HK1234452B - Lightweight precious alloy made from titanium and gold, and timepiece or jewellery item component made from a lightweight precious alloy of titanium and gold - Google Patents

Description

Lightweight precious alloys made of titanium and gold, and timepieces or jewelry parts made of the same

Technical Field

The present invention relates to a gold-titanium based lightweight noble alloy containing at least 750 mass ‰ gold.

The invention also relates to a timepiece or jewelry component made of the corresponding gold-titanium-based lightweight noble alloy.

The present invention relates to the field of structural or external parts of timepieces or jewellery made from 18-karat gold alloys.

Background Art

A common feature of most precious metal alloys used in watchmaking is their high density – above 10 g/cm ³ . In fact, gold and platinum, the two main precious metals used in watchmaking, have respective densities of approximately 19.3 and 21.5 g/cm ³ . This therefore makes their alloys relatively heavy.

Because of their high gold content, and due to the fact that they only rarely combine large amounts of lightweight elements, graded gold alloys are generally very dense. Furthermore, if gold is alloyed with large amounts of lightweight elements, this generally results in brittle components.

However, the Ti-Au system has been studied in the equiatomic intermetallic TiAu region.

In their binary or ternary form, these alloys are known to exhibit a shape memory effect, particularly alloys having the atomic compositions Ti ₅₀ Au ₅₀ and Ti ₅₀ Ni ₁₀ Au ₄₀ .

Regarding the shape memory effect, a decrease in temperature Ms was also observed after adding the ternary elements to the Ti ₅₀ Au ₅₀ alloy.

TiAuFe alloys with 5, 10, 14, 15 and 20 atomic % of iron as well as TiAuCo and TiAuCoNb alloys have been the subject of specific investigations, with no results available on the subject.

Although the biocompatibility of these alloys is often cited for medical applications, no composition has been proposed to achieve both 18 karat gold purity without excessive weight and acceptable mechanical properties for manufacturing external timepiece components.

EP Patent Application 2548982A1 discloses alloys containing 50% to 99% titanium, or more precisely, alloys containing, in addition to titanium, a noble metal, ideally 5-15% of a noble metal. It should be noted that a gold-titanium alloy containing 5-15% gold does not achieve 18-karat gold purity, since the required gold content of 75% by mass is not achieved.

US Patent 4,568,398 describes Ti-Au alloys containing 95-40 mass % titanium, but the remainder of the composition, particularly the low gold content, prevents the alloy from achieving 18-karat gold purity.

WO patent application 2008/018109A1 describes gold and titanium alloys with purities ranging from 6K to 18K that exhibit shape memory properties (which is undesirable), or superelasticity, and exhibit elongation at break. Most of these alloys contain nickel, which is undesirable for manufacturing external timepieces or jewelry components that may come into contact with human skin. The document discloses only two 18K compositions: Ti _11.23 Ni _13.77 Au ₇₅ and Ti _12.5 Ni _12.5 Au ₇₅ , by mass. Both compositions fall far short of 50 atomic percent titanium and contain nickel, making them unsuitable for external timepiece components.

AUTIUM's patent application WO 2010/027329 describes an Au-Ti-X alloy, wherein X represents at least one element selected from the approximately 115 elements of the periodic table, and in certain embodiments, more than 10% by mass of Ti, or 10-50% by mass of Ti, or 58-85% by mass of Au, or the element X is selected from Fe, Co, Cr, Mn, Mo, Pd, Nb, W, Al, Si, in an amount up to 8% by mass. The ranges disclosed are extremely broad, and while they may encompass alloys with some ductility, they do not indicate how to obtain them or any preferred narrowing range within the broadest composition. Therefore, a person skilled in the art cannot use this document to select and manufacture an alloy that can be easily formed to make a timepiece or jewelry exterior and that is lighter than conventional gold alloys while having excellent mechanical properties and can be classified as 18-karat gold.

DEGUSSA patent GB 876887 describes gold alloys for electrical resistors, in particular Au-Ti-Fe alloys containing 1-5% by mass of titanium.

SUNDER-PLASSMANN's patent DE 4306452 describes binary dental alloys containing 50-91% gold and 9-50% titanium, or dental alloys containing 0-20% platinum and/or palladium, and/or 0-15% other elements suitable for dental alloys, such as silver, copper, vanadium, iron, aluminum, niobium, tantalum, and gallium. More specifically, one embodiment limits platinum and palladium to a maximum of 10% by mass, and other elements to a maximum of 10% by mass. Another embodiment contains 50-83% gold and 17-50% titanium. The document discloses a specific mass composition, Ti42.2Au57.8, which is a brittle, fragile intermetallic compound with an atomic composition of _Ti3Au , which is not suitable for manufacturing timepiece external components. Metallurgists know that the properties of an alloy are largely influenced by its microstructure, but this document teaches the opposite in this regard. The document gives only approximate compositions, with very wide ranges for gold, titanium and alloying elements often resulting in compositions unsuitable for the intended watchmaking use, and the breadth of these ranges encompasses many possible alloys, but the document does not precisely indicate the advantages of specific ranges.

Summary of the Invention

The present invention proposes to develop an alloy classifiable as 18-karat gold that is easily shaped to produce timepieces or jewelry exteriors such as watch cases, bracelets, jewelry pieces, etc. and is also lighter than conventional gold alloys while having excellent mechanical properties, such as those met by titanium alloys.

To this end, the present invention relates to a gold-titanium-based lightweight noble alloy containing at least 750 mass ‰ of gold, characterized in that the alloy has the following composition formula:

Ti _a Au _b M _c T _d

Where a, b, c, and d are atomic proportions such that:

a+b+c+d=1,

0.45≤a≤0.55; 0.41≤b≤0.495; 0.025≤c≤0.13; 0.001≤d≤0.025,

wherein M represents one or more elements selected from the first group, the first group including Nb, V, Pd, Pt, Fe,

And wherein T represents up to two elements selected from the second group, the second group including Nb, V, Pd, Pt, Fe, Mo, Ta, W, Co, Ni, Ru, Rh, Ir, Cr, Mn, Cu, Zn, Ag, Al, B, Si, Ge, Sn, Sb, In, excluding the metal M contained in the alloy.

The present invention also relates to a timepiece or jewelry component made of the gold-titanium-based lightweight noble alloy.

Briefly, the present invention relates to a ductile alloy based on an equiatomic intermetallic compound TiAu, wherein any excess gold relative to the mass content required for 18-karat purity is replaced by another non-precious metal element, such that titanium still comprises 50-51 atomic percent of the final alloy and gold comprises 750 mass percent (i.e., 18-karat). The alloy has sufficient ductility to provide formability similar to that of conventional titanium alloys.

DETAILED DESCRIPTION

Unless otherwise stated, all concentrations expressed in this specification are atomic ratios, particularly with respect to gold.

The present invention relates to a gold-titanium-dominant alloy of the following formula:

Ti _a Au _b M _c T _d

Where a, b, c, and d are atomic proportions such that:

a+b+c+d=1,

0.45≤a≤0.55;

0.41≤b≤0.495;

0.025≤c≤0.13;

0.001≤d≤0.025,

wherein M represents one or more elements selected from the first group, the first group including Nb, V, Pd, Pt, Fe,

The gold content is greater than or equal to 750‰.

And wherein T represents up to two elements selected from the second group, the second group including Nb, V, Pd, Pt, Fe, Mo, Ta, W, Co, Ni, Ru, Rh, Ir, Cr, Mn, Cu, Zn, Ag, Al, B, Si, Ge, Sn, Sb, In, excluding the metal M contained in the alloy.

The parameter "a" defines the titanium content.

The parameter "b" defines the gold content.

The parameter "c" defines the total content of element M.

The parameter "d" defines the total content of element T.

The alloy contains 750 mass ‰ gold. This mass percentage of gold is naturally not inconsistent with the atomic ratio of the alloying elements, it is an additional condition related to the purity level and is not in any way inconsistent with the alloy composition described in the present invention.

More particularly, for applications involving parts that may come into contact with the user's skin, the alloy does not include nickel and the formulation is limited in terms of T, wherein T represents a maximum of two elements selected from the third group, which corresponds to the second group without nickel and includes: Nb, V, Mo, Ta, W, Fe, Co, Ru, Rh, Ir, Pd, Pt, Cr, Mn, Cu, Zn, Ag, Al, B, Si, Ge, Sn, Sb, In, except for the metal M contained in the alloy.

The same alternative pertains to the complete description of any alloy that may be used in similar applications.

More specifically, the content "a" of titanium, the content "b" of gold and the content "c" of element M in the formulation are limited to the following forms:

Ti _a Au _b M _c T _d

Among them, 0.48≤a≤0.52; 0.42≤b≤0.48; 0.025≤c≤0.10; 0.001≤d≤0.025.

More specifically, the content of titanium "a" and the content of M "c" in the formulation are limited to the following forms:

Ti _a Au _b M _c T _d

Among them, 0.49≤a≤0.51; 0.42≤b≤0.48; 0.025≤c≤0.09; 0.001≤d≤0.025.

More specifically, the content "a" of titanium, the content "b" of gold and the content "c" of element M in the formulation are limited to the following forms:

Ti _a Au _b M _c T _d

Among them, 0.50≤a≤0.51; 0.42≤b≤0.47; 0.025≤c≤0.08; 0.001≤d≤0.025.

The range of titanium atomic content of 0.50-0.51 corresponds to the stability range of the medium atomic ratio intermetallic phase TiAu in the binary Ti-Au system at ambient temperature.

Still more particularly, T represents a maximum of two elements chosen from a fourth group, more limited than the third group, comprising: Nb, V, Fe, Ru, Rh, Ir, Pd, Pt, Cr, Cu, Ag, B, excluding the metal M comprised in the alloy.

Still more particularly, M represents one or more elements belonging to the fifth group corresponding to the first group excluding vanadium and comprising: Nb, Pd, Pt, Fe.

Still more particularly, for the use of boron as grain refiner, T denotes on the one hand boron in a content of 0.03% to 0.3% and, on the other hand, at least in the case where the minimum value "d" of 0.1% is not reached, a sufficient amount of only one element from the sixth group, comprising: Nb, V, Fe, Ru, Rh, Ir, Pd, Pt, Cr, Cu, Ag, so that the value "d" (the sum of the atomic contents of boron and said element from the sixth group) is 0.001-0.025.

The following compositions offer particularly promising alloy formulas that combine ease of implementation, reduced density, attractive appearance, and reduced excess gold content, which are important for watchmaking and jewelry applications.

Recipes have the following types:

Ti _a Au _b M _c T _d

Among them, 0.50≤a≤0.51; 0.42≤b≤0.47; 0.025≤c≤0.08; 0.001≤d≤0.025,

wherein M represents only one element from the fifth group comprising Nb, Pd, Pt, Fe,

And wherein T represents boron in an amount of 0.03% to 0.3%, at least without reaching the minimum atomic value "d" of 0.1%, a sufficient amount of only one element from the sixth group so that the value "d" (the sum of the atomic proportions of boron and said element from the sixth group) is 0.001-0.025, said sixth group including: Nb, V, Fe, Ru, Rh, Ir, Pd, Pt, Cr, Cu, Ag.

More particularly, M is iron.

More particularly, M is niobium.

More particularly, M is platinum.

More particularly, M is palladium.

More particularly, the gold content in the alloy is less than 780‰ by mass.

Still more particularly, the gold content in the alloy is less than 760‰ by mass.

An example of an atomic composition where a=0.50 and d=0.001 is given below: - Ti _0.50 Au _0.427 Fe _0.072 B _0.001 Purity of Au: 750.5‰

a＝0.50；b＝0.427；c＝0.072；d＝0.001 -Ti _0.50 Au _0.444 Nb _0.055 B _0.001 Purity of Au: 750.6‰

a＝0.50；b＝0.444；c＝0.055；d＝0.001 -Ti _0.50 Au _0.466 Pt _0.033 B _0.001 Purity of Au: 751.3‰

a＝0.50；b＝0.466；c＝0.033；d＝0.001 -Ti _0.50 Au _0.448 Pd _0.051 B _0.001 Purity of Au: 750.3‰

a=0.50; b=0.448; c=0.051; d=0.001

Other examples where a=0.505 and d represents the atomic composition of two elements are described below: - Ti _0.505 Au _0.4295 Fe _0.050 Cr _0.015 B _0.0005 Purity of Au: 753‰

a＝0.505；b＝0.4295；c＝0.05；d＝0.0155 - Ti _0.505 Au _0.4385 Nb _0.041 Cr _0.015 B _0.0005 Purity of Au: 750.2‰

a＝0.505；b＝0.4385；c＝0.041；d＝0.0155 - Ti _0.505 Au _0.448 Pd _0.0365 Rh _0.01 B _0.0005 Purity of Au: 752.1‰

a＝0.505；b＝0.448；c＝0.0365；d＝0.0105 -Ti _0.505 Au _0.463 Pt _0.031 Ir _0.0005 B _0.0005 Purity of Au: 750.5‰

a=0.505; b=0.463; c=0.031; d=0.001.

In a variant of the present invention, a few percent, in particular 0-3%, of Zr or Hf can replace part of the titanium. The alloy formula is:

N _a Au _b M _c T _d

Where a, b, c, and d are atomic proportions such that:

a+b+c+d=1,

0.45≤a≤0.55;

0.41≤b≤0.495;

0.025≤c≤0.13;

0.001≤d≤0.025,

wherein N is a combination of titanium, zirconium, and hafnium, the atomic % of zirconium is 0% to 3% of the alloy, and the atomic % of hafnium is 0% to 3% of the alloy.

wherein M represents one or more elements selected from the first group, the first group including Nb, V, Pd, Pt, Fe,

The gold content is greater than or equal to 750‰,

And wherein T represents up to two elements selected from the second group, the second group including Nb, V, Pd, Pt, Fe, Mo, Ta, W, Co, Ni, Ru, Rh, Ir, Cr, Mn, Cu, Zn, Ag, Al, B, Si, Ge, Sn, Sb, In, excluding the metal M contained in the alloy.

The present invention further relates to a timepiece or a component for a timepiece or jewelry made of the gold-titanium-based lightweight noble alloy.

The present invention has many advantages resulting from the above features:

- These alloys have a medium hardness less than or equal to 300 HV and can therefore be formed using common deformation methods;

- They can be classified as 18-karat pure;

- They are particularly light compared to most alloys classified as 18-karat gold;

-Nickel-free alloy is harmless to the human body.

The production of timepiece exterior parts from the alloys described above advantageously allows the alloy composition to be optimized in different respects:

- Facilitating implementation by incorporating elements that lower the melting point;

- Modification of the mechanical properties of the alloy by varying the amount of elements replacing the precious metal;

- Alloys with structural hardening are obtained by making various slight modifications.

Claims (15)

1. A gold-titanium based lightweight noble alloy containing at least 750‰ gold by mass, characterized in that the alloy has the following composition: Ti _a Au _b M _c T _d Where a, b, c, and d are atomic ratios such that: a+b+c+d＝1, 0.45≤a≤0.55; 0.41≤b≤0.495; 0.025≤c≤0.13; 0.001≤d≤0.025 Where M represents one or more elements selected from the first group, which consists of the following elements: Nb, V, Pd, Pt, Fe. Where T represents a maximum of two elements selected from the second group, which consists of the following elements: Nb, V, Pd, Pt, Fe, Mo, Ta, W, Co, Ni, Ru, Rh, Ir, Cr, Mn, Cu, Zn, Ag, Al, B, Si, Ge, Sn, Sb, In, excluding the element represented by M contained in the alloy. The alloy contains boron with an atomic content of 0.03% to 0.3%. Furthermore, the alloy is characterized in that the mass content of gold is less than 780‰. 2. The alloy according to claim 1, wherein T represents at most two elements selected from a third group, the third group consisting of the following elements: Nb, V, Pd, Pt, Fe, Mo, Ta, W, Ru, Rh, Ir, Cr, Mn, Cu, Zn, Ag, Al, B, Si, Ge, Sn, In, excluding the element M contained in the alloy. 3. The alloy according to claim 1, wherein T represents at most two elements selected from a restricted second group, the restricted second group consisting of the following elements: Nb, V, Pd, Pt, Fe, Mo, Ta, W, Co, Ni, Ru, Rh, Ir, Cr, Mn, Zn, Ag, Al, B, Si, Ge, Sn, Sb. 4. The alloy according to claim 1, characterized in that 0.48≤a≤0.52; 0.42≤b≤0.48; 0.025≤c≤0.10; 0.001≤d≤0.025. 5. The alloy according to claim 4, characterized in that 0.49≤a≤0.51; 0.42≤b≤0.48; 0.025≤c≤0.09; 0.001≤d≤0.025. 6. The alloy according to claim 5, characterized in that 0.50≤a≤0.51; 0.42≤b≤0.47; 0.025≤c≤0.08; 0.001≤d≤0.025. 7. The alloy according to claim 6, wherein T represents at most two elements selected from a fourth group, the fourth group consisting of the following elements: Nb, V, Pd, Pt, Fe, Ru, Rh, Ir, Cr, B, Cu, Ag, excluding the element M contained in the alloy. 8. The alloy according to claim 7, wherein M represents one or more elements selected from the fifth group, which consists of the following elements: Nb, Pd, Pt, Fe. 9. The alloy according to any one of claims 1-8, characterized in that when the atomic proportion of boron is less than 0.10%, T includes only one other element selected from the sixth group in addition to boron, said sixth group consisting of the following elements: Nb, V, Pd, Pt, Fe, Ru, Rh, Ir, Cr, Cu, Ag, excluding the element M contained in the alloy. 10. The alloy according to claim 1, wherein M is iron. 11. The alloy according to claim 1, wherein M is niobium. 12. The alloy according to claim 1, wherein M is platinum. 13. The alloy according to claim 1, wherein M is palladium. 14. The alloy according to claim 1, wherein the mass content of gold in the alloy is less than 760‰. 15. A timepiece or jewelry component made of a gold-titanium-based lightweight precious alloy according to any one of the preceding claims.