Patent Application
20160010194
The invention concerns a solid amorphous alloy.
The invention further concerns a timepiece component made of this type of alloy.
The invention concerns the fields of horology and jewellery, in particular for the following structures: watch cases, case middles, main plates, bezels, push-buttons, crowns, buckles, bracelets, rings, earrings and others.
Amorphous alloys are increasingly used in the fields of horology and jewellery, in particular for the following structures: watch cases, case middles, main plates, bezels, push-buttons, crowns, buckles, bracelets, rings, earrings and others.
Components for external use, intended to be in contact with the user's skin, must obey certain constraints, due, in particular to the toxicity or allergenic effects of some metals, especially beryllium and nickel. Despite the specific intrinsic properties of such metals, endeavours are made to market alloys containing little or no beryllium or nickel, at least for components likely to come into contact with the user's skin.
Zirconium-based solid amorphous alloys have been known since the 1990s. The following publications concern such alloys:
[1] Zhang, et al., Amorphous Zr—Al—TM (TM═Co, Ni, Cu) Alloys with Significant Supercooled Liquid Region of Over 100 K, Materials Transactions, JIM, Vol. 32, No. 11 (1991) pp. 1005-1010.
[2] Lin, et al., Effect of Oxygen Impurity on Crystallization of an Undercooled Bulk Glass Forming Zr—Ti—Cu—Ni—Al Alloy, Materials Transactions, JIM, Vol. 38, No. 5 (1997) pp. 473-477.
[3] U.S. Pat. No 6,592,689.
[4] Inoue, et al., Formation, Thermal Stability and Mechanical Properties of Bulk Glassy Alloys with a Diameter of 20 mm in Zr—(Ti,Nb)—Al—Ni—Cu System, Materials Transactions, JIM, Vol. 50, No. 2 (2009) pp. 388-394.
[5] Zhang, et al., Glass-Forming Ability and Mechanical Properties of the Ternary Cu—Zr—Al and Quaternary Cu—Zr—Al—Ag Bulk Metallic Glasses, Materials Transactions, Vol. 48, No. 7 (2007) pp. 1626-1630.
[6] Inoue, et al., Formation of Icosahedral Quasicristalline Phase in Zr—Al—Ni—Cu—M (M═Ag,Pd,Au or Pt) Systems, Materials Transactions, JIM, Vol. 40, No. 10 (1999) pp. 1181-1184.
[7] Inoue, et al., Effect of Additional Elements on Glass transition Behavior and Glass Formation tendency of Zr—Al—Cu—Ni Alloys, Materials Transactions, JIM, Vol. 36, No. 12 (1995) pp. 1420-1426.
Amorphous alloys with the best glass forming ability, known as and referred to hereafter as “GFA”, are found in the following systems:
Given the toxicity of beryllium, alloys containing beryllium cannot be used for applications involving contact with skin, such as external watch parts or suchlike. However, zirconium-based, beryllium free amorphous alloys generally exhibit a critical diameter which is lower than that of alloys containing beryllium, which is unfavourable for making solid parts. The best composition in terms of critical diameter (Dc) and the difference ΔTx between the crystallisation temperature Tx and the vitreous transition temperature Tg (supercooled liquid region) in the Zr—Cu—Ni—Al system is the alloy Zr65Cu17.5Ni10Al7.5 [1].
Modifications are also known wherein the GFA has been improved by adding titanium and/or niobium:
In general, the addition of titanium and/or niobium increases the critical diameter of alloys, however the modification greatly decreases the gradient ΔTx and therefore the process window for any hot deformation of such alloys. Further, given its very high melting temperature (2468° C.), niobium is not easy to melt, which complicates fabrication of a homogeneous alloy.
It is also known that adding silver to ternary Zr—Cr—Al alloys increases critical diameter, especially for modifications of the composition Zr46Cu46Al8, for example Zr42Cu42Al8Ag8 [5].
However, due to the high level of copper and the absence of nickel, these alloys are not very resistant to corrosion and even tend to become discoloured (and/or turn black) over time at ambient temperature.
Further, it is known that adding more than 5% silver, gold, palladium or platinum to Zr—Cu—Ni—Al amorphous alloys stimulates the formation of quasicrystals during devitrification of such alloys by a heat treatment between Tg and Tx [6].
In publication [7], the effect of an additional element M (M═Ti, Hf, V, Nb, Cr, Mo, Fe, Co, Pd or Ag) on the GFA of a Zr—Cu—Ni—Al—M alloy was tested.
The results demonstrate that only titanium, niobium and palladium increase the critical diameter of the alloy, yet also greatly decrease the gradient ΔTx. No particular effect is cited as regards the addition of silver to the alloy.
The documents below include zirconium based alloys with silver or gold.
U.S. Pat. Nos. 5,980,652 and 5,803,996 describe alloys of the following type: Zrbar(Ti, Hf,Al,Ga)5-20-(Fe, Co, Ni,Cu)20-40-(Pd, Pt,Au,Ag)0-10 and more particularly alloys with palladium and/or platinum, a single example citing the addition of 1% gold or 1% silver, with no evaluation of the effect of this addition on the increase in critical diameter.
EP Patent No 0905268 describes alloys of the following type: (Zr, Hf)25-85-(Ni, Cu, Fe, Co, Mn)5-70-Al0-35-T>0-15 where T is an element with a negative enthalpy of mixing with one of the other elements, and is chosen from the following group: T═Ru, Os, Rh, Ir, Pd, Pt, V, Nb, Ta, Cr, Mo, W, Au, Ga, Ge, Re, Si, Sn or Ti. This document only gives one example with palladium. It does not demonstrate any positive effect of elements T on Dc and ΔTx.
EP Patent No 0905269 describes a method of manufacturing a multi-phase alloy (14-23% crystalline phase in an amorphous matrix) by a heat treatment of Zr25-85-(Ni,Cu)5-70-Al>0-35-Ag>0-15.
CN Patent No 101314838 describes alloys of the following type: Zr41-63-Cu18-46-Ni1.5-12.5-Al4-15-Ag1.5-26
In short, little is known about the effects of adding a low concentration of silver or gold to such amorphous alloys, and such effects have not been subject to any particular investigation in the literature.
The invention proposes to increase the critical diameter of zirconium based, beryllium free, amorphous alloys, while maintaining a high ΔTx value.
The invention concerns a zirconium and/or hafnium based, beryllium free, solid, amorphous alloy, with the addition of silver and/or gold and/or platinum to increase its critical diameter.
To this end, the invention concerns a solid amorphous alloy, characterized in that it is beryllium free and consists, in atomic percent values, of:
More specifically, the base composed of zirconium and/or hafnium, has a total zirconium and hafnium content with a minimum value of 57% and a maximum value of 63%;
The invention further concerns a timepiece or jewellery component made of this type of alloy.
Other features and advantages of the invention will appear upon reading the following detailed description, with reference to the annexed drawings, in which:
The invention concerns the fields of horology and jewellery, in particular for the following structures: watch cases, case middles, main plates, bezels, push-buttons, crowns, buckles, bracelets, rings, earrings and others.
The invention proposes to produce beryllium free amorphous steels, devised to have similar properties to those of amorphous alloys containing beryllium. Hereafter, an alloy containing no beryllium will be termed a “beryllium free alloy” and an alloy containing less than 0.5 atomic percent of nickel will be termed a “nickel free alloy”.
“Containing no beryllium” means that the level of beryllium is preferably zero, or very low, the same as impurities, and preferably less than or equal to 0.1%.
It is therefore sought to manufacture alloys, which include substitution elements for beryllium, and which have high values of critical diameter Dc and gradient ΔTx.
The invention further concerns a zirconium based, beryllium free, solid, amorphous alloy, with the addition of silver and/or gold and/or platinum to increase the critical diameter Dc.
More specifically, the invention concerns a solid amorphous alloy, characterized in that it contains no beryllium and in that it consists, in atomic percent values, of:
More specifically, the base composed of zirconium and/or hafnium, has a total zirconium and hafnium content with a minimum value of 57% and a maximum value of 63%;
Although numerous zirconium based amorphous compositions are known, the development of an amorphous alloy according to the composition of the invention produces an effect which is novel and extremely surprising, since in particular 2% of an additive is sufficient to significantly increase the critical diameter.
The effect of the range 1.2% to 4.5% of the second additional metal chosen from a second group including silver, gold and platinum is clear: the addition to the alloy of one or the other, or of several, of these elements increases the critical diameter in comparison to an alloy that does not contain these additives, without decreasing the gradient ΔTx.
A transition area showing a negative gradient of the critical diameter starts at around 4.5% and, beyond 5%, the critical diameter is significantly reduced with respect to the optimum quantity which is comprised (minimum and maximum values included) between the lower threshold of 1.2%, where the influence of the addition of the second additional metal starts to be seen, and the upper threshold of 4.5%.
The range from 1.2% to 4.0% is favourable, and very good results have been obtained in the range from 1.5% to 3.8% and more particularly still in proximity to 2.8% in the range from 2.6% to 3.0%.
More specifically, the gold content is between 1.5% and 2.5%.
More specifically, the platinum content is between 1.5% and 2.5%.
More specifically, the silver content is between 1.0% and 3.8%.
In a specific embodiment, the total zirconium and hafnium content in the base is limited to 60%.
In a specific variant, the alloy according to the invention does not contain titanium.
In a specific variant, the alloy according to the invention does not contain niobium.
In a specific variant, the alloy according to the invention does not contain either titanium or niobium.
Palladium did not demonstrate any positive effect during the development of the invention, unlike the metals of the second group: silver, gold and platinum. It is possible to include palladium in this second group, but its content should preferably remain very low, in particular less than or equal to 1.0%.
A non-limiting example embodiment is described hereafter: alloy charges of around 70 g are prepared in an arc furnace using pure elements (purity of more than 99.95%). The pre-alloy thereby obtained is then melted again in a centrifugal casting machine and cast in a copper mould in the shape of a cone (maximum thickness 11 mm, width 20 mm, opening angle 6.3°).
A DSC measurement is made of the vitreous transition and crystallisation temperature on samples taken from the end of each cone. A metallographic cut is made in the middle of each cone lengthways to measure the critical diameter Dc*, wherein Dc* is the thickness of the cone at the place where the crystalline area starts, as seen in
The following table summarises the test carried out (the compositions in italics are compositions known in the literature). It can be seen that with the proper quantity of silver, gold or platinum additive, the critical diameter Dc* can be increased significantly in comparison to basic alloys which do not contain these additives. Further, these additives do not decrease the gradient Δtx.
Zr65Cu15Ni10Al10
374
478
104
4.9
Zr61Ti2Nb2Cu17.5Ni10Al7.5
378
447
69
8.5
Zr58.5Cu15.6Ni12.8Al10.3Nb2.8
409
497
88
5.7
Zr52.5Ti5Cu17.9Ni14.6Al10
404
459
55
6.8
More specifically, the following alloys have given particularly satisfactory results:
A first favourable sub-family concerns a total zirconium and hafnium content of more than 57.0%, with a total first additional metal content of less than or equal to 0.5%.
A second favourable sub-family concerns a total zirconium and hafnium content of less than or equal to 53.0%, with a total first additional metal content of between 2.0% and 3.0%.
In other variants of the invention, other elements, such as iron and manganese, are incorporated.
The search for a compromise makes it possible to identify the best composition, in particular with an ideal silver content, which is advantageous due its cost which is lower than or equal to that of gold and platinum, yet provides the required effects.
To optimise the alloy, several rules were determined during experiments: Particularly favourable results were obtained with:
The question of incorporating nickel in the alloy arises because of the allergenic effects of nickel taken on its own or in an alloy composition containing certain other metals. However, the presence of nickel in an amorphous alloy is favourable for obtaining zirconium based amorphous alloys with high critical diameters and good anti-corrosion properties. By analogy, stainless steels also contain a high nickel content, and are widely used in jewellery and horology.
The important constraint to be observed is that the alloy obtained satisfies the nickel release test in conformity with EN1811.
In a particular variant of the invention, the alloy includes less than 0.5% nickel.
It is understood that it is not sufficient simply to replace nickel with another metal to obtain the equivalent characteristics. The elements having a close atomic radius are iron, cobalt, palladium, manganese and chromium. This therefore means rethinking the entire composition of the amorphous alloy.
Thus, the invention concerns a second solid amorphous alloy, characterized in that it contains no beryllium and in that it consists, in atomic percent values, of:
More specifically, the base composed of zirconium and/or hafnium, has a total zirconium and hafnium content with a minimum value of 57% and a maximum value of 63%;
More specifically, the gold content is between 1.5% and 2.5%.
More specifically, the platinum content is between 1.5% and 2.5%.
The invention also concerns a timepiece or jewellery component made of an alloy according to the invention, or a timepiece or piece of jewellery, particularly a watch, or a bracelet or suchlike.
| Number | Date | Country | Kind |
|---|---|---|---|
| 13196050.2 | Dec 2013 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/074283 | 11/11/2014 | WO | 00 |
