Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/14—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of noble metals or alloys based thereon
• • A—HUMAN NECESSITIES
  • A44—HABERDASHERY; JEWELLERY
  • A44C—PERSONAL ADORNMENTS, e.g. JEWELLERY; COINS
  • A44C27/00—Making jewellery or other personal adornments
  • A44C27/001—Materials for manufacturing jewellery
  • A44C27/002—Metallic materials
  • A44C27/003—Metallic alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C5/00—Alloys based on noble metals
  • C22C5/02—Alloys based on gold

Definitions

• the invention relates to a gold-based alloy having improved hardness.
• the invention also relates to a process for obtaining a gold-based alloy with improved hardness.
• the invention further relates to the use of a precipitate for hardening a gold alloy.
• the invention also relates to a timepiece, jewelery or jewelery comprising at least one component made of such an alloy.
• the main applications are watchmaking, jewelery, jewelery and dentistry.
• the hardening of gold is an old problem, which, since antiquity, has led to the use of alloys in order to obtain sufficient mechanical characteristics to ensure at least the holding of the manufactured objects. Indeed, the process of hardening by plastic deformation of the material, which applies well to certain metals, applies poorly to gold since it has only very little consolidation during deformation, and more, recrystallizes at relatively low temperatures.
• the process of refining the grain size, allowing theoretically to raise the elastic limit of the material is not suitable either for gold, which has a cubic face-centered structure, hereinafter called CFC, since there are enough active sliding systems for the free passage of dislocations from one grain to another.
• the dissolution of alloying elements is the most commonly used method, often empirically, and provides only poor hardness, of the order of 150 to 155 HV on the Vickers scale in the best case .
• a patent EP 0 978 572 in the name of Hafner GmbH describes an alloy composed of 70% to 80% gold, 15% to 25% copper, 0% to 15% silver, and 0% 1% to 5% gallium, which inexplicably oxidizes little during a second treatment at 400 ° C following a first treatment at 800 ° C, and acquires a hardness that increases with time at temperature room.
• the document called D1 JP 8 013060 A in the name of PILOT PEN, describes the obtaining of a gold alloy of improved hardness with several possible compositions:
• EP 0 978 572 A1 in the name of HAFNER describes an alloy with 70 to 80% gold and 15 to 25% copper, to which is added 0.1 to 5% gallium. According to certain variants it could still contain: 0.1 to 3% of zinc, and / or 0.5 to 5% of silver, and / or 0.1 to 0.5% of silicon, and / or of 0 , 1 to 2% iron and / or 0.1 to 0.3% indium, and / or 0.1 to 0.5% aluminum and / or 0.1 to 3% tin.
• US 5 38 378 A in the name of OHTA MICHIO describes a dental gold alloy with a slow aging of 20 to 30 days and during which its hardness increases further. It comprises from 82 to 67% of gold, from 18 to 33% of copper, from 0 to 2% of a hardening accelerator selected from gallium and zinc. The alloy is subjected to heating at 650-700 ° C and quenched with water. In another composition, it comprises from 2 to 8% of such an accelerator, which comprises at least one metal selected from the group consisting of 1 to 4% gallium, 0.4 to 2% aluminum, and 1 to 5% zinc. In another composition, it comprises 1 to 4% gallium. In another composition, it comprises from 1 to 5% of zinc.
• D4 Article "18 carat yellow gold alloys with increased hardness” by SUSS, RAINER, published in 2004, describes gold alloys with improved hardness, and the influence of the addition metals, both for the obtaining physical characteristics that particular colors.
• D5 Article "Metallurgy of gold” by FISCHER-BICHHNER, published on May 20, 2010, details the metallurgy of gold and its alloys.
• the invention relates to an alloy based on gold, said 18K yellow gold type 3N, characterized in that it consists of a mixture comprising in mass:
• said mixture further comprising at least one said reaction precipitate of said second metal with gold, selected from said precipitates of said second metal with gold to form an intermetallic imparting to said alloy a hardness greater than 250 HV, so as to improve hardening structural element of said alloy, said selected precipitate being the aluminum and gold precipitate AI 2 Au 5 .
• said addition metal is silver.
• said addition metal is silver and is supplemented by another addition metal of concentration lower than that of silver.
• said other addition metal is copper.
• the invention also relates to a process for obtaining a gold-based alloy, with improved hardness, characterized in that:
• a second metal is chosen for its ability to form precipitates with gold, this second metal being aluminum;
• At least one addition metal is chosen for its ability to favor a stable CFC face-centered cubic structure on the one hand, and for its ability to increase the high-temperature solubility of said second metal in gold on the other hand;
• the insertion conditions are created in a cubic face-centered CFC structure resulting from the dissolving of a mixture of gold, of said second metal, and of said at least one addition metal, of precipitates of said second metal with gold;
• said second metal and said additive metal being selected to obtain, from said precipitates of said second metal with gold, at least one said particular precipitate of said second metal with gold to form an intermetallic imparting to said alloy a hardness greater than 250 H V ;
• said mixture is brought into solution by bringing the temperature between 650 ° C. and 700 ° C .;
• a structuring income treatment is carried out at a temperature of between 200 ° C. and 250 ° C. to give rise to said at least one selected precipitate of said second metal with gold, which is the precipitate of aluminum and aluminum; or AI 2 to 5 ;
• At least one selected precipitate is grown in a controlled manner by maintaining said structuring income for a sufficient time, of at least 60 minutes, to obtain the required hardness;
• Cooling is carried out at ambient temperature.
• the selection of said at least one selected precipitate is restricted to a single precipitate.
• said structuring income is made at least 24 hours after said sudden cooling.
• silver is chosen for said addition metal.
• silver is chosen for said addition metal, and another addition metal of concentration lower than that of silver is added thereto.
• copper is chosen for the said other additive metal.
• the invention also relates to the use of a precipitate for the hardening of a gold alloy, characterized in that said precipitate is a precipitate of aluminum and gold AI 2 Au 5 for the hardening of an alloy gold containing at least 75% gold, from 0.5% to 2.1% aluminum, and from 20% to 25% of at least one addition metal selected from silver and copper and chosen for its ability to promote a stable CFC-faced cubic structure on the one hand, and for its ability to increase the solubility of aluminum in gold on the other hand, and from 0% to 0.5% d one or more components selected for the fluidity and refinement of the grain size of said gold alloy, said use resulting from the insertion of said aluminum and gold precipitate AI 2 Au 5 , in a face-centered cubic CFC structure resulting from the dissolving of said mixture of gold, aluminum, said at least one additive metal, said selected components if said alloy comprises, and aluminum precipitates with gold, said insertion being achievable by such a method.
• said precipitate is a precipitate of aluminum and gold AI 2 Au 5
• the invention also relates to a timepiece, jewelery, jewelery or dentistry comprising at least one component made of such an alloy.
• the alloy retains the specific appearance of pure gold.
• This alloy obtained by its improved hardness, is more resistant to scratches, and is entirely appropriate for timepieces, jewelery or jewelery, and in particular for their visible components such as glasses and watch frames, and jewelry structures, bracelets, clasps, buckles, and other items.
• the invention provides a simple, reproducible method of implementation, making it possible to obtain with certainty a gold alloy with a required hardness, greater than 250 HV, with a short treatment time.
• the alloy obtained is directly usable without requiring additional aging.
• FIG. 1 is a phase diagram of a pseudo-binary alloy
• Au-Ag-AI according to the invention in an 18-carat alloy example, and which represents the different phases, depending, on the one hand on the abscissa of the aluminum concentration, that is to say the ratio between the mass of aluminum and the total mass of the alloy, and on the other hand, the ordinate of the temperature, here represented in degrees Celsius;
• FIG. 2 is a Vickers hardness chart in ordinate, as a function of time on the abscissa, of an alloy according to the invention made in a preferred domain A of the diagram of FIG. 1 in comparison with an 18 carat gold obtained from standard way.
• the invention involves a method of structural hardening, by the selection of particular elements, which are chosen here to form particular precipitates.
• particular elements which are chosen here to form particular precipitates.
• the different precipitates that can form gold with other metals under very specific physicochemical conditions, it is a question of choosing those which can be controlled, by the implementation of an appropriate treatment, the germination and growth, for optimize the mechanical characteristics, and in particular here to improve the hardness.
• the mechanical characteristic that the present invention makes it possible to improve, by the creation of a particular process is the hardness, which concerns both the hardness at the core of the alloy, and the surface hardness which is very important in watches, jewelery, jewelery to resist scratches or at least to minimize the effects.
• the inventive step of the invention was to search for the possibility of insertion, in a cubic face-centered or CFC structure, of precipitates, and to grow them in a controlled manner, so as to obtain a hardness greater than the usual hardness. .
• the invention relates more particularly to the field of gold alloys with a high gold content, and particularly 18-carat alloys, comprising at least 75% of their weight of gold.
• AI 2 At the 5 do not exist in the natural state, it is necessary to manufacture them in order to be able to use them.
• the invention proposes hereinafter a preferred method of manufacture.
• the second metal may be selected from aluminum, silver, chromium, copper, iron, hafnium, manganese, niobium, palladium, platinum, vanadium, this list is not exhaustive.
• An addition metal can be chosen preferably from silver, aluminum, chromium, copper, iron, hafnium, manganese, niobium, palladium, platinum, vanadium.
• the invention has sought to create the phase diagram of the Au-Ag-AI pseudo-binary alloy, as can be seen in FIG.
• This diagram represents in a classical way the different phases, in function, on the one hand on the abscissa of the aluminum concentration, that is to say on the ratio between the mass of aluminum and the total mass of the alloy, and on the other hand on the ordinate of the temperature, here represented in degrees Celsius.
• the diagram of FIG. 1 represents the preferred case of a gold mass concentration of 75%, which is the preferred case of an 18-carat alloy.
• the concentration of aluminum, to remain in this area must remain below 2.1%.
• the range of concentrations to be respected is 0.1% to 2.1% of aluminum in order to be certain to develop only AI 2 Au 5 .
• a second domain called B in Figure 1 corresponds to a phase coexisting with the alloy elements as CFCs, precipitates of Al 2 Au 5 and AIAu 2.
• the third domain called C in FIG. 1 corresponds to a phase where only the precipitates of AIAu 2 coexist with the elements of the alloy in CFC form.
• FIG. 1 shows that, to obtain an alloy in an optimal composition in the domain A, a method of obtaining is to heat up all the elements of the alloy and then to be in the range D of Figure 1, corresponding to a dissolution of aluminum.
• a dilution heat treatment at a temperature between the solidus and the liquidus delimiting the domain D, allows a homogeneous solution in solution: the gold is in CFC structure, thanks to the element or the elements of addition chosen, in particular the silver, and the structure CFC is stable.
• High solubility of aluminum in the CFC_A1 phase is observed at high temperature, in particular at temperatures between 400 ° C. and 700 ° C. This or these addition elements also facilitate the solubility of aluminum in gold.
• the alloy is then made metastable.
• the rise in temperature carried out for example between about 400 ° C. and 700 ° C. for the end portion of area A, ideally around 650 ° C., is followed by rapid cooling, such as water quenching. , or similar.
• rapid cooling such as water quenching. , or similar.
• aluminum atoms do not have time to reorganize.
• the alloy is subjected to structuring income treatment, in the temperature range defined by the solvus of the A domain for the aluminum concentration considered. In any case, this structuring income does not exceed the temperature of 400 ° C.
• AI 2 Au 5 precipitates grow and grow.
• the structuring tempering temperature is greater than 200 ° C to facilitate this growth of the precipitates, and also limit the duration of the heat treatment.
• Figure 2 is a Vickers hardness chart in ordinate as a function of time on the abscissa.
• a hardness greater than 250 HV is obtained very quickly, after about 2 hours. This hardness will still increase if the structuring income treatment is prolonged, but asymptotically, and it is hardly useful, even if the maximum hardness is sought, to prolong the treatment beyond ten or so years. hours, where one reaches a hardness of the order of 280 HV.
• FIG. 2 shows, for comparison, the level of hardness of 150 HV obtained with an 18 K gold or 18 karat gold alloy, conventional.
• the structuring income is made at a lower temperature, for example 100 ° C, a hardness greater than 200 HV will not be obtained. after 10 to 15 hours, and the treatment must be further extended to reach a level of the order of 250 HV.
• the precipitate AI 2 Au 5 obtained is harder than gold.
• the alloy contains no other metal than gold, aluminum, and an addition metal, preferably silver, chosen to increase intermetallic solubility and to maximize phase D, in terms of range amplitude of aluminum concentrations.
• Document D3 is still devoted to the manufacture of pink gold. This document claims that the alloy remains monophasic, which is physically impossible: its teachings can not be retained. Document D4 describes a yellow gold pulling towards the rose. It is impossible to highlight the specific role of aluminum since all the other elements present in the alloy already contribute to hardening. This document notes that beyond 0.4% of aluminum the alloy darkens considerably. This disadvantage is not visible in the case of the alloy produced according to the invention, even at a content of 2% of aluminum. It should be noted that the experimenter who follows the instructions of this document D4 will not get a precipitate AI 2 Au 5 , because, on the one hand, added elements such as zinc that modify the solubility of aluminum, and on the other hand, the low concentration> 0.4% of aluminum.
• Document D5 explains the hardening of the gold (75%) - silver-copper alloy by the order / disorder transformation well known with copper.
• the composition 75% gold-12.5% silver-12.5% copper of FIG. 7.12 of document D5 suggests a hardness of 220 HV, much lower than that obtained by the invention.
• the invention differs from the prior art in that it creates the conditions for the development of Al 2 Au 5 precipitates, in an alloy of suitable composition comprising gold, aluminum, and at least one addition metal selected for its ability to promote a stable CFC structure on the one hand, and to increase the solubility of aluminum in gold on the other hand, this addition metal being preferably 'money.
• the optimum composition by weight is from 0.1% to 2.1% of aluminum, and preferably from 0.5 to 2.1%, and at least 75% of gold in order to respect the legal requirement in jewelery. and jewelery, and the complement consisting of at least one addition metal, which can be supplemented by a small proportion of at least one other component selected for fluidity and refinement of the grain size.
• the addition metal can also be copper. It is also possible to combine several metals each having the properties that this adduct must have, namely the ability to promote a stable CFC structure on the one hand, and the ability to increase the solubility of the aluminum in gold on the other hand.
• Silver is the best element, and the other metallic elements listed above can be added to adjust the tint of the alloy. This list of elements has been drawn up so that the elements contained therein satisfy the condition of increasing the solubility of aluminum in the high temperature CFC structure.
• copper is less favorable than silver for fulfilling these particular functions in the presence of gold and aluminum.
• the use of copper is still possible for reasons of cost, but is much less favorable than silver, and should always, in case of employment, be combined with money, paying attention that the concentration of money always be greater than the concentration of copper in the alloy.
• each new composition with different addition metals requires a complete experiment in order to define the corresponding phase diagrams, nonexistent in the literature, to analyze the precipitates and other intermetallics created within each of the phases, to verify that these compounds do not alter the mechanical properties of the gold-based alloy.
• These studies and Experiments are long and expensive and can not be conducted at random. They are also intended to determine, on a case by case basis, the range of aluminum concentrations to be observed in order to obtain Al 2 Au 5 precipitates, and preferably only this one.
• the invention makes it possible to obtain a gold-based alloy, called 18-carat yellow gold type 3N, characterized in that it consists of a mixture comprising, by mass:
• said mixture further comprising at least one said precipitate of said second metal with gold, selected from said precipitates of said second metal with gold to form an intermetallic imparting to said alloy a hardness greater than 250 HV, so as to improve the structural hardening of said alloy, said selected precipitate being the aluminum and gold precipitate AI 2 Au 5 .
• the second metal is aluminum and the selected precipitate is aluminum and gold precipitate Al 2 Au 5, which allows to obtain an alloy with very good characteristics of hardness, which is higher than 250 HV, and especially in the vicinity of 280 HV.
• This AI 2 Au 5 precipitate also provides the alloy with good resistance during its transformation or its machining, because it does not make the alloy brittle.
• the addition metal is silver, which ensures good dissolution of the entire mixture.
• the addition metal is silver, preferably in a mass content of from 10% to 12.5% of the total, and is supplemented with another metal of addition, preferably in a in mass from 10% to 12.5% of the total, to adjust the shade of the alloy.
• At least one said selected component for the fluidity and refinement of the grain size of said alloy is selected from zinc, cobalt or iridium.
• the process for obtaining a gold-based alloy with improved hardness preferably comprises:
• a second metal is chosen for its ability to form precipitates with gold, this second metal being aluminum;
• At least one addition metal is chosen for its ability to favor a stable CFC face-centered cubic structure on the one hand, and for its ability to increase the high-temperature solubility of said second metal in gold on the other hand;
• the insertion conditions are created in a cubic face-centered CFC structure resulting from the dissolving of a mixture of gold, of said second metal, and of said at least one addition metal, of precipitates of said second metal with gold;
• said second metal and said addition metal being selected to obtain, from said precipitates of said second metal with gold, at least one said precipitate particularly said second metal with gold to form an intermetallic imparting to said alloy a hardness greater than 250 HV, said selected precipitate being the aluminum and gold precipitate AI 2 Au 5 ;
• said mixture is brought into solution by heating to between 400 and 700 ° C, preferably between 650 ° C and 700 ° C;
• a structuring income treatment is carried out at a temperature of between 200 and 400.degree. C., preferably between 200.degree. C. and 250.degree. C., to give rise to said at least one selected precipitate of said second metal with the gold which is the precipitate of aluminum and gold AI 2 Au 5 . ;
• said at least one selected precipitate is controlledly grown by maintaining said structuring income for a sufficient duration, preferably at least 60 minutes, to obtain the required hardness;
• Cooling is carried out at ambient temperature.
• the selection of selected precipitates is restricted to a single precipitate, in this case the precipitate of aluminum and gold AI 2 Au 5 .
• the structuring income is made at least 24 hours after the quenching.
• Aluminum is preferably chosen for the second metal, and the precipitate of aluminum and gold AI 2 Au 5 is selected as the selected precipitate.
• the addition metal is silver.
• silver is used as the addition metal and another addition metal with silver-like characteristics is added to adjust the color of the alloy.
• Other processes such as mechanosynthesis or PVD can also lead to the manufacture of the aluminum and gold precipitate AI 2 Au 5 . It is however necessary to create, as in the procedures listed above, the insertion conditions of this very particular precipitate in the cubic face-centered structure of the alloy, and the conditions of development of this precipitate in order to provide the 'alloy the desired hardness characteristics.
• the invention further relates to the use of a precipitate for hardening a gold alloy.
• this precipitate is a precipitate of aluminum and gold AI 2 Au 5 for the hardening of a gold alloy comprising at least 75% gold, from 0.5% to 2.1% d aluminum, and from 20% to 25%, or preferably from 22.4% to 24.5%, of at least one addition metal selected from silver and copper and selected for its ability to promote stable face-centered cubic CFC structure on the one hand, and for its ability to increase the solubility of aluminum in gold on the other hand, and from 0% to 0.5% of one or more components selected for the fluidity and refinement of the grain size of said gold alloy, said use resulting from the insertion of said precipitate of aluminum and gold AI 2 Au 5 , in a face-centered cubic CFC structure resulting from the dissolution of said mixture consisting of gold, aluminum, said at least one metal of addition, said selected components if said alloy contains, and aluminum precipitates with gold, said insertion being feasible preferably by the method described above.
• the invention also relates to a timepiece, jewelery, jewelery or dentistry comprising at least one component made of such an alloy.

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• 2010
  • 2010-06-30 EP EP10167859.7A patent/EP2402467B1/fr active Active
• 2011
  • 2011-06-16 EP EP11725466.4A patent/EP2588635B1/fr active Active
  • 2011-06-16 JP JP2013517158A patent/JP2013531736A/ja active Pending
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• 2013
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