FR2783964A1 - MAGNETIC MATERIAL BASED ON IRON, COBALT, RARE EARTHS AND BORON AND MAGNET BASED ON THIS MATERIAL - Google Patents

Abstract

The invention concerns a magnetic material based on iron, cobalt, rare earths and boron and a magnet based on said material, in particular a bound magnet. Said material is characterised in that it has a composition corresponding to the following formula: R<1>xR<2>yFe 100-x-y-z-v-w-tCozM<1>vM<2>tBw wherein: R<1> represents at least an element selected among lanthanum, cerium, praseodymium, neodymium, samarium and europium, at least one of the praseodymium and neodymium being present in majority; R<2> represents at least an element selected among terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, at least one of the terbium and dysprosium elements being present in majority; M<1> represents at least an element selected among titanium, vanadium, molybdenum, niobium, zirconium, hafnium, tantalum, manganese and tungsten; M<2> represents at least an element selected among aluminium, copper, gallium, carbon and silicon; and wherein x, y, z, v, w and t verify the following relationships: 3 </= x </= 5, 0.1 </= y </= 1.5, 0 < z </= 15, 0 </= v </= 3, 15 </= w </= 25, 0 </= t </=3.

Description

IRON-BASED MAGNETIC MATERIAL. OF COBALT. RARE EARTHS

AND BORON AND MAGNET BASED ON THIS MATERIAL

The present invention relates to a magnetic material based on iron, cobalt, rare earths and boron and a magnet based on this material. It is known that there is, in the field of magnets, an increasing need for a material whose performances are situated between those which are low of magnets of the ferrite type and those high of the type sintered magnets based on neodymium, iron and. boron. Magnets already exist which partly satisfy this need. These are bonded magnets based on neodymium, iron and boron and obtained by quenching on a wheel (melt-spining). Magnets with a lower rare earth content and high remanence have also been proposed, but which are not entirely satisfactory because they have a coercivity.

which may be insufficient in certain applications.

The object of the present invention is to provide a magnetic material with a low rare earth content and exhibiting improved magnetic properties and,

in particular, increased coercivity.

For this purpose, the magnetic material of the invention is characterized in that it has the composition defined by the following formula R1 XR2yFe10 oxyzvwtCOzMVM2 tBw (1) in which R1 represents at least one element chosen from lanthanum, cerium, praseodymium, neodymium, samarium and europium, at least one of the elements praseodymium and neodymium being present and in the majority, R2 represents at least one element chosen from terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, at least one of the elements terbium and dysprosium being present and in the majority, M1 represents at least one element chosen from titanium, vanadium, molybdenum, niobium, zirconium, hafnium, tantalum, manganese and tungsten, M2 represents at least one element chosen from aluminum, copper, gallium, carbon and silicon, and ox, y, z, v, w and t satisfy the following relationships: 3 <x <5 0.1 y <1.5 0 <z <15 O <v <3 <w <25 O <t <3 The invention concerns not also a magnet characterized in that it is based on the material defined above. Other characteristics, details and advantages of the invention will appear further.

more fully on reading the following description, as well as the various

concrete but non-limiting examples intended to illustrate it.

The material of the invention is first of all characterized by its composition. This composition corresponds to formula (1) given above. The proportions of the different

constituent elements of the material of the invention are therefore expressed in atomic%.

R1 is chosen from the group of rare earths of the light rare earth type which was defined above with the conditions, on the one hand, that the material comprises at least as element R1 praseodymium or neodymium or a combination of these two elements and, on the other hand, that praseodymium, neodymium or the combination of these two elements is in the majority, that is to say constitutes more than 50 atomic% of all the rare earths constituting R1. The respective proportions of neodymium and of praseodymium relative to each other can be any, the neodymium possibly being more particularly in majority proportion. Preferably rare earth

R1 is neodymium.

R2 is chosen from the group of rare earths of the heavy rare earth type which was defined above with the conditions, on the one hand, that the material comprises at least as element R2 terbium or dysprosium or a combination of these two elements and, on the other hand, that the terbium, the dysprosium or the combination of these two elements is in the majority, that is to say constitutes more than 50 atomic% of all the rare earths constituting R2. The respective proportions of terbium and of dysprosium relative to each other can be any, the terbium possibly being more particularly in a majority proportion. Preferably, the rare earth R2 is

terbium.

With regard to the respective proportions of the elements given above, it can be indicated that a rare earth content lower than the minimum content described induces an insufficient coercivity of the material and a content greater than the content.

maximum described results in a loss of coercivity, which may be total, of the material.

Elements M1 and M2 are used as additives. Too much of these additives can lead to a decrease in saturation magnetization. Content

boron described makes it possible to obtain the phases in equilibrium Fe3B, Fe and (R1, R2) 2Fe14B.

Apart from this content, this combination of phases is not formed.

According to particular embodiments of the invention, the contents of elements R ′, R2, Co, M1, M2 and B can vary within smaller ranges. Thus, the values of x and y can verify the relation 3.5 <x + y <4.5. Moreover, the value of y can more particularly verify the relation 0.1 <y <1. According to another particular embodiment, z has the following value 1.5 <z <7.5 and even more particularly 2.5 <z <7.5. In addition, v or t can have values of at most

1. Finally, w can vary more particularly in the following proportions: 17 <w <20.

Of course, the invention also comprises the particular embodiment in which x, y, z, v, t and w simultaneously verify the relations which have been given in the

previous paragraph.

The element M2 can more particularly be silicon and M1 and M2 can more particularly constitute a combination of copper and niobium. In the latter case, copper and niobium may be present in equal or substantially equal amounts. It will also be noted that the material of the invention does not contain chromium as a constituent element, with the exception, however, of any traces of this element which may come from the raw materials used in the preparation of the material.

The material of the invention is generally in the form of a powder.

Usually, this powder has an average particle size of between

about 10pm and about 500pm, more particularly between 1001pm and 300tim.

The material also consists of crystallites, the average size of which can be

between 5nm and 300nm, preferably between 10 and 50nm.

A first process for preparing the material of the invention will now be described. This process comprises the following steps: a starting mixture comprising the constituent elements of the material is melted in the necessary proportions; - the molten mixture is cooled; - Optionally subjecting said product to a heat treatment, whereby it is

gets the magnetic material.

The starting mixture, for example an alloy of the different elements, is first melted, generally under an inert atmosphere, for example under

argon. The second step of the process is to cool the molten mixture.

Different techniques can be used to do this, such as wheel quenching.

Cooling rates are usually used which can vary between about 104 and about 107 C per second, preferably between 105 and 106 C per second. When the cooling is rapid, that is to say greater than 105 C / s, an essentially amorphous product is obtained. The product thus obtained can

possibly be crushed.

In a last step, the product obtained above can be subjected to a heat treatment. This treatment is not always necessary if the cooling rate is low, that is to say between 1040C / s and 105 C / s per second. On the other hand, such a treatment is useful in the case of a cooling rate greater than 105 C / s. In this case, crystallization is caused in the amorphous product and, more precisely, the appearance of fine crystallites. The temperature of this treatment can be between approximately 400 and approximately 800 ° C., more particularly between approximately 650 and approximately 750 C. The duration of the treatment can vary between approximately 0.001 seconds and approximately 2 hours, preferably between 0.01 seconds and approximately 10 minutes. The heating speed can vary from 0.1 C / s to

C / s. The treatment is preferably carried out under an inert gas such as argon.

Another process for preparing the material of the invention can also be used.

The first step of this process consists in mechanically combining the constituent elements of the material in the necessary proportions. The mechanical alloying technique is known, it consists in grinding with high energy either powders of the distinct elements concerned or premixes in the form of alloys of these elements. The heat treatment of the alloy obtained in the previous step is then carried out by implementing conditions similar to those which have been described.

for the first process.

A third method is conceivable. This process comprises, in a first step, a heat treatment under hydrogen of a mixture or of a starting alloy comprising the constituent elements of the material in the proportions

necessary then, in a second step, a heat treatment under vacuum.

The invention also relates to a permanent magnet which is based on a material such as

than that which has just been described or as obtained by the methods presented above.

The preparation of such a permanent magnet is carried out in a known manner, for example by hot pressing or by sintering. In addition, the material of the invention is particularly suitable for the preparation of bonded permanent magnets. Such bonded magnets comprise the material of the invention as described above in a matrix formed of a non-magnetic material based for example on a glass, on a polymer, on a resin, such as an epoxy resin. or based on a second alloy with a low

fusion.

Examples will now be given.

The materials are obtained as follows. An alloy comprising the necessary quantities of the various elements is melted under an argon atmosphere. The molten alloy is sprayed onto the outer surface of a wheel maintained at room temperature and the circumferential speed of which is between 20 and m / s. A material is obtained in the form of a thin strip. The material then undergoes a heat treatment at a temperature which is between 700 and 800 C under argon. The compositions of the materials of the various examples are shown below in Table 1 and in Table 2 the magnetic properties of these materials after the heat treatment. Example 20 is a comparative example because the material does not contain terbium or dysprosium. It is observed that the materials according to the invention exhibit a markedly improved coercivity with at least a remanence.

equal and generally improved.

Table 1

Example Composition 1 NdR325Tb1 Fe72 7iCo., B1 8 2 Pr3 2.Tb1Fe72 7Co. B1 R 3 Nd3.25Dy1 Fe72. 7CoBÂ 1 4 Nd3.RgTbo.5Fe727S. CorB 18 Nd4Tbo, 0Fe72.5CoiB1 g 6 Nd. R3Tbo .., Fe6.-25Co7.si1 B1 8 8 Nd.33Tb1 Fe71 75Co5Si1 B18 9 Nd, 33Tbl Fe71 75CCoTi1 B1 R Nd3. 3TbI Fe71 7,5CoCuosNbo5B1 R 11 NdS326Tbo.47Fe72.Co4.rB 19q.4

8I. 1..L LZú ú1.

'L 78 8 17 ZL

9 '99 1708 bO L t'0' L6 6 k 0 L t'O 'ú9 8Z8 6 0' 1 1 0k 989 8 'L tZ 0ú L

I L 'L ZL LZú 9

ú0 L L9 b8ú 9 Z 'I. 1.6 b8 t7 gO '89 17L ú

LO 'LL ú9 Z

'F 9L b

901. 9úcj 176ú i.

L0 Ja (ew / r)) (WNd>) OH! eoueulew H xwH enbQsu! Juui e! AioJeOealdwex3 3 neelqel -8 L kYoog-909 L: j2UVpN (p} leJedwoo) Oz 8 Lagoo8'eLaj kql 'Ue-9U'; pN 6 k YLa 'LSUU ZS U'6i ooU 'Uqj; J'Jd 8 U-e LaLUvo:> U ZLa jUt UqlZs GJd / LI UL6 g'0-no; 'UqN98'- U! S86'17og-UZe: 617'Uq16'; pN9 Ut 2 ú1. [SYLoS6aU ulÉ8p LP-8 Zk 9 V6 '/ L9 L'? 9 / .o'9 = 61'q .. 'p jI

312 101 1.18

16 349 97 1.13

17 337 92 1.17

18 333 102 1.17

19 363 88 1.11

(comparative) 273 69 1.03

Claims (10)

1- Magnetic material, characterized in that it has the composition defined by the following formula: R xR2yFe10o-xyzvw-tCozMvM2tBw (1) in which R1 represents at least one element chosen from lanthanum, cerium, praseodymium, neodymium , samarium and europium, at least one of the elements praseodymium and neodymium being present and in the majority, R2 represents at least one element chosen from terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, at least one of the elements terbium and dysprosium being present and in the majority, M1 represents at least one element chosen from titanium, vanadium, molybdenum, niobium, zirconium, hafnium, tantalum, manganese and tungsten, M2 represents at least one element chosen from aluminum, copper, gallium, carbon and silicon, and ox, y, z, v, w and t satisfy the following relationships: 3 <x <5 0, 1 <y <1.5 0 <z <15 0o <v <s3 <w <25 0 - <t <3 2- Material according to claim 1, because acterized in that x satisfies the following relation: 3.5 <x + y <4.5 3 Material according to claim 1 or 2, characterized in that y satisfies the following relation: 0.1 <y <l 4- Material according to one of the preceding claims, characterized in that z verifies the following relation: 1.5 <z <7.5, more particularly 2.5 <z <7.5 - Material according to one of the preceding claims, characterized in that w verifies the following relation: 17 <w <20 6- Material according to one of the preceding claims, characterized in that the element M2 is silicon or in that M1 and M2 constitute a combination of copper and niobium. 7- Material according to one of the preceding claims, characterized in that it is present as a powder. 8- Material according to claim 7, characterized in that it is in the form of a powder with an average particle size of between about 10 μm and about 500Jm, more particularly between 100pm and 300pm. 9- Material according to one of the preceding claims, characterized in that it is consisting of crystallites whose average size is between 5nm and 300nm. - Process for preparing a material according to one of the preceding claims, characterized in that it comprises the following steps: - a starting mixture comprising the constituent elements of the material is melted in the necessary proportions; - the molten mixture is cooled; - optionally subjecting said product to a heat treatment, whereby it is gets the magnetic material. 11- A method of preparing a material according to one of claims 1 to 9, characterized in that it comprises the following steps: - the constituent elements of the material are mechanically combined in the necessary proportions; - The product obtained in the previous step is subjected to a heat treatment, this by what we get the magnetic material. 12- Process for preparing a material according to one of claims 1 to 9, characterized in that it comprises, in a first step, a heat treatment under hydrogen of a mixture or of a starting alloy comprising the constituent elements of the material in the necessary proportions then, in a second step, heat treatment under vacuum. 13- Permanent magnet, characterized in that it is based on a material according to one of the claims 1 to 9. 14. Magnet according to claim 10 characterized in that it comprises a binder.