RARE-EARTH HIGH ENTROPY ALLOYS AND TRANSITION METAL HIGH ENTROPY ALLOYS AS BUILDING BLOCKS FOR THE SYNTHESIS OF NEW MAGNETIC PHASES FOR PERMANENT MAGNETS

Abstract

The invention relates to high entropy alloy of rare earth elements (RE-HEAs) including at least four and up to twelve elements selected form rare earth elements R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10, R.sub.11, R.sub.12, which rare earth elements R.sub.1 to R.sub.12 each represents one of elements 57 to 60, 62 to 70, 39 and 40 of the periodic system and to high entropy alloy of transition elements (TM-HEAs) including at least 3 and up to 12 elements selected from transitional elements TM.sub.1, TM.sub.2, TM.sub.3, TM.sub.4, TM.sub.5, TM.sub.6, TM.sub.7, TM.sub.8, TM.sub.9, TM.sub.10, TM.sub.11, TM.sub.12, which transitional elements TM.sub.1 to TM.sub.12 each represent at least one of elements 21 to 30, 41 to 48 and 72 to 79 of the periodic system. Such RE-HEAs and/or TM-HEAs can be used as building blocks in magnetic high entropy composite alloys, e.g. of the type (RE-HEAs).sub.x(TM-HEAs).sub.yT.sub.z, for the manufacture of magnetic devices and permanent magnets.

Claims

1. High entropy alloy of rare earth elements (RE-HEAs) including at least four and up to twelve elements selected form rare earth elements R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10, R.sub.11, R.sub.12, which rare earth elements R.sub.1 to R.sub.12 each represents one of elements 57 to 60, 62 to 70, 39 and 40 of the periodic system.

2. RE-HEAs according to claim 1, wherein the at least four to up to twelve rare earth elements are present in approximately equal proportions.

3. RE-HEAs according to claim 1, wherein the alloy includes at least one member selected from the group consisting of LaCePrNd, YLaCePrNd, YCePrNdDy, YLaCePrNdGd and LaCePrNdGdHo.

4. High entropy alloy of transition elements (TM-HEAs) including at least 3 and up to 12 elements selected from transitional elements TM.sub.1, TM.sub.2, TM.sub.3, TM.sub.4, TM.sub.5, TM.sub.6, TM.sub.7, TM.sub.8, TM.sub.9, TM.sub.10, TM.sub.11, TM.sub.12, which transitional elements TM.sub.1 to TM.sub.12 each represent at least one of elements 21 to 30, 41 to 48 and 72 to 79 of the periodic system.

5. TM-HEAs according to claim 4, wherein TM.sub.1 comprises the three elements Fe, Co and Ni.

6. TM-HEAs according to claim 4, further comprising at least one member selected from the group consisting of B, Al, Ga and In.

7. TM-HEAs according to claim 4, comprising at least one member selected from the group consisting of FeCoNi, FeCoNiMn, FeCoNiCu, FeCoNiMnAl and FeCoNiMnCuAl.

8. A magnetic high entropy composite alloy for the manufacture of magnetic devices and permanent magnets comprising the Use of RE-HEAs according to claim 1.

9. High entropy composite alloy of the formula
(RE-HEAs).sub.x(TM-HEAs).sub.yT.sub.z wherein x=1, 2 y=2, 3, 5, 12, 14, 17, z=0.5-3, and T=Mo, Ti, V, Si, N and B, and the RE-HEAs of claim 1 and a high entropy alloy of transition elements (TM-HEAs) including at least 3 and up to 12 elements selected from transitional elements TM.sub.1, TM.sub.2, TM.sub.3, TM.sub.4, TM.sub.5, TM.sub.6, TM.sub.7, TM.sub.8, TM.sub.9, TM.sub.10, TM.sub.11, TM.sub.12, which transitional elements TM.sub.1 to TM.sub.12 each represent at least one of elements 21 to 30, 41 to 48 and 72 to 79 of the periodic system.

10. High entropy composite alloy of the formula
Sm.sub.xCO.sub.y wherein Sm is replaced by RE-HEAs as defined in claim 1 and/or Co is replaced by a high entropy alloy of transition elements (TM-HEAs) including at least 3 and up to 12 elements selected from transitional elements TM.sub.1, TM.sub.2, TM.sub.3, TM.sub.4, TM.sub.5, TM.sub.6, TM.sub.7, TM.sub.8, TM.sub.9, TM.sub.10, TM.sub.11, TM.sub.12, which transitional elements TM.sub.1 to TM.sub.12 each represent at least one of elements 21 to 30, 41 to 48 and 72 to 79 of the periodic system, x=1 or 2 and y=5, 17.

11. High entropy composite alloy of the formula
(RE-HEAs).sub.2Fe.sub.14B wherein (RE-HEAs) is defined as in claim 1.

12. High entropy composite alloy of the formula
((RE-HEAs)Fe.sub.12-xT.sub.x, wherein the RE-HEAs is the RE-HEAs of claim 1, T=Mo, Ti, V, Si, N, and x=0.5-2.

13. Method of manufacture of high entropy alloys according to claim 1 comprising mixing powders comprising the elements of RE-HEAs and/or the elements of TM-REAs, melting the powders and casting the alloys into appropriate shape.

14. Method according to claim 13, in which melting is achieved via arc-melting or RF-melting in an electric resistance over or a microwave oven, preferably in an inert atmosphere.

15. A permanent magnet comprising a high entropy composite alloy according to claim 9.

16. A magnetic high entropy composite alloys for the manufacture of magnetic devices and permanent magnets comprising the RE-HEAs according to claim 4.

17. Method of manufacture of high entropy composite alloys according to claim 9 comprising mixing powders comprising the elements of RE-HEAs and/or the elements of TM-REAs, melting the powders and casting the alloys into appropriate shape.

18. High entropy composite alloy of the formula
((RE-HEAs)Fe.sub.12-xT.sub.x, wherein the RE-HEAs comprise the RE-HEAs of claim 2, T=Mo, Ti, V, Si, N, and x=0.5-2.

19. High entropy composite alloy of the formula
((RE-HEAs)Fe.sub.12-xT.sub.x, wherein the RE-HEAs comprise the RE-HEAs of claim 3, T=Mo, Ti, V, Si, N, and x=0.5-2.

20. Method of manufacture of high entropy alloys according to claim 2 comprising mixing powders comprising the elements of RE-HEAs and/or the elements of TM-REAs, melting the powders and casting the alloys into appropriate shape.

Description

FIGURE DESCRIPTION

[0057] The above and other features of this invention, nature and various advantages, are presented in conjunction with the schemes that accompany it.

[0058] FIG. 1 shows the hysteresis loop of a magnetic material, showing the parameters that are of interest for applications. Point 10 is the saturation magnetization of the material; point 20 is the residual magnetization and point 30 is the coercive field. The area of the hysteresis loop is proportional to the energy product of the material.

[0059] FIG. 2 shows the structure of the SmCo5 material by replacing the samarium with the equivalent (RE-HEAs) and replacing the cobalt with the corresponding (TM-HEAs). 10 is one (RE-HEAs) and 20 is one (TM-HEAs).

[0060] FIG. 3 shows the structure of an alloy with five elements of the periodic system and the small deformation of the lattice due to the difference in individual atomic radii. 10 could be TM.sub.1, 20 TM.sub.2, 30 TM.sub.3, 40 TM.sub.4 and 50 TM.sub.5, as stated in the text on TM-HEAs. It could also be 10 to R.sub.1, 20 to R.sub.2, 30 to R.sub.3, 40 to R.sub.4 and 50 to R.sub.5 in the case of RE-HEAs.

EXAMPLES

Example 1: Type Phase 1:5 SmCo5

[0061] At this stage it is possible to replace either rare earth Sm with (RE-HEAs), or cobalt with equivalent (TM-HEAs) or rare earth and cobalt simultaneously and on production of

(RE-HEAs)(TM-HEAs)).sub.5.

[0062] (RE-HEAs) means rare earth alloys with at least four and up to 12 elements in approximately equal proportions, e.g. with four LaCePrNd elements, five YLaCePrNd elements, or six LaCePrNdGdHo elements, etc.

[0063] These alloys are prepared by mixing rare earth metals of a purity of at least 99.9 at % and by melting by techniques such as arc melting, or with high-frequency currents in an inert atmosphere e.g. to avoid any oxidation. In addition to rare earth elements yttrium and zirconium can be used as elements too.

[0064] (TM-HEAs) define alloys with at least three and up to 12 elements in approximately equiatomic proportions and based on the three magnetic materials at room temperature from the periodic table such as iron, cobalt and nickel, e.g. with three FeCoNi components, four FeCoNiMn components, five FeCoNiMnAl components, six FeCoNiMnCuAl components, etc.

[0065] These alloys are prepared by mixing transition metals from the periodic table of at least 99.9 at % and by melting by techniques such as arc melting, or high-frequency currents in an inert atmosphere e.g. to avoid oxidation. In addition to the transition elements, elements such as boron, aluminum, gallium and indium can be used.

[0066] Magnetic phases leading to appropriate type processing (RE-HEAs)(TM-HEAs).sub.5 are made by selecting the corresponding (RE-HEAs) with the desired (TM-HEAs) in the 1:5 ratio and using the same techniques as described for the manufacture of RE-HEAs and TM-HEAs. No further processing is required and phase 1:5 is formed with very good properties.

[0067] Such a phase is (Y,Ce,Pr,Nd,Dy)Co.sub.5 with a magnetization of ˜75 emu/g, magnetocrystalline anisotropy field ˜12 T, Curie point >500° C. and a theoretical energy product of 80-130 KJ/m.sup.3.

[0068] A corresponding phase is Sm—(Fe,Co,Ni,Cu).sub.5 with a theoretical energy product of the order of 70-100 KJ/m.sup.3, but with a material cost much lower, as cobalt present in the structure is ⅕ compared to SmCo5. There are too many combinations, but in category 1:5 it is the cobalt replacement that can bring the greatest economic benefits. Greater benefits are in the Sm(Cobalt (balance)Fe.sub.xCu.sub.0.1Zr.sub.0.03).sub.7.5-5.5 series (x=0.09-0.21) as the Co/Sm ratio is even greater.

Example 2: Type Phase Nd2Fei4B

[0069] At this stage savings are only achieved by replacing the expensive neodymium (or Nd—Pr, as, in industry, neodymium-praseodymium alloy is used) with RE-HEAs which are both more abundant and cheaper, such as (Y,La,Ce,Nd—Pr,Gd,Ho, . . . ). It is not in any way in the interests of replacing iron which the more abundant and economic material in nature. If the alloy (Y,La,Ce,Pr,Nd).sub.2Fe.sub.14B is produced, it has slightly inferior magnetic properties as Nd2Fei4B, but at a lower cost of 45% and for the alloy (Y,La,Ce,Pr,Nd,Gd).sub.2Fe.sub.14B the savings can reach 40%. This phase has a magnetization of about 1000 emu/g, Curie point around 300° C. and an anisotropy of 20% less than the initial phase Nd.sub.2Fe.sub.14B. We can achieve an energy product in the range 30-40 MGOe (240-320 KJ/m.sup.3).

Example 3: Type Phase NdFe.SUB.12-x.Ti.SUB.x

[0070] At this stage savings are only achieved by replacing the expensive neodymium (in industry, neodymium-praseodymium alloy is used) with RE-HEAs which are both more abundant and cheaper, such as (Y,La,Ce,Nd—Pr,Gd, Ho, . . . ). It is not in any way in the interests of replacing iron, which is the most abundant and economic material in nature. For the alloy (Y,La,Ce,Pr,Nd)Fe.sub.12-xTi.sub.x almost the same magnetic properties as NdFe.sub.12-xTi.sub.x and twice the anisotropy field are obtained, but at a cost of 45% and for the alloy (Y,La,Ce, Pr,Nd, Gd)Fe.sub.12-xTi.sub.x savings may be as high as 40%.

[0071] There are too many combinations that highlight the value of using high entropy alloys either on the basis of rare earth elements or the transition metal elements or the combination of both in the above magnetic compounds, which by itself and by a more simpler process than has been the case to date for the manufacture of permanent magnets. This invention not only results in the saving of material and resources but also because of the properties of high entropy alloys leads to fewer stages in the preparation of alloys, but also because of mechanical properties in the production capacity of permanent magnets by casting and because of low diffusion, we can manipulate the microstructure to achieve desirable coercivity necessary for the fabrication of permanent magnets. Also, the materials of the present invention can be cast in any shape and under suitable microstructure conditions to be permanent magnets with highly desirable properties.

[0072] High entropy alloys of rare earths and transition metals as building blocks for novel magnetic phases for permanent magnets:

[0073] The technical field referred to in the invention is that of simple and complex high-entropy magnetic alloys based on the periodic table of chemical elements with excellent magnetic and mechanical properties as new building blocks for the replacement of rare earths and cobalt in magnetic phases and in the technical field of permanent magnets prepared therewith.

[0074] The high cost and limitation on the supply of raw materials, such as rare earths and cobalt, which are the main ingredients in magnetic alloys for the manufacture of high quality permanent magnets, are successfully dealt with the creation of high entropy alloys based on rare earths and transition elements, which also offer better mechanical properties. With this approach we achieve a cost reduction of raw materials of over 40% without greatly altering the magnetic properties of the new phases and with better mechanical properties for better permanent magnets.