COPPER-BASED ALLOY FOR THE PRODUCTION OF BULK METALLIC GLASSES

Abstract

The present invention relates to an alloy which has the following composition:

Cu.sub.47 at %(x+y+z)(Ti.sub.aZr.sub.b).sub.cNi.sub.7 at %+xSn.sub.1 at %+ySi.sub.z

where
c=43-47 at %, a=0.65-0.85, b=0.15-0.35, where a+b=1.00;
x=0-7 at %;
y=0-3 at %, z=0-3 at %, where y+z4 at %.

Claims

1. An alloy which has the following composition:
Cu.sub.47 at %(x+y+z)(Ti.sub.aZr.sub.b).sub.cNi.sub.7 at %+xSn.sub.1 at %+ySi.sub.z where c=43-47 at %, a=0.65-0.85, b=0.15-0.35, where a+b=1.00; x=0-7 at %; y=0-3 at %, z=0-3 at %, where y+z4 at %; wherein the alloy optionally contains oxygen in a concentration of not more than 1.7 at % and the balance is unavoidable impurities.

2. The alloy of claim 1, wherein a=0.70-0.80 and b=0.20-0.30.

3. The alloy of claim 1, wherein y=0-2 at % and z=0-2 at %.

4. The alloy of claim 1, wherein x=5-7 at %, y=0-2 at % and z=0 at %; or wherein x=5-7 at %, y=0-2 at % and 0<z2 at %.

5. The alloy of claim 1, wherein x=0<5 at %, y=0-2 at % and z=0 at %; or x=0<5 at %, y=0-2 at % and 0<z2 at %.

6. (canceled)

7. The process of claim 13, wherein the melt is poured into a mold or subjected to atomization.

8. A bulk metallic glass containing the alloy of claim 1.

9. The bulk metallic glass of claim 8 having dimensions of at least 1 mm1 mm1 mm.

10. (canceled)

11. The alloy of claim 2, wherein y=0-2 at % and z=0-2 at %.

12. The alloy of claim 2, wherein x=5-7 at %, y=0-2 at % and z=0 at %; or wherein x=5-7 at %, y=0-2 at % and 0<z2 at %.

13. A process for producing the alloy of claim 1, the process comprising the steps of creating a melt comprising elemental forms of Cu, Ti, Zr, Ni, Sn and optionally Si, wherein the melt is kept under an inert atmosphere; pouring the melt into a mold or atomizing the melt; and cooling the melt.

14. The process of claim 13 wherein the melt is poured into a mold.

15. The process of claim 13 wherein the melt is atomized.

Description

[0015] It is an object of the present invention to provide an alloy which has a very high Tx value (i.e. a wide temperature window for thermoplastic forming) but does not achieve this at the expense of glass formation capability and can be produced inexpensively. The improved heat resistance should preferably also not have an adverse effect on other relevant properties such as the hardness.

[0016] The object is achieved by an alloy which has the following composition:

Cu.sub.47 at %(x+y+z)(Ti.sub.aZr.sub.b).sub.cNi.sub.7 at %+xSn.sub.1 at %+ySi.sub.z [0017] where [0018] c=43-47 at %, a=0.65-0.85, b=0.15-0.35, where a+b=1.00; [0019] x=0-7 at %; [0020] y=0-3 at %, z=0-3 at %, where y+z4 at %; [0021] wherein the alloy optionally contains oxygen in a concentration of not more than 1.7 at % and the balance is unavoidable impurities.

[0022] In the context of the present invention, it has been recognized that alloys having the above-defined composition have high T.sub.x values and thus improved heat resistance combined with a still good glass formation capability. The alloys of the invention are thus very suitable for, for example, thermoplastic forming.

[0023] Preference is given to y=0-2 at % and z=0-2 at %. Thus, when Si is present in the alloy its concentration is not more than 2 at % (e.g. 0.5 at %Si2 at %/e), with the proviso that the total concentration of Sn and Si is not more than 4 at %.

[0024] In a preferred embodiment, x=5-7 at % and y+z4. Particular preference is given to x=5-7 at %, y=0-2 at % and z=0 at %; or x=5-7 at %, y=0-2 at % and 0<z2 at % (more preferably 0.5<z2 at %).

[0025] As an alternative, it can also be preferred that x=0<5 at % (more preferably x=0-3 at %), y=0-2 at % and z=0 at %; or x=0<5 at % (more preferably x=0-3 at %), y=0-2 at % and 0<z2 at % (more preferably 0.5<z2 at %), with in both cases preference being given to y+z4.

[0026] Preference is given to a=0.70-0.80 and b=0.20-0.30. The atomic ratio of Ti to Zr is defined by the values of a and b.

[0027] If the alloy of the invention contains oxygen, this is present in a concentration of not more than 1.7 at %, for example 0.01-1.7 at % or 0.02-1.0 at %.

[0028] The proportion of unavoidable impurities in the alloy is preferably less than 0.5 at %, more preferably less than 0.1 at %, even more preferably less than 0.05 at % or even less than 0.01 at %.

[0029] In an illustrative embodiment, the alloy of the invention has the following composition: [0030] 42-46 at % of Cu; [0031] 28-40 at % of Ti, more preferably 30-38 at % of Ti, and 7-15 at % of Zr, where Ti and Zr are together present in a concentration in the range of 43-47 at %; [0032] 7-11 at % of Ni (more preferably 7-9 at % of Ni), [0033] 1-3 at % of Sn and optionally 2 at % of Si (e.g. 0.5 at %Si2 at %), where, [0034] if Si is present, the total concentration of Sn+Si is not more than 4 at %,
wherein the alloy optionally contains oxygen in a concentration of not more than 1.7 at % and the balance is unavoidable impurities.

[0035] In a further illustrative embodiment, the alloy of the invention has the following composition: [0036] 36-42 at % of Cu, more preferably 37-41 at % of Cu; [0037] 28-40 at % of Ti, more preferably 30-38 at % of Ti, and 7-15 at % of Zr, where Ti and Zr are together present in a concentration in the range of 43-47 at %; [0038] 11-15 at % of Ni. [0039] 1-3 at % of Sn and optionally 2 at % of Si (e.g. 0.5 at %Si2 at %), where, if Si is present, the total concentration of Sn+Si is not more than 4 at %,
wherein the alloy optionally contains oxygen in a concentration of not more than 1.7 at % and the balance is unavoidable impurities.

[0040] The composition of the alloy can be determined by optical emission spectrometry using inductively coupled plasma (ICP-OEC).

[0041] The alloy of the invention preferably has a crystallization temperature T.sub.x and a glass transition temperature T.sub.g which satisfy the following condition:

T.sub.x=T.sub.xT.sub.g55 C.

[0042] Greater preference is given to T.sub.x64 C. or even 67 C., e.g. 64T.sub.x95 C. or 67T.sub.x90 C.

[0043] The glass transition temperature T.sub.g and the crystallization temperature T.sub.x are determined by DSC (differential scanning calorimetry). The onset temperature is employed in each case. The cooling and heating rates are 20 C./min. The DSC measurement is carried out under an argon atmosphere in an aluminum oxide crucible.

[0044] The alloy is preferably an amorphous alloy. In a preferred embodiment, the alloy of the invention has a crystallinity of less than 50%, more preferably less than 25% or is even entirely amorphous. An entirely amorphous material displays no diffraction reflections in an X-ray diffraction pattern.

[0045] The proportion of crystalline material is determined by means of DSC as a ratio of maximum enthalpy of crystallization (determined by crystallization of an entirely amorphous reference sample) and the actual enthalpy of crystallization in the sample.

[0046] The invention further provides a process for producing the above-described alloy, wherein the alloy is obtained from a melt containing Cu, Ti, Zr, Ni, Sn and optionally Si.

[0047] The melt is preferably kept under an inert gas atmosphere (e.g. a noble gas atmosphere).

[0048] The constituents of the alloy can each be introduced in their elemental form (e.g. elemental Cu, etc.) into the melt. As an alternative, it is also possible for two or more of these metals to be prealloyed in a starting alloy and this starting alloy then to be introduced into the melt.

[0049] Cooling and solidification of the melt produce the alloy as solid or solid body.

[0050] The melt can, for example, be poured into a mold or subjected to atomization. Atomization enables the alloy to be obtained in the form of a powder whose particles have essentially a spherical shape. Suitable atomization processes are known to those skilled in the art, for example gas atomization (e.g. using nitrogen or a noble gas such as argon or helium as atomizing gas), plasma atomization, centrifugal atomization or no-crucible atomization (e.g. a rotating electrode process (REP), in particular a plasma rotating electrode process (PREP)). A further illustrated process is the EIGA (electrode induction melting gas atomization) process, namely inductive melting of the starting material and subsequent gas atomization. The powder obtained by atomization can subsequently be used in an additive manufacturing process or else be subjected to thermoplastic forming.

[0051] Owing to the very good glass formation capability of the alloy of the invention, it can readily be obtained in the form of an amorphous alloy.

[0052] The present invention further provides a bulk metallic glass which contains or even consists of the above-described alloy.

[0053] The bulk metallic glass preferably has dimensions of at least 1 mm1 mm1 mm.

[0054] The bulk metallic glass preferably has a crystallinity of less than 50%, more preferably less than 25% or is even entirely amorphous.

[0055] The production of the bulk metallic glass can be carried out by processes known to those skilled in the art. For example, the above-described alloy is subjected to an additive manufacturing process or thermoplastic forming or is poured as melt into a mold.

[0056] For the additive manufacturing process or thermoplastic forming, the alloy can, for example, be used in the form of a powder (e.g. a powder obtained by atomization).

[0057] Components having a complex three-dimensional geometry can be produced directly by additive manufacturing processes. The term additive manufacture is used to refer to a process in which a component is built up layer-by-layer by deposition of material on the basis of digital 3D construction data. A thin layer of the powder is typically applied to the building platform. The powder is melted by means of a sufficiently high energy input, for example in the form of a laser beam or electron beam, at the areas prescribed by the computer-generated construction data. The building platform is then lowered and a further application of powder is carried out. The further powder layer is once again melted and is joined to the underlying layer at the defined areas. These steps are repeated until the component is present in its final shape.

[0058] Thermoplastic forming is usually carried out at a temperature which is between T.sub.g and T.sub.x of the alloy.

[0059] The invention will be illustrated in detail with the aid of the following examples.

EXAMPLES

[0060] Inventive alloys E1-E8 whose respective composition is indicated in Table 1 below were produced. In the comparative examples, the alloys CE1-CE5 were produced.

[0061] The production conditions were identical in all examples and only the composition was varied.

[0062] The T.sub.x value (i.e. the difference between crystallization temperature T.sub.x and glass formation temperature T.sub.g) and also the critical casting thickness D.sub.c of the alloys are reported in Table 1.

[0063] As already indicated above, the determination of the glass transition temperature T.sub.g and the crystallization temperature T.sub.x was carried out by DSC on the basis of the onset temperatures and at cooling and heating rates of 20 C./min.

[0064] The critical casting thickness D was determined as follows:

[0065] A cylinder having a length of 50 mm and a particular diameter is cast. The determination of D.sub.D is carried out by parting of the specimen at about 10-15 mm from the gate mark (in order to exclude the heat influence zone) and XRD measurement at the parting position over the total cross section.

[0066] The production of the alloys was carried out in an electric are furnace from pure elements by melting and remelting to give a compact body which was melted again and cast into a Cu chill mold.

TABLE-US-00001 TABLE 1 Composition of the alloys and T.sub.x and D.sub.c values thereof Cu Ti Zr Ni Sn Si [at [at [at [at [at [at T.sub.x D.sub.c %] %] %] %] %] %] [ C.] [mm] CE1 47 34 11 8 0 0 43 4 E1 45 34 11 8 2 0 56 7 E2 45 35.8 9.2 8 2 0 56 E3 45 37.5 7.5 8 2 0 58 E4 41.5 34 11 11.5 2 0 64 6 E5 39.8 34 11 13.2 2 0 68 5 CE2 34.5 34 11 18.5 2 0 81 0.5 CE3 48.5 34 11 4.5 2 0 47 5 CE4 50.2 34 11 2.8 2 0 43 6 E6 44.0 34 11 8 2 1 71 6 E7 43.5 34 11 8 2 1.5 73 5 E8 38.2 34 11 13.3 2 1.5 85 4 CE5 42 34 11 8 2 3 62 0.5

[0067] The alloy of comparative example CE1 has the composition Cu.sub.47Ti.sub.34Zr.sub.11N.sub.18. If a small amount of the copper is replaced by Sn, a significant increase in the T.sub.x value occurs and the D.sub.c value also increases very substantially, see example E1. A change in the relative proportions of Ti and Zr also gives this improvement in the T.sub.x value compared to the starting alloy, see examples E2 and E3.

[0068] An increase in the Ni concentration (see examples E4 and E5) leads to a further improvement in the T.sub.x value and at the same time the D.sub.c value can be kept at a relatively high level. An excessively high nickel concentration leads to a significant decrease in the D.sub.c value (see comparative example CE2), while an excessively low Ni concentration leads to a significant decrease in the T.sub.x value (see comparative examples CE3 and CE4).

[0069] As examples E6-E8 show, the presence of Si leads to a further increase in the T.sub.x value, so that values of more than 70 C. (E6 and E7) or even more than 80 C. (E8) are obtained. The D.sub.c values are in these cases still at a sufficiently high level. Owing to the very high T.sub.x values, the alloys are particularly well-suited to thermoplastic forming. As comparative example CE5 shows, an excessively high total concentration of Sn+Si leads to a deterioration in the T.sub.x and D.sub.c values.

[0070] As the data in Table 1 show, high Tx values can be achieved with the alloys of the invention (i.e. there is a wide temperature window for thermoplastic forming), while at the same time the critical casting thickness Dc can also be kept at a sufficiently high level.

[0071] In addition, the Vickers hardness was determined at a test force of 5 kilopond (HV5) for the alloys of examples E1, E5 and E6.

TABLE-US-00002 TABLE 2 Vickers hardness of the alloys HV5 Alloy of example E1 600-640 Alloy of example E5 590-612 Alloy of example E6 610-630

[0072] The data of Table 2 show that the alloys of the invention also display good hardness values.