EP3478864A1

EP3478864A1 - Solid glass-forming white gold alloy

Info

Publication number: EP3478864A1
Application number: EP17739868.2A
Authority: EP
Inventors: Oliver Gross; Isabella GALLINO; Ralf Busch; Miriam EISENBART; Ulrich Klotz
Original assignee: Universitaet des Saarlandes
Current assignee: Universitaet des Saarlandes
Priority date: 2016-06-30
Filing date: 2017-06-29
Publication date: 2019-05-08
Also published as: DE102016008074A1; WO2018001564A1

Abstract

A white gold alloy of the composition (Au_1-a-bAg_a(Pd_1-cPt_c)_b)_100-x-y(Cu_1-d- _eL_dM_e)_x(Si_1-fGe_f)_y has been produced in which L represents In, Ga or Sn or L_d represents L¹ _d1L² _d2 or L¹ _d1L² _d2L³ _d3, wherein L¹, L² and L³ are selected from the elements In, Ga, or Sn; M represents one or more elements of the elements Ni, Co, and Fe; x and y are at%, wherein x = 10 - 30 at% and y = 10 - 16.3 at%; (100-x-y), x, and y can contain unavoidable trace impurities; a, b, c, d, e, and f are a fraction of 1; a = 0.02 - 0.20, b = 0 - 0.1, c = 0 - 1, d = 0.02 -0.40, d1 = 0 to 0.4; d2 = 0 to 0.4; and d3 = 0 to 0.4, where d1 + d2 + d3 = d, e = 0 - 0.12 (total fraction of the elements Ni, Co, and Fe) and f = 0 - 0.40. The white gold alloy is suitable for a broad range of solid glass forming processes and for jewelry applications.

Description

Solid glass-forming white gold alloy

Field of the invention

The invention relates to a white gold alloy, which can form solid glasses in many areas.

Background of the invention

Metallic solid glasses are alloys that solidify at sufficiently high cooling rates to form amorphous solids. Due to their amorphous structure, metallic solid glasses have properties that make them far superior to conventional metal alloys.

The lack of a volume jump by crystallization of the sample can be made of solid glass forming alloys near net shape castings, which require a minimum of post-processing. Near-eutectic alloys exhibit excellent casting properties due to their low liquidus temperature. Furthermore, amorphous semi-finished products (eg, granules) can be removed from the glass into the

Heat and transform the area of the supercooled melt.

Metallic solid glasses can also have much higher hardness than crystalline alloys.

However, the composition of metallic solid glass can not be changed arbitrarily, since a glass formation is usually possible only in very limited concentration ranges.

Among other things, hard gold alloys are very desirable for the production of jewelry. Crystalline gold alloys also reach at tremendous

Cold deformation only values from 100 to 250 HV. An exception is red gold, which can reach hardnesses above 300 HV. State of the art

From US 8 501 087 B2 is a gold alloy having the composition:

(Aui.x (Agi.y (Pd t) y) x) a (Cui-z (Ni _I Co, Fe, Cr _> Mn) _z ) b ((Sii.vPv) iw (GeAI, Y, Be) w ) c

where a, b, c are at% (atomic percent), x, y, z, v and w are fractions of 1, a is in the range of about 25 to about 75 at%, b is in the range of about 10 about 50 is at%, c is in the range of about 12 to about 30 at%, and for the fractions x, y, z, v and w the following restrictions apply: x is 0 to 0.5; y is 0 to 1; z is 0 to 0.5; v is 0 to 0.5 and w is 0 to 1. Some of these alloys form

Solid glass, including the alloy Au49Ag5.5Pd2.3Cu26.9Sii6.3 [Au-BMG1], which has a white gold color and is classified as "Premium White" when polished.The glass transition temperature (Tg) is 128 ° C.

However, with this alloy a strong discoloration (down to the off-white range [1]) can be observed [2,3], which takes place under different conditions but is particularly pronounced in experiments with artificial saliva or artificial sweat The strong color change, also referred to as "tarnish", is observed among other things also at room temperature or slightly elevated temperatures such as body temperature.

Investigations by the inventors [1] have shown that the combination of the three main constituents (gold, copper, silicon) is responsible for the start-up process [2,3]. The corrosion mechanism is due to the formation of amorphous

Silica branches growing in the base material and embossed with copper oxide layers on the surface. The rapid formation of silica at such low temperatures is very unusual, but has also been in crystalline

Systems found in the combination of silicon and copper [5,6]. Au-Cu-Si-based alloys show low nucleation temperatures along the Au-Cu axis at silicon concentrations of about 15-20 at% and solidify at sufficiently high cooling rates to form a glass. Replacing Cu with Au results in the glass transition temperature dropping well below 100 ° C, [7] making the alloys less suitable for jewelry applications. A low copper content does not necessarily lead to a higher corrosion resistance [1]. Another solid gold-forming gold alloy having the composition Au5oSn6Cu26Sii8 is known from S. Wang and T. Chin, "Tin-modified gold-based bulk metallic glasses", Gold Bull. (2012) 45: 3-8, [8] a very low Tg of 82 ° C, which makes them less suitable for jewelry applications, and second, it was evidently only possible to obtain a cast thickness of 1 mm for the alloy,

When cast, these alloys can reach a hardness of up to 360 HV. The thermoplastic molding process of these alloys may take place in a temperature range of about 100 to about 160 ° C, depending on the alloy composition.

The aim of the invention was a suitable for jewelry applications

To provide gold alloy, which can form solid glass in a wide range and less color change or corrosion, for. when wearing a jewelry made from it.

Summary of the invention

The invention relates to an alloy of the composition. The invention relates to an alloy of the composition:

(AUL-a-Baga (Pdi _-c Ptc) b) lOO-xy (Cul-d-eLdMe) x (Sil-fGef) y

wherein:

L stands for In, Ga or Sn or

L d is L ¹ diL ² d2 or L ¹ diL ² d2L ³ d3, where L ¹ , L ² and L ^{3 are selected} from the elements In, Ga or Sn, and M is one or more of the elements Ni, Co and Fe stands; x and y are at%, where

x = 10 - 30 at%, y = 10 - 16.3 at%,

where (100-x-y) and x and y may contain unavoidable trace impurities, a, b, c, d, e and f are a fraction of 1, where

a = 0.02-0.20,

b = 0 - 0.1,

c = 0-1,

d = 0.02-0.40,

d1 = 0 to 0.4;

d2 = 0 to 0.4;

d3 = 0 to 0.4, where

d1 + d2 + d3 = d,

e = 0 - 0.12 (total fraction of elements Ni, Co and Fe) and

f = 0-0.40,

except the following alloys:

AU49Ag5,5Pd2.3CU25,9SniSil6,3,

AU49Ag5,5Pd2,3CU25,9GaiSil6,3,

AU65,2Ag5CU5Ga9,3Sl15,5,

AU52,1lAg7,52Cui5,57Ga9,3Sil5,5.

Another object of the invention is the production of this alloy and its use in the jewelry sector.

Brief description of the figures

FIGS. 1-3 show thermal DSC analyzes of three different alloy compositions according to the invention. The glass transition, the area of the supercooled melt and the crystallization event are clearly visible up to a thickness of 3 mm.

Fig. 1: Alloy composition (at%):

Au51, 59Ag5,79Pd2,42Cu20,175Ga6,725Si13,3 ("NGL6") Fig. 2: Alloy composition (at%):

Au52.59Ag5.79Pd2.42Cu18.675Ga8.22Si12.3 ("NGL8")

Fig. 3: Alloy composition (at%):

Au48.5Ag9.88Pd2.42Cu18.675Ga8.22Si12.30 ("N G L8_Ag_M ax")

Detailed description

It was surprisingly found that white gold alloys with the

Composition (Aui-a-bAga (Pdi-cPtc) b) 100-xy (Cui-d-eLdMe) x (Sii-fGef) _y , where L is In, Ga or Sn or Ld is L di L ² d2 or L ^{1 is} L ² d ² L ³ d3, wherein L ¹ , L ² and L ^{3 are selected} from the elements In, Ga or Sn, M is one or more elements of the elements Ni, Co and Fe and a, b, c, d, e, f, x and y are as defined above, forming solid glasses in a wide compositional range.

It has surprisingly been found that, e.g. in comparison with the known solid glass-forming alloy Au49Ag5, 5Pd2,3Cu26,9Sii6,3, at the same time

Reducing the silicon content of copper by in particular In, Ga and / or Sn can be substiutiert without the ability of solid glass formation is lost, whereby the susceptibility to corrosion is reduced.

In alloys preferred for jewelry applications, e = 0.

Further, a = 0.075-0.12, more preferably a = 0.085-0.12.

Depending on the intended use are also in preferred

Alloy compositions y, y, a, b, d, d1, d2, d3, e and f are as follows:

Alloy Composition 1A:

x = 10 - 30 at%,

y = 10 - 16.3 at%,

a = 0.05 - 0.15, b = 0.02 = 0.08,

c = 0-0.5

d = 0.075 -0.35,

d1 = 0 to 0.35;

d2 = 0 to 0.35;

d3 = 0 to 0.35; and

d1 + d2 + d3 = d,

e = 0,

f = 0-0.20.

Alloy Composition 1B: x = 15-27 at%,

y = 12-16.3at%,

a = 0.05-0.15,

b = 0.02-0.08,

c = 0 - 0.5,

d = 0.075 -0.35,

d1 = 0 to 0.35;

d2 = 0 to 0.35;

d3 = 0 to 0.30; and

d1 + d2 + d3 = d.

e = 0,

f = 0-0.20.

Alloy composition 1C: x = 15-27at%,

y = 1-2-16.3 at%,

a = 0.075-0.12,

b = 0.03-0.065,

c = 0

d = 0.1 -0.30,

d1 = 0 to 0.30;

d2 = 0 to 0.3.0:. d3 = 0 to 0.30; and

d1 + d2 + d3 = d,

e = 0,

f = 0.

Alloy composition 1D: x = 20-27 at%,

y = 12-16%,

a = 0.075-0.12,

b = 0.03-0.065,

c = 0

d = 0.1 -0.30,

d1 = 0 to 0.30;

d2 = 0 to 0.30;

d3 = 0 to 0.30; and

d1 + d2 + d3 = d,

e = 0,

f = 0.

Alloy composition 1E: x = 20-27 at%,

y = 12-16%,

a = 0.085 -0.12,

b = 0.036 -0.05,

c = 0,

d = 0.2 -0.28,

d1 = 0 to 0.28;

d2 = 0 to 0.28;

d3 = 0 to 0.28; and

d1 + d2 + d3 = d,

e = 0,

f = 0. Alloy composition 1 F: x = 24 - 27 at%,

y = 12-14at%,

a = 0.085-0.12,

b = 0.036 - 0.05,

c = 0,

d = 0.2 -0.28,

d1 = 0 to 0.28;

d2 = 0 to 0.28;

d3 = 0 to 0.28; and

d1 + d2 + d3 = d

e = 0,

f = 0.

Alloy composition 1G x = 24 - 27 at%,

y = 12- 1 at%,

a = 0.095-0.1,

b = 0.036 -0.05,

c = 0

d = 0.24-0.26,

d1 = 0 to 0.26;

d2 = 0 to 0.26;

d3 = 0 to 0.26; and

d1 + d2 + d3 = d

e = 0,

f = 0.

Alloy composition 2A x = 20 - 27 at%,

y = 10-14.3 at%,

a = 0.05-0.15, b ^ 0.02 -0.08,

c = 0-0.5,

d = 0.25 -0.35,

d1 = 0 to 0.35;

d2 = 0 to 0.35;

d3 = 0 to 0.30; and

d1 + d2 + d3 = d.

e = 0,

f = 0-0.20.

Alloy Composition 2B:

x = 25-27 at%,

y = 10-13.3 at%,

a = 0.05-0.15,

b = 0.02-0.08,

c = 0,

d = 0.3 -0.35,

d1 = 0 to 0.35;

d2 = 0 to 0.35;

d3 = 0 to 0.30; and

d1 + d2 + d3 = d.

e = 0,

f = 0.

The preparation of the alloys can be accomplished as follows.

The purity of the starting element materials employed is not particularly critical, a purity of more than 99%, preferably more than 99.9%, nor

more preferably at least 99.99% is often convenient. Also the special form of the starting material materials (eg granules, platelets, flakes) is not critical. The starting material materials are weighed according to the desired stoichiometry with a precision balance. Subsequently, the output elements in a suitable device, for example a modified (water cooling, improved

Gaskets) Kippgussanlage (e.g., Indutherm MC15), in a suitable crucible, e.g. an alumina crucible with or without Zirkonoxidbeschichtung arranged. For example, the following order of elements in the crucible can be maintained (from bottom to top): Pd / Pt-Ag-Au-Cu / Ni / Co / Fe-Ga / Sn / In-Si / Ge, since this results in the formation of palladium - and / or platinum silicides is unlikely. However, a different order of the elements in the crucible can also lead to the desired result. The elements are inductively melted and homogenized. The melt is slowly heated to a temperature (effluent temperature) generally well above the liquidus temperature, typically about 400-450 ° C above, to ensure melt homogeneity, but longer residence times may also result in lower effluent temperatures. The temperature is constantly controlled by a pyrometer. When the desired effluent temperature is reached, the melt is poured into a suitable mold, e.g. a water-cooled copper mold, cast. The process preferably takes place under protective gas (Ar or N2). The casting can also be carried out in a vacuum. Already alloyed and remelted material can be cast at lower temperatures.

Alternatively, the individual elements can also be used in an electric arc furnace

melted and homogenized. The alloys can also be used in the

Centrifugal casting method in which uncooled copper molds are used can be produced. Furthermore, the use of pressure-assisted casting process for the production of amorphous castings is possible (die-casting, suction casting method).

In this way, e.g. Pour jewelry directly.

It is also possible to produce amorphous granules. These can then be used as semi-finished products for thermoplastic molding (TPF) or 3D printing processes. For example, rods of the new alloys with a diameter made of 2-3 mm and thermoformed. It is obvious that jewelry can also be formed in this way.

Other applications of the new alloys, such as in dental prostheses, nanoimprinting and micro-electromechanical systems (MEMS), are of course also possible.

Examples

Example 1: Production example of the alloy

AU51.59Ag5.79Pd2.42CU20.175Ga6.725Sil3.3

The pure elements (purity: Au (granules 1-5 mm), Ag (platelets), Pd (platelets): highest commercial purity; ln: 99.9975% (granules 1 -5 mm), Ga: 99.9999%

(Granules 1 -5 mm), Sn: 99.995% (granules 1 -5 mm), Cu: 99.99% (granules 1 -5 mm), Si: 99.9995% (flakes)) were weighed with a fine balance. For the preparation of 10 g of the alloy Au5i.59Ag5.79Pd2.42Cu20.i 75Ga6.725Sii3.3 (at%), 7.7168 g Au, 0.4743 g Ag, 0.1956 g Pd, 0.9736 g Cu, 0.3561 g Ga and 0.2837 g Si

weighed. Subsequently, the elements were modified in a

(Water cooling, improved seals) Tipping system (Indutherm MC15) positioned in an alumina crucible. The following order of the elements in the crucible was observed: (from bottom to top): Pd-Ag-Au-Cu-Ga-Si.

The elements were inductively melted and homogenized. The melt was heated slowly to a temperature of 1100 ° C-1200 ° C, the temperature was constantly monitored by a pyrometer. When the desired effluent temperature of 1100 ° C-1200 ° C was reached, the melt was cooled to the water

Cast copper mold. The process took place under protective gas (Ar).

The prepared sample is a rod with a diameter of 3 mm. The sample has a premium white color (according to classification of white gold alloys by the Yellowness Index (Yl D1925)). The

Glass transition temperature is 103 ° C at a heating rate of 20 ° C / min. The crystallization starts at 155 ° C. The solidus temperature is 340 ° C, the liquidus temperature 408 ° C.

Example 2: Prepared massive glass-forming alloys

The following alloys were prepared in a similar manner as in Example 1:

Table 1

Au52Ag6,38Pd2,42Cu18,675Ga8,225Si12,30> 1

Au51, 5Ag6,88Pd2,42Cu18,675Ga8,225Si12,30> 1

Au50.5Ag7.88Pd2.42Cu18.675Ga8.225Si 2.30> 1

Au48.5Ag9.88Pd2.42Cu18.675Ga8.225Si12.30> 1

Au52.99Ag5.79Pd2.02C1 l8.675Ga8.225Si12.30> 1

Au52.79Ag5.79Pd2.22Cu18.675Ga8.225Si12.30> 1

Au52,39Ag5,79Pd2,62Cu18,675Ga8,225Si12,30> 1

Au52, 19Ag5,79Pd2,82Cu18,675Ga8,225Si12,30> 1

Au49Ag5.5Pd2.3Cu23.54Sn3 _; 36Si16,3 3d _c

Au49Ag5,5Pd2,3Cu20,175Sn6,725Si16,3 ~ 1

Au50.29 Ag5.65 Pd2.36 Cu23.54 Sn3.36 Si14.8 3-sec

Au51, 59Ag5.79Pd2.42Cu20.175Sn6.725Si13.3 3Sd _c

Au49Ag5,5Pd2,3Cu23,54ln3,36Si16,3 3 ^ d _c

Au49Ag5.5Pd2.3Cu20, 175ln6.725Si16.3 1 -5d _c <3

Au51, 59Ag5,79Pd2,42Cu20,175ln6,725Si13,3

Au51, 59Ag5,79Pd2,42Cu20,18ln3,36Sn3,36Si13,3

Au51, 59Ag5,79Pd2,42Cu20,18ln3,366a3,36Si13,3

Au51, 59Ag5.79Pd2.42Cu20, 18Ga3.36Sn3.36Si13.3

The critical thickness of the samples (the thickness to which the sample remains amorphous) was determined by making samples of different diameter. The completely amorphous character of the samples was confirmed by X-ray diffractometry (Cu Kalpha, 20 ° <2Θ <80 °). In addition, was in calorimetric

Measurements (Perkin Elmer DSC8500) determined the enthalpy of crystallization of the respective X-ray amorphous 1 mm sample. By comparing the

Crystallization enthalpies can thus confirm the completely amorphous character of thicker samples. bibliography

C.W. Corti; What is a white gold? Progress on the Issues; The Santa Fe

Symposium, 2005, 103-120

[2] Eisenbart, M., Klotz, U.E., Busch, R. & Gallino, I. A colorimetric and

Microstructural study of the tarnishing of gold-based bulk metallic glasses.

(2014), Corrosion Science, 85, 258-269.

[3] Eisenbart, M ,, Klotz, U, E., Busch, R ,, & Gallino, I. On the abnormal room

tennperature tarnishing of an 18k gold bulk metallic glass altoy. (2014) Journal of Alloys and Compounds, 615, S118-S122.

[4] Eisenbart, M. On the Processing and the Tarnishing Mechanism of Gold-based Bulk Metallic Glasses, Saarland University 2015

[5] Harper, J .; Charai, A .; Stolt, L; d'Heurle null, F. & Fryer, P. Room Temperature Oxidation of Silicon Catalyzed by Cu $ _3 $ Si. (1990) MRS Proceedings, 187, 2519-2521

[6] Alford, T.L .; Jaquez, E.J .; Theodore, N, D .; Russell, S.W .; Diale, M .; Adams, D. & Anders, S. Influence of interfacial copper on the room temperature oxidation of silicon. (1996) Journal of Applied Physics, AIP, 79, 2074-2078

[7] Guo, H., Zhang, W., Chen, MW, Saotome, Y., Fukuhara, M., & Inoue, A. Effect of Au on Cu-Ag-Si bulk metallic glasses. (2011) Metallurgical and Materials Transactions A, 42 (6), 1486-1490.

[8] Wang, S. & Chin, T. Tin-modified gold-based bulk metallic glasses. (2012) Gold Bull. 45, 3-8.

Claims

claims

1. White gold alloy of composition:

(AUL-a-Baga (Pdl _-c Ptc) b) lOO-xy (Cul-d-eLdMe) x (Sil-fGef) y

wherein:

L stands for In, Ga or Sn or

Ld is L diL ² d20derLdiL ² d2L ³ d3, wherein L, L ² and L ^{3 are selected} from the elements In, Ga or Sn, and M is one or more elements of the elements Ni, Co and Fe; x and y are at%, where

x = 10-30 at%,

y = 10-16.3at%,

where (100-x-y) and x and y may contain unavoidable trace impurities,

a, b, c, d, e and finely are fraction of 1, where

a = 0.02-0.20,

b = 0-0.1,

c = 0-1,

d = 0.02-0.40,

d1 = 0 to 0.4;

d2 = 0 to 0.4;

d3 - 0 to 0.4, where

d1 + d2 + d3 = d,

e = 0 - 0.12 (total fraction of elements Ni, Co and Fe) and

f = 0-0.40,

with the exception of the following alloys

AU49Ag5.5Pd2.3CU25.9Sm Sl16.3,

AU49Ag5,5Pd2,3CU25,9GaiSil6,3,

AU65,2Ag5CU5Ga9,3Sl ^'l5,5,

AU52,1lAg7,52CUl5,57Ga9,3Sil5,5.

2. white gold alloy according to claim 1, characterized in that e = 0.

3. white gold alloy according to claim 1 or 2, characterized in that a = 0.075 - 0, 12, preferably a = 0.085 - 0, 12th

4. white gold alloy according to claim 1 or 2, characterized in that x = 10-30 at%,

y = 10-16.3 at%,

a = 0.05-0.15,

b = 0.02-0.08,

c = 0-0.5

d = 0.075 -0.35,

d1 = 0 to 0.35;

d2 = 0 to 0.35;

d3 = 0 to 0.35; and

d1 + d2 + d3 = d,

e = 0,

f = 0-0.20.

5. white gold alloy according to one of claims 1 to 4, characterized

marked that

x = 15-27 at%,

y = 12-16.3at%,

a = 0.075-0.12,

b = 0.03-0.065,

c = 0

d = 0.1 -0.30,

d1 = 0 to 0.30;

d2 = 0 to 0.30;

d3 = 0 to 0.30; and

d1 + d2 + d3 = d,

e = 0,

f = 0.

6. white gold alloy according to one of claims 1 to 5, characterized in that

x = 20-27 at%,

y = 12-16%,

a = 0.085-0.12,

b = 0.036 -0.05,

c = 0,

d = 0.2 -0.28,

d1 = 0 to 0.28;

d2 = 0 to 0.28;

d3 = 0 to 0.28; and

d1 + d2 + d3 = d,

e = 0,

f = 0.

7. white gold alloy according to one of claims 1 to 6, characterized in that

x = 24-27 at%,

y = 12-14at%,

a = 0.095-0.1,

b = 0.036 -0.05,

c = 0

d = 0.24-0.26,

d1 = 0 to 0.26;

d2 = 0 to 0.26;

d3 = 0 to 0.26; and

d1 + d2 + d3 = d

e = 0,

f = 0.

8. white gold alloy according to claim 1 or 2, characterized in that x = 25 - 27 at%,

y = 10 - 13.3 at%,

a = 0.05 - 0.15,

b = 0.02-0.08,

c = 0,

d = 0.3 -0.35,

d1 = 0 to 0.35;

d2 = 0 to 0.35;

d3 = 0 to 0.30; and

d1 + d2 + d3 = d.

e = 0,

f = 0.

9. A method for producing a white gold alloy according to any one of claims 1 to 8, wherein the starting material materials according to the desired

Stoichiometry weighed and placed in a suitable crucible, then inductively melted and homogenized, the melt is then slowly heated to a desired Abgusstemperatur above the liquidus to ensure homogeneity of the melt and the melt is then poured into a suitable mold, prefers the following order

Elements in the crucible from bottom to top are observed: Pd / Pt-Ag-Au-Cu / Ni / Co / Fe-Ga / Sn / In-Si / Ge.

10. Use of a white gold alloy according to one of claims 1 to 8 in the manufacture of jewelry.