ATBECHDEDKESFRGBGRITLILUNLSEMCPTIESILTLVFIROMKCYALTRBGCZEEHUPLSKBAHRIS..MTNORSMESMMAKHTNMD..........
J
BDM Ver 1.7.2 (20 November 2019) - 1100000/0
3812477
EUROPEAN PATENT APPLICATION
A1
20210428
EP
19306367.4
20191021
en
en
en
20210428
202117
20210428
202117
C22C 5/02 20060101AFI20200204BHEP
A44C 27/00 20060101ALI20200204BHEP
C22F 1/14 20060101ALI20200204BHEP
de
GOLDHALTIGE METALLLEGIERUNG
en
METAL ALLOY COMPRISING GOLD
fr
ALLIAGE MÉTALLIQUE COMPRENANT DE L'OR
Richemont International SA
101604670
PP002341 WPE NR
10 Route des Biches
1752 Villars-sur-Glane
CH
LALIRE, Fanny
11 rue Edith Cavell
90000 BELFORT
FR
THEDY, Louis
13 Rue Bellecombe
69100 VILLEURBANNE
FR
Ipsilon
101854227
Le Centralis 63, avenue du Général Leclerc
92340 Bourg-la-Reine
FR
AL
AT
BE
BG
CH
CY
CZ
DE
DK
EE
ES
FI
FR
GB
GR
HR
HU
IE
IS
IT
LI
LT
LU
LV
MC
MK
MT
NL
NO
PL
PT
RO
RS
SE
SI
SK
SM
TR
BA
ME
KH
MA
MD
TN
The present invention concerns a metal alloy comprising at least four metallic elements different from gold (Au), each of said metallic elements being in an amount from 1.0 to 55.0 atomic percent, characterized in that the metal alloy further comprises gold (Au) in an amount of at least 58.3 % by weight over the total weight of the metal alloy.
The present invention relates to a metal alloy comprising several metallic elements including gold (Au), and a process of manufacturing said metal alloy.
More particularly, the metal alloy is used to manufacture luxury goods.
It exists several types of metal alloys used to manufacture luxury goods such as a time-piece or a jewel. One can cite the document WO 2019/073023 concerning a metal alloy comprising at least four metallic elements such as scandium (Sc), aluminum (Al), titanium (Ti) and lithium (Li).
However, despite the various metal alloys which are commercially available, there is still a need to have new alternative metal alloys able to be used in the domain of luxury goods, with optimized properties.
In this respect, the present invention seeks to provide a new metal alloy, having optimized mechanical properties, while being easy to shape.
To this end, an object of the present invention is a metal alloy comprising at least four metallic elements different from gold (Au), each of said metallic elements being in an amount from 1.0 to 55.0 atomic percent (at%), characterized in that the metal alloy further comprises gold (Au) in an amount of at least 58.3% by weight over the total weight of the metal alloy.
The present invention advantageously provides a metal alloy with an improved hardness, while guaranteeing a good ductility. More particularly, the hardness of the metal alloy can advantageously be of at least 150 Vickers hardness (HV) (i.e. kilograms-force per square millimeter), more preferably of at least 200 HV, and even more preferably of at least 250 HV.
The metal alloy is also advantageously easy to shape, especially to manufacture luxury good.
The metal alloy of the present invention has advantageously a high entropy.
More particularly, the entropy of the metal alloy can be of at least 0.69R, more preferably at least 1.00R, and even more preferably at least 1.20R, R being the molar gas constant.
The entropy can be easily determined by the man skilled in the art, according to the well-known Boltzmann's definition related to the following equation: ΔS_{conf} = - RΣX_iIn(X_i), where X_i represents the atomic fraction of element i and R is the molar gas constant.
A high entropy can favor the formation of a solid solution, which may help to improve the ductility of the metal alloy.
The metal alloy of the present invention can be a solid solution. A solid solution is well known in the art and can be considered as a solid-state solution comprising several metallic elements wherein the metallic elements remain in a single homogeneous phase in the metal alloy. Thus, the metal alloy of the invention can preferably be a single-phase alloy.
In the present invention, gold (Au) is used as main metallic element among the at least five metallic elements constituting the metal alloy.
Indeed, among the at least five metallic elements, the metal alloy comprises an amount of gold (Au) superior or equal to 58.3 % by weight over the total weight of the metal alloy.
An amount of gold (Au) of at least 58.3 % by weight over the total weight of the metal alloy is particularly advantageous since it corresponds to an amount of 583 ‰ (per mille) by weight of gold (Au) over the total weight of the metal alloy. With this lower limit of at least 583 ‰ by weight of gold (Au), the metal alloy can be considered as a precious material of 14-karat gold (i.e. 14k), under the karat standard system for gold alloy.
In a particular embodiment, the metal alloy can comprise at least 70.0 % by weight of gold (Au), and more preferably 75.0 % by weight of gold (Au), over the total weight of the metal alloy.
An amount of gold (Au) of at least 75.0 % by weight over the total weight of the metal alloy is particularly advantageous since it corresponds to an amount of 750 ‰ (per mille) by weight of gold (Au) over the total weight of the metal alloy. With this lower limit of at least 750 ‰ by weight of gold (Au), the metal alloy can be considered as a precious material of 18-karat gold (i.e. 18k), under the karat standard system for gold alloy.
In the present invention, the metal alloy comprises at least four metallic elements different from gold (Au), each of said four metallic elements being in an amount from 1.0 to 55.0 atomic percent (at%), and more preferably from 5.0 to 30.0 atomic percent.
The atomic percent of each metallic elements constituting the metal alloy is expressed over the total atomic percent (100%) of the metallic elements constituting the metal alloy.
The four metallic elements can be selected among silver (Ag), aluminum (Al), manganese (Mn), copper (Cu), palladium (Pd), iron (Fe), and chromium (Cr), platinum (Pt), and cobalt (Co).
In a first embodiment, the four metallic elements can be copper (Cu), silver (Ag), manganese (Mn), and aluminum (Al).
According to this first embodiment, the metal alloy can be for example, in at%, Au_{34.4}Cu_{25.9}Ag_{22.8}Mn_{9.6}Al_{7.3} or Au_{52.5}Cu_{20.3}Ag_{15.2}Mn_{6.5}Al_{5.5}.
In a second embodiment, the four metallic elements can be palladium (Pd), silver (Ag), chromium (Cr), and iron (Fe).
According to this second embodiment, the metal alloy can be for example, in at%, Au_{36.6}Pd_{16.4}Ag_{16.2}Cr_{15.4}Fe_{15.4}.
In a third embodiment, the four metallic elements can be silver (Ag), chromium (Cr), palladium (Pd), and cobalt (Co).
According to this third embodiment, the metal alloy can be for example, in at%, Au_{38.0}Ag_{15.5}Cr_{15.5}Pd_{15.5}Co_{15.5}.
In a fourth embodiment, the four metallic elements can be silver (Ag), cobalt (Co), palladium (Pd), and iron (Fe).
According to this fourth embodiment, the metal alloy can be for example, in at%, Au_{38.0}Ag_{15.5}Co_{15.5}Pd_{15.5}Fe_{15.5}.
In a fifth embodiment, the four metallic elements can be silver (Ag), platinum (Pt), palladium (Pd), and iron (Fe).
According to this fifth embodiment, the metal alloy can be for example, in at%, Au_{67.0}Ag_{8.25}Pt_{8.25}Pd_{8.25}Fe_{8.25}.
The gold (Au) used in the metal alloy of the invention can preferably have a purity of at least 99.5 %, and more preferably of at least 99.9 % and even more preferably of at least 99.99 %.
The metallic elements different from gold (Au) can also have a purity of at least 99.0 %, and more preferably of at least 99.9 %.
Another object of the present invention is a process of manufacturing said metal alloy, the process comprising the following steps:
1. i. forming a molten alloy comprising gold (Au) and the at least four metallic elements different from gold,
2. ii. cold rolling the alloy obtained in step i, and
3. iii. optionally, annealing the alloy obtained in step ii.
The step i can include a mixture of the metallic elements as such and/or one or several pre-alloy(s).
The step i can be done in using an arc furnace, classically in placing the metallic elements and/or the pre-alloy(s) in a crucible, and submitting then with an electric arc producing a temperature of up to 3000°C. This process makes it possible to produce alloys from pure elements with different melting temperatures. The metallic element mixture can then be cooled to room temperature (around 25°C).
In another embodiment, the step i can be done in using an induction furnace, classically in placing the metallic elements and/or the pre-alloy(s) in a crucible, and submitting then with an induction heating. The metallic element mixture can then be cooled to room temperature (around 25°C).
A pre-alloy can be a mixture of at least two metallic elements having similar melting temperature. For example, a pre-alloy can be formed with two metallic elements having a melting temperature difference inferior or equal to 150°C, and more preferable inferior or equal to 100°C.
The pre-alloys can be formed in using an arc furnace. The metallic element mixture can then be cooled to room temperature (around 25°C).
The alloy obtained in step i is then rolled in order to increase its mechanical properties and modify its internal structure. The rolling step can be done at room temperature (around 25°C) in using a rolling mill. The rolling step can usually be performed after cooling to room temperature (around 25°C) the alloy obtained in step i.
The step iii can be advantageously done to improve the yield strength and the hardness of the alloy, especially when several cold rolling passes are done.
The temperature and annealing time depend on the nature of the alloy, the rate of cold work previously applied and the properties required, according to the conditions well-known in the art.
For example, the annealing step can be done at a temperature around 750°C, during 30 minutes.
In a particular embodiment, when the step iii is performed, the step iii can be followed by one or several steps of cold rolling as detailed in step ii.
Another object of the present invention is an item obtained from the metal alloy.
The item can comprise or consist of the metal alloy according to the present invention. Accordingly, the metal alloy can be used in order to manufacture luxury goods, such as for example a time-piece and/or a jewel. The time-piece and/or the jewel can have a part or a component comprising the metal alloy according to the present invention.
More particularly, the item according to the present invention can be a jewel, a leather good, or a clothing accessory. It may also be a watch, a writing accessory, or a decorative item.
For instance, the item can be any of the followings: ring; ear ring; necklace; bracelet; pendant; watch such as case, bezel, caseback, crown, bracelet links, clasp, buckle, automatic movement rotor; buckle (e.g. belt or purse); tie bar; cuff links; money clip; hair pin; pen; paper knife.
The present invention will become more fully understood from the examples given herein below, which are given by way of illustration only, and thus, which are not limits of the present invention.

Examples:

1. Preparation of the metal alloys according to the invention
Different metal alloys according to the present invention, i.e. Metal alloy 1, Metal alloy 2, Metal alloy 3, Metal alloy 4 and Metal alloy 5, have been prepared and are respectfully gathered in the following Tables 1 to 5.
The amounts in Tables 1 to 5 are expressed:
- in atomic percent (at%) over all the metallic element constituting the metal alloy, and
- in weight percent (wt%) over the total weight of the metal alloy.
According to the amount of gold, Metal alloy 1, Metal alloy 3 and Metal alloy 4 can be considered as a precious alloy of 14-karat gold, and Metal alloy 2 and Metal alloy 5 can be considered as a precious alloy of 18-karat gold.

Table 1
Metal alloy 1 | Au | Cu | Ag | Mn | Al | Total
Atomic percent (at%) | 34.4 | 25.9 | 22.8 | 9.6 | 7.3 | 100
Weight percent (wt%) | 58.4 | 14.2 | 21.2 | 4.5 | 1.7 | 100

Table 2
Metal alloy 2 | Au | Cu | Ag | Mn | Al | Total
Atomic percent (at%) | 52.5 | 20.3 | 15.2 | 6.5 | 5.5 | 100
Weight percent (wt%) | 75.1 | 9.3 | 12.0 | 2.6 | 1.0 | 100

Table 3
Metal alloy 3 | Au | Pd | Ag | Cr | Fe | Total
Atomic percent (at%) | 36.6 | 16.4 | 16.2 | 15.4 | 15.4 | 100
Weight percent (wt%) | 58.3 | 14.1 | 14.1 | 6.5 | 7.0 | 100

Table 4
Metal alloy 4 | Au | Ag | Cr | Pd | Co | Total
Atomic percent (at%) | 38.0 | 15.5 | 15.5 | 15.5 | 15.5 | 100
Weight percent (wt%) | 59.8 | 13.3 | 6.4 | 13.2 | 7.3 | 100

Table 5
Metal alloy 5 | Au | Ag | Pt | Pd | Fe | Total
Atomic percent (at%) | 67.0 | 8.25 | 8.25 | 8.25 | 8.25 | 100
Weight percent (wt%) | 77.47 | 5.22 | 9.45 | 5.15 | 2.71 | 100
The preparation of the metal alloys gathered in Tables 1-5 is described as follows.
Firstly, a molten alloy is formed (step i) in using an arc furnace, in placing and mixing all the metallic elements constituting a metal alloy, in a crucible.
After cooling to room temperature (around 25°C) the alloy obtained in step i, a rolling step is performed (step ii) at room temperature (around 25°C), with several passes, in using a roller mill.
The rolling step is of:
- 83% to obtain the Metal alloy 1,
- 90% to obtain the Metal alloy 2,
- 70% to obtain the Metal alloy 3,
- 70% to obtain the Metal alloy 4,
- 60% to obtain the Metal alloy 5,
The rolled alloy is under the form of a bar.

2. Characterization of the metal alloys
Some properties of the metal alloys obtained in the preparation as described above can be easily determined, such as entropy, ΔE and hardness.

2.1. Determination of the entropy
The entropy is determined following the equation ΔS_{conf}= - RΣX_iIn(X_i), where X_i represents the atomic fraction of element i and R is the molar gas constant.

2.2. Determination method of the color
In order to evaluate the color of a metal alloy, the CIELAB coordinates, which are well known as color space specified by the International Commission on Illumination (known in French with the acronym CIE), are used.
The three coordinates of CIELAB represent the lightness of the color (L* = 0 yields black and L* = 100 indicates diffuse white), its position between red/magenta and green (a*, negative values indicate green while positive values indicate magenta) and its position between yellow and blue (b*, negative values indicate blue and positive values indicate yellow).
To compare two different colors, or to characterize the evolution of a sample, the expression "ΔE*" can be used. ΔE* corresponds to the distance between two colors placed in the CIELAB color space which is calculated with the formula of the Euclidian distance. ΔE* can also be written ΔE or ΔE_{ab}.
ΔE* is classically known as follows:
Δ
E
*=
L
2
*
−
L
1
*
2
+
a
2
*
−
a
1
*
2
+
b
2
*
−
b
1
*
2
wherein:
L
1
*
,
a
1
*
,
b
1
*
are the coordinates of the first color to compare, and
L
2
*
,
a
2
*
,
b
2
*
are the coordinates of the second color to compare.
The illuminant used to evaluate the metal alloy color is the CIE D65 standard illuminant, with a viewing angle of 10°.
The evolution of the metal alloy color is studied according to the test Tuccillo-Nielsen wheel method, which aims at evaluating the tarnish testing of an alloy in contact with the skin. In this respect, the metal alloy is immersed during 30 seconds in artificial sweet and then dried in the open air during 30 seconds, in a continuous way. The artificial sweet composition used for the test is the composition according to European Committee for Standardization EN 1811, which is a solution of 0.5% NaCl, 0.1% urea and 0.1% lactic acid, with a pH adjusted to 6.5 using NH_4OH. Color measurements are taken at t=0, 4, 7, 15 and 25 days.
Finally, ΔE between t=0 and t=25 days is calculated. Hence, a low ΔE means a low color evolution.

2.3. Determination method of the hardness
In order to evaluate the hardness of a metal alloy, a Vickers micro-hardness tester on polished samples has been used. The samples have been indented linearly on the surfaces at five different positions and the average have been recorded. The indentation load was 2 kg with an indentation time of 10 seconds.
In the present invention, the hardness of the metal alloy can advantageously be of at least 200 HV, more preferably of at least 250 HV, and even more preferably of at least 300 HV. Said hardness (i.e. final hardness) is more particularly the one determined on the metal alloy obtained after the steps i, ii and optionally iii.
Another advantage is that the alloy obtained before the step ii can have a hardness of at least 200 HV. Said hardness (i.e. raw hardness) is more particularly the one determined on the alloy obtained in step i, or in other words, before step ii.

2.4. Results
In order to show the effects of the present invention, a comparative example has been performed (Metal alloy 6), and is gathered in the below table 6.
The amounts in Table 6 are expressed in weight percent (wt%) over the total weight of the metal alloy.

Table 6
Metal alloy 6 | Au | Ag | Cu | Total
Weight percent (wt%) | 58.5 | 26.5 | 15.0 | 100
The preparation of said Metal alloy 6 is similar to the preparation described in the above item 1, except that the rolling step (step ii) is of 75%.
The results are gathered in the following Table 7.

Table 7
| Metal alloy 1 | Metal alloy 2 | Metal alloy 3 | Metal alloy 4 | Metal alloy 5 | Metal alloy 6
Entropy | 1.47R | 1.29R | 1.47R | 1.52R | 1.29R | 0.99R
ΔE | 2.57 | 3.66 | Not measured | Not measured | 1.02 | 3.53
Raw hardness | 230 | 150 | 194 | 188 | 228 | 175
Final hardness | 330 | 320 | 253 | 237 | 246 | 260
1. Metal alloy comprising at least four metallic elements different from gold (Au), each of said metallic elements being in an amount from 1.0 to 55.0 atomic percent, characterized in that the metal alloy further comprises gold (Au) in an amount of at least 58.3 % by weight over the total weight of the metal alloy.
2. Metal alloy according to claim 1, characterized in that the metal alloy comprises at least 75.0 % by weight of gold (Au), over the total weight of the metal alloy.
3. Metal alloy according to any one of the preceding claims, characterized in that the metal alloy comprises from 5.0 to 30.0 atomic percent of each of said four metallic elements.
4. Metal alloy according to any one of the preceding claims, characterized in that the four metallic elements are selected among silver (Ag), aluminum (Al), manganese (Mn), copper (Cu), palladium (Pd), iron (Fe), chromium (Cr), platinum (Pt), and cobalt (Co).
5. Metal alloy according to claim 4, characterized in that the four metallic elements are copper (Cu), silver (Ag), manganese (Mn), and aluminum (Al).
6. Metal alloy according to claim 4, characterized in that the four metallic elements are palladium (Pd), silver (Ag), chromium (Cr), and iron (Fe).
7. Metal alloy according to claim 4, characterized in that the four metallic elements are silver (Ag), chromium (Cr), palladium (Pd), and cobalt (Co).
8. Metal alloy according to claim 4, characterized in that the four metallic elements are silver (Ag), cobalt (Co), palladium (Pd), and iron (Fe).
9. Metal alloy according to claim 4, characterized in that the four metallic elements are silver (Ag), platinum (Pt), palladium (Pd), and iron (Fe).
10. Metal alloy according to any one of the preceding claims, characterized in that the gold (Au) has a purity of at least 99.5 %, and more preferably of at least 99.9 %.
11. Process of manufacturing a metal alloy according to any one of the preceding claims, characterized in that the process comprises the following steps:
i. forming a molten alloy comprising gold (Au) and the at least four metallic elements different from gold,
ii. cold rolling the alloy obtained in step i, and
iii. optionally, annealing the alloy obtained in step ii.
12. Time-piece or jewel having a part or a component comprising the metal alloy according to any one of claims 1 to 11.
PP002341 WPE NR
EP
19306367.4
Richemont International SA
MN
20200210
C22C
C22F
A44C
CN
108588467
A
BEIJING CHUNSHU ELECTRONIC MAT CO LTD
20180928
X
1-4,10-12
A
5-9
* examples 1-3 *
US
2014328718
A1
RAYKHTSAUM GRIGORY [US]
20141106
X
1,2,4,10-12
A
3,5-9
* paragraphs [0001], [0019]; table 2 *
GB
372236
A
CARTIER SA
19320505
X
1,2,4,10-12
A
3,5-9
* examples 1,2 *
JP
2001207226
A
KYOCERA CORP
20010731
X
1,2,4,10-12
A
3,5-9
* examples 7,10,15,18; table 1 *
US
2018171436
A1
VINCENT DENIS [CH] ET AL
20180621
X
1-4,10-12
A
5-9
* paragraphs [0002], [0020], [0037], [0044], [0045]; table 1 *
EP
0008975
A1
LOUYOT COMPTOIR LYON ALEMAND [FR]
19800319
X
1-4,9-11
A
5-8,12
* pages 2,3,6,8; examples 2-13; table 1 *
US
5221207
A
SCHOECK GERNOT [DE] ET AL
19930622
X
1-4,10
A
5-9,12
* examples 1-13; table 1 *
Brown, Andrew
Munich
20200131
CN
108588467
A
20180928
NONE
US
2014328718
A1
20141106
NONE
GB
372236
A
19320505
NONE
JP
2001207226
A
20010731
NONE
US
2018171436
A1
20180621
CN
108203771
A
20180626
EP
3339455
A1
20180627
HK
1255967
A1
20190906
JP
6740204
B2
20200812
JP
2018100448
A
20180628
US
2018171436
A1
20180621
EP
0008975
A1
19800319
CH
640570
A5
19840113
EP
0008975
A1
19800319
ES
8200407
A1
19811101
FR
2434870
A1
19800328
US
5221207
A
19930622
AT
98466
T
19940115
AU
638609
B2
19930701
BR
9104248
A
19920602
CA
2052646
A1
19920404
DE
4031169
C1
19920423
DK
0478932
T3
19940221
EP
0478932
A1
19920408
ES
2047367
T3
19940216
GR
3023868
T3
19970930
IL
99631
A
19951231
JP
2525527
B2
19960821
JP
H04246140
A
19920902
US
5221207
A
19930622
ZA
917893
B
19930331

REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description
- WO
2019073023
A
[0003]