CH714882A1 - 14K gold alloy resistant to tarnishing and its production method. - Google Patents

Abstract

Alloy, in particular for Jewelery, characterized by the fact that it includes: - Gold in an amount between 540 620 and 620 peso in weight; - Copper in amounts between 360 ‰ and 415 peso in weight; - Palladium in amounts between 10 ‰ and 30 peso in weight.

Description

Illl II II II11111111111 II

SWISS CONFEDERATION

FEDERAL INSTITUTE OF INTELLECTUAL PROPERTY (11) CH 714 882 A1 (51) Int. Cl .: C22C 5/02 (2006.01)

Patent application for Switzerland and Liechtenstein

Patent Treaty of 22 December 1978 between Switzerland and Liechtenstein (12) PATENT APPLICATION (21) Application number: 00465/18 (71) Applicant:

ARGOR-HERAEUS SA, Via Moree, 14

6850 Mendrisio (CH) (22) Filing date: 12.04.2018 (72) Inventor / ln wind ri:

Sergio Arnaboldi, 23867 Suello (LC) (IT)

Marta Rossini, 22100 Como (IT)

Marco Nauer, 6834 Morbio Inferiore (CH) (43) Application published: 15.10.2019 (74) Authorized representative:

Ing. Emanuele Del Pero c / o PGA S.P.A., MILAN, Lugano Branch, Viale Castagnola, 21 / c 6900 Lugano (CH) (54) 14K gold alloy resistant to tarnishing and production method of the same.

(57) Alloy, in particular for jewelery, characterized in that it comprises:

- Gold in an amount between 540% »and 620%» by weight;

- Copper in an amount between 360% »and 415%» by weight;

- Palladium in an amount between 10% »and 30%» by weight.

CH 714 882 A1

Description

Field of the invention [0001] The present invention refers to the sector of gold alloys and in particular concerns a gold alloy with a gold title substantially equal to 14 carats (14K).

[0002] The present invention also relates to a method of producing a gold alloy.

[0003] The gold alloy and the gold alloy production method according to the invention are respectively an alloy and a gold alloy production method for jewelery and watchmaking applications.

Prior art [0004] In the jewelery and watchmaking sector, gold is not used in pure form as it is too flexible. For jewelery and watchmaking applications, gold alloys are typically used for jewelery or watchmaking, characterized by greater hardness than gold in pure form and / or compared to gold alloys with low hardness or high ductility.

[0005] It is known that, in general, gold alloys can undergo unwanted color changes over time, following interactions with aggressive environments. These interactions lead to the formation of thin layers of reaction products, which, remaining adherent to the surface of the alloy, cause an alteration of the color and brightness (document "Observations of onset of Sulfide tarnish on gold-base alloys"; JPD, 1971, Vol. 25, issue 6, pages 629-637).

[0006] There are many environments capable of promoting alterations in the color of gold alloys and are linked to their applications.

[0007] The colors of the gold alloys can be uniquely measured in the CIELAB 1976 color space, which defines a color on the basis of a first parameter L *, a second parameter a * and a third parameter b *, in which the first parameter L * identifies the brightness and assumes values between 0 (black) and 100 (white) while the second parameter a * and the third parameter b * represent chromaticity parameters. In particular, in the CIELAB 1976 color chart, the achromatic gray scale is identified by the points where a * = b * = 0; positive values for the second parameter a * indicate a color tending more to red the higher the value of the second parameter is; negative values for the second parameter a * indicate a color tending all the more to green the more the value of the second parameter a * is in absolute high value, even if negative; positive values for the third parameter b * indicate a color tending all the more to yellow the higher the value of the third parameter is; negative values for the third parameter b * indicate a color tending all the more to blue the more the value of the third parameter b * is in absolute high value, even if negative. Furthermore, it is possible to transform the second parameter a * and the third parameter b * into polar parameters defined as follows:

Cab * = 7 (a * ² + b * ² ) h-ab * [0008] The parameter C _ab * is defined as "chroma"; the higher the value of the parameter C _ab *, the greater the color saturation; the lower the value of the parameter C _ab *, the lower the color saturation, which will tend to grayscale. To the Applicant's knowledge, alloys with a Gold content higher than 750% or, which can be used as such as white or gray Gold alloys and do not require rhodium-plated surface treatments, arbitrarily present values of C _ab * <8. The parameter h _ab * instead identifies the hue of the color.

[0009] In particular, the ISO DIS 8654: 2017 standard defines seven color designations with regard to gold alloys for jewelery. In particular, these alloys are defined according to the following table, in which the color is defined on a standard reference named between ON and 6N.

Color Designation ON Yellow green 1N Dark yellow 2N Light yellow 3N Yellow 4N Rose 5N Red 6N Dark red

Table!

CH 714 882 A1 [0010] For the measurement of the color of a gold alloy, in particular, the ISO DIS 8654 standard states that the measuring device must comply with CIE publication N ° 15.

Furthermore, the ISO DIS 8654: 2017 standard tabulates the nominal values L *, a *, b * in trichromatic coordinates for the 0N-6N standard color alloys, including tolerances. Below is an extract of the standard which defines the color limits of the alloys defined by the ISO DIS 8654: 2017 standard as pink / red.

Color Trichromatic coordinates (2nd observer) Nominal values Tolerances L* to* b * L * [MAX / Min] to* b * 4N 88.9 6:13 21:23 90.6 7:48 22:45 6.63 19:44 87.1 4.89 19.98 5:48 23:06 5N 87.7 8:32 18:58 89.4 9.74 19:55 8.62 16.97 85.9 6.96 17:55 7.89 20:19 6N 86.3 10:13 15:57 88.1 11.65 16:44 10:14 14:06 84.4 8.70 14.65 9.99 17:12

Table 2 [0012] In relation to the previous table it is therefore possible to obtain, within the CIELAB 1976 color space, a plurality of areas, each of which represents the color ranges within which it is possible to assert that an alloy has a 0N color. ..6N and more specifically a 5N-6N color. These areas are represented in detail in fig. 1.

[0013] ISO DIS 8654: 2017 also proposes recommended chemical compositions for each of the 0N-6N alloys. Particularly for the pink / red alloys, the compositions are those shown in the table:

Color Chemical composition -% by weight Au ag Cu 4N 75.0 8.5-9.5 Remaining part 5N 75.0 4.5-5.5 6N 75.0 0-1.0

Table 3 [0014] The Applicant has observed that the known pink / red gold alloys have a substantial color instability, in particular when exposed to environments where chlorides or sulphides are present.

[0015] Variations in the color of a gold alloy according to the color as defined on the CIE 1976 color card and expressed by the coordinate E = f (L *, a *, b *), defined:

- L * _or as the first parameter in original conditions, at time t ₀ = 0;

- a * or as second parameter in original conditions, at time t ₀ = 0;

- b * _or as third parameter in original conditions, at time t ₀ = 0; are defined by the following equation:

àE (L *, a *, b * ') = V (L * - Γ ₀ ) ² + (a * - a $) ² + (è * - b * ₀ ) ² [0016] It has also been observed that l the human eye of a technician expert in precious materials is able to distinguish color variations ΔΕ (L *, a *, b *)> 1.

In particular, the Applicant has observed that the 5N ISO DIS 8654: 2017 Gold alloy in the formulation that uses the minimum reference value as regards the Silver content, exposed to thioacetamide vapors for 150 hours (according to the UNI EN ISO 4538: 1998 standard), has a color variation ΔΕ (L *, a *, b *) equal to 5.6; when

CH 714 882 A1 exposed to the action of an aqueous solution 50g / liter of Sodium Chloride (NaCI) at 35 ° C for 175 hours, the 5N Gold alloy shows a color variation ΔΕ (L *, a *, b * ) equal to 3.6.

There are also known alloys for jewelery, comprising gold with a title equal to or substantially equal to 14K. These gold alloys are typically used to make jewels of lower value than those made with 18K gold alloys or higher. In particular, among the alloys comprising Gold with a title equal to or substantially equal to 14K, there are known alloys containing Copper, apt to appear with a pink or red color, according to an increasing percentage of Copper in the alloy.

[0019] In alloys comprising Gold with a title equal to or substantially equal to 14K, it is known that the presence of Copper has the disadvantage of being rather prone to varying color in particular when the jewelry object is worn and exposed to human sweating and / or saline environment. The same alloys, including gold with a titer equal to or substantially equal to 14K, are known to have significant color variation even only after exposure in the air.

For this reason, typically jewelery items made with alloys comprising Gold with a title equal to or substantially equal to 14K, in particular when comprising Copper, are covered with a plating with Gold alloys with a title significantly higher than 14K, typically for example at 18K. This plating has some further drawbacks. A first drawback derives from the fact that it is difficult to create a plating whose color is perfectly superimposable to that of the base alloy with which the jewelry object is made.

Furthermore, the plating of a jewelry item with high gold alloys is expensive, and contributes significantly to the increase in the production cost of the object not only because of the cost of the high gold alloy itself, but also because of the further processing necessary on the jewelry object, which incidentally for forms of jewelry objects of considerable complexity, may not be trivial.

[0022] Finally, the plating, representing the surface layer of the object, is the portion most subject to wear or in any case removal; with the removal of the plating, the jewelry object may have exposed portions of alloy with a Gold title equal to or substantially equal to 14K, which - exposed to chemically aggressive environments - may have a different color than the portions that still carry the alloy of plating.

The purpose of the present invention is therefore to describe a gold alloy, in particular for jewelery and watchmaking, with a gold title equal to or substantially equal to 14K, which solves the drawbacks described above, in particular being poorly prone color when exposed to environments with air, Thioacetamide or NaCI in solution.

[0024] The object of the present invention is also to describe a method of production of an alloy containing Gold with a titer equal to or substantially equal to 14K, which solves the drawbacks described above.

Finally, the purpose of the present invention is to describe a jewelry object or part of an object for jewelry, made with the alloy object of the invention, which does not have the drawbacks described above.

Summary [0026] These and further objects are obtained by the alloy and the production method of the same described in the following aspects.

[0027] A first aspect of the invention forms an alloy, in particular for jewelery, characterized in that it comprises:

- Gold in an amount between 540% or 620% or by weight;

- Copper in an amount between 360% or 415% or by weight;

- Palladium in an amount between 10% or 30% or by weight.

[0028] The said alloy in particular can consist of:

- Gold in an amount between 540% or 620% or by weight;

- Copper in an amount between 360% or 415% or by weight;

- Palladium in an amount between 10% or 30% or by weight and, optionally, at least one of Silver in an amount less than or equal to 80% or by weight, Zinc in an amount less than or equal to 80% or by weight, Indium in an amount less than or equal to 20% or by weight, tin in an amount less than or equal to 20% or by weight, iron in an amount less than or equal to 15% or by weight, gallium in an amount less than or equal to 10% or by weight , Iridium or Ruthenium in an amount less than or equal to 0.5% or by weight, Rhenium in an amount less than or equal to 0.1% or by weight.

According to the present invention, "alloy for jewelry" means an alloy, in particular a gold alloy, in which materials toxic to humans are absent and whose formulation is suitable for, specifically designed for , making jewels, or parts of them. In particular, an alloy for jewelery is an alloy that presents, in the absence of work hardening, a hardness, measured on the Vickers scale and in particular with the HV5 method, greater than 95, preferably greater than 98.

[0030] In accordance with a non-limiting 2nd aspect, the alloy according to the first aspect is a gold alloy characterized by a pearly red color. According to the present invention, "pearly red" is arbitrarily meant to be a color which, in terms of color a *, b * according to the CIE 1976 color chart, is not included in the intervals defined by ISO DIS 8654: 2017 and is enclosed within a polygon at least defined by the following points (Fig. 1):

CH 714 882 A1

Color Trichromatic coordinates (2nd observer) It goes nominal golds 'olleranze L* to* b * L * [MAX / Min] to* b * pearly red 86.1 8 11.60 87.8 6.5 10.8 8.2 10.3 84.3 9.5 12.7 7.7 13.5

Table 4 [0031] According to the third non-limiting aspect, the alloy according to the first or second aspect is a tarnishing-resistant alloy and / or has a lower color variation in NaCI saline solution, optionally after a time equal to at least 24 hours of exposure, compared to the color change undergone by a reference alloy with a Silver content of 40% oe / o compared to the 5N alloy according to the ISO DIS 8654: 2017 standard.

In accordance with a 4th non-limiting aspect, the alloy according to one or more of the foregoing aspects comprises Palladium in an amount comprised between 12% or, more preferably 15% or by weight, and 27% or, more preferably 25% or by weight.

In accordance with a 5th non-limiting aspect, the alloy according to one or more of the foregoing aspects further comprises Iron in an amount ranging from 2% or by weight to 15% or by weight, more preferably between 4% or by weight and 13% or by weight, even more preferably between 5% or by weight and 10% or by weight.

[0034] According to a 6th non-limiting aspect, the alloy according to one or more of the previous aspects is a ternary or quaternary alloy, and / or the sum of the amounts of Gold, Copper and Palladium is at least equal to 910% or by weight.

According to the present invention, by ternary or quaternary gold alloy is meant an alloy in which there are respectively 3 or 4 components whose amount is not negligible, and in particular higher than 2% or by weight and more preferably higher at 1% or by weight. In other words quaternary or quinary alloys do not include components in excess of 2% or by weight and more preferably 1% or by weight in addition to those explicitly mentioned.

In accordance with a 7th non-limiting aspect, the alloy according to the sixth aspect has a sum of the amounts of Gold, Copper and Palladium at least equal to 950% or by weight, more preferably 960% or by weight, still more preferably 970% or by weight.

[0037] According to an 8th non-limiting aspect, in the alloy according to one of the previous aspects when dependent on the 5th, the sum of the amounts of Palladium and Iron is equal to or less than 37% or by weight, more preferably less than 35 % or by weight.

[0038] According to a 9th non-limiting aspect, in the alloy according to one of the previous aspects when dependent on the 5th, the Iron is comprised in an amount comprised between 5% o and 10% o.

[0039] According to a 10th non-limiting aspect, in the alloy according to one or more of the previous aspects, the Gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% o by weight and 595% o by weight, and Copper is present between 370% o and 405% o by weight, and Palladium is between 12% or, more preferably 15% o by weight, and 27% or more preferably 25% or by weight.

[0040] According to an 11th non-limiting aspect, in the alloy according to one or more of the previous aspects when dependent on the 5th aspect, the Gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% o by weight and 595% o by weight, and the Copper is present between 370% o and 405% o by weight, and the sum of the amounts of Palladio and Ferro is between 23% o and 27 % o, even more preferably substantially equal to 25% o.

[0041] According to a 12th non-limiting aspect, in the alloy according to one of the aspects from 1st to 3rd and / or from 5th to 9th, Palladium is present in an amount between 13% or by weight and 17% by weight, preferably between 14% by weight and 16% by weight and even more preferably in an amount substantially equal to 15% or by weight.

[0042] According to a 13th non-limiting aspect, in the alloy according to the 12th aspect and according to the 5th aspect, the Gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and the Copper is present between 370% and 405% or by weight, and the sum of the amounts of Palladium and Iron is between 25% and 30% or.

According to a 14th non-limiting aspect, in the alloy according to the 12th aspect and according to the 5th aspect, the Gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and the Copper is present between 370% and 405% or by weight, and the sum of the amounts of Palladium and Iron is between 30% and 35% or.

CH 714 882 A1 [0044] According to a 15th non-limiting aspect, the alloy according to the 6th aspect also includes Silver in an amount less than 40% or by weight, and / or Zinc in an amount less than 40% or by weight o Silver and Zinc whose sum of the respective amounts by weight is less than 40% o.

In particular, according to a 16th non-limiting aspect, the alloy according to the 10th aspect is iron-free.

[0046] According to a 17th non-limiting aspect, the alloy according to one or more of the previous aspects is an alloy whose color, on the CIELAB1976 color paper, has a coordinate a * included in the range [6.5-9.5] and a coordinate b * <13.5, preferably in the range [10-13.5].

[0047] According to an 18th non-limiting aspect, the alloy according to one or more of the previous aspects is an alloy characterized by the absence of Vanadium and other materials capable of generating carbides and oxides, in particular free of Magnesium, Silicon , Titanium, Tungsten, Molybdenum, Niobium, Tantalum, Zirconium, Yttrium, Germanium. Thanks to this aspect it is possible to prevent the formation of carbides.

[0048] According to a 19th non-limiting aspect, the alloy according to one or more of the previous aspects, is a gold alloy for jewelery free of Nickel, Cobalt, Arsenic and Cadmium. Thanks to this aspect, the alloy is a gold alloy worn by subjects whose allergic tolerance is significantly low.

[0049] In accordance with a 20th independent aspect, the method of production of a gold alloy is also the object of the invention; said method is characterized in that it comprises:

a) a step (hereafter defined as homogenization) in which all the pure elements making up the alloy are melted in such a way as to obtain a homogeneous solution or mixture; this mixture comprises at least by weight:

- Gold in an amount between 540% or 620% or by weight;

- Copper in an amount between 360% or 415% or by weight;

- Palladium in an amount comprised between 10% or 30% or by weight, to form a mixture; is

b) a step of introducing the mixture into a melting crucible, and of a subsequent melting by heating until melting.

[0050] According to a 21 ° non-limiting aspect, dependent on the previous 20 ° aspect, the said step comprises mixing in particular Palladio in an amount comprised between 12% or, more preferably 15% or by weight, and 27% or, more preferably 25% or by weight.

[0051] In accordance with a 22 ° non-limiting aspect, dependent on one or more of the previous 20 ° -21 ° aspects, it includes in particular mixing, in addition to the previous elements, also Iron in an amount between 2% or 15 % o by weight, more preferably between 4% o and 13% o by weight, even more preferably between 5% o and 10% o by weight.

[0052] According to a 23rd non-limiting aspect, the alloy according to one or more of the previous aspects from the 20th to the 22nd, the sum of the amounts of Gold, Copper and Palladium is at least equal to 910% or in weight.

[0053] According to a 24th non-limiting aspect, the alloy according to the 23rd aspect has a sum of the amount of Gold, the step includes mixing Copper and Palladium in an amount at least equal to 950% or by weight, more preferably 960% or by weight.

According to a 25th non-limiting aspect, the alloy according to the 22nd aspect comprises mixing the aforementioned elements with an amount of the sum of Palladium and Iron equal to or less than 37% or by weight, more preferably less than 35% or by weight.

[0055] According to a 26th non-limiting aspect, dependent on the aforementioned 22nd aspect or on one of the aspects dependent on it, the method comprises mixing iron in an amount comprised between 5% o and 10% o.

[0056] According to a 27th non-limiting aspect, when dependent on one or more of the 18th and following aspects, the method comprises mixing the Gold in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and Copper in an amount between 370% or 405% or by weight, and Palladium in an amount between 12% or, more preferably 15 % or by weight, and 27% or, more preferably 25% or by weight.

[0057] According to a 28th non-limiting aspect, dependent on one or more of the previous aspects when dependent on the 22nd aspect, the method includes mixing the Gold in an amount comprised between 565% or by weight and 605% or by weight , and more preferably between 575% or by weight and 595% or by weight, and Copper in an amount between 370% or 405% or by weight, and the sum of Palladium and Iron in an amount between 23% oe 27% or by weight, even more preferably substantially equal to 25% or by weight.

[0058] According to a 29th non-limiting aspect, dependent on one or more of the previous 18 ° -20 ° and 22 ° aspects, the method comprises mixing Palladio in an amount comprised between 13% or by weight and 17% or by weight, preferably between 14% or 16% or by weight and even more preferably in an amount substantially equal to 15% or by weight.

According to a 30 ° non-limiting aspect, dependent on the 22 ° aspect and the 29 ° aspect, the method comprises mixing the Gold in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, Copper in an amount between 370% or 405% or by weight, Palladium and Iron in an amount whose sum is between 25% or 30% or by weight.

CH 714 882 A1 [0060] According to a 31st non-limiting aspect, dependent on the 22nd and 29th aspects, the method includes mixing the Gold in an amount between 565% or by weight and 605% or by weight, and more preferably between 575% or 595% or by weight, and Copper in an amount between 370% or 405% or by weight, and the sum of Palladium and Iron in an amount between 30% or 35% or in weight.

[0061] According to a 32 ° non-limiting aspect, the alloy according to one or more of the previous aspects starting from the 20 °, the method comprises obtaining an alloy whose color, optionally at the time of cooling, on the color paper CIELAB1976, has a coordinate a * in the range [6.5-8.8] and a coordinate b * <13, preferably in the range [10-13].

[0062] According to a 33 ° non-limiting aspect, dependent on one or more of the previous aspects starting from the 20th, the method excludes the mixing of Vanadium and other materials capable of generating carbides and oxides, in particular without Magnesium, Silicon, Titanium, Tungsten, Molybdenum, Niobium, Tantalum, Zirconium, Yttrium, Germanium. The absence of such carbides or oxides, in particular but not limited to processing, makes the gold alloy suitable for jewelery and watchmaking applications where polishing or diamond-coating of finished objects is required.

[0063] According to a 34th non-limiting aspect, dependent on one or more of the aspects starting from the 20th, depending on one or more of the previous aspects starting from the 33rd, the method excludes the mixing of Nickel, Cobalt , Arsenic and Cadmium. Thanks to this aspect, the alloy is a gold alloy that can be worn by subjects whose allergic tolerance is significantly low.

[0064] According to a 35th non-limiting aspect, dependent on one or more of the aspects starting from the 20th, said homogenization is a discontinuous melting, comprising a casting phase in which the molten material is poured into a refractory form or refractory or metal ingot mold.

According to a 36th aspect, dependent on one or more of the aspects starting from the 20th, during said melting, the melting crucible is subjected to a controlled atmosphere of gas and in particular is subjected, at least temporarily, under vacuum conditions.

According to a 37th non-limiting aspect, dependent on one or more of the aspects starting from the 20th, in said casting phase said crucible is subjected to a controlled atmosphere, at pressures lower than the environmental one.

[0067] According to a 38th non-limiting aspect, dependent on one or more of the aspects starting from the 20th, the said controlled atmosphere is an inert gas preferably argon and / or the said pressure is a pressure lower than 800 mbar, preferably less than 700 mbar.

According to a 39th non-limiting aspect, dependent on one or more of the aspects starting from the 20th, said gas is a gas preferably reducing a hydrogen-nitrogen mixture and / or said pressure is a pressure lower than 800 mbar, preferably less than 700 mbar.

[0069] According to a 40th non-limiting aspect, said casting is a continuous casting, comprising a melting and homogenization phase in a graphite crucible and a subsequent casting phase in which the molten alloy is poured into a realized die in graphite and wherein said alloy is an alloy of metals chemically not similar to graphite and more specifically, in particular at least free of Vanadium, Magnesium, Silicon, Titanium, Tungsten, Molybdenum, Niobium, Tantalum, Zirconium, Yttrium, Germanium.

[0070] The absence of elements chemically similar to graphite allows an excellent flow of the molten alloy within the die and facilitates its extraction after solidification. On the contrary, the presence of elements chemically similar to graphite, causes an adhesion effect of the alloy to the die, preventing its extraction. Furthermore, the absence of carbides and oxides makes the gold alloy suitable for jewelery and watchmaking applications where the polishing or diamond-coating of finished objects is required.

[0071] According to a 41 ° non-limiting aspect, dependent on one or more of the aspects starting from the 20th, following continuous or discontinuous casting, said alloy is subjected to a cooling step followed by one or more steps hot or cold plastic deformation and one or more heat treatments.

[0072] In accordance with a 42nd aspect, the object of the present invention also forms a jewelry object, comprising a gold alloy in accordance with one or more of the previous aspects concerning the said gold alloy.

According to a 43 ° aspect dependent on the previous aspect, the said jewelry object comprises a jewel or a watch or a bracelet for a watch or a movement or part of a mechanical movement for a watch.

According to a 44th aspect, dependent on the previous aspect, the said watch or mechanical movement for a watch are configured to be worn or installed in wristwatches respectively.

[0075] According to a 45 ° aspect, a production method of an object for jewelery or part of an object for jewelery is made, said method being characterized in that it comprises one or more mechanical working steps of a gold alloy according to one or more of the aspects from 1st to 19th.

CH 714 882 A1

Description of the drawings [0076] The invention will be described below in preferred and non-limiting embodiments, the description of which is associated with the annexed figures in which:

Fig. 1 illustrates a portion of the CIE 1976 color space in accordance with the coordinates L *, a *, b * in which an area corresponding to permissible color ranges or tolerances for gold alloys is identified in accordance with the ISO DIS 8654: 2017 standard 5N and 6N, and in which the typical color position for alloys object of the present invention is represented;

Fig. 2 shows a color variation diagram according to the exposure time to saturated sodium chloride solution for part of the alloys object of the present invention in relation to the color variation assumed by the 5N alloy according to ISO composition used as reference sample and in relation the change in color of a 14K ternary red alloy Gold, Silver and Copper of reference (LRS 503, defined below in Tab.6);

Fig. 3 shows a color variation diagram according to the exposure time to Thioacetamide according to UNI EN ISO 4538 for part of the alloys object of the present invention, in relation to the color variation assumed by the 5N alloy according to ISO composition used as reference sample and in relation to the color variation of a 14K ternary red alloy Gold, Silver and Copper of reference (LRS 503, defined below in Tab.6).

Detailed description of the invention [0077] First of all the object of the invention is a family of gold alloys, in particular for jewelery, with a gold title substantially between 13K and 15K, which have tarnishing resistance characteristics.

The alloys which are described in the present invention have been tested in terms of resistance to color variation (tarnishing) in environments comprising solutions of Thioacetamide and Sodium Chloride (NaCI). In this description, any reference to tests carried out in an environment including Thioacetamide is carried out in accordance with the indications of the UNI EN ISO 4538: 1998 standard. For the purpose of carrying out the tests, according to the present invention, the specimens are exposed to thioacetamide ch3csnh2 vapors in an atmosphere with relative humidity of 75% maintained through the presence of a saturated solution of sodium acetate tri-hydrate CH ₃ COONa 3H ₂ O in a test chamber whose capacity must be between 2 and 20 liters and in which all the materials used for the construction of the chamber must be resistant to volatile sulphides and must not emit any gas or vapor that could influence the test results.

[0079] As regards the evaluation of the resistance to corrosion and color variation in environments characterized by the presence of Sodium Chloride solutions, the tests were carried out by immersing the samples of a Gold alloy in a 50g / L NaCI solution. at neutral pH, thermostated at 35 ° C.

[0080] In order to obtain tarnishing resistance properties, in particular in environments comprising solutions of Thioacetamide and NaCI in accordance with the regulations described above and likewise obtaining a gold alloy whose color, measured in accordance with ISO DIS 8654 : 2017 is contained in the range of colors defined as "pear red", the applicant conceived a family of gold alloys comprising:

- Gold in an amount between 540% or 620% or by weight;

- Copper in an amount between 360% or 415% or by weight;

- Palladium in an amount between 10% or 30% or by weight.

[0081] More specifically, preferably but not limited to, the gold alloy according to the invention can consist of: Gold in an amount between 540% or 620% or by weight; Copper in an amount between 360% or 415% or by weight; Palladium in an amount between 10% or 30% or by weight; Palladium in an amount between 10% or 30% or by weight and, optionally, at least one of Silver in an amount less than or equal to 80% or by weight, Iron in an amount less than or equal to 15% or by weight, Zinc in a lesser amount or equal to 80% or by weight, Iridium or Ruthenium in an amount less than or equal to 0.5% or by weight, Rhenium in an amount less than or equal to 0.1% or by weight, Tin in an amount less than or equal to 20% or by weight .

According to the present invention, "tarnishing" means a surface corrosion of the gold alloy which causes a variation in the coloring of the alloy.

[0083] The family of gold alloys object of the invention includes at least ternary alloys, and more particularly ternary or quaternary alloys. Therefore, the number of elements that are included in a not negligible amount in the family of gold alloys object of the invention is at least equal to 3 and, preferably, not greater than 4, although quinary formulations may still be possible and include elements not included in the previous table.

The Applicant has carried out numerous experiments to evaluate the tarnishing resistance and the color of the alloys thus obtained, and in particular has carried out experiments on the specific embodiments indicated in the following table:

CH 714 882 A1 [0085]

Nominal composition [% o] League LRS Au ag Cu Pd Fe In Total 14 K 501 585.5 394.5 20 1000 502 585.5 389.5 25 1000 509 585.5 389.5 20 5 1000 510 585.5 384.5 20 10 1000 511 585.5 389.5 15 10 1000

Table 5 [0086] In the previous table, as in the other tables of the present description, where the cells are empty, it is meant that the content of the respective element is equal to zero.

[0087] The alloys according to the previous formulations are preferred and non-limiting examples of gold alloy for jewelery with a title equal to or substantially equal to 14K. The tarnishing resistance tests that have been carried out by the Applicant and that are shown below have been carried out with respect to a reference alloy, in particular a ternary reference alloy comprising Gold, Copper and Silver, therefore not optimized for tarnishing resistance by nature of its composition, shown below:

Reference alloy nominal composition [% o] LRS 503 Au ag Cu Pd Fe Total 585.5 40 374.5 1000

Table 6 [0088] The alloys according to the family generally described as the object of the invention and, consequently, the specific realizations described in table 5 are realizations preferably characterized by the absence of Silver. Silver is known to be a material that contributes to increasing the hardness of the alloy. By way of example, the LRS 503 alloy subject of the reference test has a hardness according to HV5 equal to 130 in the absence of work hardening, equal to 173 with work hardening at 25%, equal to 230 with work hardening at 50% and equal to 258 with work hardening equal to 75%. In particular, for the alloys listed in table 5, an alternative solution to silver was sought, which could also contribute to maintaining the hardness of the specific formulation of alloy suitable for jewelry applications, such as to make the formulation "for jewelry" as according to the previous definition, avoiding the tarnishing tendency that silver brings for the alloys where it is contained.

The following table illustrates the hardnesses obtained for the specific alloy formulations according to the present invention, as well as for the alloy LRS 503 used as a reference test.

work hardening HV5 0 25 50 75 501 127 173 220 240 502 119 175 231 244 503 130 173 230 258 509 129 171 225 242 510 125 171 232 248 511 135 180 235 251

Table 7 [0090] The Applicant has observed that the specific gold alloy formulations described in table 7 have hardness, in particular in the annealed state, compatible with that of jewelery alloys according to the present invention. In particular, the LRS 509 and LRS 511 formulations are respectively the closest to the behavior in terms of hardness possessed by the LRS 503 (whose alignment in the table is offset for ease of representation) used as a reference test, and even better, at least up to a work hardening equal to 50% with respect to the behavior obtained by the LRS 503 alloy. The Applicant has therefore found that for alloys with a Gold title equal to or substantially equal to 14K, and in particular for the specific constructions tested, it is possible to replace the Silver with mixtures of Palladium and Iron, to obtain the same or higher performances in terms of hardness, moreover with less quantity of extra elements compared to Gold

CH 714 882 A1 and Copper. In fact, specifically for the case of the formulation LRS 511, the sum of the amounts of Palladio and Ferro is equal to 35% or, while in the case of LRS 503, used as a reference test, the silver was equal to 40% or .

[0091] From an observation of the behavior in terms of hardness between the formulation LRS 509, LRS 510 and the formulation LRS 511, it has also been observed that the iron and copper content, taken in sum, is decisive in increasing the hardness. .

[0092] The Applicant has observed how it will be better described later that all the alloys object of the invention and belonging to the family mentioned above, and in particular but not limited to the alloys object of table 5, have performances in Air, in Thioacetamide and in NaCI solution under the above conditions, in terms of resistance to color variation, better than what can be obtained with the LRS 503 alloy used as the reference test The graphs in fig. 2 and fig. 3 respectively illustrate the evolution of the color of some specific alloy formulations as the number of hours of exposure to saline solution of NaCl and Thioacetamide increases as per the specifications highlighted above.

[0093] All the alloys according to the general formulation, and in particular all the specific realizations of the alloys according to table 5, exhibit better behavior, both in NaCI solution and in Thioacetamide, than the LRS 503 alloy used as reference test . This shows that the elimination of silver, among other things, is beneficial for reducing the tendency of the alloy to turn color when exposed to a chemically aggressive environment. In fact, although the alloy used as a reference test has a color that is not compatible with that of the alloys object of the invention, these latter alloys have a tendency to turn significantly lower color.

[0094] Surprisingly, the Applicant has observed that the alloys according to the general formulation presented above, and in particular all the specific realizations of the alloys according to table 5 show a behavior in NaCI saline solution as per the specifications highlighted above even better than the behavior obtained by the 5N alloy according to the ISO standard, whose Gold content is significantly higher, being in fact equal to 18K.

In particular, the Applicant has observed that the optimization of the behavior of the alloy in terms of tarnishing is optimized - in the ranges identified in the previous family, for Palladium values included in the following range: [8% or -32% o] by weight, and even more preferably for Palladium values in the range [10% or -30% o] by weight.

In particular, it has been observed that in NaCI saline solution the absolute best behavior in terms of resistance to color variation, in particular for exposures greater than 5 hours, is that of alloy LRS 502, which includes the highest content of Palladio among the specific formulations of table 5 and is characterized by the absence of iron; although iron is known for optimizing the performance of alloys in an environment containing thioacetamide ((WO 2014/0 872 216 A1), the Applicant has surprisingly found that the LRS 509 alloy, as well as the LRS 510 alloy, despite having both Iron in measure respectively equal to 5% «and 10% or they have performances substantially similar to those of the alloy according to the formulation LRS 502 and better than those of the alloy according to the formulation LRS 501, ternary, which only presents Palladio in an amount equal to 20% or. experimental tests carried out show that sums of iron and palladium equal to or substantially equal to 25% or in a ternary gold-copper-palladium or quaternary gold-copper-palladium-iron alloy, lead to an optimization of the characteristics in terms of resistance to the variation of color.

The following table describes the color variation characteristics ΔΕ (L *, a *, b *) according to the exposure time in saline solution of NaCl.

Time (h) ΔΕ 0 2 6 24 5N 12:00 1:58 1.85 2:07 LRS 501 12:00 00:43 0.95 1:39 LRS 502 12:00 00:55 0.70 1:00 LRS 503 (Ref.14K) 12:00 1:37 1:59 1.80 LRS 509 12:00 00:37 0.75 1:08 LRS 510 12:00 0.71 0.80 1:14 LRS 511 12:00 0.64 0.82 1:35 Ella abella 8

Vice versa, as represented in the diagram of fig. 3, in Thioacetamide an alloy such as those object of the present invention fails to present a resistance to the color variation equal to that which is typical of an 18K Gold alloy such as ISO 5N, which after 24 hours of exposure presents a variation of color ΔΕ (L *, a *, b *) substantially equal to 3.6, while all the tested alloys - and more generally the alloys according to the general formulation expressed above - have in the same conditions a color variation greater than ΔΕ ( L *, a *, b *)> 4. However, the alloys object of the invention exhibit a significantly better behavior than the alloy LRS 503 used as a reference test, which after 24h of exposure in Thioacetamide presents an equal color variation to 6.20.

CH 714 882 A1 [0099] The alloy with the best behavior in Thioacetamide is the alloy according to the formulation LRS 511, which after 24 hours of exposure presents in particular a color variation ΔΕ (L *, a *, b *) = 4.56 . From a comparison with the alloy according to the formulation LRS 510, which has the same iron content, but a variation in color which in the above mentioned conditions is equal to ΔΕ (L *, a *, b *) = 5.80 it is clear that for par Iron content, the increase in Palladium's title contributes to worsening the alloy's performance in terms of resistance to color variation in Thioacetamide.

[0100] The following table describes the color variation characteristics ΔΕ (L *, a *, b *) according to the exposure time in Thioacetamide.

[0101]

Time (h) 0 2 4 8 24 5N 12:00 0.67 1.82 2:39 3.61 LRS 501 12:00 0.90 1:30 3.90 5:22 LRS 502 12:00 0.77 1:45 3.88 5:35 LRS 503 (Ref.l4K) 12:00 0.84 2:06 4.68 6:20 LRS 509 12:00 00:58 1.77 3.98 5:40 LRS 510 12:00 00:45 1:54 4:01 5.80 LRS 511 12:00 0.73 1:42 3:26 4:56 Tabe the 9

[0102] In order to reduce the risk that the inclusion of third elements in the previous family of alloys could lead to unpredictable behavior, the Applicant has observed that preferably the alloy must be ternary or quaternary, with the necessary presence of Palladio and with the sum of the amounts of Gold, Copper and Palladium at least equal to 900% or by weight. The remaining 100% or by weight can be of different materials, including Silver or Zinc or combinations of Silver or Zinc in order to vary at least the specific color of the alloy while remaining within the color previously defined as "pear red".

[0103] As can be seen from the graph in fig. 1, all the alloys object of the invention, in particular included in the previous general formulation and even more in particular the specific realizations of table 5 are enclosed in the box generally defined as "pear red". The following table shows the values of the coordinates L *, a *, b * for the alloys object of the invention and for the alloy used as a reference test.

Observer 2nd L* to* b * 501 85.4 8.8 11.9 502 84.9 8.3 11.4 503 (ref.14k) 87.1 9.6 15.2 509 85.4 8.0 11.7 510 85.7 7.4 11.6 511 85.6 7.8 12.2

Table 10 [0104] From the previous table 10 it is clear that the alloy LRS 503 used as the reference test is the only one to have a significantly distinct color with respect to the others, and which, moreover, is not "pearled red" within the meaning of the present invention, since it falls within the tolerance limits defined for alloys whose color complies with the 6N ISO standard.

[0105] In particular, all the embodiments specifically identified in table 5 are specific optimized embodiments drawn from a subfamily of alloys in which the sum of the amounts of Gold, Copper and Palladium is at least equal to 960% or by weight and, still more preferably 970% or by weight; alloys with this last characteristic exhibit a similar behavior overall, observing the color variations in air, in Thioacetamide and in NaCL solution [0106] In developing the alloys subject to the specific formulations of table 5, alloys were conceived according to a first subfamily which includes Palladio in an amount comprised between 12% or, more preferably 15% or by weight, and 27% or, more preferably 25% or by weight.

CH 714 882 A1 [0107] Furthermore, starting from the alloys according to the general formulation expressed above, alloys which include Iron in an amount ranging from 2% or by weight and 15% or by weight, more preferably between 4% or by weight and 13% or by weight, even more preferably between 5% or by weight and 10% or by weight.

[0108] In particular, the general formulation, as well as the alloys according to table 5, includes formulations whose sum of the amounts of Palladium and Iron is equal to or less than 37% or by weight, more preferably less than 35% or by weight. The presence of iron and palladium in an amount less than 37% or by weight, more preferably less than 35% or contributes to optimizing the tarnishing resistance in thioacetamide and in NaCL saline solution In particular, when iron is included in an amount between 5% o and 10% o, especially with Palladio in an amount equal to or substantially equal to 20% o, the performance of Thioacetamide alloys has improved.

[0109] Part of the family in the general formulation of the invention, and within which the specific formulations of the Gold alloy according to table 5 are also included, in particular a subfamily of alloys is highlighted in which Gold is present in amount between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and the Copper is present between 370% and 405% or by weight, and Palladium is comprised between 12% or, more preferably 15% or by weight, and 27% or, more preferably 25% or by weight. All these alloys have a better performance in Thioacetamide and in NaCl saline solution compared to the reference alloy LRS 503 in terms of resistance to color variation.

[0110] A subfamily of alloys has also been studied in which Gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and Copper is present between 370% o and 405% o by weight, and the sum of the amounts of Palladio and Ferro is between 23% o and 27% o, even more preferably substantially equal to 25% o. The presence of Palladium and Iron in the amounts described above contributes to optimizing the performance of the alloy in saline solution of NaCl, in particular for low iron contents, in an amount equal to or substantially equal to 5% or.

[0111] Where iron is also present, it is possible to make alloy families in which gold is present in an amount ranging from 565% or by weight to 605% or by weight, and more preferably between 575% or by weight and 595. % o by weight, and the Copper is present between 370% o and 405% o by weight, and the sum of the amounts of Palladio and Ferro is between 25% o and 30% o.

[0112] Otherwise it is the case in which Palladium is present in an amount between 13% and 17% or by weight, preferably between 14% and 16% or by weight and even more preferably in an amount substantially equal to 15 % or by weight. In fact, in particular if the iron is in an amount substantially equal to 10% o, the performance of the thioacetamide alloy is substantially maximized. Therefore, with maximized performance, it is possible to make gold alloys for jewelery in which gold is present in an amount between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and the Copper is present between 370% »and 405% or by weight, and the sum of the amounts of Palladio and Ferro is between 30% or 35% o [0113] It is possible to alternatively make alloys of Gold according to the formulation generally expressed above wherein Silver in an amount less than 40% or by weight, and / or Zinc in an amount less than 40% or by weight or Silver and Zinc whose sum of the respective amounts by weight is less than 40 %or.

[0114] The alloys according to the general formulation set out above, in particular, have a color which, on the CIELAB1976 color paper, has a coordinate a * in the range [6.5-9.5] and a coordinate b * <13.5, preferably within the range [10-13.5].

[0115] In alloys according to the general formulation above, the absence of Vanadium allows to avoid the formation of carbides and oxides; preferably but not limited to, the alloy according to the invention is also free of Magnesium, Silicon, Titanium, Tungsten, Molybdenum, Niobium, Tantalum, Zirconium, Yttrium, Germanium, and is also free of Nickel, Arsenic and Cobalt. Thanks to this last aspect, the alloy is a gold alloy compatible with being worn or wearable by subjects whose allergic tolerance is significantly low.

[0116] Without prejudice to the exclusion of unwanted impurities, the alloys according to the invention can comprise further materials in a total amount, that is in sum, not more than 2% or more preferably not more than 1% _or ; the list of said additional materials includes Iridium, Indium, Ruthenium and Rhenium. Such materials may have, under certain conditions better explained below, grain refinement properties.

[0117] In particular, iridium is preferably used in alloys that contain high copper contents, since it binds in particular with the latter element; preferably, but not limited to, when it is present, iridium is present in a maximum amount of 0.5% or by weight. The use of Ruthenium and Rhenium is rarer, in sometimes lesser amounts, but in any case up to 0.5% or by weight. Ruthenium and Rhenium are preferably used in gold alloys that contain Palladio.

[0118] However, it should be noted that the use of Iridium or Rhenium and Ruthenium is subject to the inclusion of these elements in pre-alloys. In fact, it has been observed that these elements, if not pre-linked with the related material, but directly introduced into the crucible, do not bind, thus contributing to a worsening of the characteristics of the alloy. On the other hand, only if used in pre-alloy with Copper (Iridium) or Palladio (Renium and Ruthenium), taking care to make the pre-alloy bind with the rest of the elements making up the alloy itself, is it possible to refine the grain.

[0119] The object of the invention is also a production process of a gold alloy, in particular a gold alloy for jewelery, comprising gold, copper, palladium and optionally iron in accordance with what is described above. The alloys

CH 714 882 A1 d'Oro which form the subject of the invention are made from pure elements, in particular from 99.99% gold, 99.99% Cu, 99.95% Pd, 99.99% Fe, 99.99% Ag.

[0120] The process of melting the pure elements for the creation of the gold alloys according to the invention can be in detail a discontinuous gold melting process or a continuous gold melting process. The discontinuous gold casting process is a process in which the mixture is melted and poured into a refractory or refractory or metallic ingot mold. In this case the elements indicated above are melted and poured in a controlled atmosphere. More specifically, the melting operations are carried out only after preferably carrying out at least 3 cycles of conditioning of the atmosphere of the melting chamber. This conditioning involves first of all reaching a vacuum level up to pressures lower than 1x10 ^-2 mbar and a subsequent partial saturation with Argon at 500 mbar. During the melting, the Argon pressure is maintained at pressure levels between 500 mbar and 800 mbar. When the complete melting of the pure elements has been reached, an overheating phase of the mixture takes place, during which the mixture is heated up to a temperature of about 1250 ° C, and in any case at a temperature above 1200 ° C, at in order to homogenize the chemical composition of the metal bath. During the overheating phase, the pressure value in the melting chamber again reaches a vacuum level lower than 1x10 ^-2 mbar, useful to eliminate part of the slag produced by the melting of the pure elements.

[0121] At this point, in a casting phase, the molten material is poured into a graphite mold or ingot, and the melting chamber is again pressurized with an inert gas, preferably argon, injected at a pressure lower than 800 mbar and in particular less than 700 mbar.

[0122] After solidification, the bars or spindles are extracted from the bracket. When the alloy is solidified, gold alloy rods or spindles are obtained from the graphite conduit which are subjected to rapid cooling by immersing them in water, in order to reduce and possibly avoid phase variations. In other words, the bars or spindles are subjected to a rapid cooling phase, preferably but not limited to in water, in order to avoid phase variations in the solid state.

[0123] In a more general embodiment, the production process of the gold alloy according to the invention includes, starting from the pure elements in accordance with what described above, the mixing of:

- Gold in an amount between 540% or 620% or by weight;

- Copper in an amount between 360% or 415% or by weight;

- Palladium in an amount between 10% or 30% or by weight;

and a step of introducing the mixture into a melting crucible, and of a subsequent melting by heating until melting.

[0124] The continuous casting process is a process in which solidification and extraction of the solidified gold are carried out continuously starting from a free end of a bar or gold spindle. In particular, a graphite die is used in the continuous casting process. The use of a graphite die is known since graphite is a solid lubricant, and typically has low friction between its surfaces and those of the molten metal typically allowing to obtain an easy extraction of the element contained therein without fractures and with the minimum quantity of defects on its surface. [0125] When the inclusion of materials such as Iridium, Indium, Ruthenium and Rhenium for grain refining is present, the production process includes a step in the formation of a pre-alloy, in which the said pre-alloy includes:

a) Iridium pre-linked to Copper in the amounts already indicated, or alternatively

b) Rhenium or Ruthenium pre-linked to Palladio in the amounts already indicated.

[0126] Subsequently, the bars or spindles obtained by discontinuous or continuous casting are subjected to a step of cold plastic deformation, preferably but not limited to flat rolling.

[0127] During flat lamination and more generally during the cold plastic working phases, the different compositions synthesized according to the previously described melting procedure are deformed up to 70% and then subjected to a heat treatment of solubilization at a temperature above 680 ° C, to be subsequently cooled.

[0128] Particular embodiments of the method described above comprise an initial phase in which Palladium in particular is mixed in an amount comprised between 12% or, more preferably 15% o, and 27% or, more preferably 25% or by weight and / or, in addition to the previous elements, also iron comprised between 2% or by weight and 15% or by weight, more preferably between 4% or by weight and 13% or by weight. In particular, iron can be comprised between 5% and 10% or by weight. According to a particular embodiment, the method comprises mixing Gold, Copper and Palladium in such a way that the sum in thousandths of their weights is at least equal to 910% or, more preferably 950% or, and even more preferably 960% or even 970 %or.

[0129] In a particular embodiment of the method of making the Gold alloy, the sum of the amounts of Gold, Copper and Palladium is at least equal to 900% or by weight, and more particularly in the amount at least equal to 960% or by weight, more preferably 970% or by weight. In this case it is possible that the sum of Palladium and Iron is less than 37% or by weight, and more preferably less than 35% or by weight, where the Iron is included in an amount between 5% or 10% or in weight.

[0130] A further and specific realization of the method comprises mixing the Gold in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and Copper between 370% or 405% by weight, and

CH 714 882 A1

Palladium between 12% or, more preferably 15% or by weight, and 27% or, more preferably 25% or by weight, or alternatively Gold in an amount between 565% or 605% or by weight, and more preferably between 575% or 595% or by weight, and Copper between 370% »and 405% or by weight, with the sum of the amounts of Palladium and Iron included between 23% or 27% or, even more preferably equal to 25% or .

[0131] Through the invention it is therefore possible to realize a method of production of an object for jewelery or part of object for jewelery, said method being characterized in that it comprises one or more mechanical working steps of a gold alloy according to what previously described.

[0132] The advantages offered by the alloy object of the invention are clear in light of the description obtained above. The alloys are characterized by a low tendency to tarnishing for the environments in which a typically jewelery item is to be used, consequently it allows to create jewelery items or parts of objects for jewelery resistant to tarnishing, in substantially red color as defined above , without the need for subsequent plating with high titer gold alloys. Consequently, the jewelry object thus created is less expensive and less demanding to work as well as characterized by a substantially more uniform color also following wear.

[0133] Finally, it is clear that modifications, additions or variations may be applied to the object of the present invention, obvious to a person skilled in the art, without thereby departing from the scope of protection provided by the appended claims.

Claims (10)

claims 1. Alloy, in particular for jewelery, characterized in that it consists of: - Gold in an amount between 540% or 620% or by weight; - Copper in an amount between 360% or 415% or by weight; - Palladium in an amount between 10% or 30% or by weight; and optionally at least one of Silver in an amount less than or equal to 80% or by weight, Zinc in an amount less than or equal to 80% or by weight, Indium in an amount less than or equal to 20% or by weight, Tin in a minor amount or equal to 20% or by weight, Iron less than or equal to 15% or by weight, Gallium less than or equal to 10% or by weight, Iridium or Ruthenium less than or equal to 0.5% or by weight, Rhenium in an amount less than or equal to 0.1% or by weight. 2. Alloy according to claim 1, characterized in that it comprises a "pear red" color and / or in the fact that it includes a color which, on the CIELAB1976 color paper, has a coordinate a * in the range [6.5-9.5] and a coordinate b * <13.5, preferably in the range [10-13.5]. 3. Alloy according to any one of the preceding claims, characterized in that it comprises Palladium in an amount comprised between 12% or, more preferably 15% or by weight, and 27% or, more preferably 25% or by weight. Alloy according to any one of the preceding claims, characterized in that it further comprises iron in an amount comprised between 2% or by weight and 15% or by weight, more preferably between 4% or by weight and 13% or by weight, even more preferably between 5% or by weight and 10% by weight and / or by the fact that the sum of the amounts of Gold, Copper and Palladium is at least equal to 910% by weight, more preferably 950% or by weight, even more preferably 960% or by weight, and even more preferably 970% or by weight. 5. Alloy according to claim 4, characterized in that the sum of the amounts of Palladium and Iron is equal to or less than 37% or by weight, more preferably less than 35% or by weight and by the fact that Iron is included in the amount between 5% or Θ 10% or. Alloy according to any one of the preceding claims, wherein the gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and Copper is present between 370% or 405% or by weight, and Palladium is between 12% or, more preferably 15% or by weight, and 27% or, more preferably 25% or by weight. 7. Alloy according to claim 4 or claim 5, characterized in that the gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight, and the Copper is present between 370% o and 405% o by weight, and the sum of the amounts of Palladio and Ferro is between 23% o and 27% o, even more preferably substantially equal to 25% o. 8. Alloy according to claim 5, characterized in that it comprises Palladium in an amount comprised between 13% or by weight and 17% or by weight, preferably between 14% or by weight and 16% or by weight and even more preferably in an amount substantially equal to 15% or by weight. 9. Alloy according to claim 4 or claim 5, wherein the gold is present in an amount comprised between 565% or by weight and 605% or by weight, and more preferably between 575% or by weight and 595% or by weight , and the Copper is present between 370% o and 405% o by weight, and the sum of the amounts of Palladio and Ferro is between 30% o and 35% o 10. Alloy according to one or more of the preceding claims, characterized by the absence of Vanadium and other materials capable of generating carbides and oxides, in particular without Magnesium, Silicon, Titanium, Tungsten, Molybdenum, Niobium, Tantalum, Zirconium, Yttrium , Germanium and / or the fact that it is free of Nickel, Arsenic and Cobalt. CH 714 882 A1