Alloy with complex composition

Abstract

Alloy characterized in that it comprises scandium (Sc) at a fraction of greater than or equal to 30 at%, titanium (Ti), zirconium (Zr) and / or vanadium (V) and / or oxides, hydrides, borides, carbides and / or nitrides thereof, wherein at least two of the elements titanium, zirconium and vanadium and / or their oxides, hydrides, borides and / or carbides have a fraction greater than or equal to 15 at%.

Description

[0001] The invention relates to an alloy, for example for a watch component, and to a watch component as such, in particular intended for the cladding of a watch such as a watch case, comprising such an alloy. It also relates to any other component of a transport vehicle or any apparatus comprising such an alloy. It also relates to a timepiece, such as a watch, or a piece of jewelry, comprising such an alloy. Finally, it also relates to a method for manufacturing such an alloy.

[0002] A watch case must be very hard to provide good shock resistance and resist scratches that degrade its aesthetic appearance. In the state of the art, a watch case is generally made of a metallic material or a metal alloy. However, it is also very advantageous for a comfortable fit that a watch case is light. These two properties of hardness and lightness are generally incompatible, hard metals being naturally heavy and light metals naturally soft. In addition to watch cases, a hard and light material would be advantageous for many other watch components. Existing solutions are therefore unsatisfactory in that they do not allow for a good hardness / density compromise.

[0003] WO 2005 / 045532 A2 discloses a watch component, which comprises an alloy of scandium and titanium (Ti.)

[0004] EP 2 565 289 A1 also discloses an alloy of scandium, titanium and zirconium.

[0005] Thus, an object of the present invention is to find a solution for forming a hard and light watch component.

[0006] Naturally, such a solution will have to advantageously achieve other advantageous properties sought for a watch component, even essential ones, such as an attractive aesthetic appearance, high resistance to wear, in particular resistance to oxidation and corrosion, a non-magnetic property, etc.

[0007] For this purpose, the invention relates to an alloy, characterized in that it consists of scandium (Sc) in a fraction greater than or equal to 30 at%, scandium being the element of the alloy which has the largest atomic percentage, of titanium (Ti), of zirconium (Zr) and / or of vanadium (V) and / or their oxides, hydrides, borides, carbides and / or nitrides, at least two of the elements among titanium, zirconium and vanadium and / or their oxides, hydrides, borides and / or carbides having a fraction greater than or equal to 15 at%, and optionally of magnesium (Mg) and / or manganese (Mn) and / or yttrium (Y), and / or rare earths.

[0008] The alloy does not include aluminum (AI) and / or does not include lithium (Li).

[0009] The alloy can be chosen from: Sc 30 Ti 25 V 20 Zr 25 SC 60 Ti 20 V 20 Sc 33 Ti 33 V 33 Sc 40 Ti 20 V 20 Zr 20 Sc 33 Ti 33 Zr 33 Sc 60 Zr 20 Ti 20

[0010] Additionally, the alloy may include magnesium (Mg) and / or manganese (Mn) and / or yttrium (Y), and / or rare earths.

[0011] According to embodiments of the alloy: any element of the alloy other than scandium (Sc), titanium (Ti), zirconium (Zr) and vanadium (V) has an atomic proportion less than or equal to 5% at, or even less than or equal to 3.5% at, or even less than or equal to 2% at; and / or the total proportion of the elements scandium (Sc), titanium (Ti), zirconium (Zr) and vanadium (V) is greater than or equal to 70% at, or even greater than or equal to 80% at, or greater than or equal to 90% at; and / or the total proportion of the elements scandium (Sc), titanium (Ti), zirconium (Zr), vanadium (V), magnesium (Mg), manganese (Mn), yttrium (Y), and / or rare earths is greater than or equal to 90% at, or even greater than or equal to 95% at.

[0012] The alloy can consist of an alloy of 4 to 13 elements inclusive.

[0013] The alloy may include: scandium between 30 and 70% at inclusive, or even between 40 and 70% at inclusive, or even between 50 and 65% at inclusive, or even between 30 and 60% at inclusive, or even between 30 and 47% at inclusive, or even between 30 and 45% at inclusive; and titanium between 5 and 35% at inclusive, or even between 5 and 30% at inclusive, or even between 15 and 25% at inclusive, or even between 15 and 20% at inclusive; and zirconium between 0 and 30% at inclusive, or even between 5 and 30% at inclusive, or even between 5 and 25% at inclusive, or even between 15 and 25% at inclusive, or even between 15 and 20% at inclusive, or even between 10 and 20% at inclusive; and vanadium between 0 and 30% at inclusive, or between 5 and 30% at inclusive, or between 5 and 25% at inclusive, or between 15 and 25% at inclusive, or between 15 and 20% at inclusive, or between 10 and 20% at inclusive.

[0014] Scandium is the element in the alloy with the highest atomic percentage.

[0015] The alloy may have a density less than or equal to 4.5 g cm -3< , or even less than or equal to 4.2 g cm -3< , or even less than or equal to 4 g cm -3< , measured after its shaping and before any other treatment.

[0016] The alloy may have a hardness greater than or equal to 400 Hv, or even greater than or equal to 500 Hv, or even greater than or equal to 600 Hv, measured after its shaping and before any other treatment.

[0017] The alloy consists of scandium (Sc), titanium (Ti), zirconium (Zr) and / or vanadium (V), and / or their oxides, hydrides, borides, carbides and / or nitrides, and optionally magnesium (Mg), manganese (Mn), yttrium (Y), and / or rare earths

[0018] The invention also relates to a watch component, characterized in that it comprises an alloy as described above, or in that it is entirely formed from an alloy as described above.

[0019] The watch component can be a watch case, a bezel, a dial, a bracelet link, a strap, or a bracelet clasp.

[0020] The invention also relates to a timepiece, in particular a watch, jewelry or jewelry, characterized in that it comprises a watch component as described previously or in that it comprises an alloy as described previously.

[0021] The invention also relates to a component dedicated to aeronautics, automobiles, a transport vehicle, a measuring device, an exploration robot, a weapon or an energy production or storage device, characterized in that it comprises an alloy as described previously.

[0022] The component may be integrally formed from an alloy as described above or may be a solid part comprising an alloy as described above extending substantially throughout its thickness.

[0023] The invention also relates to a method for manufacturing an alloy as described above or a component as described above, characterized in that it comprises the following steps: grinding of pure element powders to form an alloy powder; cold forming of the alloy powder.

[0024] The shaping step may include a spark plasma sintering step.

[0025] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of particular embodiments made without limitation.

[0026] The invention is based on the manufacture and use of a metal alloy having both low density and high hardness.

[0027] To achieve this, the invention is based on the definition of a multiphase alloy with a complex composition. The concept of complex concentrated alloys derives in particular from high entropy alloys (HEA). The latter can consist of at least five elements in proportions close to equimolar and forming a single solid solution.

[0028] More generally, the combination of at least four elements, or even at least five elements, forms a set that makes it possible to achieve remarkable properties, far removed from the usual natural properties of simple metal alloys. The definition of complex concentrated alloys extends that of high-entropy alloys by including alloys composed of three or four elements, multi-phase alloys, and the concentration of one of the elements advantageously exceeding 35%-at.

[0029] The alloy according to the invention comprises the following four main elements: scandium (Sc), titanium (Ti), zirconium (Zn) and vanadium (V) and / or their oxides, hydrides, borides and / or carbides. By main elements we mean that these elements are the four elements in greatest proportion present in the alloy. Preferably, these four main elements represent at least 70% at inclusive, or even at least 80% at inclusive, or even at least 90% at inclusive of the alloy (the percentages mentioned are therefore atomic percentages).

[0030] The alloy according to the invention comprises scandium in a fraction greater than or equal to 30 at%. In addition, at least two of the elements among titanium, zirconium and vanadium have a fraction greater than or equal to 15 at%.

[0031] Each major element contributes a unique property to the alloy. For example, scandium contributes its lightness, color, and mechanical properties. Titanium contributes its hardness. Zirconium provides resistance to oxidation. Vanadium provides hardness.

[0032] Furthermore, the combination of these four main elements makes it possible to form a multi-phase alloy with a complex composition. This makes it possible to form an alloy whose remarkable properties go well beyond the simple addition of the properties of each element, as will be explained later. To achieve this alloy, it was also necessary to select elements whose chemical compatibility with each other was found to be particularly good.

[0033] According to a first embodiment of the invention, the alloy consists of these four main elements. Among the alloys of this first embodiment, we can identify the following alloys (the indices representing the atomic percentages of each element): Sc 30 Ti 25 V 20 Zr 25 Sc 40 Ti 20 V 20 Zr 20

[0034] In a simplified variant, the embodiment may not include zirconium or may not include vanadium. By way of example, the following alloys can be used within the scope of the invention: Sc 60 Ti 20 V 20 Sc 33 Ti 33 V 33 Sc 33 Zr 33 Ti 33 Sc 60 Zr 20 Ti 20.

[0035] Advantageously, the alloy contains neither aluminum (AI) nor lithium (Li). In other words, traces of aluminum and / or lithium are not detectable in the alloy. Since aluminum is very reactive with scandium, it would form intermetallics that would weaken the alloy. Lithium is very volatile, which would make processing complex, and would also weaken the alloy by forming intermetallics.

[0036] As mentioned previously, the alloy may comprise one of the oxides and / or nitrides and / or hydrides and / or borides and / or carbides of the following elements: scandium, titanium, zirconium and vanadium.

[0037] According to a second embodiment of the invention, the alloy comprises at least one other so-called secondary element, the at least one secondary element being able to be magnesium (Mg) and / or manganese (Mn) and / or yttrium (Y), and / or rare earths.

[0038] Advantageously, any secondary element will be present in an atomic proportion less than or equal to 5% at, or even less than or equal to 3.5% at, or even less than or equal to 2% at.

[0039] Advantageously, the total proportion of the elements scandium (Sc), titanium (Ti), zirconium (Zr), vanadium (V), magnesium (Mg), manganese (Mn), yttrium (Y), and / or rare earths is greater than or equal to 90% at, or even greater than or equal to 95% at.

[0040] Finally, the alloy according to the invention can thus comprise 3, 4 or 5 elements. Alternatively, it can comprise more than 5 elements, in particular between 6 and 13 elements.

[0041] Thus, the alloy may consist of scandium (Sc), titanium (Ti), zirconium (Zr) and / or vanadium (V), and optionally magnesium (Mg), manganese (Mn), yttrium (Y), and / or rare earths

[0042] Advantageously, in all these embodiments, each of the four main elements will be present in the following atomic proportions: scandium between 30 and 70% at inclusive, or even between 40 and 70% at inclusive, or even between 50 and 65% at inclusive, or even between 30 and 60% at inclusive, or even between 30 and 47% at inclusive, or even between 30 and 45% at inclusive; and titanium between 5 and 35% at inclusive, or even between 5 and 30% at inclusive, or even between 15 and 25% at inclusive, or even between 15 and 20% at inclusive; and zirconium between 0 and 30% at inclusive, or even between 5 and 30% at inclusive, or even between 5 and 25% at inclusive, or even between 15 and 25% at inclusive, or even between 15 and 20% at inclusive, or even between 10 and 20% at inclusive; and vanadium between 0 and 30% at inclusive, or between 5 and 30% at inclusive, or between 5 and 25% at inclusive, or between 15 and 25% at inclusive, or between 15 and 20% at inclusive, or between 10 and 20% at inclusive.

[0043] Advantageously, in all embodiments of the invention, scandium will be present with the greatest atomic percentage.

[0044] It appears that such an alloy according to the invention makes it possible to achieve a low density and a high hardness. Advantageously, the elements of the alloy will be chosen so that the resulting alloy has a density less than or equal to 4.5 g cm -3< , or even less than or equal to 4.2 g cm -3< , or even less than or equal to 4 g cm -3< and a hardness greater than or equal to 400 Hv, or even greater than or equal to 500 Hv, or even greater than or equal to 600 Hv, measured after the shaping step described below and before any other possible treatment. It is also notable that the alloy according to the invention has a high microstructural stability, even being able to withstand temperatures above 900°C, or even above 1000°C.

[0045] Advantageously, the alloy is a completely metallic alloy. It appears that the invention makes it possible to obtain an alloy that is lighter than aluminum and harder than hardened steel, while being completely stainless and non-magnetic.

[0046] Such an alloy may have a crystalline structure, in particular nanocrystalline, simple, single-phase or two-phase. Alternatively, the alloy may have an amorphous structure.

[0047] The invention also relates to a watch component, characterized in that it comprises an alloy as described above. According to one embodiment, the watch component may be entirely formed from an alloy according to the invention. Alternatively, only a portion of said component may be formed from such an alloy.

[0048] According to one embodiment, the watch component may be a watch case, a bezel, a dial, a bracelet link, a bracelet, a bracelet clasp, etc.

[0049] The invention also relates to a timepiece, piece of jewelry or jewelry, which comprises an alloy as described previously or a watch component as described above. The timepiece according to one embodiment of the invention may be a watch, such as a wristwatch.

[0050] The invention was designed for the field of watchmaking, or even jewelry. However, it appears that the alloy according to the invention could advantageously be used in other fields due to its numerous remarkable properties. Thus, this alloy could for example be used in aerospace, aeronautics, automobiles, more generally for any transport industry, as well as for the fields of energy and armaments. Thus, the invention also relates to a component dedicated to aerospace, aeronautics, automobiles, a transport machine, a measuring device such as a robot intended to take measurements and / or a space exploration robot, an energy production or storage device, etc., which is formed in whole or in part from the alloy of the invention. A component comprising this alloy may advantageously be entirely composed of the alloy, that is to say that the alloy will form a solid component.The alloy will therefore extend over the entire thickness of the component. Alternatively, such a component may be predominantly formed of said alloy, which extends in particular into its core. Said alloy may optionally be covered with a surface coating to give it a particular color or a particular appearance or a particular surface protection.

[0051] Finally, the invention also relates to a method of manufacturing an alloy as described above. There already exist methods of manufacturing high entropy alloys, and methods of manufacturing alloys comprising many elements.

[0052] With the alloy according to the invention, the elements exhibit high reactivity in the liquid state. For example, molten scandium is extremely difficult to handle in the liquid state. Liquid titanium is highly reactive with atmospheric oxygen, forming embrittling oxides.

[0053] Thus, according to the embodiment of the invention, the manufacturing method comprises a step of mechanical alloying.

[0054] More specifically, in the first step of the process, the pure elements of the alloy to be manufactured, in powder form, are placed in a high-energy planetary mill. The energy generated by the impacts between the mill balls and the powders of pure elements has two effects: A first mechanical crushing effect allows the different elements to come into contact. The ductile particles deform to encompass the solid particles; a second effect is that the heat generated by the shocks activates the diffusion of the elements in the solid state, and causes the alloy to be dissolved.

[0055] After a certain grinding time, the result is a new alloy powder with a constant composition. Note that grinding is carried out under vacuum or in the presence of an inert gas.

[0056] Then the alloy powder is shaped in a second step.

[0057] The technique used to shape the alloy is spark plasma sintering. The plasma flash sintering technique involves the simultaneous application of a pulsed current through the powder and pressure. It allows for lower sintering temperatures and shorter pressure holding times, thus achieving rapid sintering. This technique produces a fine microstructure with grain sizes in the nanometer range.

[0058] As a note, this second step uses low sintering temperatures, to avoid any risk of evaporation, and a short duration, to avoid any risk of demixing of the alloy.

[0059] After densification, the sintered shapes obtained by the second stage can undergo any conventional processing in a third stage. For example, they can be machined conventionally.

Claims

1. An alloy, characterized in that it consists in scandium (Sc) according to a fraction of greater than or equal to 30 at%, scandium being the element of the alloy which exhibits the greatest atomic percentage, titanium (Ti), zirconium (Zr) and / or vanadium (V) and / or their oxides, hydrides, borides, carbides and / or nitrides, at least two of the elements among titanium, zirconium and vanadium and / or their oxides, hydrides, borides, carbides and / or nitrides, exhibiting a fraction of greater than or equal to 15 at%, and optionally magnesium (Mg), and / or manganese (Mn), and / or yttrium (Y) and / or rare earth metals.

2. The alloy as claimed in the preceding claim, characterized in that it is chosen from: - Sc30Ti25V20Zr25 - Sc60Ti20V20 - Sc33Ti33V33 - Sc40Ti20V20Zr20 - Sc33Ti33Zr33 - Sc60Zr20Ti203. The alloy as claimed in one of the preceding claims, characterized in that it comprises magnesium (Mg) and / or manganese (Mn) and / or yttrium (Y) and / or rare earth metals.

4. The alloy as claimed in the preceding claim, characterized in that: - any element of the alloy other than scandium (Sc), titanium (Ti), zirconium (Zr) and vanadium (V) exhibits an atomic proportion of less than or equal to 5 at%, indeed even of less than or equal to 3.5 at%, indeed even of less than or equal to 2 at%; and / or - the total proportion of the elements scandium (Sc), titanium (Ti), zirconium (Zr) and vanadium (V) is greater than or equal to 70 at%, indeed even greater than or equal to 80 at%, indeed greater than or equal to 90 at%; and / or - the total proportion of the elements scandium (Sc), titanium (Ti), zirconium (Zr), vanadium (V), magnesium (Mg), manganese (Mn), yttrium (Y) and / or rare earth metals is greater than or equal to 90 at%, indeed even greater than or equal to 95 at%.

5. The alloy as claimed in either of claims 3 and 4, characterized in that it consists of an alloy of 4 to 13 elements inclusive.

6. The alloy as claimed in one of the preceding claims, <b>characterized in that it comprises: - scandium between 30 and 70 at% inclusive, indeed even between 40 and 70 at% inclusive, indeed even between 50 and 65 at% inclusive, indeed even between 30 and 60 at% inclusive, indeed even between 30 and 47 at% inclusive, indeed even between 30 and 45 at% inclusive; and - titanium between 5 and 35 at% inclusive, indeed even between 5 and 30 at% inclusive, indeed even between 15 and 25 at% inclusive, indeed even between 15 and 20 at% inclusive; and - zirconium between 0 and 30 at% inclusive, indeed even between 5 and 30 at% inclusive, indeed even between 5 and 25 at% inclusive, indeed even between 15 and 25 at% inclusive, indeed even between 15 and 20 at% inclusive, indeed even between 10 and 20 at% inclusive; and - vanadium between 0 and 30 at% inclusive, indeed even between 5 and 30 at% inclusive, indeed even between 5 and 25 at% inclusive, indeed even between 15 and 25 at% inclusive, indeed even between 15 and 20 at% inclusive, indeed even between 10 and 20 at% inclusive.

7. The alloy as claimed in one of the preceding claims, characterized in that it exhibits a density of less than or equal to 4.5 g.cm-3, indeed even of less than or equal to 4.2 g.cm-3, indeed even of less than or equal to 4 g.cm-3, measured after its shaping and before any other treatment.

8. The alloy as claimed in one of the preceding claims, characterized in that it exhibits a hardness of greater than or equal to 400 Hv, indeed even of greater than or equal to 500 Hv, indeed even of greater than or equal to 600 Hv, measured after its shaping and before any other treatment.

9. A watch component, characterized in that it comprises an alloy as claimed in one of the preceding claims or in that it is entirely formed of an alloy as claimed in one of the preceding claims.

10. The watch component as claimed in the preceding claim, characterized in that it is a watch case, a bezel, a dial, a strap link, a strap or a clasp for a strap.

11. A timepiece, in particular a watch, or a piece of jewelry, characterized in that it comprises a watch component as claimed in claim 9 or 10 or in that it comprises an alloy as claimed in one of claims 1 to 8.

12. A component dedicated to the aeronautical sector, to the motor vehicle sector, to a means of transportation, to a measuring apparatus, to an exploration robot, to a weapon or to an energy production or storage device, characterized in that it comprises an alloy as claimed in one of claims 1 to 18.

13. The component as claimed in claim 9, 10 or 12, characterized in that it is entirely formed of alloy as claimed in one of claims 1 to 11 or in that it is a bulk part comprising an alloy as claimed in one of claims 1 to 8 extending substantially over its entire thickness.

14. A process for the manufacture of an alloy as claimed in one of claims 1 to 8 or of a component as claimed in one of claims 9, 10 and 12, <b>characterized in that it comprises the following stages: - grinding of powders of pure elements to form an alloy powder; - cold shaping of the alloy powder.

15. The process for the manufacture of an alloy or of a component as claimed in the preceding claim, characterized in that the shaping stage comprises a spark plasma sintering stage.