JP7251053B2 - RFeB magnet and method for manufacturing RFeB magnet - Google Patents

Description

The present invention relates to a method for producing an RFeB magnet containing R (rare earth element), Fe (iron) and B (boron). Here, "rare earth element" is a generic term for 17 elements belonging to Group 3A of the periodic table. light rare earth elements R ^L , and heavy rare earth elements R ^H , which collectively refer to the three elements of Tb (terbium), Dy (dysprosium) and Ho (holmium). The present invention particularly provides an ^RL FeB sintered magnet obtained by sintering after orienting crystal grains ⁱⁿ a raw material powder of an RL FeB alloy powder containing light rare earth elements ^RL , Fe, and B in a magnetic field. , from a ^RL FeB-based hot plastically worked magnet (see Non-Patent Document 1) in which the crystal grains in the raw material powder are oriented by performing hot plastic working after performing hot press working on a similar raw material powder The present invention relates to an RFeB-based magnet that has undergone a treatment (grain boundary diffusion treatment) for diffusing atoms of a heavy rare earth element ^RH in a base material, and a method for manufacturing an RFeB-based magnet.

RFeB-based magnets were discovered by Masato Sagawa et al. Therefore, RFeB magnets are used in various products such as drive motors for hybrid and electric vehicles, motors for electrically assisted bicycles, industrial motors, voice coil motors such as hard disks, speakers, headphones, and permanent magnet magnetic resonance diagnostic equipment. used for

Early ^RFeB magnets had a drawback of relatively low coercive force H _cJ among various magnetic properties. was found to improve. Coercive force is the force that can withstand reversal of magnetization when a magnetic field is applied to the magnet ⁱⁿ the direction opposite to the direction of magnetization. It is thought to have the effect of

On the other hand, when the content of the heavy rare earth element ^RH in the RFeB magnet increases, there arises a problem that the remanent magnetic flux density _Br decreases and the maximum energy product (BH) _max also decreases. In addition, the heavy rare earth element ^RH is expensive and rare as a resource, and the areas where it is produced are unevenly distributed. It is undesirable to increase the content of ^RH .

Therefore, grain boundary diffusion treatment is performed in order to increase the coercive force while suppressing the content of the heavy rare earth element ^RH (see Patent Documents 1 and 2, for example). In the grain boundary diffusion treatment, on the surface of the R ^L FeB system sintered magnet containing the light rare earth element R ^L as a rare earth element or the R ^L FeB system hot plastic deformation magnet, the R ^H containing material containing the heavy rare earth element R ^H are adhered and then heated, the atoms of the heavy rare earth element ^RH penetrate into the interior of the magnet through the grain boundaries, and the heavy rare earth element ^RH is diffused only in the vicinity of the surface of each crystal grain. Hereinafter, the R ^L FeB system sintered magnet or the R ^L FeB system hot plastically worked magnet before the grain boundary diffusion treatment is referred to as a "base material". The decrease in coercive force occurs when magnetization reversal occurs in the crystal grains near the surface and then spreads throughout the crystal grains ^. By increasing the concentration, magnetization reversal can be suppressed and the coercive force can be increased. On the other hand, since the heavy rare earth element ^RH is unevenly distributed only in the vicinity of the surface (grain boundary) of each crystal grain, it is possible to suppress the content as a whole, thereby suppressing the decrease in residual magnetic flux density and maximum energy product. In addition, RFeB magnets can be stably supplied to the market at low cost.

JP 2011-159983 A International publication WO2014/148353 Japanese Patent Application Laid-Open No. 2006-019521

Keiko Hioki, Atsushi Hattori, "Development of Dy-saving Nd-Fe-B system hot-worked magnets made from ultra-quenched powder", Sokeizai Vol.52, No.8, pp.19-24, General Incorporated Foundation Sokeizai Center, published in August 2011 L.G. Zhang et al., "Thermodynamic assessment of Al-Cu-Dy system", Journal of Alloys and Compounds, Elsevier, (Netherlands), 480, 403 -408 pages, July 8, 2009

In the invention described in Patent Document 1, various alloys composed of one or more heavy rare earth elements ^RH and one or more other metal elements M are listed as materials to be attached to the surface of the substrate. ing. In the same document, the ratio of the mass of the other metal element M to the mass of the heavy rare earth element ^RH in this alloy (referred to as "M/R ^H ratio") is 1/100 to 5/1 (1 to 500 %), and more preferably 1/20 to 2/1 (5 to 200%). However, when the M/R ^H ratio is several percent and when it is several hundred percent, the amount of the heavy rare earth element R ^H reaching the vicinity of the surface of the inner crystal grain through the grain boundary of the base material is completely different. Furthermore, in Patent Document 1, the metal element in the ^RH- containing material diffuses to the grain boundary, so that the rare earth-rich phase, which has a higher rare earth element content than the crystal grains, is easily melted. It is described that the heavy rare earth element R ^H is easily diffused into the grain boundary, but the ease of melting of the rare earth rich phase in the grain boundary depends on the M/R ^H ratio of the R ^H inclusion and the metal element It depends on the type of M. In this way, the amount of the heavy rare earth element R ^H that reaches the vicinity of the surface of the inner crystal grain is determined not only by the magnitude of the M/R ^H ratio but also by complex factors. It is not always possible to increase the coercive force over other ^RH inclusions.

On the other hand, in Patent Document 2, an RH ^NiAl alloy containing ^RH , Ni and Al at a mass ratio of about 92:4:4 is used as a material for the ^RH inclusion attached to the surface of the base material. is described. The reason for using Ni and Al is that these elements have the effect of lowering the melting point of the rare earth-rich phase, and the rare earth-rich phase in the grain boundary melts during the grain boundary diffusion treatment, so the heavy rare earth element ^RH can be easily diffused into the base material. However, the R ^H NiAl alloy is not necessarily the most suitable material for the R ^H inclusion used in the grain boundary diffusion treatment, and a more suitable material is desired.

The problem to be solved by the present invention is that it is possible to efficiently perform grain boundary diffusion treatment using ^RH- containing materials made of materials more suitable than conventional ones, thereby reliably producing RFeB magnets with high coercive force and An object of the present invention is to provide a method for manufacturing the RFeB magnet.

A method for manufacturing an RFeB magnet according to the present invention, which has been made to solve the above problems, comprises:
Containing heavy rare earth elements R _C ^H consisting of one or more heavy rare earth elements R ^H , consisting of _Cu and ^Al , the coordinates of eight points (R _C ^H _at% , Cu _at% , Al _at% )=(50, 40, 10), (58, 30, 12), (58, 20, 22), (48, 20, 32), (33, 24, 43 ), (17, 50, 33), (17, 60, 23) and (33, 58, 9) with ^RH having a composition represented by points within or on the sides of the octagon a deposit preparation step of preparing a deposit containing a CuAl alloy;
^{RL FeB} system sintered magnet ^body containing light rare earth elements _RCL , Fe and B or ^RL FeB system hot plastic ^working magnet body A deposit attaching step of attaching to the surface of the substrate consisting of
a heating step of heating the substrate to which the deposit is attached to a predetermined temperature at which the atoms of the heavy rare earth element R _C ^H contained in the deposit diffuse into the substrate through the grain boundaries of the substrate. It is characterized by

The ^RH CuAl alloy has six coordinates (R _{CH at%} , Cu _at% , Al _at% ⁾ = (50, 40, 10), (50, 32, 18), ( 33, 24, 43), (17, 50, 33), (17, 60, 23) and (33, 58, 9) as points within or on the sides of the hexagon It is preferred to have the composition

In the method for producing an RFeB magnet according to the present invention, an ^RH CuAl alloy is used in which Cu is used instead of Ni in the ^RH NiAl alloy described in Patent Document 2. Here, the included heavy rare earth element R _CH contained in the ^RH CuAl alloy is one or more heavy rare earth elements ^RH , i.e. one, two or three ^of Tb, Dy and Ho. . In addition, in the ^RH NiAl alloy of Patent Document 2, the Ni content is about 4% by mass, that is, about 9 atomic%, whereas in this ^RH CuAl alloy, the Cu content is at least 20 atomic%. is. By using such deposits containing ^RH CuAl alloys ( ^RH CuAl alloy-containing materials) that are different from the RH NiAl alloys of Patent Document 2, R ^{L FeB} -based sintered magnet bodies or R ^L FeB The grain boundaries of the base material made of the hot plastically worked magnet body are easily melted. As a result, the atoms of the heavy rare earth element R _C ^H contained in the R ^H CuAl alloy can more efficiently reach the vicinity of the surface of the crystal grain, and the coercive force can be increased while suppressing the decrease in the residual magnetic flux density and the maximum energy product. A high quality RFeB system sintered magnet and RFeB system hot plastic working magnet can be obtained.

On the other hand, in ^RH CuAl alloys, there are generally multiple types _of ^RH CuAl phases ^with different ^composition ratios of RH _, Cu and Al ₍ RH ^CuAl , ^RH _Cu4Al8 , ^RH2Cu17Al17 , _{RH Cu5Al5} , ^RH _CuAl3 , ^RH4Cu4Al11 , _{RHCu3Al3 , etc. )} , Al-free ^RH Cu phase _{, or} Cu-free ^RH Al phase ^mixed becomes. The contents of ^RH , Cu and Al in the ^RH CuAl alloy as a whole determine which of these phases are included. In order to ^{increase the coercive force of RFeB sintered magnets and RFeB hot plastically deformed magnets, the RH CuAl phase} ( ^RH , Cu, Al is 1:1:1) is preferably included. Therefore, the coordinates of six points in the ternary composition diagram (R ^CH _at% , Cu _at% , Al _at% ) ⁼ ₍ 50, 40, 10), (50, 32 , 18), (33, 24, 43), (17, 50, 33), (17, 60, 23) and (33, 58, 9) in or on the sides of the hexagon It is desirable to use an R ^H CuAl alloy (see Non-Patent Document 2) having a composition represented by a point.

Furthermore, according to _experiments conducted by the present inventors, coordinates (R ^CH _at% , Cu _at% , Al _at% ) ⁼ (50, 40, 10), (58, 30, 12), (58, 20, 22), (48, 20, 32), (33, 24, 43) and (50, 32, 18) are vertices ( Among them, (50, 40, 10), (33, 24, 43) and (50, 32, 18) are common with the vertices of the hexagon) within the second hexagon or in the second hexagon It was confirmed that the same effect is obtained when using the R ^H CuAl alloy having the composition represented by the points on the side. Therefore, a deposit containing a R ^H CuAl alloy having a composition represented by a point within or on a side of the octagon, which is the area of the combined hexagon and the second hexagon, can be used to obtain grains. By performing the field diffusion treatment, it is possible to obtain an RFeB-based sintered magnet or an RFeB-based hot plastically worked magnet having high coercive force while suppressing a decrease in residual magnetic flux density and maximum energy product.

Further, according to the method for producing an RFeB magnet according to the present invention, Cu is diffused into the grain boundaries of the RFeB sintered magnet and the RFeB hot plastically worked magnet, so that the RFeB magnet is more effective than the case where the ^RH NiAl alloy is used. It also has the effect of improving the corrosion resistance of the magnet.

An RFeB magnet having the following configuration is obtained by the method for manufacturing an RFeB magnet according to the present invention. The RFeB-based magnet according to the present invention includes a light rare earth element R _C ^L composed of one or two light rare earth elements R ^L , a heavy rare earth element R C ^H composed of one or more heavy rare earth elements _R ^H , Fe An RFeB-based sintered magnet or an RFeB-based hot plastically worked magnet containing two surfaces substantially parallel to each other and containing B and B,
the content of the contained heavy rare earth R _C ^H is higher at the grain boundaries than in the grains of the crystal grains,
In the plane equidistant from the two surfaces in the RFeB magnet, the content of heavy rare earth elements R _C at grain boundaries is 0.40 to 1.25% by mass, the content of Cu is 3.9 to ^14.0 % by mass, and Al The content of 0.09 to 1.00% by mass
It is characterized by

The contents of R _C ^H , Cu, and Al in the R ^H CuAl alloy in the method for producing an RFeB magnet according to the present invention are shown in terms of atomic percentages, but R _C ^H at the grain boundaries of the RFeB magnet according to the present invention , Cu and Al are shown in mass percentage based on actual measurements. The grain boundaries contain R _C ^H , Cu, and Al derived from the R ^H CuAl alloy, as well as R _C ^L , Fe, B, etc. that existed at the grain boundaries of the base material.

The coercive force increases as the content of the heavy rare earth element R _CH in the grain boundaries increases within a ^relatively small range. However, according to the measured values described later, when a base material having two surfaces facing substantially parallel to each other is subjected to a grain boundary diffusion treatment after attaching the deposits to those surfaces, the inside of the RFeB magnet If the content of the heavy rare earth element R _CH exceeds 1.25% by mass in a plane equidistant from the two surfaces, the coercive force does not increase even if the ^content is increased. Therefore, even if the content of the heavy rare earth elements R _C ^H at the grain boundaries exceeds 1.25% by mass, the heavy rare earth elements R _C ^H are wasted. Therefore, in the RFeB magnet according to the present invention, the upper limit of the content of the heavy rare earth element R _CH in the grain boundary is set to 1.25% ^by mass. On the other hand, if the content of the heavy rare earth elements R _C ^H at the grain boundaries _is ^less than 0.40, sufficient coercive force cannot be obtained. The lower limit of is set to 0.40% by mass. The range of the content of Cu and Al at the grain boundary is determined by using the R ^H CuAl alloy having a composition within the range specified in the method for producing an RFeB magnet according to the present invention, and the heavy rare earth R _C ^H It was found by actually measuring the contents of Cu and Al at grain boundaries when the grain boundary diffusion treatment was performed so that the content of Cu and Al was 0.40 to 1.25% by mass.

If it is necessary to further increase the coercive force and a slight decrease in the residual magnetic flux density is acceptable, the base material may contain a heavy rare earth element ^RH . When the base material ^used in the method for producing an RFeB magnet according to the present invention contains the heavy rare earth element R ^H , in the RFeB magnet produced thereby, the content of the heavy rare earth element R _C at the grain boundaries and , the content of the heavy rare earth element R _C ^H is not 0 even in the crystal grains. In this way, when a substrate containing a heavy rare earth element ^RH and having two surfaces facing substantially parallel to each other is subjected to a grain boundary diffusion treatment after the deposit is attached to the surfaces, the RFeB system In a plane equidistant from the two surfaces in the magnet, the value obtained by subtracting the content of the heavy rare earth R _C ^H contained in the grain from the content of the heavy rare earth R _C ^H contained in the grain boundary is 0.40 to 1.25% by mass. On the other hand, the amounts of Cu and Al contained in the base material are very small. Therefore, the content of Cu and Al in the grain boundaries in the plane of the RFeB magnet manufactured by adding the heavy rare earth element ^RH to the base material by the method according to the present invention is 3.9 to 14.0% by mass, and 0.09 to 1.00% by mass for Al.

According to the present invention, the grain boundary diffusion treatment can be efficiently performed using the ^RH- containing material made of a material more suitable than the conventional one. A high RFeB magnet and a method for manufacturing the RFeB magnet are obtained.

FIG. 3 is a ternary composition diagram showing the composition of the R ^H CuAl alloy used in the method for producing an RFeB magnet according to the present invention. Schematic diagrams showing steps of a method for manufacturing an RFeB magnet according to the present embodiment. FIG. 4 is a diagram showing an example of designating a location for composition analysis based on an image of a sample obtained by an EPMA apparatus; 4 is a graph showing the results of measuring the coercive force iHc of the RFeB-based magnet produced by the RFeB-based magnet manufacturing method of the present example. 4 is a graph showing the results of measuring the content of Tb in the grain boundaries of the RFeB-based magnet produced by the RFeB-based magnet manufacturing method of the present example. FIG. 3 is a ternary composition diagram showing the composition of another R ^H CuAl alloy used in the method for producing an RFeB magnet according to the present invention. 4 is a graph showing the results of a corrosion resistance test performed on the RFeB magnets of Examples and Comparative Examples.

An embodiment of an RFeB magnet and a method for manufacturing the same according to the present invention will be described with reference to FIGS. 1 to 7. FIG.

(1) Embodiment of RFeB magnet manufacturing method according to the present invention
(1-1) Substrate The substrate used in the method for producing an RFeB magnet according to the present embodiment is R containing one or two light rare earth elements R ^L , that is, Nd or/and Pr, Fe and B. It consists of an ^L FeB based sintered magnet or an R ^L FeB based hot plastically worked magnet. Of these, the ^RL FeB-based sintered magnet body may be produced by a press method in which the raw material ^RL FeB-based alloy powder is sintered after being press-molded while being oriented by a magnetic field. As in (1) above, a PLP (Press-less process) method may be used in which the ^RL FeB-based alloy powder is oriented by a magnetic field in a mold without being press-molded and then sintered as it is. The PLP method is preferable in that the coercive force can be increased and that an ^RL FeB based sintered magnet body having a complicated shape can be produced without machining. The R ^L FeB system hot plastically worked magnet body can be produced by the method described in Non-Patent Document 1.

(1-2) ^RH CuAl alloy Fig. 1 shows the composition of the ^RH CuAl alloy used in the method for producing an RFeB magnet according to the present embodiment. This diagram is generally called a ternary composition diagram, and one point in the ^diagram indicates the content of the three elements R _CH , Cu and Al. Here, ^R _CH may be any of Tb, Dy and Ho. In this figure, R _C ^H is assumed to be one type of element (that is, one of Tb, Dy and Ho), but in the actual R ^H CuAl alloy, Tb, Dy and Ho Atoms of two or three elements may be mixed.

The content of R _CH is 100 atomic % at the vertex of the triangle indicated as "R _CH ^" in FIG. 1 and 0 atomic % at the opposite side of ^the vertex. For example, in FIG. 1, ^a straight line extending from point 3 parallel to the ^opposite side and intersecting with the side indicated as "R _CH content" is "33", which is the value of R _CH at point 3. It shows that the content is 33 atomic %. Similarly, at point 3, the Cu content is 24 atomic % and the Al content is 43 atomic %.

Table 1 shows the content of R _C ^H , Cu and Al atoms at points 1 to 9 in FIG. In addition to the atomic content, Table 1 also shows the mass content when R CH is Dy and when R _C ^H is Tb.

In the method for producing an RFeB magnet according to the present embodiment, in the grain boundary diffusion treatment described later, a first hexagon (from the upper left in the figure) having points 1 to 6 as vertices indicated by a thick solid line in FIG. A R ^H CuAl alloy having the R _C ^H , Cu and Al atom contents indicated by the dots in (shown with diagonal lines toward the lower right) or on the sides of the hexagon can be used. . In the R ^H CuAl alloy having such a content, the R H CuAl phase, which is a ternary system ⁱⁿ which the composition ratio of R _C ^H is larger than that of the other phases (the composition ratio of R _C ^H , Cu, and Al is 1:1 :1) exists, so the coercive force of RFeB sintered magnets and RFeB hot plastically worked magnets can be increased. The range in which the R ^H CuAl phase exists is based on the ternary composition diagram at 573 K (300° C.) shown in Non-Patent Document 2.

In addition, in the method for manufacturing an RFeB magnet of the present embodiment, in the grain boundary diffusion treatment to be described later, second grains indicated by the thick broken lines in FIG. R having a content of each atom of R _CH , Cu and Al indicated by a point within a hexagon (hatched from upper right to lower left in the figure) ^or on a side of the hexagon ^H CuAl alloys can also be used. The ^RH CuAl alloys having these contents have been shown by experiments described later to have the same effect as the ^RH CuAl alloys whose contents are indicated by the first hexagons.

Therefore, in the manufacturing method of the RFeB magnet of the present embodiment, points 1, 7, 8, 9, 3, 4, 5, and 6, which are the combination of the first hexagon and the second hexagon, are the vertices. An R ^H CuAl alloy is used having the R _C ^H , Cu and Al atom contents indicated by the points within the octagon or on the sides of the octagon.

(1-3) Deposits (R ^H CuAl Alloy Containing Matter), Deposit Preparing Step The deposits used in the method for manufacturing the RFeB magnet of the present embodiment contain the R ^H CuAl alloy. The deposit may consist of only ^RH CuAl alloy, such as RH CuAl alloy powder or foil, but should not be ^a mixture of RH ^CuAl alloy powder and other materials as described below. may An organic solvent is typically used as a substance to be mixed with the ^RH CuAl alloy powder. By using an organic solvent, it is possible to make the deposits adhere to the surface of the base material easily. Among organic solvents, silicone grease, silicone oil, or a silicone-based organic solvent composed of a mixture thereof can be preferably used. By using such a silicone-based organic solvent, the adherence to the substrate is enhanced, and the R _CH atoms are easily moved to the grain boundary of the substrate during the grain boundary diffusion ^treatment . Therefore, the coercive force of the RFeB magnet can be further enhanced. By mixing silicone grease and silicone oil at an appropriate ratio, the viscosity of the deposit can be adjusted.

(1-4) Grain Boundary Diffusion Treatment Grain boundary diffusion treatment is performed as follows using the base material and deposits prepared as described above. First, the deposit 12 is attached to the surface of the base material 11 (Fig. 2(a), deposit (R ^H CuAl alloy containing material) attaching step). The deposit 12 may be attached to the entire surface of the substrate 11 or may be attached only to a portion of the surface. For example, the deposit 12 mixed with a silicone-based organic solvent can be applied to two plate surfaces of the plate-like substrate 11 by coating. In this case, the adhering matter 12 is not applied to the side surface of the substrate 11 .

Next, the substrate 11 coated with the deposit 12 is heated to a predetermined temperature (FIG. 2(b), heating step). Here, the predetermined temperature is the temperature at which the atoms of the heavy rare earth element R _C ^H contained in the deposit 12 diffuse into the substrate 11 through the grain boundaries of the substrate 11, and is typically 700 to 1000°C. . This heating process causes the atoms of the heavy rare earth element R _C ^H contained in the deposit 12 to diffuse into the base material 11 through the grain boundaries of the base material 11 , thereby causing the crystal grains in the base material 11 to diffuse mainly near the surface of the crystal grains. The concentration ^of R _CH increases. On the other hand, the atoms of ^the contained heavy rare earth element R _CH are difficult to penetrate into the crystal grains. Therefore, by this heating step, an RFeB-based magnet (RFeB-based sintered magnet or RFeB-based hot plastically worked magnet) having a higher content of the heavy rare ^earth element _RCH at the grain boundaries than in the grains of the crystal grains can be obtained. . After that, if necessary, aging treatment (treatment of heating at a relatively low temperature of about 500° C.), grinding treatment for removing residues of deposits 12 remaining on the surface of base material 11, and magnet molding treatment are performed. Thus, an RFeB-based magnet, which is the final product, is obtained.

The content of the heavy rare earth elements R _C ^H contained in the grain boundaries of the obtained RFeB magnet is similar to the content of the heavy rare earth elements R _C ^H contained in the R ^H CuAl alloy and the type of light rare earth elements R _C ^L contained in the base material 11. Although it depends, the mass percentage is 0.45 to 1.25% by mass. The grain boundary of the obtained RFeB magnet has a Cu content of 3.9 to 14.0% by mass and an Al content of 0.09 to 1.00% by mass.

(2) Examples of the RFeB-based magnet manufacturing method according to the present invention and embodiments of the RFeB-based magnet according to the present invention Examples of composition analysis at the grain boundaries of the obtained RFeB-based magnets will be described, and embodiments of the RFeB-based magnets according to the present invention will be described based on the experimental results of the examples.

In Example 1, the base material was a plate-shaped R ^L FeB-based sintered plate with a thickness of 5 mm containing no R ^H and a small amount of Cu and Al (Cu: 0.1% by mass, Al: 0.2% by mass). A magnet body was used. _The ^RH CuAl alloy has a ^Tb content of 46.00 atomic percent (74.53 mass percent), a Cu content of 30.00 atomic percent (19.01 mass percent), and an Al content of 24.00 Atomic % (6.46 mass %) was made by strip casting. The content of each element in this ^RH CuAl alloy corresponds to the point marked with a triangle in FIG. The deposit was produced by mixing silicone grease with ^RH CuAl alloy powder obtained by pulverizing this ^RH CuAl alloy by a hydrogen pulverization method and then removing hydrogen. A plurality of experiments with different amounts of deposits were conducted by adjusting the amount of deposits deposited on the substrate so that the mass of Tb in the deposits with respect to the mass of the substrate was within the range of 0.2 to 1.4%. The deposit was adhered to the entire two plate surfaces of the plate-shaped base material, and was not adhered to the four side surfaces. The grain boundary composition analysis of the obtained RFeB magnet was performed using an EPMA apparatus (manufactured by JEOL Ltd., JXA-8500F). In this analysis, positions in the grain boundary were randomly selected at a depth of 2.5 mm from the position corresponding to the surface of the substrate (i.e., equidistant from both surfaces of the substrate), and A total of 7 locations were specified, and the average value at 5 locations excluding the 2 locations with the highest and lowest Tb contents was obtained. FIG. 3 shows an example in which the positions (i) to (vii) in the seven grain boundary triple points are specified based on the backscattered electron image of the sample obtained by the EPMA apparatus.

FIG. 4 shows the results of measuring the coercive force iHc of the obtained RFeB magnet, and FIG. 5 shows the results of measuring the content of Tb in grain boundaries. As shown in FIG. 4, when the mass of Tb in the deposit relative to the mass of the substrate is within the range of 0.2 to 1.2% by mass, the coercive force increases as the mass of Tb in the deposit increases. On the other hand, when the mass of Tb in the deposit relative to the mass of the substrate exceeds 1.2% by mass, no such increase in coercive force is observed. As shown in FIG. The content is 0.40-1.25% by mass.

Therefore, for the TbCuAl alloys shown in Table 1, which have six types of compositions corresponding to points 1 to 6 in FIG. , and 1.2% by mass, RFeB magnets were produced under the same conditions as in Example 1 except for the TbCuAl alloy used, and the contents of Tb, Cu and Al in the grain boundaries were measured. In addition, TbCuAl alloys having three types of compositions shown in Table 1 corresponding to points 7 to 9 in FIG. 1, and points A to F in FIG. 6 and TbCuAl alloys having six types of compositions shown in Table 2 Regarding, when the mass of Tb in the deposit relative to the mass of the base material is 1.0% by mass, RFeB magnets were produced under the same conditions as in Example 1 except for the TbCuAl alloy used, and Tb in the grain boundary, The contents of Cu and Al were measured (above, Example 2). Here, points A to F in FIG. 6 all lie within the aforementioned octagon.

The results of Example 2 are shown in Table 3.

From Table 3, the content of Tb at the grain boundary of each sample was almost the same value as in Example 1. Also, the content of Cu in the grain boundary was 3.9 to 14.0% by mass, and the content of Al was 0.09 to 1.00% by mass.

Next, RFeB based sintered magnets of Comparative Examples 1 to 6 were produced in the same manner as in Examples 1 and 2 using deposits containing alloys having the compositions shown in Table 4. The alloy in the deposits used alloys containing Ni or Co instead of Cu in Comparative Examples 1-3, and consisted of Tb and one of Cu, Ni, Co (Al (not containing) was used. The amount of deposit in each example was adjusted so that the amount of Tb in the deposit deposited on the substrate was the same in all examples. For the RFeB sintered magnets of Examples 1 and 2 and Comparative Examples 1 to 6 thus produced, samples were prepared by polishing each of the two plate surfaces of the base material by 0.15 mm, and the amount of Tb in these samples was measured. It was measured. The reason why this kind of polishing was performed here is that the surface of the actual RFeB sintered magnet product is also polished as a finishing process, and that residual particles near the surface of the base material do not diffuse into the base material. Since the wasteful Tb exists, the purpose is to remove the wasteful Tb in order to confirm the efficiency of the grain boundary diffusion treatment. The amount of Tb in each sample is shown in Table 4 as a ratio to the amount of Tb in the deposit applied to the substrate. In Table 4, "Example 2-X" (X is one of 7 to 9 and A to F) represents the composition of the TbCuAl alloy used, Tables 1 and 2, Figures 1 and It is the symbol shown in FIG.

From the results of this experiment, it was confirmed that Examples 1 and 2 had a larger amount of Tb in the sample than Comparative Examples 1 to 6, and that Tb could be diffused into the substrate more efficiently.

Next, the results of a corrosion resistance test performed on the samples of Example 1 and Comparative Example 1 are shown in FIG. In this test, after measuring the mass of the sample, the sample was maintained for 400 to 1000 hours under high temperature and high humidity conditions with a temperature of 120°C, humidity of 100%, and pressure of 2 atm (saturated water vapor pressure). was determined to determine the mass reduction rate of the sample. It means that the smaller the absolute value of the mass reduction rate, the higher the corrosion resistance. From FIG. 7, in Comparative Example 1, the absolute value of the mass reduction rate increases as the time maintained under high temperature and high humidity conditions increases, whereas in Example 1, it was maintained under high temperature and high humidity conditions for 1000 hours. However, the mass reduction rate was almost zero. From this corrosion resistance test, it was confirmed that the sample of Example 1 had higher corrosion resistance than that of Comparative Example 1. Presumably, this is because the presence of Cu at the grain boundaries in the example raised the potential at the grain boundaries, and suppressed the elution of the rare earth-rich (Nd-rich) grain boundary phase and the falling off of the RFeB (NdFeB) particles. be done.

Next, as an embodiment of the method for producing an RFeB magnet according to the present invention, the results of grain boundary diffusion treatment performed on a base material containing R ^H using an R ^H CuAl alloy will be shown. In this embodiment, ^RH contains 0.20% by mass, 4.40% by mass, and 10.0% by mass of Tb, respectively, and the same amount of Cu and Al as in Example 1 (Cu: 0.1% by mass, Al: 0.2% by mass). Three types of RFeB-based sintered magnet base materials and deposits of TbCuAl alloys having compositions indicated by points 8, B and F in FIG. 6 were used as R ^H CuAl alloys. The amount of deposit was adjusted so that the content of Tb in the deposit relative to the substrate was 0.20% by mass or 1.00% by mass. For 18 types of samples that combined these three types of substrates, three types of deposit compositions, and two types of Tb content in the deposits, Tb in the grain boundary was measured under the same conditions as in Examples 1 and 2. , Cu and Al contents were measured. In addition, the content of Tb in the crystal grains at the same depth from the base material surface as the content of Tb in the grain boundary was also measured by EPMA. A total of 7 locations were designated to measure the Tb content within the crystal grains, one from each of the different crystal grains, and the average value of the five locations excluding the two locations with the highest and lowest Tb content was obtained. rice field. FIG. 3 shows an example in which seven positions (A) to (G) in crystal grains are designated based on the backscattered electron image of the sample obtained by the EPMA apparatus.

From Table 5, the content of Tb in the grain boundary ranges widely from 0.67 to 11.06% by mass, depending on the Tb content in the base material. is within the range of 0.40 to 1.25% by mass regardless of the Tb content in the substrate. This range is the amount of Tb(R ^H ) supplied to the grain boundary just enough for the coercive force improvement effect of the grain boundary diffusion treatment.

11... Base material 12... Deposits (R ^H CuAl alloy inclusions)

Claims (3)

Coordinates of eight points (Tb _at% , Cu _at% , Al _at% ) = (50 , 40, 10), (58, 30, 12), (58, 20, 22), (48, 20, 32), (33, 24, 43), (17, 50, 33), (17, 60 , 23) and (33, 58, 9) and a deposit preparation step of preparing a deposit containing a TbCuAl alloy having a composition represented by points within or on the sides of the octagon;
An attachment ^{that adheres to the surface of a base material comprising an R L FeB-based sintered magnet body containing one or two light rare earth elements R L ,} _Fe , and B. an attachment step;
A method for producing an RFeB magnet, comprising heating the substrate to which the deposit is attached to a predetermined temperature within a range of 700 to 1000°C. The TbCuAl alloy has six coordinates (Tb _at% , Cu _at% , Al _at% )=(50, 40, 10), (50, 32, 18), (33, 24, 43), (17, 50, 33), (17, 60, 23) and (33, 58, 9) having a composition represented by points within or on the sides of the hexagon The method for manufacturing an RFeB magnet according to claim 1, characterized by: An RFeB-based sintered magnet containing light rare earth elements R ^{C L} composed of one or two light rare earth elements R _L , Tb, Fe and B ^, and having two surfaces facing substantially parallel to each other,
The content of Tb is higher at grain boundaries than inside grains,
In the plane equidistant from the two surfaces in the RFeB sintered magnet, the value obtained by subtracting the Tb content in the crystal grain from the Tb content in the grain boundary is 0.73 to 1.25% by mass,
The content of Cu in the grain boundary is 3.9-14.0% by mass, and the content of Al is 0.09-1.00% by mass.
An RFeB-based sintered magnet characterized by:

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