METAL ALLOY

Abstract

The present invention relates to conductive multicomponent multiphase metal alloy. The metal alloy has the following (in atom-%):Ni, in a total amount of 35-70; wherein the remaining 30-65 comprises at least three elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V in a total amount of at least 30. The metal alloy comprises at least three distinct crystalline phases, at least one phase being an intermetallic phase. The present invention also relates to an electrode material comprising said alloy, to a method for forming a coating on said alloy, and to a method for manufacturing said alloy.

Claims

1. A conductive electrode for aluminum processing comprising a conductive multicomponent multiphase metal alloy having the following composition (in atom-% of the metal alloy) Ni, in a total amount of 35-70; at least three elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V in a total amount of at least 30-65; the balance being Ni and optionally naturally occurring impurities in an amount of less than 0.4; wherein the metal alloy comprises at least three distinct crystalline phases, at least one phase being an intermetallic phase.

2. The conductive electrode according to claim 1, wherein the metal alloy comprises at least four elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V, in a total amount of 30-60 atom-% of the metal alloy.

3. The conductive electrode according to claim 1, wherein the metal alloy comprises 6-14 elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V, in a total amount of 30-50 atom-% of the metal alloy.

4. The conductive electrode according to claim 1, the metal alloy having the following composition (in atom-% of the metal alloy) TABLE-US-00030 Ni >35, and Cr 1-25 Mn 1-10 Nb and/or Ta 0.1-10.sup.  Fe 0.1-5   Ti 0.1-5   Sn 1-20 in a total amount of Cr, Mn, Nb, Ta, Fe and Ti of at least 20 and, optionally, TABLE-US-00031 Zr ≤15 B ≤10 Si ≤15 Ce and/or La ≤10 Gd ≤5 Nd ≤5 Sm and/or Y ≤5 Hf ≤10 P ≤10 Al ≤10 V ≤10 Ca ≤10 in a total amount of Zr, B, Si, Ce, La, Gd, Nd, Sm, Y, Hf, P, Al, V, Ca of no more than 45.

5. The conductive electrode according to claim 4, the metal alloy having the following composition (in atom-% of the metal alloy) TABLE-US-00032 Cr  3-20 Mn 1-4 Nb and/or Ta 0.5-10  Fe 0.4-1.2 Ti 0.4-1.2 Sn  1-20 in a total amount of Cr, Mn, Nb, Ta, Fe and Ti of at least 20 and, optionally, TABLE-US-00033 Zr .sup. 7-12 B 0.3-4  Si .sup. 5-14 Ce and/or La 0.3-8  Gd 0.5-2  Nd 0.1-1  Sm and/or Y 0.1-10 Hf 0.1-10 P 0.1-10 Al 0.1-10 V 0.1-10 in a total amount of Zr, B, Si, Ce, La, Gd, Nd, Sm, Y, Hf, P, Al, V, Ca of no more than 45; the balance being Ni in an amount of at least 45 atom-%, and optionally other naturally occurring impurities.

6. The conductive electrode according to claim 4, wherein the metal alloy comprises (in atom-% of the metal alloy) TABLE-US-00034 Ni 53-63; and Cr   10-25 Mn   1-10 Nb and/or Ta 0.1-5 Fe 0.1-5 Ti 0.1-5 Zr   5-15 Sn   5-15 B 0.1-3 in a total amount Cr, Mn, Nb, Ta, Fe, Ti, Zr, Sn and B of at least 37.

7. The conductive electrode according to claim 4, wherein the metal alloy comprises (in atom-% of the metal alloy TABLE-US-00035 Ni 47-57, and Cr   10-25 Mn   1-5 Nb and/or Ta 0.1-5 Fe 0.1-5 Ti 0.1-5 Zr   5-15 Sn   1-5 Si   5-15 Ce and/or La 0.1-3 Gd 0.5-2 Nd 0.1-2 in a total amount Cr, Mn, Nb and Ta, Fe, Zr, Sn, Si, Ce, La, Gd and Nd of at least 43.

8. The conductive electrode according to claim 4, wherein the metal alloy comprises (in atom-% of the metal alloy) TABLE-US-00036 Ni 55-65, and Cr 3-20 Mn 1-7  Nb and/or Ta 3-12 Fe 0.1-5   B 1-10 Sn 8-22 Ti 0.1-5   in a total amount of Cr, Mn, Nb, Ta, Fe, B, Sn, Ti of at least 45.

9. The conductive electrode according to claim 8, wherein the metal alloy comprises (in atom-% of the metal alloy) TABLE-US-00037 Cr  5-15 Mn 1-5 Nb and/or Ta  5-10 Fe 0.1-1.5 B 1-5 Sn 10-20 Ti 0.1-1.5 the balance being Ni and optionally other naturally occurring impurities.

10. The conductive electrode according to claim 4, wherein the metal alloy comprises (in atom-% of the metal alloy) TABLE-US-00038 Ni 63-73, and Cr 1-15 Mn 1-5  Nb and/or Ta 0.1-10   Ce and/or La 1-10 Fe 0.1-5   Sn 8-22 Ti 0.1-5   in a total amount of Cr, Mn, Nb, Ta, Ce, La, Fe, Sn, Ti of at least 27.

11. The conductive electrode according to claim 10, wherein the metal alloy comprises (in atom-% of the metal alloy) TABLE-US-00039 Cr  1-10 Mn 1-3 Nb and/or Ta 2-6 Ce and/or La 3-7 Fe 0.1-1.5 Sn 10-20 Ti 0.1-1.5 the balance being Ni and optionally other naturally occurring impurities.

12. The conductive electrode according to claim 1, wherein the metal alloy has a compositional entropy S.sub.mix of at least 1.0R, R being the gas constant.

13. The conductive electrode according to claim 1, wherein said metal alloy is adapted to form, upon contact with oxygen and a molten salt comprising fluoride, an intrinsic surface coating comprising at least one oxide, fluoride or oxyfluoride selected from the list of IMA approved minerals consisting of: TABLE-US-00040 Zircon (Zr, Hf)SiO.sub.4 Hafnon (Hf, Zr)SiO.sub.4 Stetindite (Ce, REE)SiO.sub.4 Xenotime (Y, Ce, La, REE)PO.sub.4 Wakefieldite (Ce, La, Y, Nd, Pb)VO.sub.4 Schiavinatoite (Nb, Ta)BO.sub.4 Béhierite (Ta, Nb)BO.sub.4 Ixiolite (Ta, Nb, Sn, Fe, Mn, Zr, Hf, Ti).sub.4O.sub.8 Wodginite (Mn, Ti, Sn, Fe, Ce, La)(Ta, Nb).sub.2O.sub.8 Samarskite (Y, Fe, Mn, REE, Th, U, Ca).sub.2(Nb, Ta, Ti).sub.2O.sub.8 Euxenite (Y, Ca, Ce, La, Th, U)(Nb, Ta, Ti).sub.2O.sub.6 Polycrase (Y, Ca, Ce, La, Th, U)(Ti, Nb, Ta).sub.2O.sub.6 Tapiolite (Fe, Mn)(Ta, Nb).sub.2O.sub.6 Fersmite (Ca, Ce, La, Na)(Nb, Ta, Sn, Ti).sub.2O.sub.5F Aeschynite (Ce, Ca, Fe, Th, Nd, Y)(Ti, Nb).sub.2O.sub.6 Fluornatromicrolite (Na, Ca, Ce, La, REE, U, Pb).sub.2(Ta, Nb, Sn, Ti).sub.2O.sub.6F Zirconolite (Ca, Y, REE)Zr(Ti, Nb, Al, Fe).sub.2O.sub.6F Kobeite (REE, Fe, U).sub.3Zr(Ti, Nb).sub.3O.sub.12 Gagarinite Na(Ca, Ce, La, Y, REE).sub.2F.sub.6 Davidite (La, Ce, Ca)(Y, U)(Ti, Fe).sub.20O.sub.38 Fluocerite (Ce, La, Y, REE, Ca)F.sub.3 Simpsonite Al.sub.4(Ta, Nb, Sn, Ti).sub.3O.sub.13 Albite (Na, Ca)AlSi.sub.3O.sub.8 Wöhlerite NaCa.sub.2(Zr, Hf, Nb, Ta, Ti)Si.sub.2O.sub.7F.sub.2 Nioboholtite (Nb, Ta)Al.sub.6BSi.sub.3O.sub.18 Vigezzite (Ca, Ce, La)(Nb, Ta, Ti).sub.2O.sub.6) Loparite-Ce Na(Ce, La, REE)(Ti, Nb, Ta).sub.2O.sub.6 Vlasovite (Na.sub.2ZrSi.sub.4O.sub.11) Normandite (NaCa(Mn, Fe)(Ti, Nb, Ta, Zr)(Si.sub.2O.sub.7)OF) Lakargiite Ca(Zr, Sn, Ti)O.sub.3 Foordite Sn(Nb, Ta).sub.2O.sub.6 Ainalite Sn(Nb, Fe, Ta)O.sub.2.

14. The conductive electrode according to claim 1, wherein the metal alloy further comprises, on at least one outer surface, an intrinsic surface coating comprising at least one oxide, fluoride or oxyfluoride selected from the list of IMA approved minerals consisting of: TABLE-US-00041 Zircon (Zr, Hf)SiO.sub.4 Hafnon (Hf, Zr)SiO.sub.4 Stetindite (Ce, REE)SiO.sub.4 Xenotime (Y, Ce, La, REE)PO.sub.4 Wakefieldite (Ce, La, Y, Nd, Pb)VO.sub.4 Schiavinatoite (Nb, Ta)BO.sub.4 Béhierite (Ta, Nb)BO.sub.4 Ixiolite (Ta, Nb, Sn, Fe, Mn, Zr, Hf, Ti).sub.4O.sub.8 Wodginite (Mn, Ti, Sn, Fe, Ce, La)(Ta, Nb).sub.2O.sub.8 Samarskite (Y, Fe, Mn, REE, Th, U, Ca).sub.2(Nb, Ta, Ti).sub.2O.sub.8 Euxenite (Y, Ca, Ce, La, Th, U)(Nb, Ta, Ti).sub.2O.sub.6 Polycrase (Y, Ca, Ce, La, Th, U)(Ti, Nb, Ta).sub.2O.sub.6 Tapiolite (Fe, Mn)(Ta, Nb).sub.2O.sub.6 Fersmite (Ca, Ce, La, Na)(Nb, Ta, Sn, Ti).sub.2O.sub.5F Aeschynite (Ce, Ca, Fe, Th, Nd, Y)(Ti, Nb).sub.2O.sub.6 Fluornatromicrolite (Na, Ca, Ce, La, REE, U, Pb).sub.2(Ta, Nb, Sn, Ti).sub.2O.sub.6F Zirconolite (Ca, Y, REE)Zr(Ti, Nb, Al, Fe).sub.2O.sub.6F Kobeite (REE, Fe, U).sub.3Zr(Ti, Nb).sub.3O.sub.12 Gagarinite Na(Ca, Ce, La, Y, REE).sub.2F.sub.6 Davidite (La, Ce, Ca)(Y, U)(Ti, Fe).sub.20O.sub.38 Fluocerite (Ce, La, Y, REE, Ca)F.sub.3 Simpsonite Al.sub.4(Ta, Nb, Sn, Ti).sub.3O.sub.13 Albite (Na, Ca)AlSi.sub.3O.sub.8 Wöhlerite NaCa.sub.2(Zr, Hf, Nb, Ta, Ti)Si.sub.2O.sub.7F.sub.2 Nioboholtite (Nb, Ta)Al.sub.6BSi.sub.3O.sub.18 Vigezzite (Ca, Ce, La)(Nb, Ta, Ti).sub.2O.sub.6) Loparite-Ce Na(Ce, La, REE)(Ti, Nb, Ta).sub.2O.sub.6 Vlasovite (Na.sub.2ZrSi.sub.4O.sub.11) Normandite (NaCa(Mn, Fe)(Ti, Nb, Ta, Zr)(Si.sub.2O.sub.7)OF) Lakargiite Ca(Zr, Sn, Ti)O.sub.3 Foordite Sn(Nb, Ta).sub.2O.sub.6 Ainalite Sn(Nb, Fe, Ta)O.sub.2.

15. The conductive electrode according to claim 1, wherein the electrode is an anode.

16. The conductive electrode according to claim 1, wherein the electrode is a cathode.

17. A method for forming an intrinsic coating on a conductive electrode comprising: providing a metal alloy as defined in claim 1; providing a molten salt composition comprising fluoride; and submerging at least part of the metal alloy in the molten salt composition, thereby forming a mineral coating.

18. The method according to claim 17, wherein the molten salt comprises cryolite.

19. A method for oxidizing a conductive electrode comprising providing a metal alloy as defined in claim 1; providing an oxygen containing atmosphere; and heating at least part of the metal alloy in the oxygen containing atmosphere, thereby forming at least one oxide.

20. A method for fluoridizing a conductive electrode comprising providing a metal alloy as defined in claim 1; providing a fluoride containing atmosphere; and heating at least part of the metal alloy in the fluoride containing atmosphere, thereby forming at least one fluoride.

21. A method for manufacturing a conductive electrode comprising providing Ni in an amount of at least 35-70 atom-% of the metal alloy; providing a total of 30-65 atom-% of at least three elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al and V; melting the provided elements to form a melt; agitating said melt; and solidifying said melt to form a metal alloy.

22. The conductive electrode according to claim 2, wherein the metal alloy comprises at least five elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V, in a total amount of 30-60 atom-% of the metal alloy.

23. The conductive electrode according to claim 13, wherein the metal alloy has a compositional entropy S.sub.mix of 1.1R-1.5R, R being the gas constant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0141] FIG. 1 shows a micrograph of the external surface of an alloy according to the invention, after cryolite testing.

[0142] FIG. 2 shows a micrograph of the external surface of an alloy according to the invention, after cryolite testing.

[0143] FIG. 3 shows a micrograph of the bulk, in cross-section, of an alloy according to the invention, after cryolite testing.

[0144] FIGS. 4A and B shows micrographs of the cross-section of the alloy, showing both the bulk and the intrinsic coating, after cryolite testing.

[0145] FIG. 5 shows a micrograph of the bulk, in cross-section, of an alloy according to the invention, after cryolite testing.

[0146] FIGS. 6A and B shows micrographs of the cross-section of the alloy, showing both the bulk and the intrinsic coating, after cryolite testing.

[0147] FIG. 7 show ionic radius plotted against the ionic charge for numerous elements.

EXAMPLES

[0148] Multicomponent metallic alloys (alloys 1-4) with a plurality of HFSEs (usually 5-8) have been produced by vacuum induction melting (VIM). Pure elements were weighed, cleaned, inductively heated, agitated and melted at >1300° C. under vacuum, and, then under low-pressure argon, poured into copper moulds for rapid freezing to achieve ingots having fine grain sizes of 1-10 microns. Alloy ingots had a typical mass of 1.5 kg and were shaped into both cylinders and blocks. These ingots were then used for cryolite testing at 975° C. for several weeks, with continuous >1000-hour exposure to both Na.sub.3AlF.sub.6, Al.sub.2O.sub.3, CaF.sub.2, and O.sub.2 gas, by submerging samples of the ingots into molten cryolite having a temperature of 975 ° C. After roughly 1000 hours, the samples were collected from the cryolite melt and analysed using optical microscope and scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDS)

[0149] In all cases, the alloy samples formed a multitude of stable oxides, fluorides and oxy-fluorides at their external surfaces, with the typical mineral compositions listed above. The outer mineral layers were clearly visible in the cross-sections of metallographic samples after cryolite testing. SEM-EDS could pinpoint and detect specific mineral compounds, both on the surface and in the bulk of the material. Electrical conductivity tests were also performed on the mineral layers. The fact that stable, non-dissolving, mineral layers form on the alloys bodes well for high-purity aluminium production.

[0150] The results of the testing of the four alloys (Alloy 1-4, with compositions according to Tables 1-4, respectively), are summarised below, with reference to micrographs taken at the samples after cryolite testing.

Alloy 1

[0151]

TABLE-US-00013 TABLE 1 Alloy 1 composition (at %). 57.3 Ni 17.7 Cr 3.2 Mn 0.8 Nb/Ta 0.8 Fe 0.8 Ti 8.7 Zr 9.7 Sn 1.0 B

[0152] Assessment after cryolite testing as described above: no major corrosion on the surface, sample intact, no spalling, light blue appearance at surface, shiny metallic alloy underneath the mineral layer, electrically conductive.

[0153] In the bulk alloy, at least one of the following intermetallics formed, as specified by SEM-EDS: Cr.sub.2B, Nb.sub.3B.sub.2, ZrNi.sub.5 and ZrNi.sub.2Sn.

[0154] Mineral layers at surface: numerous phases and solid-solutions of zirconolite, schiavinatoite, ixiolite, kobeite, etc.

[0155] Alloy 1 is a multicomponent metallic alloy comprising distinct equilibrium phases, as specified by SEM-EDS. FIG. 1 is a micrograph showing the external surface of the alloy after cryolite testing. The external surface shows

[0156] i) Solid solution of Ni—Cr—Sn with small additions of Nb, Ta, Zr, Fe, Mn, Ti.

[0157] ii) Mixed mineral layer, comprising zirconolite, schiavinatoite, ixiolite, kobeite, etc. NB. traces of Na, Ca, Al and F come from the cryolite salt mixture

[0158] The entropy of mixing for alloy 1 was calculated using formula 1 to S.sub.mix=1.34 R.

Alloy 2

[0159]

TABLE-US-00014 TABLE 2 Alloy 2 composition (at %). 52.6 Ni 16.2 Cr 3.0 Mn 0.8 Nb/Ta 0.7 Fe 0.7 Ti 9.0 Zr 9.0 Si 3.0 Ca 0.7 Ce 2.9 Sn 1.1 Gd 0.3 Nd

[0160] Assessment after cryolite testing as described above: no major corrosion on the surface, sample intact, no spalling, brown-green appearance at surface, shiny metallic alloy underneath the mineral layer, electrically conductive.

[0161] In the bulk alloy, the following intermetallics formed, as determined by SEM-EDS: ZrSi and (Ce,Gd,Nd,Ca)Ni.sub.5Sn

[0162] Mineral layers at surface: numerous phases and solid-solutions of zirconolite, euxenite, gagarinite, ixiolite, tapiolite etc.

[0163] Alloy 2 is a multicomponent metallic alloy comprising three distinct equilibrium phases, as specified by SEM-EDS. FIG. 2 is a micrograph showing the external surface of the alloy after cryolite testing. The external surface shows

[0164] i) Solid solution of Ni—Cr—Nb—Sn with small additions of Zr, Ta, Fe, Mn, Ti, Si.

[0165] ii) Mixed mineral layer, comprising zirconolite, euxenite, gagarinite, ixiolite, tapiolite, etc. NB. traces of Na, Ca, Al and F come from the cryolite salt mixture.

[0166] The entropy of mixing for alloy 2 was calculated using formula 1 to S.sub.mix=1.59 R.

Alloy 3

[0167]

TABLE-US-00015 TABLE 3 Alloy 3 composition (at %). 60.72 Ni 14.18 Sn 7.78 Nb/Ta 9.52 Cr 3.20 B 2.76 Mn 0.92 Fe 0.92 Ti

[0168] Assessment after cryolite testing as described above: no major corrosion on the surface, sample intact, no spalling, grey-blue appearance at surface, shiny metallic alloy underneath the mineral layer, electrically conductive.

[0169] Mineral layers at surface: numerous phases and solid-solutions of schiavinatoite, béhierite, ixiolite, tapiolite, fersmite etc.

[0170] A cross-section of Alloy 3 is shown in FIGS. 4A and B. The cross-sections of the alloy show multi-component metallic alloy interior 35, 37 and the mineral coating on the external surface 34, 36 comprising a combination of schiavinatoite, béhierite, ixiolite, tapiolite, fersmite, etc (specified by SEM-EDS).

[0171] Another micrograph of Alloy 3 is shown as FIG. 3, taken at a cross-section of the metal alloy, in the bulk of the metal alloy. FIG. 3 shows three distinct equilibrium phases (having been specified with SEM-EDS):

[0172] i) Solid solution of Ni—Cr—Nb, with small additions of Ta, Fe, Mn, Ti, Sn with a volume fraction of approximately 45 vol %, 31.

[0173] ii) Intermetallic of Ni.sub.3Sn, with small additions of Nb, Ta, Fe, Mn, Ti with a volume fraction of approximately 45 vol %, 32.

[0174] iii) Intermetallic of Nb.sub.3B.sub.2, with small additions of Ta, Cr, Ti, Ni, with a volume fraction of approximately 10 vol %, 33.

[0175] The entropy of mixing for alloy 3 was calculated using formula 1 to S.sub.mix=1.30 R.

Alloy 4

[0176]

TABLE-US-00016 TABLE 4 Alloy 4 composition (at %). 67.53 Ni 15.16 Sn 4.03 Nb/Ta 4.81 Cr 5.17 Ce/La 1.98 Mn 0.66 Fe 0.66 Ti

[0177] Assessment after cryolite testing as described above: no major corrosion on the surface, sample intact, no spalling, light green appearance at surface, shiny metallic alloy underneath the mineral layer, electrically conductive.

[0178] Mineral layers at surface: numerous phases of wodginite, aeschynite, ixiolite, tapiolite, fersmite etc

[0179] FIGS. 6A and B show micrographs of Alloy 4. The micrograph shows a cross-section of the multi-metal component metallic alloy interior 45, 46 and the mineral coating on the external surface 44, 47, comprising a combination of wodginite, aeschynite, ixiolite, tapiolite, fersmite, etc (specified by SEM-EDS).

[0180] FIG. 5 shows a micrograph of alloy taken at a cross-section of the metal alloy, in the bulk of the metal alloy, which shows a multicomponent metallic alloy comprising three distinct equilibrium phases, as specified by SEM-EDS:

[0181] i) solid solution of Ni—Cr—Nb, with small additions of Ta, Fe, Mn, Ti, Sn with a volume fraction of approximately 35 vol-%, 41.

[0182] ii) Intermetallic of Ni.sub.3Sn, with small additions of Nb, Ta, Fe, Mn, Ti, with a volume fraction of approximately 35 vol-%, 42.

[0183] iii) intermetallic of (Ce, La)Ni.sub.5Sn, with small additions of Ta, Cr, Ti, Ni, with a volume fraction of approximately 30 vol-%, 43.

[0184] The entropy of mixing for alloy 4 was calculated using formula 1 to S.sub.mix=1.15 R.

[0185] Thus, it has been shown that metal alloys according to the present invention can form a coating as described above. Therefore, the alloys are capable of withstanding molten cryolite having a temperature of >975° C., in an oxygen containing atmosphere for at least 1000 hours. Furthermore, it has been shown that the inventive metal alloy, in which the amounts of specific HFSE can vary significantly. In the four metal alloys, the amount of the various elements varies according to table 5, which shows the lowest and highest amount of each element in the alloys 1-4. Clearly, the properties of the metal alloy are not so much governed by the specific HFSE elements, but rather by the fact that the metal alloy comprises a sufficient total amount of HFSE. This is supported by the findings in the Pitinga mine, from which it is clear that HFSE elements are present in minerals capable of withstanding molten cryolite.

TABLE-US-00017 TABLE 5 Elements and their lowest and highest amount in alloys 1-4. Element Lowest amount Highest amount Ni 52.6 67.53 Sn 2.9 15.16 Nb/Ta 0.8 7.78 Cr 4.81 17.7 Mn 1.98 3.2 Fe 0.66 0.92 Ti 0.8 0.92 Zr 9 9.7 B 1 3.2 Si 9 9 Ca 3 3 Ce/La 0.7 5.17 Gd 1.1 1.1 Nd 0.3 0.3

[0186] Clearly, the HFSE elements of the metal alloy can be varied significantly, while still yielding a metal alloy capable of withstanding molten cryolite having a temperature of >975° C., in an oxygen containing atmosphere for at least 1000 hours. It is contemplated that a Ni in amount of at least 35 atom-%, and a remainder comprising a majority of HFSE elements are capable of forming the metal alloy according to the invention. The total amount of HFSE elements in the metal alloy may be 20-65 atom-%, such as 20-60 atom-%, preferably 25-55 atom-%, such 30-50 atom-%. Furthermore, the number of HFSE elements in the metal alloy may be at least 3, such as at least 4, or at least 5, or at least 6, or at least 7 or at least 8 or at least 9 or at least 10, or at least 11, or at least 12, or at least 13, or at least 14, such as at least 15. The number of HFSE elements in the metal alloy may be 5-5 elements, such as 5-14 elements, preferably 6-14 elements such as 8-14 elements. The term “HFSE elements” refers to Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V.

Itemized list of embodiments

General Items

[0187] 1. A conductive multicomponent metal alloy having the following composition (in atom-%)

[0188] Ni, in a total amount of 35-70; wherein the remaining 30-65 comprises

[0189] at least three elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Rare earth elements (REEs), Ti, Zr, Mn, Hf, Si, P, Al and V in a total amount of at least 30; wherein

[0190] the metal alloy comprises at least three distinct crystalline phases, at least one phase being an intermetallic phase. [0191] 2. The metal alloy according to item 1, wherein the metal alloy comprises at least four elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V, in a total amount of 20-65. [0192] 3. The metal alloy according to item 1 or 2 comprising (in atom-%)

[0193] Sn in a total amount of 1-25

[0194] Nb and/or Ta in total amount of 0.1-20 and

[0195] one or several elements selected from the list consisting of B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al and V, in a total amount of from 10-55. [0196] 4. The metal alloy according to any one of items 1-3 comprising (in atom-%)

[0197] Sn in a total amount of 1-20

[0198] Nb and/or Ta in a total amount of 0.5-10

[0199] and, one or several elements selected from the consisting of B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V in a total amount of from 10-50. [0200] 5. The metal alloy according any one of the preceding items, wherein the metal alloy comprises 4-10 elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V. [0201] 6. The metal alloy according to item 5, wherein the metal alloy comprises 5-8 elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V. [0202] 7. The metal alloy according to any one of items 3-6, wherein said metal alloy consist of consists of 4 to 15 elements. [0203] 8. The metal alloy according to any one of the preceding items, comprising Cr in a total amount of 3-20 atom-%. [0204] 9. The metal alloy according to any one of the preceding items, comprising Mn in a total amount of 1-5 atom-%. [0205] 10. The metal alloy according to any one of the preceding items, comprising Fe in a total amount of 0.1-3 atom-%. [0206] 11. The metal alloy according to any one of the preceding items, comprising Ti in a total amount of 0.1-3 atom-%. [0207] 12. The metal alloy according to any one of the preceding items, wherein the total amount of Sn is in the range of 1-20 atom-%. [0208] 13. The metal alloy according to any one of the preceding items, wherein the total amount of Nb and/or Ta in the metal alloy is in the range of from 0.1-10 atom-%. [0209] 14. The metal alloy according to any one of the preceding items, wherein the balance is Ni, and optionally naturally occurring impurities. [0210] 15. The metal alloy according to item 5, wherein the amount of Ni in the metal alloy is in the range of from 40-70 atom-%. [0211] 16. The metal alloy according any one of the preceding items, having the following composition (in atom-%)

TABLE-US-00018 Ni 35-75, wherein the remaining 25-65 comprises Cr 1-25 Mn 1-10 Nb and/or Ta 0.1-10   Fe 0.1-5   Ti 0.1-5   Sn 1-20 in a total amount of at least 25 and, optionally, Zr ≤15 B ≤10 Si ≤15 Ce and/or La ≤10 Gd ≤5 Nd ≤5 Sm and/or Y ≤10 Hf ≤10 P ≤10 Al ≤10 V ≤10 Ca ≤10 in a total amount no more than 30. [0212] 17. The metal alloy according to item 16, having the following composition (in atom-%)

TABLE-US-00019 Cr .sup. 3-20 Mn  1-4 Nb and/or Ta 0.5-10 Fe  0.4-1.2 Ti  0.4-1.2 Sn .sup. 1-20 and, optionally, Zr .sup. 7-12 B 0.3-4  Si .sup. 5-14 Ce and/or La 0.3-8  Gd 0.5-2  Nd 0.1-1  Sm 0.1-10 Hf 0.1-10 P 0.1-10 Al 0.1-10 V 0.1-10
the balance being Ni in an amount of at least 45 atom-%, and optionally other naturally occurring impurities. [0213] 18. The metal alloy according to item 16, wherein the metal alloy comprises (in atom-%)

TABLE-US-00020 Ni 53-63, and wherein the remaining 37-47 comprises Cr 1-25 Mn 1-10 Nb and/or Ta 0.1-10   Fe 0.1-5   Ti 0.1-5   Zr 1-15 Sn 1-25 B 0.1-10   in a total amount of at least 37. [0214] 19. The metal alloy according to item 18, wherein the metal alloy comprises (in atom-%)

TABLE-US-00021 Cr 15-20 Mn 1-5 Nb and/or Ta 0.1-1.5 Fe 0.1-1.5 Ti 0.1-1.5 Zr  5-15 Sn  5-15 B 0.3-2.sup. 

[0215] the balance being Ni and optionally other naturally occurring impurities. [0216] 20. The metal alloy according to item 16, wherein the metal alloy comprises (in atom-%)

TABLE-US-00022 Ni 47-57, wherein the remaining 43-53 comprises, Cr 1-25 Mn 1-10 Nb and/or Ta 0.1-10   Fe 0.1-5   Ti 0.1-5   Zr 1-15 Sn 1-25 Si 1-15 Ce and/or La 0.1-10   Gd 1-5  Nd 0.1-5   in a total amount of at least 43. [0217] 21. The metal alloy according to item 20, wherein the metal alloy comprises (in atom-%)

TABLE-US-00023 Cr 10-20 Mn 1-5 Nb and/or Ta 0.1-1.5 Fe 0.1-1.5 Ti 0.1-1.5 Zr  5-15 Sn  5-15 Si  5-15 Ce/La 0.1-1.5 Gd 0.1-5.sup.  Nd 0.1-5.sup. 

[0218] the balance being Ni and optionally other naturally occurring impurities. [0219] 22. The metal alloy according to item 16, wherein the metal alloy comprises (in atom-%)

TABLE-US-00024 Ni 55-65, wherein the remaining 45-55 comprises, Cr 1-25 Mn 1-10 Nb and/or Ta 0.1-10   Fe 0.1-5   B 1-10 Sn 1-25 Ti 0.1-5   in a total amount of at least 45. [0220] 23. The metal alloy according to item 22, wherein the metal alloy comprises (in atom-%)

TABLE-US-00025 Cr  5-15 Mn 1-5 Nb and/or Ta  5-10 Fe 0.1-1.5 B 1-5 Sn 10-20 Ti 0.1-1.5

[0221] the balance being Ni and optionally other naturally occurring impurities. [0222] 24. The metal alloy according to item 16, wherein the metal alloy comprises (in atom-%)

TABLE-US-00026 Ni 63-73, wherein the remaining 27-37 comprises Cr 1-25 Mn 1-10 Nb and/or Ta 0.1-10   Ce and/or La 1-10 Fe 0.1-5   Sn 8-22 Ti 0.1-5   in a total amount of at least 27. [0223] 25. The metal alloy according to item 24, wherein the metal alloy comprises (in atom-%)

TABLE-US-00027 Cr  1-10 Mn 1-3 Nb and/or Ta 2-7 Ce and/or La 3-7 Fe 0.1-1.5 Sn 10-20 Ti 0.1-1.5

[0224] the balance being Ni and optionally other naturally occurring impurities. [0225] 26. The metal alloy according to any one of the preceding items, wherein the metal alloy has a compositional entropy S at least 1.0R, as calculated by formula 1, R being the gas constant. [0226] 27. The metal alloy according to any one of the preceding items, wherein said metal alloy is adapted to form, upon contact with oxygen and a molten salt comprising fluoride, an intrinsic surface coating comprising at least one oxide, fluoride or oxyfluoride selected from the list of IMA approved minerals consisting of:

TABLE-US-00028 Zircon (Zr, Hf)SiO.sub.4 Hafnon (Hf, Zr)SiO.sub.4 Stetindite (Ce, REE)SiO.sub.4 Xenotime (Y, Ce, La, REE)PO.sub.4 Wakefieldite (Ce, La, Y, Nd, Pb)VO.sub.4 Schiavinatoite (Nb, Ta)BO.sub.4 Béhierite (Ta, Nb)BO.sub.4 Ixiolite (Ta, Nb, Sn, Fe, Mn, Zr, Hf, Ti).sub.4O.sub.8 Wodginite (Mn, Ti, Sn, Fe, Ce, La)(Ta, Nb).sub.2O.sub.8 Samarskite (Y, Fe, Mn, REE, Th, U, Ca).sub.2(Nb, Ta, Ti).sub.2O.sub.8 Euxenite (Y, Ca, Ce, La, Th, U)(Nb, Ta, Ti).sub.2O.sub.6 Polycrase (Y, Ca, Ce, La, Th, U)(Ti, Nb, Ta).sub.2O.sub.6 Tapiolite (Fe, Mn)(Ta, Nb).sub.2O.sub.6 Fersmite (Ca, Ce, La, Na)(Nb, Ta, Sn, Ti).sub.2O.sub.5F Aeschynite (Ce, Ca, Fe, Th, Nd, Y)(Ti, Nb).sub.2O.sub.6 Fluornatromicrolite (Na, Ca, Ce, La, REE, U, Pb).sub.2(Ta, Nb, Sn, Ti).sub.2O.sub.6F Zirconolite (Ca, Y, REE)Zr(Ti, Nb, Al, Fe).sub.2O.sub.6F Kobeite (REE, Fe, U).sub.3Zr(Ti, Nb).sub.3O.sub.12 Gagarinite Na(Ca, Ce, La, Y, REE).sub.2F.sub.6 Davidite (La, Ce, Ca)(Y, U)(Ti, Fe).sub.20O.sub.38 Fluocerite (Ce, La, Y, REE, Ca)F.sub.3 Simpsonite Al.sub.4(Ta, Nb, Sn, Ti).sub.3O.sub.13 Albite (Na, Ca)AlSi.sub.3O.sub.8 Wöhlerite NaCa.sub.2(Zr, Hf, Nb, Ta, Ti)Si.sub.2O.sub.7F.sub.2 Nioboholtite (Nb, Ta)Al.sub.6BSi.sub.3O.sub.18 Vigezzite (Ca, Ce, La)(Nb, Ta, Ti).sub.2O.sub.6) Loparite-Ce Na(Ce, La, REE)(Ti, Nb, Ta).sub.2O.sub.6 Vlasovite (Na.sub.2ZrSi.sub.4O.sub.11) Normandite (NaCa(Mn, Fe)(Ti, Nb, Ta, Zr)(Si.sub.2O.sub.7)OF) Lakargiite Ca(Zr, Sn, Ti)O.sub.3 Foordite Sn(Nb, Ta).sub.2O.sub.6 Ainalite Sn(Fe, Ta, Nb)O.sub.2. [0227] 28. The metal alloy according to any one of items 1-26, wherein the metal alloy further comprises, on at least one outer surface, an adherent, intrinsic surface coating comprising at least one oxide, fluoride or oxyfluoride selected from the list of IMA approved minerals consisting of:

TABLE-US-00029 Zircon (Zr, Hf)SiO.sub.4 Hafnon (Hf, Zr)SiO.sub.4 Stetindite (Ce, REE)SiO.sub.4 Xenotime (Y, Ce, La, REE)PO.sub.4 Wakefieldite (Ce, La, Y, Nd, Pb)VO.sub.4 Schiavinatoite (Nb, Ta)BO.sub.4 Béhierite (Ta, Nb)BO.sub.4 Ixiolite (Ta, Nb, Sn, Fe, Mn, Zr, Hf, Ti).sub.4O.sub.8 Wodginite (Mn, Ti, Sn, Fe, Ce, La)(Ta, Nb).sub.2O.sub.8 Samarskite (Y, Fe, Mn, REE, Th, U, Ca).sub.2(Nb, Ta, Ti).sub.2O.sub.8 Euxenite (Y, Ca, Ce, La, Th, U)(Nb, Ta, Ti).sub.2O.sub.6 Polycrase (Y, Ca, Ce, La, Th, U)(Ti, Nb, Ta).sub.2O.sub.6 Tapiolite (Fe, Mn)(Ta, Nb).sub.2O.sub.6 Fersmite (Ca, Ce, La, Na)(Nb, Ta, Sn, Ti).sub.2O5.sub.F Aeschynite (Ce, Ca, Fe, Th, Nd, Y)(Ti, Nb).sub.2O.sub.6 Fluornatromicrolite (Na, Ca, Ce, La, REE, U, Pb).sub.2(Ta, Nb, Sn, Ti).sub.2O.sub.6F Zirconolite (Ca, Y, REE)Zr(Ti, Nb, Al, Fe).sub.2O.sub.6F Kobeite (REE, Fe, U).sub.3Zr(Ti, Nb).sub.3O.sub.12 Gagarinite Na(Ca, Ce, La, Y, REE).sub.2F.sub.6 Davidite (La, Ce, Ca)(Y, U)(Ti, Fe).sub.20O.sub.38 Fluocerite (Ce, La, Y, REE, Ca)F.sub.3 Simpsonite Al4(Ta, Nb, Sn, Ti).sub.3O.sub.13 Albite (Na, Ca)AlSi.sub.3O.sub.8 Wöhlerite NaCa2(Zr, Hf, Nb, Ta, Ti)Si.sub.2O7F.sub.2 Nioboholtite (Nb, Ta)Al.sub.6BSi.sub.3O.sub.18 Vigezzite (Ca, Ce, La)(Nb, Ta, Ti).sub.2O.sub.6) Loparite-Ce Na(Ce, La, REE)(Ti, Nb, Ta).sub.2O.sub.6 Vlasovite (Na.sub.2ZrSi.sub.4O.sub.11) Normandite (NaCa(Mn, Fe)(Ti, Nb, Ta, Zr)(Si.sub.2O.sub.7)OF) Lakargiite Ca(Zr, Sn, Ti)O.sub.3 Foordite Sn(Nb, Ta).sub.2O.sub.6 Ainalite Sn(Fe, Ta, Nb)O.sub.2. [0228] 29. A conductive electrode for aluminum processing, comprising the alloy as defined in any one item 1-26. [0229] 30. The conductive electrode according to item 29, further comprising an intrinsic coating as defined in item 27 or 28. [0230] 31. The conductive electrode according to any one of items 29 or 30, wherein the electrode is an anode. [0231] 32. The conductive electrode according to any one of items 29 or 30, wherein the electrode is a cathode. [0232] 33. A method for forming an intrinsic coating on a metal alloy comprising [0233] providing a metal alloy as defined in any one of items 1-26; [0234] providing a molten salt composition comprising fluoride; [0235] submerging at least part of the metal alloy in the molten salt composition, thereby forming a mineral coating as defined in item 27 or 28. [0236] 34. The method according to item 30, wherein the molten salt comprises cryolite. [0237] 35. A method for manufacturing a metal alloy as defined in any one of the preceding items, comprising [0238] providing Ni; [0239] providing at least three elements selected from the list consisting of Sn, Nb, Ta, B, Cr, Ce, Fe, La, Nd, Sm, Gd, Ti, Zr, Mn, Hf, Si, P, Al, Y and V; [0240] melting the provided elements to form a melt; [0241] agitating said melt; [0242] solidifying said melt to form a metal alloy.

Abbreviations

[0243] Herein, the respective elements are referred to by their symbol in the periodic table.