2006.02.398).
• US Patent 8,807,198 describes a method for producing by injection of a metallic component, in which the cavity of a mold is provided with a sacrificial core to produce a cavity inside the metallic component. The metal is injected and cooled. After demolding, the sacrificial core attached to the molded part is destroyed.
• the insert can be made of a refractory metal.
• Document US2017 / 0087626 A1 describes a complex process for manufacturing an amorphous metal alloy part, comprising in particular the steps of three-dimensional printing of a wax model of the shape of the part, the introduction of a model in wax in the casting mold, the pouring of a sacrificial shell of constant thickness between the casting mold and the wax model, the dissolution of the wax model, the casting of an AMA in place of the wax model , the quenching of the part in cast AMA and the demolding of said part.
• US Patent 9,314,839 describes a method of producing a piece of metallic glass, by injecting a metallic alloy into a cavity defined between two parts of a mold, one part of the mold having a protuberance forming a core engaged in the other part. After demolding, the protuberance engaged in the molded component is destroyed by etching.
• AMA parts specifically manufactured to serve as a device for verifying authenticity.
• AMA parts can be produced either by casting and then pressing the cast alloy or by thermoforming an alloy in a mold comprising a region with an irregular surface having a roughness Ra of between 0.1 ⁇ m and 1000 ⁇ m.
• the manufacturing processes described in this document are not, however, suitable for obtaining a part, made of AMA of lower thermal stability, and of very small dimensions and of complex geometry or having a high height / thickness ratio.
• the casting and pressing process imposes a time during which the alloy will be in contact with the mold without applying pressure and therefore without perfectly filling the imprint. This will create cold spots, which may prevent industrialization and the good repeatability of the manufacturing process, in particular for the following potentially cumulative reasons:
• AMA parts of very small dimensions in particular of length between 0.1 mm and 25 mm, preferably 0.5 mm and 10 mm in the largest dimension of the part
• a height / thickness ratio important and very fine geometrical characteristics (surface pattern with an accuracy of less than 5 ⁇ m or even less than or equal to 1 ⁇ m)
• thermoforming processes consist in heating to a temperature higher than the glass transition temperature of GAMA (Tg) a piece of alloy in solid form and already having an amorphous structure and to form it using a pressure mechanical. These methods therefore require first obtaining amorphous pieces by casting, these pieces then being thermoformed. During thermoforming, they undergo a rise in temperature, a temperature which is maintained throughout the shaping. Once the forming is complete, the alloy is cooled to a temperature below Tg.
• GAMA glass transition temperature
• the alloy In order to preserve the amorphous structure of the part during thermoforming, the alloy must therefore have sufficient thermal stability to allow shaping without crystallizing. This is all the more important in the case of shaping of microcomponents with high aspect ratios, where a longer shaping time is necessary.
• the parameters used are a temperature making it possible to obtain a viscosity between 10 6 and 10 8 Pa.s and times for maintaining at these temperatures before crystallization of the order of 3 to 5 min (Kumar et al. .
• compositions having significant thermal stability that is to say thermal stability such that DTc of GAMA is greater than 100, with DTc, the temperature difference DT between the crystallization temperature Tx and the glass transition temperature Tg and / or even such that the standard thermal stability criterion, ATx / (Tl-Tg) is greater than 0.18.
• thermally stable AMAs limits the compositions of usable alloys and the most stable alloys do not necessarily have the most advantageous property compromises depending on the intended application.
• alloys with good thermal stability generally include elements such as precious metals, which are therefore very expensive and not suitable for industrialization.
• Other alloys with good thermal stability contain harmful elements such as beryllium.
• thermoforming step requires at least at least manufacturing steps (casting the slug and then thermoforming) and very long shaping times, which makes such processes difficult to industrialize.
• a device for injection molding of a metal alloy, intended for the manufacture of at least one part made of an amorphous metal alloy or metallic glass, which comprises:
• an injection mold defining a cavity which has a receiving face and a front molding face opposite the receiving face
• At least one sacrificial insert placed in said cavity and having a rear face of which at least one bearing zone is adjacent to at least one bearing zone of said cavity receiving face and a front face situated opposite said molding face of the mold and provided with a hollow shape
• a movable injection piston in a mold chamber, which communicates with the molding impression
• the molding imprint is configured so that the diameter of the geometric spheres inscribed in this molding imprint and having at least one point of contact with the sacrificial insert is at most equal to one and a half times (1.5 times ) the critical diameter of the metal alloy, preferably at most equal to once and two tenths of times (1, 2 times) the critical diameter of the metal alloy, or again at most equal to once (1 time) the critical diameter (De) of the specific metal alloy.
• Said cavity can be configured so that after demolding of the part provided with the sacrificial insert, at least said bearing area of the rear face of the sacrificial insert is uncovered.
• the cavity may have a peripheral face joined to the receiving face.
• the peripheral edge of the receiving face can be joined to the end edge, which is adjacent to it, of the peripheral face of the cavity.
• the sacrificial insert can be in the form of a plate.
• the front molding face may include a face of the mold cavity.
• the front molding face may include a front face of the injection piston.
• the support area of the rear face of the sacrificial insert can be glued above the support area of the receiving face of the mold cavity.
• At least part of the periphery of the sacrificial insert can be inserted between two parts of the mold.
• the receiving face of the cavity may have a recess in which the sacrificial insert is at least partially engaged.
• the sacrificial insert can comprise a plurality of superimposed layers defining between them at least one space for extending the imprint.
• the sacrificial insert can be composed of at least one material having a thermal conductivity of at least 20 W m- 1 K- l, preferably at least 40 W m- 1 K- l.
• the device can be adapted for the production of parts having an elastic deformation capacity of at least 1.2%, preferably at least 1.5%.
• a method of manufacturing at least one piece of an amorphous metal alloy is also proposed, using an injection mold as described above, comprising the following steps:
• a method of manufacturing at least one piece of an amorphous metal alloy is also proposed, using an injection mold as described above, comprising the following steps:
• the mold comprising the sacrificial insert can be heated prior to the injection step to a temperature between 250 ° C and Tg + 100 ° C, preferably between Tg- 150 ° C and Tg + 30 ° C and more preferably still to Tg ⁇ 20 ° C, with Tg the glass transition temperature of the metal alloy.
• the separation of the insert and the molded part can be carried out by destruction of the sacrificial insert, preferably by destruction of the sacrificial insert by a selective chemical attack in a bath.
• a step of removing the excess material can be carried out so as to obtain a final part.
• the method may include a subsequent step of heat treatment of the molded part and / or of a final part obtained.
• the step of injecting the metal alloy may have a duration of less than 100 ms, preferably less than 50 ms and more preferably still less than 20 ms.
• the amorphous metal alloy has:
• a DTc less than 100 ° C, preferably less than 80 ° C and more preferably still less than 60 ° C,
• the part has a) a thickness less than OOpm and a height / thickness ratio greater than 8 or b) a thickness less than 50 pm and a height / thickness ratio greater than 4 or c) a thickness less than 40 pm and a ratio height / thickness greater than 2.
• the sides of the part flanks formed using the sacrificial insert may have an average roughness Ra of less than 1 ⁇ m, preferably less than 0.5 ⁇ m and more preferably still less than 0.1 ⁇ m.
• the part can be made of a metal alloy having a Tl greater than 700 ° C.
• FIG 1 shows a longitudinal section of a molding device, along the axis of an injection piston
• FIG 2 shows a cross section along II-II of the molding device of Figure 1
• FIG 3 shows a cross section of an alternative embodiment of the molding device of Figure 1;
• FIG 4 shows a cross section of another alternative embodiment of the molding device of Figure 1;
• FIG 5 shows a cross section of another alternative embodiment of the molding device of Figure 1;
• FIG 6 shows a longitudinal section of another molding device, along the axis of an injection piston.
• FIG 7 represents a DRX analysis of an amorphous metal alloy.
• FIG 8 represents a DRX analysis of a partially amorphous metal alloy.
• FIG 9 represents a DRX analysis of a crystalline metal alloy.
• FIG 10 represents a DRX analysis of the parts obtained in Example 1. Description of the embodiments
• One or “one” means “at least one” or “at least one” respectively.
• amorphous metallic alloy or “AMA” or “metallic glass” is understood here to mean metals or metallic alloys which are not crystalline, that is to say those whose atomic distribution is predominantly random. However, it is difficult to obtain a one hundred percent amorphous metallic glass since there is most often 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 in the majority. Generally, the fraction of the amorphous phase is greater than 50%.
• molded part having at least partially an amorphous structure is meant a part whose fraction of the amorphous phase is greater than 50%.
• a metallurgical structure is said to be amorphous or entirely amorphous when an analysis by X-ray diffraction , as described below does not reveal peaks of crystallization.
• critical diameter (De) of a specific metal alloy is understood to mean the maximum limit thickness below which the metal alloy has an entirely amorphous metallurgical structure or beyond which it is no longer possible to obtain an entirely amorphous metallurgical structure, when the metal alloy is molded from a liquid state and is subjected to rapid cooling such that the transfer of heat inside the metal alloy is optimal. More specifically, the critical diameter is determined by successive molding of cylindrical bars (generally of length greater than 50 mm) 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);
• the alloy is molded in a copper mold of CuCl type and is cooled to a maximum temperature of around twenty degrees Celsius (20 ° C).
• the alloy is developed and molded under an inert atmosphere of high purity (eg under argon of quality 6.0) or under secondary vacuum (pressure ⁇ 10 ⁇ 4 mbar).
• the alloy is molded with a system allowing the application of a pressure differential to facilitate the molding of the alloy and ensure intimate contact between the alloy and the mold walls in order to ensure rapid cooling of the alloy.
• the molding step can be carried out under a pressure of 20 MPa.
• This system can be mechanical (e.g. piston) or gaseous (application of overpressure).
• the bars are cut in order to obtain a wafer (cross section of the cylinder preferably located towards the middle of the bar, thickness between 1 and 10 mm) and analyzed by X-ray diffraction (DRX) at a minimum to determine whether the slices have 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 bumps characteristics of AMA is then highlighted by X-ray diffraction). Since there are most often faults in metallurgical structures, a 100% amorphous alloy is almost impossible to obtain and the critical diameter can be defined as the diameter above which an X-ray diffraction analysis clearly shows evidence of peaks of crystallinity.
• the metal alloys according to the present description are preferably chosen from alloys, the majority of which is chosen from zirconium, copper, nickel, iron, palladium, titanium, cobalt and hafnium. According to a preferred embodiment, it is an alloy chosen from those mentioned in appendix 2 (pp. 189-192) of the doctoral thesis "Study of the relationships between structural characteristics and vibration dissipation in massive metallic glasses . Application to inertial sensors. »Supported on November 22, 2006 by Cédric Haon.
• liquid state metal alloy is understood to mean a metal alloy having a temperature greater than or equal to its liquidus temperature.
• the liquidus temperature being determined with DTA (differential thermal analyzer) analyzes as described in particular in the document Li et al., 2012 (Li et al. (2012) “Effects of Cu, Fe and Co addition on the glass-forming ability and mechanical properties of Zr-Al- Ni bulk metallic glasses ”, in particular accessible via the internet link: https://doi.org/10.1007/s 1 1433-012-4919-y).
• the thermal stability of AMAs can be characterized in several ways, in particular by assessing:
• the temperatures are measured using a DSC at a rate of rise of 20 ° C / min.
• the temperatures Tg, Tx are then extracted from the DSC curves.
• the liquidus temperature Tl is determined with DTA analyzes as explained above. In particular, the determination of the liquidus temperature Tl can be carried out according to the method indicated in the article. An example is shown in the article Li et al., 2012 (Li et. Al.
• the average roughness Ra of the molded part is determined according to standard ISO 25178.
• “Sacrificial insert” means part of a single-use injection mold.
• the sacrificial insert can be made of silicon, pyrolytic graphite, a metal (for example aluminum or copper), a glass (for example in silica) or a ceramic (for example in alumina). It is destroyed after the solidification step of the cast metal alloy. The destruction is preferably carried out by a selective chemical attack, more preferably by a selective chemical attack in a bath.
• the thermal conductivity of the insert is evaluated according to the Flash method (Parker et al. (2004) “Flash Method of Determining Thermal Diffusivity, Heat Capacity, and Thermal Conductivity”, in particular accessible via the internet link: https: // doi. Org / 10.1063 / l. 1728417).
• geometric spheres means the geometric spheres whose maximum diameters are as they are wedged or immobilized between points on the walls of the molding impression.
• the AMA parts molded into the cavities of the sacrificial insert have a height, a length and a thickness.
• the upper surface of the front face of the sacrificial Finsert 9 or 109 is defined as being the front face 9 or 109 without the faces included in the cavities 17 or 11 of the sacrificial Finsert.
• the upper surface of the front face of the sacrificial insert 9 or 109 is for example represented by the plane of the surface 16 of FIG. 1.
• the height can be defined as the greatest normal distance to the surface of the part formed by the upper surface of the front of the sacrificial insert 9 or 109 and measured between the surface of the part formed by the upper surface of the front face of the sacrificial insert 9 or 109 and the surfaces of the part formed by the cavity 17 or 1 17 of the sacrificial insert.
• the sides of the part are defined as being the surfaces formed by the cavity 17 or 1 17 of sacrificial finert adjacent to the surface of the part formed by the upper surface of the front face of the sacrificial insert 9 or 109.
• the sides of parts are generally perpendicular to the surface of the part formed by the upper surface of the front face of the sacrificial insert 9 or 109, with a tolerance interval of + or - 5 °.
• the sidewalls can also have angles less than or greater than 90 °.
• the thickness is defined as being the smallest diameter of the geometric spheres inscribed in the zones of the part formed by the cavity 17 or 1 17 of sacrificial Finsert having at least one point of contact with two sides of the part.
• the aspect ratio or height / thickness ratio is defined as the ratio of height and thickness in a given area of the part (section perpendicular to the surface of the part formed by the upper surface of the front face of the sacrificial finert 9 or 109).
• a room can therefore have a different height / thickness ratio for each given area of the room (depending on the dimensional variations observed in the different areas thereof).
• ratio height / thickness of the part the maximum ratio that said part can have.
• the height, thickness and length of the piece can be defined as follows:
• the upper surface of the front face of the sacrificial insert 9 or 109 is defined beforehand as being the front face 9 or 109 without the faces included in the cavities 17 or 1 17 of the sacrificial insert.
• the upper surface of the front face of the sacrificial insert 9 or 109 is represented by the plane of the surface 16 in Figure 1.
• the length is defined as being the largest dimension in the plane of the part formed by the upper surface of the front face of the sacrificial insert 9 or 109.
• the thickness is defined as being the smallest distance parallel to the plane of the part formed by the upper surface of the front face of the sacrificial insert 9 or 109 measured between the faces of the part formed by the cavity 17 or 1 17 of the sacrificial insert.
• the height can be defined as the greatest distance normal to the plane of the part formed by the upper surface of the front face of the sacrificial insert 9 or 109 and measured between the upper surface of the front face of the sacrificial insert 9 or 109 and the surfaces of the part formed by the cavity 17 or 11 of the sacrificial insert.
• the aspect ratio or height / thickness ratio is defined as the ratio of height and thickness in a given area of the part.
• a room can therefore have a different height / thickness ratio for each given area of the room
• FIGs 1 and 2 there is illustrated a device 1 for injection molding, intended for the manufacture of metal glass parts.
• the molding device 1 comprises a permanent injection mold 2, in several parts, which delimits a cavity 3 which has a receiving face 4, a front face 5 opposite the receiving face 4 and a peripheral face 6.
• the receiving face 4 and the peripheral face 6 of the cavity 3 are joined.
• the peripheral edge of the receiving face 4 is joined to the end edge, which is adjacent thereto, of the peripheral face.
• the cavity 3 is therefore formed entirely on one side of the receiving face 4.
• the molding device 1 comprises a sacrificial conformation insert 7, in the form of a plate, placed in the cavity 3 and having a rear face 8, a support area of which is adjacent to a support area of the receiving face 4 of the cavity 3 and a front face 9 located opposite the front face 5.
• a molding imprint 10 is thus created corresponding to the space left free in the cavity 3 after having placed the sacrificial insert 7 inside the cavity 3, above the bearing area of the receiving face. 4 from cavity 3.
• a shape of the part to be molded in the molding cavity 10 is determined by a specific shape of the sacrificial insert 7, which constitutes the negative of the part to be molded.
• the shape of the final part to be produced can be included in the specific shape of the sacrificial insert
• the rest of the molding footprint 10 can constitute a surplus of material.
• the molding device 1 comprises an injection piston 11 movable in an injection chamber 12 of the mold, which communicates with the molding impression 10.
• the molding device 1 allows injection molding of a part in a single step (pressure injection of the molten metal alloy). This allows in particular to have an excellent control of the filling time and the conformation of the part.
• the injection molding step taking place in a single step, the filling / shaping time is thus minimized, thus allowing the molding of complex geometries and small dimensions. Indeed, rapid filling of the imprint makes it possible to limit the cooling of the alloy during filling and makes it possible to fill cavities of very small dimensions and very precisely (very good conformation of the alloy in the cavities of the sacrificial insert).
• the parts formed in the cavity of the sacrificial insert can then have the characteristics of very low thickness and high height / thickness ratio as claimed as well as an average roughness Ra of their sides less than 1 ⁇ m, preferably less than 0 .5 pm and more preferably still less than 0.1 pm
• Controlling the filling time also makes it possible to fill the section with a molding imprint configured so that the diameter of the geometric spheres inscribed, in contact with its opposite side walls and having at least one point of contact with the sacrificial insert, or less than 1mm, preferably less than 0.75mm and even more preferably less than 0.5mm.
• This type of cavity allows better thermal control (cooling of the alloy, temperature of the sacrificial insert and interface temperature AMA / sacrificial insert). This thermal control therefore also allows the manufacture of parts, with the geometric characteristics mentioned above, with alloys having De of small dimensions and / or having low thermal stability.
• the thermal control also makes it possible to avoid surface crystallization, which can for example appear during the injection of alloys with liquidus temperatures higher than 700 ° C or with alloys composed of elements which will react quickly with the material of the sacrificial insert.
• surface crystallization can for example appear during the injection of alloys with liquidus temperatures higher than 700 ° C or with alloys composed of elements which will react quickly with the material of the sacrificial insert.
• the shorter the cooling time of the alloy and the more the interface temperature will be limited the more the diffusion phenomena that can take place between the sacrificial insert and GAMA will be limited, or even eliminated.
• Preventing surface crystallization makes it possible to obtain better quality parts, with, for example, better resistance to corrosion or fatigue.
• the molding device 1 can be used in the following manner.
• the permanent mold 2 being open so as to open the cavity 3, the sacrificial insert 7 is placed above the receiving face 4 of the cavity 3.
• the parts of the permanent mold 2 are assembled so as to close the cavity 3 and constitute the molding impression 10.
• the parts of the permanent mold 2 are disassembled so as to demold the part produced, at the same time as the sacrificial insert 7 is extracted.
• the cavity 3 is advantageously configured so that after demolding of the produced part, provided with the sacrificial insert 7, at least the bearing zone of the rear face 8 of the sacrificial insert 7 above the zone of support of the receiving face 4 of the cavity 3 is uncovered.
• the sacrificial insert 7 is destroyed, for example by a selective chemical attack of dissolution in a suitable bath, so as to keep only the molded part. After which, in a subsequent step, a surplus material is removed from the molded part so as to obtain the desired final part.
• the surplus material is removed from the molded part, then the sacrificial insert 7 is destroyed.
• the final part can be determined solely by the material contained inside the hollow form 17. The part of the molding imprint 10 located between the face 16 of the sacrificial insert 7 and the front face 5 of the cavity then constitutes a surplus of material to be removed.
• the conditions linked to the thermal properties of the permanent mold 2 and of the sacrificial insert 7, the temperature of the metal alloy in the liquid state and the speed of injection, are favorable for obtaining, from the metallic alloy in the liquid state, of a molded piece of metallic glass, that is to say having a metallurgical structure at least partially amorphous.
• the permanent mold 2 can be made of copper, a suitable steel, a refractory alloy.
• the sacrificial insert 7 is composed of at least one material having a thermal conductivity of at least twenty Watts per meter and per Kelvin degree 20 W m 1 K 1 , advantageously at least forty Watts per meter and per Kelvin degree ( 40 W m 1 K 1 ).
• the sacrificial insert 7 can be made of silicon, pyrolytic graphite, a metal (for example aluminum or copper), a glass (for example silica) or a ceramic (for example alumina).
• the molding imprint 10 is configured so that the diameter of the geometric spheres inscribed in this molding imprint 10 and having at least one point of contact with the sacrificial insert is at most equal to one and a half times (1.5 times ), advantageously at most equal to once and two tenths of times (1, 2 times), the critical diameter (De) of the specific metal alloy used, and more preferably still at most equal to once (1 time ), the critical diameter (De) of the specific metal alloy used.
• the molding impression is configured so that the diameter of the geometric spheres inscribed in this molding impression and having at least one point of contact with the sacrificial insert is at most equal to lmm, preferably at most equal to 0.75mm and even more preferably at most equal to 0.5mm.
• Such a configuration of the imprint is thus produced with the aim of obtaining a molded part having the metallurgical characteristics of an amorphous metal alloy or metallic glass, the geometric spheres inscribed and the critical diameter having been defined previously.
• the receiving face 4 of the cavity 3 comprises a recess 13 in which the sacrificial insert 7 is engaged.
• the bottom 14 of the recess 13 constitutes a zone of support for the rear face 8 of the sacrificial insert 7.
• the peripheral face 6 of the cavity 3 is at a distance from the peripheral edge of the recess 13, so that the receiving face 4 comprises a portion 15 which surrounds the recess 13.
• the bottom 14 of the recess 13 and the portion 15 are parallel to each other and are parallel to the front face 5 of the cavity 3.
• the periphery of the recess 13 is adjusted to the periphery of the sacrificial insert 3, without play or with little play.
• the front face 9 of the sacrificial insert 3 comprises a surface 16 situated in the plane of the portion 15 of the face 4 of the cavity 3 and, in depression with respect to this surface 16, a shape 17 corresponding to the negative of a shape of a part or a portion of a part to be molded.
• the front face 9 of the sacrificial insert 3 comprises a surface 16 located in depression relative to the plane of the portion 15 of the face 4 of the cavity 3 and, in depression relative to this surface 16 , a shape 17 corresponding to the negative of a shape of a part or to a portion of a part to be molded.
• This embodiment is particularly advantageous in the embodiment illustrated in FIG. 4 and detailed below in order to avoid any pressure and / or bending of the sacrificial insert during assembly of the mold.
• the hollow shape 17 defined by the sacrificial insert 7, facing the face 5 of the cavity 3, can be produced over part of the thickness of the sacrificial insert 7.
• the hollow shape 17 may have one or more parts which pass through the sacrificial insert 7, so that this hollow shape 17 extends to the receiving face 4 of the cavity 3.
• the bearing areas of the sacrificial insert 7 and of the receiving face 4 of the cavity 3, above one over the other, for example at the bottom of the recess 13, are reduced.
• one of the sides of the peripheral face 6 of the cavity 3, namely the side 6a, is open and communicates with the injection chamber 12 of the mold 2.
• the axis 18 of the chamber 12 and the piston 1 1 is situated in the plane of the portion 15. of the receiving face 4 of the cavity 3.
• the piston 1 1 produces a lateral injection of the material into the molding impression 10.
• Such a Configuration of the device has the advantage of facilitating the repeatability of the process.
• the imprint formed by the cavity (3) and the sacrificial insert in fact ensures that the diameters of the geometric spheres inscribed in the molding imprint 10 and having at least one point of contact with the sacrificial insert are always the same even if the quantity of the alloy injected varies slightly from one injection to another.
• the mold 2 comprises two parts 19 and 20 whose joint plane 21 is located in the plane of the portion 15 of the receiving face 4 of the cavity 3, which also contains the axis 18.
• the axis 18 of the chamber 12 and the piston 1 1 is arranged horizontally.
• the sacrificial insert 3 can be placed on the bottom 14 of the recess 13. During the injection of the metal alloy into the molding cavity 10, the injection pressure applies the rear face 8 of the insert sacrificial above the bottom 14 of the recess 13. However, the sacrificial insert 3 can be glued to the bottom 14 of the recess 13.
• a layer 22 of a heat-conducting material is interposed between at least the support zone of the rear face 8 of the sacrificial insert 7 and the support zone of the receiving face 4 of the cavity 3 of the mold 2.
• the heat conducting layer 22 can be - for example graphite or aluminum, adapting to the roughness of the bearing faces of the permanent mold 2 and of the sacrificial insert 7.
• the heat conducting layer 22 is located between the bottom 14 of the recess 13 and the rear face 8 of the sacrificial insert 7 inserted in this recess 13.
• the recess 13 of the receiving face 4 of the cavity 3 extends, over at least part of its periphery, beyond the peripheral wall 6 of the cavity 3 and the sacrificial insert 7 disposed in such a recess.
• the sacrificial insert 7 also extends, correspondingly, beyond the peripheral wall 6 of the cavity 3.
• a peripheral part 23 of 1 the sacrificial insert 7 is adjusted or inserted, without play or with little play, between the two parts 19 and 20 of the permanent mold 2.
• the axis 18 of the chamber 12 and of the piston 11 is arranged vertically.
• the supply chamber 12 is placed below the cavity 3 and therefore of the molding impression 10.
• the sacrificial insert 7 is held above the receiving face 4 of the cavity 3, for example in the recess 13, by means of a layer of adhesive or by means of an arrangement equivalent to that described above with reference to FIG. 4.
• the sacrificial insert 7 comprises a plurality of superimposed layers 24 assembled one on the other.
• the hollow shape 17 of the sacrificial insert 7 can have parts extending locally between two successive layers, so as to produce complex parts in steps in the molding cavity 10 which includes such a shape hollow 17 complex.
• FIG. 6 there is illustrated an injection molding device 101 which differs from the injection molding device 1 described above by the fact that a cavity 103 of a mold 102, in several parts, is formed by a part end of a supply chamber 1 12 in which an injection piston 1 1 1 is movable along an axis 1 18.
• a receiving face 104 is formed and located opposite a radial front face 1 1 1 a piston 1 1 1 movable in the injection chamber 1 12.
• the receiving face 1 17, substantially radial is joined to the peripheral wall 106 of the chamber 1 12.
• a peripheral edge of the face of reception 104 is joined to a peripheral edge at the end of the peripheral wall 106 of the chamber 1 12.
• the cavity 103 is therefore formed entirely on one side of the reception face 4, that is to say on the side of the front face 1 1 1 a of the piston 1 1.
• a sacrificial insert 107 is disposed above the receiving face 104, on the side of the front face 1 1 1 a of the piston 1 1 1.
• the arrangements and shapes described above with respect to the receiving face 4 and the sacrificial insert 7 can be applied to the receiving face 104 and to the sacrificial insert 107.
• the sacrificial insert 7 has, from a front face 109 situated opposite the front face 1 1 1 a of the piston 1 1 1, a hollow shape 1 17 corresponding, at least partially, to the negative of a part to mold.
• the piston 1 1 1 produces a frontal injection of the material in the direction of the receiving face 104 and therefore of the sacrificial insert 107. It follows that a mold impression 1 10, including the hollow shape 1 17, is defined in the terminal injection position of the piston 1 1 1, between the receiving face 104 provided with the sacrificial insert 107 and the front face 1 1 1 a of the piston 1 1 1.
• the mounting of the sacrificial insert 107 on the receiving face 104 can be equivalent to any of the mounting of the sacrificial insert 7 on the receiving face 4 of the cavity 3 described above.
• the final position of injection of the piston 1 1 1, which delimits the configuration of the molding imprint 1 10, is determined so that the diameter of the geometric spheres inscribed in this molding imprint 1 10 is at most equal to one and a half times (1, 5 times), advantageously once and two tenths of a time (1, 2 times), the critical diameter (De) of the specific metal alloy used, as defined above, for the purpose of '' obtain a molded part having the metallurgical characteristics of an amorphous metal alloy or metallic glass.
• the diameter of the geometric spheres inscribed in the molding impression 1 10 is at most equal to once (1 time) the critical diameter (De) of the specific metal alloy, preferably at most equal to 1mm, more preferably at most equal to 0.75mm and even more preferably at most equal to 0.5mm.
• De critical diameter
• Such an advantageous mode allows in particular to further avoid a reaction with the sacrificial insert and to obtain parts having an optimized surface state, substantially free of surface crystals. A surface crystallization is problematic in particular for the fatigue resistance of the parts or even the corrosion resistance.
• an intermediate molding cavity can be formed between the chamber 12 of the mold 102 and the front face 109 of the sacrificial insert 1 17.
• the section of such a molding cavity is configured so that the diameter of the inscribed geometric spheres, in contact with its opposite side walls and having at least one point of contact with the sacrificial insert, is at most equal to one and a half times (1.5 times), preferably once and two tenths of times (1, 2 times), and more preferably still at most equal to once (1 time), the critical diameter (De) of the specific metal alloy used.
• the molding imprint is configured so that the diameter of the geometric spheres inscribed in this molding imprint and having at least one point of contact with the sacrificial insert is at most equal to 1mm, preferably at most equal to 0.75mm and even more preferably at most equal to 0.5mm.
• this intermediate molding cavity extends axially to the chamber 1 12 and is advantageously cylindrical, its diameter being at most equal to one and a half times. (1.5 times), advantageously once and two tenths of a time (1.2 times), and more preferably still at most equal to once (1 time), the critical diameter (De) of the specific metal alloy used.
• the molding imprint is configured so that the diameter of the geometric spheres inscribed in this molding imprint and having at least one point of contact with the sacrificial insert is at most equal to 1 mm, preferably at most equal to 0, 75mm and even more preferably at most equal to 0.5mm.
• the main advantage of the injection molding device previously described and presented in FIG. 6 is that it is modular.
• modular we mean here the ease by which it is possible to modify the injection configuration.
• the diameters of the geometric spheres inscribed in the molding imprint (1 10) and having at least one point of contact with the sacrificial insert can be easily modified by increasing or decreasing the quantity of alloy injected, without having to modify the parts forming the mold (102).
• the injection mold as described above allows the manufacture of at least one part of an amorphous metal alloy, according to a process comprising the following steps:
• the order of the steps of setting up the sacrificial insert above the face for receiving at least one part of the mold and for assembling the parts of the mold can be reversed.
• This embodiment is particularly preferred during an automatic loading of the insert into the mold. The assembly of the molds is then carried out and the insert is placed via a dedicated opening.
• the injection and solidification steps are carried out under secondary vacuum, preferably at a pressure of 10-4 to 10-6 mbar.
• the vacuum makes it possible in particular to limit the pollution of the alloy during its shaping as well as to facilitate the filling of the mold, therefore allowing a perfect match between the mold and cast GAMA (absence of trapped gas).
• the injection and solidification steps are carried out under primary vacuum (from 10-1 to 10-3 mbar) or else under a controlled atmosphere, for example under argon.
• the mold and the insert Prior to the injection stage, the mold and the insert are heated in order to facilitate their filling and to prevent the molten alloy from freezing before reaching the bottom of the molding impression as well as in order to to ensure a very good conformation of the cavities by the alloy (reproduction of the surface states). Heating also helps limit thermal shock.
• the heating temperature is advantageously close to the glass transition temperature Tg of the molded amorphous metal alloy, preferably the heating temperature, expressed in ° C, is between 250 ° C and Tg + 100 ° C, more preferably still between Tg - 150 ° C and Tg + 30 ° C and even more preferably at Tg ⁇ 20 ° C.
• pressure is exerted on the molten alloy to ensure the filling of the mold and allow good heat exchange between the mold and the alloy as well as ensuring high precision in molding.
• This pressure can be exerted using a mechanical system (e.g. a piston) and / or using a gas overpressure.
• a negative pressure differential can also be used.
• the pressure is greater than 1 MPa, preferably greater than 10 MPA.
• it is between l MPa and 150MPa, preferably between OMPa and 80MPa.
• the filling of the imprint is carried out in a time of less than 100 ms, preferably less than 50 ms and more preferably still less than 20 ms.
• the step of injecting the metal alloy has a duration of less than 100 ms, preferably less than 50 ms and more preferably still less than 20 ms.
• the sacrificial insert is removed and / or dissolved.
• a KOH bath with a concentration between 10 and 40% and a temperature between 60 and 90 ° C allowing a high dissolution rate of silicon and a possible layer of SiO2 is generally used.
• the method does not include an additional step of removing material after molding.
• material is used here to mean the amorphous metal alloy.
• the AMA part obtained by injection, solidification and separation of the insert can therefore be used as it is and corresponds to the final part.
• the AMA part can then undergo one (or more) post-processing operations allowing the final geometry to be obtained.
• These operations are generally of the "material removal” type. These material removals can be carried out by machining (mechanical, chemical, ultrasound, EDM, water jet, laser). The material removal step can be carried out before or after separation of the sacrificial insert and the molded part.
• the manufacture with extreme precision, for example an accuracy less than or equal to 5 pm, of AMA parts of very small dimensions (in particular of length between 0.5 and 10 mm in the largest dimension of the part) and having a high height / thickness ratio requires complex manufacturing processes involving in particular a casting step and a thermoforming step.
• the alloy In order to preserve the amorphous structure of the part during thermoforming, the alloy must therefore have sufficient thermal stability to allow shaping without crystallizing.
• the specific method described above makes it possible, unlike the methods of the prior art, to obtain parts such as
• the amorphous metal alloy has:
• a DTc less than 100 ° C, preferably less than 80 ° C and more preferably still less than 60 ° C,
• the part has a) a thickness less than OOpm and a height / thickness ratio greater than 8 or b) a thickness less than 50 pm and a height / thickness ratio greater than 4 or c) a thickness less than 40 pm and a ratio height / thickness greater than 2.
• the part obtained according to the specific method described above is such that the faces of these sides formed using the sacrificial insert have an average roughness Ra of less than 1 ⁇ m, preferably less than 0.5 ⁇ m and more preferably still less than 0.1 pm.
• the metal alloy constituting the part has a Tl greater than 700 ° C.
• the final parts that can be manufactured by using the molding devices 1 or 101 may have, after optional removal of the excess material, small dimensions, complex shapes and various shapes.
• the final parts may have precise dimensions, that is to say small manufacturing tolerance intervals, for example of a few microns.
• the final pieces may have, in the thickness direction of the sacrificial inserts 7 and 11, thicknesses ranging from less than a tenth of a millimeter to a few millimeters.
• the molding devices described can be applied to the manufacture of parts having an elastic deformation capacity of at least one and two tenths of a percent (1, 2%), advantageously of at least one and a half percent (1, 5%).
• the sacrificial insert is a silicon type insert (SOI), the cavities of which have the following geometries:
• the sacrificial insert is a silicon type insert (SOI), the cavities of which have the following geometries:
• the silicon remaining on the part was dissolved in a 20% KOH solution and at a temperature of 80 ° C.
• the DRX analysis carried out on the part resulting from the process confirmed the amorphous character of the part obtained.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)

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• 2018
  • 2018-12-20 FR FR1873662A patent/FR3090431B1/fr active Active
• 2019
  • 2019-12-20 EP EP19850758.4A patent/EP3899072A1/de active Pending
  • 2019-12-20 WO PCT/FR2019/000215 patent/WO2020128170A1/fr unknown
  • 2019-12-20 US US17/415,992 patent/US20220161319A1/en active Pending

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