Method for producing an RTB-based sintered magnet

Abstract

A method for producing a sintered RTB-based magnet, wherein R is at least one rare earth element which always comprises Nd, wherein T is at least one transition metal element which always comprises Fe and wherein B is partially replaceable by C, wherein the RTB-based magnet consists of a main phase which consists essentially of an R2T 14 B substance, and a grain boundary phase which lies at grain boundaries of the main phase, the method comprising: a step of providing an R1-T1-X-based sintered alloy compact, wherein R1 is at least one rare earth element which always includes Nd, the R1-T1-X-based sintered alloy compact containing R1 in a proportion of not less than 27 mass % and not more than 35 mass %; wherein T1 is Fe or Fe and M, wherein M is at least one element selected from the group consisting of Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, and Ag, wherein X is B, wherein B is partially replaceable with C, and wherein a molar ratio of [T1] / [X] is not less than 13.0, the R1-T1-X-based sintered alloy compact being formed by sintering particles each having a size of not less than 1 µm and not more than 10 µm; a step of providing an R2-Ga-Cu-based alloy, wherein R2 is at least one rare earth element which always includes Pr, wherein Pr accounts for 50 mol% or more of R2, wherein the R2-Ga-Cu-based alloy contains R2 in a proportion of not less than 65 mol% and not more than 95 mol%, and wherein a molar ratio of [Cu] / ([Ga]+[Cu]) is not less than 0.1 and not more than 0.9; and while allowing at least a part of the R2-Ga-Cu-based alloy to come into contact with at least a part of a surface of the R1-T1-X-based sintered alloy compact, a step of performing a heat treatment at a temperature of not lower than 450°C and not higher than 600°C in a vacuum or an inert gas environment.

Description

Technical area

[0001] The present invention relates to a method for producing a sintered RTB-based magnet. background

[0002] Sintered RTB-based magnets (where R is at least one rare earth element, always including Nd; T is at least one transition metal element, always including Fe; and B is boron) are known as the highest-performance permanent magnets and are used in voice coil motors (VCMs) of hard disk drives, various types of motors such as motors for electric vehicles (EV, HV, PHV, etc.) and motors for industrial devices, home use products, and the like.

[0003] A sintered RTB-based magnet consists of a main phase, which essentially consists of an R2T 14B-material, and a grain boundary phase (hereinafter referred to simply as the “grain boundaries”) located at the grain boundaries of the main phase. The R2T 14 B-material is a ferromagnetic phase with high magnetization and provides a basis for the properties of a sintered RTB-based magnet.

[0004] The coercivity H cJ (hereinafter referred to simply as “coercivity” or as “H cJ The flux loss (which can be referred to as "high flux loss") of sintered RTB-based magnets decreases at high temperatures, causing irreversible flux loss. For this reason, sintered RTB-based magnets for application in electric vehicle motors must, in particular, have a high H cJ at high temperatures, ie at room temperature a larger H cJ have.

[0005] It is known that H cJis improved when a light rare earth element (essentially Nd and / or Pr) which is present in R of the R2T 14 B material of a sintered RTB-based magnet is partially replaced by a heavy rare earth element (mainly Dy and / or Tb). H cJ is further improved as the amount of substituted heavy rare earth element increases.

[0006] Replacing the light rare earth element RL in the R2T 14 B-substance by a heavy rare earth element can H cJ of the sintered RTB-based magnet, but its remanence B decreases r (hereinafter simply referred to as “B r"). In addition, heavy rare earth elements, especially Dy and the like, are rare resources and are found only in limited areas. For this and other reasons, there are problems of uncertain supply, significantly fluctuating prices, etc. Therefore, in recent years, users have needed an improved H cJ , using as few heavy rare earth elements as possible, without B r to reduce.

[0007] Patent Document 1 discloses, while a R 1 i -M 1 jalloy (15 <j≦99) einer bestimmten Zusammensetzung, welche zu 70 vol.-% oder mehr eine Phase eines intermetallischen Stoffes enthält, an der Oberfläche des gesinterten Presskörpers einer bestimmten Zusammensetzung vorhanden sein darf, das Durchführen einer Hitzebehandlung für 1 Minute bis 30 Stunden in einem Vakuum oder einem Inertgas bei einer Temperatur, welche gleich der oder kleiner als die Sintertemperatur des gesinterten Presskörpers ist. Ein Element oder zwei oder mehr Elemente von R 1 and M 1 contained in the alloy diffuse into the grain boundary regions within the aforementioned sintered compact and / or into the main phase in the grain boundary regions. As concrete examples, Patent Document 1 discloses performing a diffusion heat treatment at 800°C for 1 hour while applying a Nd 33 Al 67 alloy containing a NdAl2 phase or a Nd 35 Fe 25 Co 20Al 20 -alloy containing a Nd(Fe,Co,Al)2 phase, or the like with a sintered compact of Nd 16 Feb a1 Co 1.0 B 5.3 may come into contact.

[0008] Patent Document 2 discloses a method in which an Nd-Fe-B-based sintered compact and a source containing Pr are placed in a container and heated, thereby introducing Pr into the magnet interior. It is disclosed that by optimizing conditions in the method according to Patent Document 2, Pr is allowed to exist only at the grain boundaries and Pr is prevented from penetrating into the main phase crystal grains, thereby improving coercivity not only at room temperature but also at high temperatures (e.g., 140°C). As a concrete example, Patent Document 2 discloses heating at 660°C to 760°C using an appropriate amount of Pr metal powder.

[0009] Patent Document 3 discloses that an RE-M alloy containing an M element (specifically, Ga, Mn, In) with a certain vapor pressure and whose melting point is equal to or lower than 800°C is allowed to come into contact with an RE-TB-based sintered compact, and heat treatment is performed at a temperature 50°C to 200°C higher than the vapor pressure curve of the M element. Through this heat treatment, the RE element permeates the compact by diffusion from the melt of the RE-M alloy. Patent Document 3 states that the M element is prevented from penetrating into the magnet interior because the M element evaporates during the process, allowing only the RE element to penetrate efficiently. As a specific example, Patent Document 3 discloses using Nd-20at%Ga and heat treatment at 850°C for 15 hours. Citation listPatent documents [Patent document 1] JP 2008 - 263 179 A [Patent document 2] JP 2014 - 112 624 A [Patent Document 3] JP 2014 - 086 529 A

[0010] The prior art also includes the documents WO 2015 / 020 181 A1, EP 2 270 822 A1 and WO 2015 / 020 183 A1. Summary of the inventionTechnical problem

[0011] The methods described in Patent Documents 1 to 3 are noteworthy in that they are capable of improving the coercivity of a sintered RTB-based magnet without using any heavy rare earth elements. However, only the magnet surface region is improved in coercivity in these methods, while almost no improvement in coercivity occurs in the magnet interior. As described in Patent Document 3, the thickness of grain boundaries (especially any grain boundaries located between two main phase portions; these may hereinafter be referred to as "intergranular grain boundaries") decreases drastically from the magnet surface to the magnet interior, causing a large difference in coercivity between the magnet surface region and the magnet interior.In this respect, there is a problem that if the portion with the improved coercivity is removed by surface grinding or the like, which is performed to adjust the magnet dimensions in the general magnet manufacturing steps, the effects of the improved coercivity are significantly lost.

[0012] Various embodiments of the present invention provide methods for producing a sintered RTB-based magnet in which the intergranular grain boundaries can be made thick not only in the magnet surface region but also in the magnet interior, so that the effect of improved coercivity is not significantly lost even if a surface has been ground to adjust the magnet dimensions, and which provide high coercivity without using a heavy rare earth element. Solution to the problem

[0013] A method for producing a sintered RTB-based magnet according to the present invention is a method for producing a sintered RTB-based magnet, wherein R is at least one rare earth element which always includes Nd; T is at least one transition metal element which always includes Fe; and B is partially replaceable by C, wherein the RTB-based magnet consists of a main phase consisting essentially of an R2T 14B substance, and a grain boundary phase located at grain boundaries of the main phase, the method comprising: a step of providing an R1-T1-X-based sintered alloy compact, wherein R1 is at least one rare earth element which always includes Nd and accounts for not less than 27 mass % and not more than 35 mass %, wherein T1 is Fe or Fe and M, wherein M is at least one element selected from Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo and Ag, wherein X is B, wherein B is partially replaceable by C and wherein a molar ratio of [T1] / [X] is not less than 13.0, wherein the R1-T1-X-based sintered alloy compact is formed by sintering particles each having a size of not less than 1 µm and not more than 10 µm;a step of providing an R2-Ga-Cu-based alloy, wherein R2 is at least one rare earth element always comprising Pr, with Pr accounting for 50 mol% or more of R2, the R2-Ga-Cu-based alloy containing R2 in a proportion of not less than 65 mol% and not more than 95 mol%, and a molar ratio of [Cu] / ([Ga]+[Cu]) being not less than 0.1 and not more than 0.9; and while allowing at least a part of the R2-Ga-Cu-based alloy to come into contact with at least a part of a surface of the R1-T1-X-based sintered alloy compact, a step of performing a heat treatment at a temperature of not less than 450°C and not more than 600°C in a vacuum or an inert gas environment;

[0014] In one embodiment, T1 in R1-T1-X comprises Fe and M, where M is at least one element selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, and Ag.

[0015] In one embodiment, a molar ratio of [T1] / [X] in the R1-T1-X based sintered alloy compact is 13.6 or more.

[0016] In one embodiment, a molar ratio of [T1] / [X] in the R1-T1-X based sintered alloy compact is 14 or more.

[0017] In one embodiment, any heavy rare earth element constitutes 1 mass percent or less of the R1-T1-X based sintered alloy compact.

[0018] In one embodiment, the step of providing an R1-T1-X based sintered alloy compact comprises pulverizing a raw material alloy to a size of not less than 1 µm and not more than 10 µm, then pressing the pulverized raw material alloy in a magnetic field and sintering.

[0019] In one embodiment, the step of providing an R1-T1-X-based sintered alloy compact after sintering comprises performing a high-temperature heat treatment at a temperature which is above 600°C and below a sintering temperature.

[0020] In one embodiment, the R2-Ga-Cu-based alloy does not contain a heavy rare earth element.

[0021] In one embodiment, R2 in the R2-Ga-Cu-based alloy consists only of Pr, apart from unavoidable impurities.

[0022] In one embodiment, R2 in the R2 Ga Cu based alloy further comprises Nd.

[0023] In one embodiment, a portion of R2 in the R2-Ga-Cu-based alloy is a heavy rare earth element, wherein the heavy rare earth element is contained at 10 mol% or less of the total R2-Ga-Cu-based alloy.

[0024] In one embodiment, a portion of R2 in the R2-Ga-Cu-based alloy is a heavy rare earth element, wherein the heavy rare earth element is contained at 5 mol% or less of the total R2-Ga-Cu-based alloy.

[0025] In one embodiment, in the R2-Ga-Cu-based alloy, part of R2 is a heavy rare earth element and Pr constitutes all of R2, excluding the heavy rare earth element and apart from unavoidable impurities.

[0026] In one embodiment, the temperature in the step of performing a heat treatment is not less than 480°C and not more than 540°C.

[0027] In one embodiment, in the step of performing a heat treatment, an R12T1 14 X-phase in the R1-T1-X-based sintered alloy compact with a liquid phase originating from the R2-Ga-Cu-based alloy, so that a R6T 13Z phase, where Z always comprises Ga and / or Cu, is generated at least partially within the sintered magnet.

[0028] In one embodiment, the step of performing a heat treatment comprises applying and / or dispersing a powder of the R2-Ga-Cu-based alloy to at least a portion of the surface of the R1-T1-X-based sintered alloy compact such that the R2-Ga-Cu-based alloy comes into contact with at least a portion of the surface of the R1-T1-X-based sintered alloy compact.

[0029] In one embodiment, the powder of the R2-Ga-Cu-based alloy to be dispersed and / or coated on the surface of the R1-T1-X-based sintered alloy compact has, based on 100 parts by mass of the R1-T1-X-based sintered alloy compact, not less than 0.2 parts by mass and not more than 0.5 parts by mass. Advantageous effects of the invention

[0030] According to the present invention, a method for producing a sintered RTB-based magnet is provided in which the intergranular grain boundaries can be made thick not only in the magnet surface region but also in the magnet interior, so that the effects of improved coercivity are not significantly lost even after grinding a surface to adjust the magnet dimensions, and which provides high coercivity without using a heavy rare earth element. Brief description of the drawings Fig. Figure 1A is a partially enlarged cross-sectional view schematically showing a sintered RTB-based magnet. Fig. Figure 1B shows a further enlarged cross-sectional view showing the interior of a Fig. 1A schematically represents the rectangular area shown with dashed lines. Fig.2 shows an explanatory diagram schematically illustrating how an R1-T1-X-based sintered alloy compact and an R2-Ga-Cu-based alloy may be arranged during a heat treatment step. Fig. Figure 3 shows a photograph showing the magnetic surface area of Sample No. 6-1 as seen with a scanning electron microscope. Fig. Figure 4 shows a photograph showing the magnetic central region of sample No. 6-1 as seen with a scanning electron microscope. Fig. Figure 5 shows a photograph showing the magnetic surface area of Sample No. 9-1 as seen with a scanning electron microscope. Fig. Figure 6 shows a photograph showing the magnetic central region of sample No. 9-1 as seen with a scanning electron microscope. Description of the embodiments

[0031] In the methods described in Patent Documents 1 and 2, a relatively high temperature is used for heat treatment, typically a temperature of 650°C or more. This is presumably because some of the grain boundaries located between main phase regions of the sintered compact melt at a temperature of 650°C or more, allowing external elements to penetrate through this region as a diffusion path. In other words, it is considered effective to perform treatment at a relatively high temperature to ensure that a certain amount of a liquid phase is reliably provided in the sintered compact.

[0032] On the other hand, in the method described in Patent Document 3, Ga or the like is used to lower the melting point of the rare earth alloy serving as a diffusion source. By utilizing the vapor pressure of Ga, a rare earth element (which is Nd in Patent Document 3) penetrates into the interior of the sintered compact while preventing Ga from penetrating into the interior of the sintered compact. As a result, thick intergranular grain boundaries can be formed even at a relatively low heat treatment temperature, thereby improving coercivity. However, in the method of Patent Document 3, thick intergranular grain boundaries are formed only in the magnet surface region, and the intergranular grain boundaries in the magnet interior remain thin.

[0033] Through vigorous studies aimed at solving the above problems, the present inventors arrived at a method which carries out heat treatment at a relatively low temperature while allowing an R2-Ga-Cu-based alloy of a certain composition in which a molar ratio of [Cu] / ([Ga]+[Cu]) is not less than 0.1 and not more than 0.9 to come into contact with a sintered alloy compact of a composition (a molar ratio of [T] / [B] is 14 or more) which is richer in T and poorer in B (or a sum of B and C when B is partially replaced by C) than R2T 14B, i.e., the stoichiometric composition of the main phase of a conventional sintered RTB-based magnet. With this method, a liquid phase derived from the R2-Ga-Cu-based alloy can penetrate from the surface of the sintered compact into the interior by diffusion across grain boundaries in the sintered compact. Furthermore, it was found that thick intergranular grain boundaries containing Ga and / or Cu can be easily formed all the way to the interior of the sintered compact. By creating such a structure, the magnetic coupling between main phase crystal grains is significantly facilitated, whereby a sintered RTB-based magnet with a very high coercivity can be obtained without using a heavy rare earth element.In further studies based on these results, it was found that even when a molar ratio of [T1] / [X] in the sintered alloy compact is 13.0 or more but less than 14, a high coercivity is achieved, which is close to that of a sintered RTB-based magnet manufactured using a sintered alloy compact in which a molar ratio of [T1] / [X] is 14 or more.

[0034] Before describing embodiments of a method for manufacturing a sintered RTB-based magnet, the basic structure of a sintered RTB-based magnet will first be described.

[0035] The sintered RTB-based magnet has a structure in which powder particles of a raw material alloy are bonded together by sintering, and consists of a main phase which is essentially composed of an R2T 14B-material, and a grain boundary phase, which lies at the grain boundaries of the main phase.

[0036] Fig. Figure 1A is a partially enlarged cross-sectional view schematically showing a sintered RTB-based magnet. Fig. Figure 1B is a further enlarged cross-sectional view showing the interior of a Fig. 1A schematically shows a rectangular area drawn with a dashed line. In Fig. 1A, an arrow representing a length of 5 µm is shown as an example of a reference length for illustrating the size. As in Fig. 1A and Fig. As shown in Figure 1B, the sintered RTB-based magnet consists of a main phase, which essentially consists of an R2T 14 B-material 12, and a grain boundary phase 14, which lies at the grain boundaries of the main phase 12. As in Fig. 1B, the grain boundary phase 14 comprises an intergranular grain boundary phase 14a, at which two R2T14 B-material grains are adjacent to each other, and grain boundary triple points 14b, at which three R2T 14 B-substance grains border each other.

[0037] The main phase 12, ie the R2T 14 B-material, is a ferromagnetic material with high magnetization saturation and an anisotropic field. In a sintered RTB-based magnet, it is therefore possible to use B r by increasing the frequency ratio of the R2T 14 B substance, which is the main phase 12. To improve the frequency ratio of the R2T 14 B-material, the R-amount, the T-amount and the B-amount in the raw material alloy can be made closer to the stoichiometric ratio of the R2T 14 B substance (ie the R amount : the T amount : the B amount = 2:14:1). If the B amount or the R amount in the R2T 14B substance falls below the stoichiometric ratio, small parts of a magnetic substance with anisotropic fields, for example an Fe phase or an R2T 17 -phase, in the grain boundary phase 14, whereby H cJ drops drastically.

[0038] Non-limiting and exemplary embodiments of the present invention are described below. (1) Step of providing an R1-T1-X based sintered alloy compact

[0039] In a step of providing an R1-T1-X-based sintered alloy compact (which may hereinafter be simply referred to as a “sintered compact”), the sintered compact has a composition as follows: R1 is at least one rare earth element, which always includes Nd, and accounts for not less than 27 mass % and not more than 35 mass %; T1 is Fe or is Fe and M, where M is at least one element selected from Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, and Ag; where X is B, where B is partially replaceable by C; where a molar ratio of [T1] / [X] is 13.0 or more, preferably 13.6 or more, and more preferably 14 or more.

[0040] R1 is at least one rare earth element, which always includes Nd. Besides Nd, another example of a rare earth element may be Pr. Furthermore, heavy rare earth elements such as Dy, Tb, Gd, and Ho, which are commonly used to improve the coercivity of a sintered RTB-based magnet, may be contained in small amounts. However, the present invention enables a sufficiently high coercivity to be obtained without using the aforementioned heavy rare earth elements in large amounts. Therefore, it is preferable that the heavy rare earth elements are contained at 1 mass % or less, more preferably 0.5 mass % or less of the entire R1-T1-X-based sintered alloy compact (i.e., the heavy rare earth element accounts for 1 mass % or less in the R1-T1-X-based sintered alloy compact); and more preferably, no heavy rare earth element is contained (i.e.,essentially 0 mass percent).

[0041] Preferably, R1 accounts for not less than 27 mass % and not more than 35 mass % of the entire R1-T1-X-based sintered alloy compact. If R1 is less than 27 mass %, a liquid phase does not sufficiently appear during sintering, and it is difficult for the structure of the sintered compact to become sufficiently dense. On the other hand, if R1 exceeds 35 mass %, the effects of the present invention are achieved, but the alloy powder is very active during the manufacturing steps of the sintered compact, and significant oxidation, ignition, etc. of the alloy powder may possibly occur; therefore, 35 mass % or less is preferred. More preferably, R1 is not less than 28 mass % and not more than 33 mass %; further preferably, R1 is not less than 28.5 mass % and not more than 32 mass %.

[0042] T1 is Fe or is Fe and M; and M is at least one of Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, and Ag. In other words, T1 may be Fe alone (although unavoidable impurities may be contained) or may be composed of Fe and M (although unavoidable impurities may be contained). When T1 is composed of Fe and M, it is preferable that the amount of Fe be 80 mol% or more in the entire T1. When T1 is composed of Fe and M, M may be at least one of Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, and Ag.

[0043] X is B, where B is partially replaceable by C (carbon). When B is partially replaced by C, this can be not only what is intentionally added during the manufacturing steps of the sintered compact, but also what comes from the solvent or the like (during wet forming) and remains in the sintered compact. The C coming from a pressing additive, a solvent, etc., is unavoidable but can be controlled within a certain range (i.e., adjustment of added amounts or decarbonization treatment); therefore, taking these considerations into account, the amount of B and the amount of C that are intentionally added can be set so that the relationship between T1 and X described below is satisfied.In order to intentionally add C during the manufacturing steps of the sintered compact, for example, C may be added as a raw material when the raw material alloy is manufactured (i.e., a raw material alloy containing C may be manufactured); a C source (carbon source), such as a certain amount of carbon black, may be added to the alloy powder during the manufacturing steps (i.e., a coarsely pulverized powder existing before the pulverization with a jet mill or the like described below, or a finely pulverized powder existing after pulverization); etc. B preferably accounts for 80 mol% or more, and more preferably 90 mol% or more of the total X. Furthermore, X preferably accounts for not less than 0.8 mass % and not more than 1.0 mass % of the total R1-T1-X-based sintered alloy compact.When X is less than 0.8 mass%, the effects of the present invention are achieved, but B. r be greatly reduced, which is undesirable. On the other hand, if X exceeds 1.0 mass percent, the molar ratio of [T1] / [X] as described below cannot be made equal to or greater than 13.0, and the effects of the present invention are not achieved, which is undesirable. More preferably, X is not less than 0.83 mass percent and not more than 0.98 mass percent, and further preferably not less than 0.85 mass percent and not more than 0.95 mass percent.

[0044] The above-mentioned T1 and X are determined such that a molar ratio of [T1] / [X] is 14 or more. This condition indicates a molar ratio which corresponds to that of [T] / [B] (=14) in R2T 14B, i.e., the stoichiometric composition of the main phase of a conventional sintered RTB-based magnet, or is richer in T and poorer in B than this. As described above, at the beginning of the invention, the inventors believed that if the molar ratio of [T1] / [X] is less than 14, as in the composition of a conventional sintered RTB-based magnet (i.e., poorer in T and richer in B than the molar ratio of [T] / [B] in the stoichiometric composition R2T 14B), the intergranular grain boundaries in the magnet surface area and in the magnet interior cannot be made thick in the ultimately obtained sintered RTB-based magnet, and therefore, it would be difficult to obtain a sintered RTB-based magnet with high coercivity without using heavy rare earth elements. However, in further studies, they found that even at lower T and higher B than the molar ratio of [T] / [B] in R2T 14 B, ie, the stoichiometric composition of the main phase of a conventional sintered RTB-based magnet, a molar ratio of [T1] / [X] which is 13.0 or more can still provide a coercivity which, if not exceeding, is very close to the coercivity achieved for a sintered alloy compact of 14 or more.

[0045] In other words, the molar ratio of [T1] / [X], which is set to 14 or more, is based on the assumption that B and C, which constitute X, are completely consumed in the formation of the main phase. However, in general, X (especially C) is not completely consumed in the formation of the main phase, but will also exist in the grain boundary phase. It has therefore been found that in practice, [X] can be set somewhat larger (i.e., poorer in T and richer in B); i.e., the molar ratio of [T1] / [X] can be set to 13.0 or more, and high coercivity can still be achieved.It is difficult to determine an accurate relationship of how X is distributed between the main phase and the grain boundary phase; however, when the molar ratio of [T1] / [X] is 13.0 or more, assuming that X consumed during the formation of the main phase has a molar ratio of [X'] (where [X']≤[X]), it is assumed that [T1] / [X'] is 14 or more. If the molar ratio of [T1] / [X] is less than 13.0, the aforementioned [T1] / [X'] cannot be made 14 or more; in this case, the intergranular grain boundaries in the magnet surface region and the magnet interior cannot be made thick in the finally obtained sintered RTB-based magnet, making it difficult to obtain a sintered RTB-based magnet with high coercivity without using heavy rare earth elements.While the molar ratio of [T1] / [X] of 13.0 or more as described above provides high coercivity, the molar ratio of [T1] / [X] is preferably 13.6, more preferably 13.8 or more, and still more preferably 14 or more in order to achieve even higher coercivity and to always achieve high coercivity in a mass production process.

[0046] An R1-T1-X-based sintered alloy compact can be provided using a general method for producing an RTB-based sintered magnet, such as an Nd-Fe-B-based sintered magnet. For example, a raw material alloy produced by a strip casting method or the like can be pulverized to not less than 1 μm and not more than 10 μm using a jet mill or the like, then pressed in a magnetic field, and then sintered at a temperature of not less than 900°C and not more than 1100°C. It is irrelevant whether the coercivity in the resulting sintered compact is very low.If the pulverized particle size (with a volume average value obtained by an air-drift distribution laser diffraction method, = D50) of the raw material alloy is smaller than 1 µm, it becomes very difficult to produce pulverized powder, resulting in greatly reduced manufacturing efficiency, which is undesirable. On the other hand, if the pulverized particle size exceeds 10 µm, the final sintered RTB-based magnet will have a crystal grain size too large to achieve high coercivity, which is undesirable, although thick intergranular grain boundaries can be formed.

[0047] As long as the above conditions are met, the R1-T1-X-based sintered alloy compact can be manufactured from one type of raw material alloy (single raw material alloy) or by a process in which two or more types of raw material alloys are used and mixed (mixed process). Furthermore, the R1-T1-X-based sintered compact may contain unavoidable impurities, such as O (oxygen), N (nitrogen), and C (carbon), which are contained in the raw material alloy or introduced during the manufacturing steps.

[0048] When preparing the R1-T1-X-based sintered alloy compact, high-temperature heat treatment can also be performed after sintering at a temperature above 600°C and below the sintering temperature. Performing high-temperature heat treatment at such a temperature can, in some cases, further improve the magnetic properties of the final sintered RTX-based magnet.Performing heat treatment at a temperature below 600°C on the R1-T1-X-based sintered alloy compact alone would only increase the number of steps without contributing to further improving the properties of the final sintered RTX-based magnet. This is because this sintered compact is subsequently subjected to heat treatment at a temperature of 600°C or less while in contact with the R2-Ga-Cu-based alloy. On the other hand, if the high-temperature heat treatment temperature is above the sintering temperature, abnormal grain growth may occur, thereby reducing the coercivity of the ultimately obtained sintered RTX-based magnet or deteriorating the squareness of its demagnetization curve.

[0049] Particularly, when at least one of Si, Ga, Al, Zn, and Ag is contained in T1 of the R1-T1-X-based sintered alloy compact at 0.1 mass percent or more than an M element, the above-described high-temperature heat treatment is preferably carried out at a temperature of not less than 700°C and not more than 1000°C. When such an M element is contained, an R1-T1-M phase (e.g., an R6Fe 13Ga phase) may occur, so that when heat treatment is performed at a temperature of 600°C or less while the R2-Ga-Cu-based alloy is placed in contact, a liquid phase originating from the R2-Ga-Cu-based alloy diffuses from the surface of the sintered compact into the interior via grain boundaries in the sintered compact. Such high-temperature heat treatment is particularly effective when the sintered compact contains Ga. (2) Step of providing an R2-Ga-Cu-based alloy

[0050] In a step of providing an R2-Ga-Cu-based alloy, the R2-Ga-Cu-based alloy has a composition as follows: R2 is at least one rare earth element, which always includes Pr, and accounts for not less than 65 mol% and not more than 95 mol%; and a molar ratio of [Cu] / ([Ga]+[Cu]) is not less than 0.1 and not more than 0.9. The R2-Ga-Cu-based alloy always contains both Ga and Cu. If both Ga and Cu are not included, the intergranular grain boundaries in the magnet surface region and the magnet interior cannot be made thick in the finally obtained sintered RTB-based magnet, making it difficult to obtain a sintered RTB-based magnet with high coercivity without using heavy rare earth elements.

[0051] R2 is at least one rare earth element, which always includes Pr. Herein, it is preferred that Pr (and optionally Nd) accounts for 90 mol% or more, more preferably that Pr accounts for 50 mol% or more of the total R2, and even more preferably that R2 alone is Pr (although unavoidable impurities may be contained). R2 may contain small amounts of heavy rare earth elements, for example, Dy, Tb, Gd, and Ho, which are commonly used to improve the coercivity of a sintered RTB-based magnet. According to the present invention, a sufficiently high coercivity can be obtained without using the aforementioned heavy rare earth element(s) in large amounts. Therefore, the aforementioned heavy rare earth element(s) is / are contained in a proportion that preferably accounts for 10 mol% or less of the total R2-Ga-Cu-based alloy (i.e.the heavy rare earth element(s) constitute(s) 10 mol% or less in the R2-Ga-Cu-based alloy), more preferably 5 mol% or less, and even more preferably not contained at all (substantially 0 mol%). When R2 of the R2-Ga-Cu-based alloy contains the above-mentioned heavy rare earth element(s), it is preferable that 50 mol% or more of the total R2 excluding the heavy rare earth element(s) is Pr, and further preferred that R2 excluding the heavy rare earth element(s) is Pr alone (although unavoidable impurities may be contained).

[0052] When R2 accounts for not less than 65 mol% and not more than 95 mol% of the entire R2-Ga-Cu-based alloy, and a molar ratio of [Cu] / ([Ga]+[Cu]) is not less than 0.1 and not more than 0.9, a sintered RTB-based magnet is provided in which the intergranular grain boundaries can be made thick not only in the magnet surface region but also in the magnet interior, so that the effects of improved coercivity are not significantly lost even after surface grinding to adjust the magnet dimensions, and which provides high coercivity without using a heavy rare earth element. More preferably, R2 accounts for not less than 70 mol% and not more than 90 mol% of the entire R2-Ga-Cu-based alloy, and even more preferably, not less than 70 mol% and not more than 85 mol%.In addition, it is further preferable that a molar ratio of [Cu] / ([Ga]+[Cu]) is not less than 0.2 and not more than 0.8, and even more preferably not less than 0.3 and not more than 0.7.

[0053] The R2-Ga-Cu-based alloy may contain small amounts of Al, Si, Ti, V, Cr, Mn, Co, Ni, Zn, Ge, Zr, Nb, Mo, Ag, and the like. A small amount of Fe may be contained, and the effects of the present invention are still obtained when Fe is contained at 20 mass percent or less. However, if the Fe content exceeds 20 mass percent, the coercivity may be reduced. In addition, unavoidable impurities such as O (oxygen), N (nitrogen), C (carbon), and the like may be contained.

[0054] The R2-Ga-Cu alloy can be provided by a raw material alloy manufacturing method used in general methods for manufacturing a sintered RTB-based magnet, such as a die casting method, a strip casting method, a single-roll rapid quenching method (a melt spinning method), an atomizing method, or the like. Furthermore, the R2-Ga-Cu-based alloy can be that obtained by pulverizing an alloy obtained as above with a known pulverizing means, such as a pin mill. (3) Heat treatment step

[0055] While at least a part of the R2-Ga-Cu-based alloy provided as described above is allowed to come into contact with at least a part of the surface of the R1-T1-X-based sintered alloy compact provided as described above, a heat treatment is carried out in a vacuum or an inert gas environment at a temperature of not less than 450°C and not more than 600°C. As a result, a liquid phase is generated from the R2-Ga-Cu-based alloy, and this liquid phase penetrates into the sintered compact from the surface of the sintered compact into the interior by diffusion via grain boundaries, so that thick intergranular grain boundaries containing Ga and Cu easily penetrate into the interior of the sintered compact between crystal grains of the main phase, i.e., the R12T1 14X-phase, can be formed, thereby greatly facilitating magnetic coupling between main-phase crystal grains. As a result, a sintered RTB-based magnet with a very high coercivity can be obtained without using heavy rare earth elements. The temperature at which the heat treatment is performed is preferably not lower than 480°C and not higher than 540°C. Higher coercivity can be achieved.

[0056] Generally, an area of about 200 μm is removed from the surface of the sintered compact when the surface is ground to adjust the magnet dimensions. Therefore, the effects of the present invention can be obtained when there exists an area in which thick intergranular grain boundaries exist up to about 250 μm from the surface of the R1-T1-X-based sintered alloy compact. However, in such a case (thick intergranular grain boundaries exist up to about 250 μm), H cJ near the center of the RTX-based sintered compact is not sufficiently improved after heat treatment, so the squareness of the demagnetization curve may be deteriorated. Regarding H cJ near the center of the R1-T1-X based sintered alloy compact, it is therefore preferable that H cJ ≥1200 kA / m and further preferred that H cJ≥1360 kA / m when heat treatment is carried out at a temperature of not less than 450°C and not more than 600°C without contact with the R2-Ga-Cu-based alloy (i.e., a common heat treatment to improve the coercivity of the sintered RTB-based magnet). The use of such a sintered compact enables the magnet as a whole to exhibit high H cJ and the squareness of the demagnetization curve is good even when the intruded amount of the R2-Ga-Cu alloy is small, so that a high B r and a high H cJ can be easily achieved.

[0057] Regarding H cJNear the center of the R1-T1-X-based sintered alloy compact, an R1-T1-X-based sintered compact that satisfies HcJ≥1200 kA / m when heat treatment is performed at a temperature of not lower than 450°C and not higher than 600°C without contacting the R2-Ga-Cu-based alloy can be easily obtained if Ga is contained in T1. The Ga content is preferably not less than 0.05 mass % and not more than 1 mass %, more preferably not less than 0.1 mass % and not more than 0.8 mass %, and even more preferably not less than 0.2 mass % and not more than 0.6 mass % in the entire R1-T1-X-based sintered compact.

[0058] In the above-described heat treatment step, the R2-Ga-Cu-based alloy alone may be disposed in contact with at least a part of the surface of the R1-T1-X-based sintered alloy compact, or methods described in the above Patent Documents 1 to 3 may be used, for example, a method in which a powder of the R2-Ga-Cu-based alloy is dissolved in an organic solvent or the like and applied to the surface of the R1-T1-X-based sintered alloy compact; or a method in which a powder of the R2-Ga-Cu-based alloy is dispersed on the surface of the R1-T1-X-based sintered alloy compact.

[0059] By dispersing and / or applying an R2-Ga-Cu-based alloy powder to at least a part of the surface of the R1-T1-X-based sintered alloy compact, at least a part of the R2-Ga-Cu-based alloy can be more easily brought into contact with at least a part of the surface of the R1-T1-X-based sintered alloy compact.

[0060] The amount of the liquid phase originating from the R2-Ga-Cu-based alloy that penetrates into the R1-T1-X-based sintered alloy compact can be controlled based on the treatment temperature and treatment time. When the R2-Ga-Cu-based alloy is distributed and / or applied on the surface of the R1-T1-X-based sintered alloy compact, it is preferable that the distributed amount or the applied amount be controlled. The distributed or applied amount of the R2-Ga-Cu-based alloy is preferably, based on 100 parts by mass of the R1-T1-X-based sintered alloy compact, not less than 0.2 parts by mass and not more than 5.0 parts by mass, and more preferably not less than 0.2 parts by mass and not more than 3.0 parts by mass. Such conditions enable a high B r and a high H cJcan be easily obtained. When the R2-Ga-Cu-based alloy is distributed or applied to only a part of the surface of the R1-T1-X-based sintered alloy compact, it is preferably distributed or applied to a surface perpendicular to the orientation direction.

[0061] The heat treatment includes maintaining a temperature of not less than 450°C and not more than 600°C in a vacuum or inert gas environment, followed by cooling. By performing heat treatment at a temperature of not less than 450°C and not more than 600°C, at least a part of the R2-Ga-Cu-based alloy is melted, whereby the generated liquid phase penetrates from the surface of the sintered compact into the interior by diffusion across grain boundaries in the sintered compact, whereby thick intergranular grain boundaries can be formed. If the heat treatment temperature is lower than 450°C, no liquid phase appears at all, so thick intergranular grain boundaries cannot be obtained. If it exceeds 600°C, it is also difficult to form thick intergranular grain boundaries. The heat treatment temperature is preferably not less than 460°C and not more than 570°C.The reason why it is difficult to form thick intergranular grain boundaries when heat treatment is carried out at a temperature exceeding 600°C is currently unknown, but it is likely due to the kinetics related to the dissolution of the main phase caused by the liquid phase penetrating into the sintered compact and the generation of R6T. 13Z phase (where R is at least one rare earth element which always includes Pr and / or Nd; T is at least one transition metal element which always includes Fe; and Z always includes Ga and / or Cu), etc. The heat treatment time can be set to an appropriate value depending on the composition and dimensions of the R1-T1-X-based sintered alloy compact, the composition of the R2-Ga-Cu-based alloy, the heat treatment temperature, etc., but it is preferably not less than 5 minutes and not more than 10 hours, more preferably not less than 10 minutes and not more than 7 hours, and even more preferably not less than 30 minutes and not more than 5 hours.

[0062] The above-described heat treatment temperature of not less than 450°C and not more than 600°C is substantially the same as the temperature of a conventional heat treatment for coercivity improvement of a sintered RTB-based magnet. Therefore, after performing heat treatment at a temperature of not less than 450°C and not more than 600°C, it is not always necessary to perform coercivity improvement heat treatment. Moreover, the heat treatment temperature of not less than 450°C and not more than 600°C is a very low temperature compared to the temperatures of the diffusion heat treatments performed in Patent Documents 1 to 3 above. As a result, the R2-Ga-Cu-based alloy component is prevented from diffusing into the interior of the main phase crystal grains.For example, if Pr is used alone for R2, a heat treatment temperature exceeding 600°C would simply cause Pr to penetrate into the outermost part of the main phase crystal grains, resulting in a problematic decrease in the temperature dependence of coercivity. At a heat treatment temperature of no less than 450°C and no more than 600°C, such problems are greatly suppressed.

[0063] The sintered RTB-based magnet obtained by the heat treatment step can be subjected to known surface treatments, for example, known machining operations such as dicing or cutting, or coating to apply corrosion protection.

[0064] There are still unclear aspects of the mechanism by which thick intergranular grain boundaries are formed between crystal grains of the main phase and which leads to very high coercivity. Based on the knowledge available to date, the mechanism as understood by the present inventors is described below. It should be noted that the following description of the mechanism is not intended to limit the scope of the present invention.

[0065] Through extensive studies, the inventors have come to the conclusion that: Cu, through its presence in the liquid phase arising from the heat treatment, reduces the interfacial energy between the main phase and the liquid phase, thus contributing to the efficient penetration of the liquid phase from the surface of the sintered compact into the interior via the intergranular grain boundaries; and that Ga, through its presence in the liquid phase having penetrated into the intergranular grain boundaries, causes the surface area of the main phase to be dissolved, thus contributing to the formation of thick intergranular grain boundaries.

[0066] Furthermore, as described above, thick intergranular grain boundaries are easily obtained by the heat treatment by ensuring that the R1-T1-X based sintered alloy compact has a composition richer in T1 and poorer in X than the stoichiometric composition (R12T1 14 X), that is, the molar ratio of [T1] / [X] is 14 or more. This is presumably because, in the above-mentioned composition range, the liquid phase originating from the R2-Ga-Cu alloy penetrates the intergranular grain boundaries in the sintered compact, and the main phase in the region of intergranular grain boundaries in the sintered compact is dissolved due to the above-mentioned effects of Ga, this simply a R6T 13Z phase (Z always includes Ga and / or Cu) forms and becomes stable at a very low temperature of 600°C or below; therefore, thick intergranular grain boundaries are maintained even after cooling, resulting in a very high observable coercivity. As described above, generally, X is not completely consumed in the formation of the main phase; therefore, as long as [T1] / [X] is 13.0 or more, a thick intergranular grain boundary is successfully formed, and high coercivity is achieved.

[0067] On the other hand, if the R1-T1-X based sintered alloy compact has a composition poorer in T1 and richer in X than the stoichiometric composition (R12T1 14 X), especially when [T1] / [X] is less than 13.0, it is difficult to obtain thick intergranular grain boundaries. This is probably because the main phase (R12T1 14X-phase), once dissolved, is likely to precipitate back into the main phase, preventing the grain boundaries from becoming thick.

[0068] In the aforementioned R6T 13 Z-phase (R6T 13 Z-material) R is at least one rare earth element, which always includes Pr and / or Nd; T is at least one transition metal element, which always includes Fe; and Z always includes Ga and / or Cu. A representative R6T 13 Z-material is a Nd6Fe 13 Ga material. Furthermore, the R6T 13 Z-substance a La6Co 11 Ga3-type crystal structure. Depending on its state, the R6T 13 Z-Stoff the shape of an R6T 13-δ Z 1+δ -substance. Even if Z is Ga alone, it can take the form of R6T 13- δ(Ga 1-x-y-z Cu x Al y Si z ) 1+ δ when Cu, Al and Si are included in the sintered RTB-based magnet. [Examples]

[0069] The present invention will be described in more detail by way of examples; however, the present invention is not limited thereto. Experimental Example 1[Providing an R1-T1-X-based sintered alloy compact]

[0070] Using an Nd metal, an iron-boron alloy, an iron-carbon alloy, and an electrolytic iron (each metal having a purity of 99% or more), the composition (excluding Al, Si, and Mn) of a sintered compact was adjusted to result in the compositions of labels 1-A to 1-I shown in Table 1. These raw materials were melted and cast by a strip casting method, thereby obtaining raw material alloys in the form of chips with a thickness of 0.2 mm to 0.4 mm. After each resulting raw material alloy in the form of chips was hydrogen pulverized, it was subjected to dehydrogenation by heating to 550°C in a vacuum and then cooling, thereby obtaining a coarsely pulverized powder.Next, zinc stearate was added as a solvent to the resulting coarsely pulverized powder in an amount of 0.4 mass percent based on 100 mass percent of the coarsely pulverized powder. After mixing, an air jet crusher (jet mill) was used to perform dry grinding in a nitrogen jet, thereby obtaining a finely pulverized powder (alloy powder) with a particle size D50 of 4 µm. Note that the particle size D50 is a volume average value (volume median particle diameter) obtained by a laser diffraction method using an air jet dispersion technique. To adjust the amount of C in the sintered compact, carbon black was added to a portion of the resulting finely pulverized powder.

[0071] Zinc stearate was added to the finely pulverized powder as a solvent in an amount of 0.05 mass percent based on 100 mass percent of the finely pulverized powder. After mixing, the finely pulverized powder was pressed in a magnetic field to obtain a compact. A so-called orthogonal magnetic field press (transverse magnetic field press), in which the direction of the applied magnetic field is orthogonal to the pressing direction, was used as the pressing device.

[0072] The resulting compact was sintered in a vacuum for 4 hours at temperatures of not less than 1000°C and not more than 1040°C (for each sample, a temperature was selected at which a sufficiently dense structure would be achieved by sintering) and then rapidly cooled to obtain an R1-T1-X-based sintered alloy compact. Each resulting sintered compact has a density of 7.5 Mg / m³. 3or more. The components in the resulting sintered compacts and the gas analysis results (C (carbon content)) thereof were as shown in Table 1. The corresponding components in Table 1 were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES). C (carbon content) was measured using a gas analyzer based on a combustion infrared absorption method. The oxygen content in each sintered compact was measured by a gas fusion infrared absorption method, all of which had a value around 0.4 mass %.In Table 1, "[T1] / [X]" is a ratio (a / b) between: (a) a sum of values obtained by dividing an analytical value (mass percent) of each element constituting T1 (including unavoidable impurities, which in this experimental example are Al, Si, and Mn) by the atomic weight of that element; and (b) a sum of values obtained by dividing analytical values (mass percent) of B and C by the atomic weights of these elements. The same applies to all subsequent tables. Note that each composition in Table 1 does not sum to 100 mass percent. This is because, as described above, a different analytical method is used for each component, and further because components other than those entered in Table 1 (e.g., O (oxygen), N (nitrogen), and the like) are present. The same applies to the other tables. [Table 1] Label Composition (mass percent) of the R1-T1-X-based sintered alloy compact R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Al Si Mn B C 1-A 30.6 0.06 67.3 0.05 0.04 0.03 0.87 0.05 30.7 14.3 1-B 30.1 0.10 68.1 0.06 0.05 0.04 0.90 0.05 30.2 14.0 1-C 30.6 0.10 67.2 0.05 0.04 0.03 0.93 0.12 30.7 12.6 1-D 30.5 0.10 67.2 0.05 0.04 0.04 1.00 0.05 30.6 12.5 1-E 30.6 0.10 67.5 0.05 0.05 0.04 0.87 0.32 30.7 11.3 1-F 30.6 0.51 67.4 0.10 0.05 0.02 0.88 0.09 31.1 13.6 1-G 30.7 0.45 67.5 0.11 0.05 0.02 0.90 0.08 31.2 13.5 1-H 30.5 0.52 67.3 0.11 0.05 0.02 0.92 0.08 31.0 13.2 1-I 30.4 0.61 67.3 0.10 0.05 0.02 0.93 0.09 31.0 12.9 [Providing an R2-Ga-Cu-based alloy]

[0073] Using a Pr metal, a Ga metal, and a Cu metal (each metal having a purity of 99% or more), the composition of an alloy was adjusted to the composition shown in Label 1-a in Table 2. These raw materials were dissolved; an alloy in ribbon or chip form was obtained by a single-roll rapid quenching process (melt spinning process). Using a mortar, the resulting alloy was pulverized in an argon atmosphere and then passed through a sieve with an opening of 425 µm, thereby providing an R2-Ga-Cu-based alloy. The composition of the resulting R2-Ga-Cu-based alloy is shown in Table 2. [Table 2] Label Composition (mol%) of the R2-Ga-Cu-based alloy R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu 1-a 75 12.5 12.5 75 0.5 [Heat treatment]

[0074] The R1-T1-X-based sintered alloy compacts labeled 1-A to 1-I in Table 1 were sectioned and cut into 2.4 mm x 2.4 mm cubes.

[0075] Next, as in Fig. 2, the R2-Ga-Cu-based alloy according to label 1-a shown in Table 2 was arranged in a processing container 3 made of niobium foils above and below each of the R1-T1-X-based sintered alloy compacts according to labels 1-A to 1-I such that mainly a surface of the R1-T1-X-based sintered alloy compact 1, which is perpendicular to the orientation direction (ie, the direction shown by arrows in the figures), was in contact with the R2-Ga-Cu-based alloy 2.

[0076] Subsequently, heat treatment was performed in argon controlled at a reduced pressure of 200 Pa at a heat treatment temperature shown in Table 3 using a tubular flow furnace, followed by cooling. To remove thickened portions of the R2-Ga-Cu-based alloy present in the surface region of each sample after heat treatment, a surface grinder was used to cut off 0.2 mm from the entire surface of each sample, thereby obtaining 2.0 mm × 2.0 mm × 2.0 mm cube-shaped samples (sintered RTB-based magnets). [Evaluation of samples]

[0077] The resulting samples were placed in a vibrating sample magnetometer (VSM:VSM-5SC-10HF, manufactured by TOEI INDUSTRY CO., LIMITED) with a superconducting coil; and after applying a magnetic field of up to 4 MA / m, the magnetic hysteresis curve of the sintered compacts was measured in the alignment direction while the magnetic field was changed to -4 MA / m. Coercivity (H cJ ) obtained from the resulting hysteresis curves are shown in Table 3. From Table 3, it can be seen that a high H cJ is obtained when the molar ratio of [T1] / [X] in the R1-T1-X based sintered alloy compact is 13.0 or more and a very high H cJ which exceeds 1900 kA / m is obtained especially at 14 or more. Table 3 Sample No. Manufacturing conditions A cJ (kA / m) Notes Composition of R1-T1-X-based sintered alloy compact Composition of the R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 1-1 1-A 30.7 14.3 1-a 75 0.5 500°C×4h 2130 Example of the invention 1-2 1-B 30.2 14.0 1-a 75 0.5 500°C×4h 1920 Example of the invention 1-3 1-C 30.7 12.6 1-a 75 0.5 500°C×4h 350 Comparison example 1-4 1-D 30.6 12.5 1-a 75 0.5 500°C×4h 630 Comparison example 1-5 1-E 30.7 11.3 1-a 75 0.5 500°C×4h 80 Comparison example 1-6 1-F 31.1 13.6 1-a 75 0.5 500°C×4h 1925 Example of the invention 1-7 1-G 31.2 13.5 1-a 75 0.5 500°C×4h 1930 Example of the invention 1-8 1-H 31.0 13.2 1-a 75 0.5 500°C×4h 1895 Example of the invention 1-9 1-I 31.0 12.9 1-a 75 0.5 500°C×4h 1028 Comparison example

[0078] Of the samples shown in Table 3, a cross section of Sample No. 1-1 (an example of the present invention) having the R1-T1-X-based sintered alloy compact according to Label 1-A with a molar ratio of [T1] / [X] of 13.0 or more, and a cross section of Sample No. 1-4 (Comparative Example) having the R1-T1-X-based sintered alloy compact according to Label 1-D with a molar ratio of [T1] / [X] of less than 13.0 were obtained by means of a scanning electron microscope (SEM: S4500, manufactured by Hitachi, Ltd.). The results showed that thick intergranular grain boundaries of 100 nm or more were formed in Sample No. 1-1 (an example of the present invention) from the magnet surface region to the central region of the magnet. On the other hand, in Sample Nos. 1-4 (comparative example), thick intergranular grain boundaries were formed only in the area of the magnet surface. Furthermore, a cross-section of Sample No.1-1, which is an example of the present invention, was analyzed by energy dispersive X-ray spectroscopy (EDX: HITS4800, manufactured by Hitachi, Ltd.), whereby Ga and Cu were also detected in the grain boundaries of the central region of the magnet, a part of which region was considered to be an R6T based on its constituents. 13 Z phase, which contains Ga and Cu, was identified. Experimental Example 2

[0079] Several R1-T1-X-based sintered alloy compacts were prepared by a method similar to that of Experimental Example 1, except that the composition (ignoring Al, Si, and Mn) of a sintered compact was adjusted to obtain the composition according to Label 2-A shown in Table 4. [Table 4] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Al Si Mn B C 2-A 30.6 0.06 67.3 0.05 0.04 0.03 0.87 0.05 30.7 14.3

[0080] R2-Ga-Cu-based alloys were prepared by a method similar to that of Experimental Example 1, except that it was adapted so that the alloys had compositions according to the labels 2-a to 2-u shown in Table 5. [Table 5] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Nd Pr Ga Cu 2-a 0 100 0 0 100 - 2-b 0 97 1.5 1.5 97 0.5 2-c 0 95 2.5 2.5 95 0.5 2-d 0 90 5 5 90 0.5 2-e 0 85 7.5 7.5 85 0.5 2-f 0 75 12.5 12.5 75 0.5 2-g 0 70 15 15 70 0.5 2-h 0 60 20 20 60 0.5 2-i 0 50 25 25 50 0.5 2-j 0 75 25 0 75 0 2-k 0 75 22.5 2.5 75 0.1 2-1 0 75 20 5 75 0.2 2-m 0 75 17.5 7.5 75 0.3 2-n 0 75 7.5 17.5 75 0.7 2-o 0 75 5 20 75 0.8 2-p 0 75 2.5 22.5 75 0.9 2-q 0 75 0 25 75 1 2-r 18.75 56.25 12.5 12.5 75 0.5 2-s 56.25 18.75 12.5 12.5 75 0.5 2-t 75 0 12.5 12.5 75 0.5 2-u 0 90 1 9 90 0.9

[0081] After the plurality of R1-T1-X-based sintered alloy compacts were prepared similarly to Experimental Example 1, the R2-Ga-Cu-based alloys according to Labels 2-a to 2-u and the R1-T1-X-based sintered alloy compact according to Label 2-A were arranged to be in contact with each other in a similar manner to Experimental Example 1, and heat treatment and processing were carried out similarly to Experimental Example 1 except that the heat treatment temperatures were adjusted as shown in Table 6, thereby obtaining samples (sintered RTB-based magnets). The resulting samples were measured by a method similar to that of Experimental Example 1, whereby the coercivity (H cJ) was determined. The results are shown in Table 6. Note that Table 6 shows results for the conditions that provided the greater coercivity between a heat treatment at 500°C and a heat treatment at 600°C. As shown in Table 6, a high H cJ obtained when R2 in the R2-Ga-Cu-based alloy was not less than 65 mol% and not more than 95 mol% and the molar ratio of [Cu] / ([Ga]+[Cu]) was not less than 0.1 and not more than 0.9. Regarding R2, a high H cJ obtained when Pr accounted for 50 mol% or more in the total R2 (compare sample No. 2-18 with sample Nos. 2-19 and 2-20); higher H cJ were obtained when R2 was Pr alone (apart from other rare earth elements at impurity level); and the highest H cJ was obtained in particular when sample 2-f (Pr 75 Ga 12.5 Cu 12.5 (mol%)) than the R2-Ga-Cu based alloy was used. [Table 6] Sample No. Manufacturing conditions A cJ (kA / m) Notes R1-T1-X based sintered alloy compact R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 2-1 2-A 30.7 14.3 2-a 100 - 500°C×4h 43 Comparison example 2-2 2-A 30.7 14.3 2-b 97 0.5 500°C×4h 127 Comparison example 2-3 2-A 30.7 14.3 2-c 95 0.5 500°C×4h 1690 Example of the invention 2-4 2-A 30.7 14.3 2-d 90 0.5 500°C×4h 2048 Example of the invention 2-5 2-A 30.7 14.3 2-e 85 0.5 500°C×4h 2088 Example of the invention 2-6 2-A 30.7 14.3 2-f 75 0.5 500°C×4h 2130 Example of the invention 2-7 2-A 30.7 14.3 2-g 70 0.5 500°C×4h 2048 Example of the invention 2-8 2-A 30.7 14.3 2-h 60 0.5 600°C×4h 968 Comparison example 2-9 2-A 30.7 14.3 2-i 50 0.5 500°C×4h 47 Comparison example 2-10 2-A 30.7 14.3 2-j 75 0 600°C×4h 1329 Comparison example 2-11 2-A 30.7 14.3 2-k 75 0.1 600°C×4h 1799 Example of the invention 2-12 2-A 30.7 14.3 2-1 75 0.2 600°C×4h 1910 Example of the invention 2-13 2-A 30.7 14.3 2-m 75 0.3 500°C×4h 2128 Example of the invention 2-14 2-A 30.7 14.3 2-n 75 0.7 500°C×4h 2008 Example of the invention 2-15 2-A 30.7 14.3 2-o 75 0.8 500°C×4h 1950 Example of the invention 2-16 2-A 30.7 14.3 2-p 75 0.9 500°C×4h 1849 Example of the invention 2-17 2-A 30.7 14.3 2-q 75 1 600°C×4h 888 Comparison example 2-18 2-A 30.7 14.3 2-r 75 0.5 500°C×4h 2035 Example of the invention 2-19 2-A 30.7 14.3 2-s 75 0.5 500°C×4h 1889 Comparison example 2-20 2-A 30.7 14.3 2-t 75 0.5 500°C×4h 1850 Comparison example 2-21 2-A 30.7 14.3 2-u 90 0.9 500°C×4h 1768 Example of the invention Experimental Example 3

[0082] An R1-T1-X-based sintered alloy compact was prepared by a method similar to that of Experimental Example 1, except that the composition (ignoring Al, Si, and Mn) of a sintered compact was adjusted to result in the composition according to Label 3-A shown in Table 7. [Table 7] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Al Si Mn B C 3-A 30.6 0.06 67.3 0.05 0.04 0.03 0.87 0.05 30.7 14.3

[0083] An R2-Ga-Cu-based alloy was prepared by a method similar to that of Experimental Example 1, so that the alloy composition was the composition according to Label 3-a shown in Table 8. [Table 8] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Nd Pr Ga Cu 3-a 0 75 12.5 12.5 75 0.5

[0084] After the R1-T1-X-based sintered alloy compact was processed similarly to Experimental Example 1, the R2-Ga-Cu-based alloy according to Label 3-a and the R1-T1-X-based sintered alloy compact according to Label 3-A were arranged to be in contact with each other in a similar manner to Experimental Example 1, and heat treatment and processing were carried out similarly to Experimental Example 1 except that the heat treatment temperatures were adjusted as shown in Table 9, thereby obtaining samples (sintered RTB-based magnets). The resulting samples were measured by a method similar to that of Experimental Example 1, whereby the coercivity (H cJ ) was determined. The results are shown in Table 9. As shown in Table 9, a high H cJobtained if the heat treatment temperature was not less than 450°C and not more than 600°C. [Table 9] Sample No. Manufacturing conditions A cJ (kA / m) Notes R1-T1-X based sintered alloy compact R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 3-1 3-A 30.7 14.3 3-a 75 0.5 400°C×4h 38 Comparison example 3-2 3-A 30.7 14.3 3-a 75 0.5 450°C × 4h 1652 Example of the invention 3-3 3-A 30.7 14.3 3-a 75 0.5 500°C×4h 2130 Example of the invention 3-4 3-A 30.7 14.3 3-a 75 0.5 600°C×4h 1769 Example of the invention 3-5 3-A 30.7 14.3 3-a 75 0.5 700°C×4h 1420 Comparison example 3-6 3-A 30.7 14.3 3-a 75 0.5 800°C×4h 1168 Comparison example Experimental Example 4

[0085] An R1-T1-X-based sintered alloy compact was prepared by a method similar to that of Experimental Example 1, except that the composition (without considering Al, Si, and Mn) of a sintered alloy compact was adjusted to obtain the compositions according to labels 4-A to 4-D shown in Table 10. [Table 10] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Cu Al Si Mn B C 4-A 30.8 0.61 66.6 0.12 0.07 0.05 0.02 0.87 0.08 31.4 13.7 4-B 30.7 0.55 66.7 0.1 0.07 0.05 0.02 0.89 0.09 31.3 13.4 4-C 30.6 0.51 66.8 0.15 0.08 0.05 0.02 0.92 0.08 31.1 13.1 4-D 30.7 0.60 66.7 0.14 0.08 0.05 0.02 0.94 0.08 31.3 12.8

[0086] An R2-Ga-Cu-based alloy was prepared by a method similar to that of Experimental Example 1, so that the alloy composition was the composition according to Label 4-a shown in Table 11. [Table 11] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu 4-a 75 12.5 12.5 75 0.5

[0087] After the R1-T1-X-based sintered alloy compact was processed similarly to Experimental Example 1, the R2-Ga-Cu-based alloy according to Label 4-a and the R1-T1-X-based sintered alloy compacts according to Labels 4-A to 4-D were arranged to be in contact with each other similarly to Experimental Example 1, and heat treatment and processing were carried out similarly to Experimental Example 1, except that the heat treatment temperature was adjusted as shown in Table 12, thereby obtaining samples (sintered RTB-based magnets). The obtained samples were measured by a method similar to that of Experimental Example 1, whereby the coercivity (H cJ ) was determined. The results are shown in Table 12. From Table 12 it can be seen that even with the R1-T1-X sintered compact to which Cu was added, a high H cJis obtained when the molar ratio of [T1] / [X] is 13.0 or more, and in particular a very high H cJ which exceeds 1900 kA / m is obtained at 14 or more. [Table 12] Sample No. Manufacturing conditions A cJ (kA / m) Notes R1-T1-X based sintered alloy compact R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 4-1 4-A 31.4 13.7 4-a 75 0.5 500°C×4h 1955 Example of the invention 4-2 4-B 31.3 13.4 4-a 75 0.5 500°C×4h 1954 Example of the invention 4-3 4-C 31.1 13.1 4-a 75 0.5 500°C×4h 1892 Example of the invention 4-4 4-D 31.3 12.8 4-a 75 0.5 500°C×4h 980 Comparison example Experimental Example 5

[0088] An R1-T1-X-based sintered alloy compact was prepared by a method similar to that of Experimental Example 1, except that the composition (without considering Al, Si, and Mn) of a sintered alloy compact was adjusted to obtain the compositions according to labels 5-A to 5-D shown in Table 13. [Table 13] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Co Al Si Mn B C 5-A 30.7 0.55 66.1 0.98 0.08 0.05 0.02 0.87 0.09 31.4 13.7 5-B 30.5 0.51 66.2 1.01 0.07 0.05 0.02 0.89 0.09 31.3 13.5 5-C 30.8 0.49 66.0 0.99 0.07 0.05 0.02 0.92 0.08 31.1 13.0 5-D 30.7 0.52 66.1 0.97 0.08 0.05 0.02 0.94 0.08 31.3 12.9

[0089] An R2-Ga-Cu-based alloy was prepared by a method similar to that of Experimental Example 1, so that the alloy composition was the composition according to Label 5-a shown in Table 14. [Table 14] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu 5-a 75 12.5 12.5 75 0.5

[0090] After the R1-T1-X-based sintered alloy compact was processed similarly to Experimental Example 1, the R2-Ga-Cu-based alloy according to Label 5-a and the R1-T1-X-based sintered alloy compacts according to Labels 5-A to 5-D were arranged to be in contact with each other in a similar manner to Experimental Example 1, and heat treatment and processing were carried out similarly to Experimental Example 1, except that the heat treatment temperature shown in Table 15 was adjusted, thereby obtaining samples (sintered RTB-based magnets). The resulting samples were measured by a method similar to that of Experimental Example 1, whereby the coercivity (H cJ) was determined. The results are shown in Table 15. From Table 15 it can be seen that even with the R1-T1-X sintered compact to which Co was added, a high H cJ is obtained when the molar ratio of [T1] / [X] is 13.0 or more, and a very high H cJ which exceeds 1900 kA / m, especially at 14 or more. [Table 15] Sample No. Manufacturing conditions A cJ (kA / m) Notes Composition of R1-T1-X-based sintered alloy compact Composition of the R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 5-1 5-A 31.4 13.7 5-a 75 0.5 500°C×4h 1988 Example of the invention 5-2 5-B 31.3 13.5 5-a 75 0.5 500°C×4h 1939 Example of the invention 5-3 5-C 31.1 13.0 5-a 75 0.5 500°C×4h 1838 Example of the invention 5-4 5-D 31.3 12.9 5-a 75 0.5 500°C×4h 1097 Comparison example Experimental Example 6[Providing an R1-T1-X-based sintered alloy compact]

[0091] An R1-T1-X-based sintered alloy compact was manufactured by a method similar to that of Experimental Example 1, except that the composition (without considering Al, Si, and Mn) of a sintered compact was adjusted to obtain the composition according to Label 6-A shown in Table 16. [Table 16] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Al Si Mn B C 6-A 30.6 0.06 67.3 0.05 0.04 0.03 0.87 0.08 31.2 13.9 [Providing an R2-Ga-Cu-based alloy]

[0092] An R2-Ga-Cu-based alloy was prepared by a method similar to that of Experimental Example 1, so that the alloy composition was the composition according to Label 6-a shown in Table 17. [Table 17] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu 6-a 75 12.5 12.5 75 0.5 [Heat treatment]

[0093] The R1-T1-X-based sintered alloy compact according to Sample 6-A in Table 16 was sectioned and cut into a 4.4 mm x 4.4 mm x 4.4 mm cube. Next, as shown in Fig.2, the R2-Ga-Cu-based alloy according to Label 6-a shown in Table 17 was arranged in a processing container 3 made of niobium foils above and below the corresponding R1-T1-X-based sintered alloy compact according to Label 6-A, such that mainly a surface perpendicular to the orientation direction of the R1-T1-X-based sintered alloy compact 1 (ie, the direction shown by arrows in the figure) comes into contact with the R2-Ga-Cu-based alloy 2.

[0094] Subsequently, heat treatment was performed in argon controlled at a reduced pressure of 200 Pa at the heat treatment temperature shown in Table 18 using a tubular flow furnace, followed by cooling. To remove a thickened portion in the R2-Ga-Cu-based alloy present in the surface area of each sample after heat treatment, a surface grinder was used to cut off the entire surface of each sample, resulting in samples each in the shape of a 4.0 mm x 4.0 mm x 4.0 mm cube (sintered RTB-based magnet). [Evaluation of samples]

[0095] The resulting samples were placed in a vibrating sample magnetometer (VSM:VSM-5SC-10HF, manufactured by TOEI INDUSTRY CO., LIMITED) with a superconducting coil. After applying a magnetic field of up to 4 MA / m, the magnetic hysteresis curve of the sintered compacts was measured in the orientation direction while the magnetic field was changed to -4 MA / m. Coercivity (Hc) values J ) obtained from the resulting hysteresis curves are shown in Table 18. From Table 18, it can be seen that when the molar ratio of [T1] / [X] in the R1-T1-X based sintered alloy compact is 13.0 or more, a high H cJ is obtained even when a relatively large 4.4 mm x 4.4 mm x 4.4 mm sintered compact is used. [Table 18] Sample No. Manufacturing conditions A cJ (kA / m) Notes Composition of R1-T1-X-based sintered alloy compact Composition of the R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 6-1 6-A 31.2 13.9 6-a 75 0.5 500°C×4h 2044 Example of the invention 6-2 6-A 31.2 13.9 6-a 75 0.5 500°C×8h 2165 Example of the invention

[0096] A cross section of Sample No. 6-1, as shown in Table 18, (an example of the present invention) was obtained with a scanning electron microscope (SEM: JCM-6000, manufactured by JEOL, Ltd.). The results are shown in Fig. 3 and Fig. 4 shown. Fig. Figure 3 is a photograph showing the magnetic surface area of sample No. 6-1 as obtained with a scanning electron microscope. Fig. 4 is a photo showing the magnetic center area. As in Fig. 3 and Fig. 4, in Sample No. 6-1 (an example of the present invention), thick intergranular grain boundaries of 100 nm or more are formed from the magnet surface region to the magnet center region (i.e., a distance of 2.0 mm or more from the surface). Experimental Example 7

[0097] An R1-T1-X-based sintered alloy compact was prepared by a method similar to that of Experimental Example 1, except that the composition (without considering Al, Si in Mn) of a sintered compact was adjusted to obtain the composition according to Label 7-A shown in Table 19. [Table 19] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Ga Al Si Mn B C 7-A 30.7 0.55 66.5 0.20 0.08 0.05 0.02 0.87 0.05 31.3 14.2

[0098] An R2-Ga-Cu-based alloy was prepared by a method similar to that of Experimental Example 1, so that the alloy composition was the composition according to Label 7-a shown in Table 20. [Table 20] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu 7-a 75 12.5 12.5 75 0.5

[0099] After the R1-T1-X-based sintered alloy compact was processed similarly to Experimental Example 1, the R2-Ga-Cu-based alloy according to Label 7-a and the R1-T1-X-based sintered alloy compact according to Label 7-A were arranged to be in contact with each other in a similar manner to Experimental Example 1, and heat treatment and processing were carried out similarly to Experimental Example 1, except that the heat treatment temperature shown in Table 21 was adjusted, thereby obtaining a sample (sintered RTB-based magnet). The resulting sample was measured by a method similar to that of Experimental Example 1, whereby the coercivity (H cJ ) was determined. The result is shown in Table 21. As shown in Table 21, with the R1-T1-X sintered compact to which Ga is added, a high H cJobtained when the molar ratio of [T1] / [X] is 13.0 or more. [Table 21] Sample No. Manufacturing conditions A cJ (kA / m) Notes R1-T1-X based sintered alloy compact R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 7-1 7-A 31.3 15.2 7-a 75 0.5 500°C×4h 1976 Example of the invention Experimental Example 8[Providing an R1-T1-X-based sintered alloy compact]

[0100] The respective elements were sized to obtain R1-T1-X-based sintered alloy compacts with compositions according to labels 8-A to 8-C shown in Table 22 (without considering Si and Mn), and alloys were prepared by a strip casting technique. Each resulting alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. Each coarsely pulverized powder was finely pulverized in a jet mill, producing a finely pulverized powder with a particle size D50 (volume average as obtained by a laser diffraction method using an air-flow dispersion technique) of 4 μm. Into the finely pulverized powder, 0.05 parts by mass of zinc stearate was added as a solvent, based on 100 parts by mass of the finely pulverized powder; after mixing, it was pressed in a magnetic field to obtain a compact.A so-called orthogonal magnetic field press (transverse magnetic field press), in which the direction of the applied magnetic field is orthogonal to the pressing direction, was used as the pressing device. Each resulting compact was sintered by holding it at 1070°C to 1090°C, depending on the composition, for 4 hours in a vacuum, followed by cooling. It was then held at 800°C for 2 hours in an argon atmosphere for a high-temperature heat treatment, and then cooled to room temperature to obtain an R1-T1-X-based sintered compact. The R1-T1-X-based alloy sintered compact had a density of 7.5 Mg / m. 3or more. Component analysis results of these R1-T1-X-based sintered alloy compacts are shown in Table 22. The respective components in Table 22 were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES). C (carbon content) was measured using a gas analyzer based on a combustion infrared absorption method. In Table 22, "[T1] / [X]" denotes a ratio (a / b) between: (a) a sum of values obtained by dividing an analytical value (mass percent) of each T1-constituent element (including unavoidable impurities, which are Si and Mn in this experimental example) by the atomic weight of that element; and (b) a sum of values obtained by dividing analytical values (mass percent) of B and C by the atomic weights of these elements. The same applies to all subsequent tables.It should be noted that each composition in Table 22 does not sum to 100 mass percent. This is because, as previously described, a different analytical method is used for each component, and further because components other than those listed in Table 22 are present. [Table 22] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Co Cu Ga Al B C 8-A 24.0 7.0 66.4 1.0 0.1 0.3 0.2 0.98 0.05 31.0 12.9 8-B 24.0 7.0 68.8 1.0 0.1 0.0 0.2 0.87 0.05 31.0 14.9 8-C 23.0 7.0 67.0 0.5 0.1 0.2 0.1 0.88 0.06 30.0 14.1 [Providing an R2-Ga-Cu-based alloy]

[0101] Using an Nd metal, a Pr metal, a Dy metal, a Ga metal, and a Cu metal (each metal having a purity of 99% or more), the composition of an alloy was adjusted to result in the compositions according to labels 8-a to 8-d shown in Table 23. These raw materials were dissolved; thus, an alloy in ribbon or chip form was obtained by a single-roll rapid quenching process (a melt spinning process). Using a mortar, the resulting alloy was pulverized in an argon atmosphere and then passed through a sieve with an opening of 425 µm, thereby providing an R2-Ga-Cu-based alloy. The composition of the resulting R2-Ga-Cu-based alloy is shown in Table 23. [Table 23] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Nd Pr Dy Tb Ga Cu 8-a 0.0 76.0 0.0 0.0 12.4 11.6 76.0 0.5 8-b 0.0 68.1 7.7 0.0 12.5 11.8 75.8 0.5 8-c 8.6 59.3 0.0 7.8 12.5 11.8 75.7 0.5 8-d 0.0 72.1 3.8 0.0 11.4 11.7 75.9 0.5 [Heat treatment]

[0102] The R1-T1-X-based sintered alloy compacts labeled 8-A to 8-C in Table 22 were divided and cut into 7.4 mm x 7.4 mm x 7.4 mm cubes. Next, the R2-Ga-Cu-based alloy was distributed on the two faces of this sintered compact perpendicular to the orientation direction at a ratio shown in Table 24, based on 100 parts by mass of the R1-T1-X-based sintered alloy compact.

[0103] Subsequently, heat treatment was performed in argon controlled at a reduced pressure of 50 Pa at the heat treatment temperature shown in Table 24 using a tubular flow furnace, followed by cooling. To remove a thickened region in the R2-Ga-Cu-based alloy, which existed in the surface area of each sample after heat treatment, a surface grinder was used to cut off 0.2 mm from the entire surface of each sample, resulting in samples each in the shape of a 7.0 mm x 7.0 mm x 7.0 mm cube (sintered RTB-based magnet). [Evaluation of samples]

[0104] After each resulting sample was magnetized in a pulsed magnetic field of 3.2 MA / m or more, its magnetic properties were measured at room temperature and at 140°C using a pulsed BH tracer (VSM-5SC-10HF, manufactured by TOEI INUSTRY CO., LTD.). The resulting remanence values (B r ) and coercivity values (H cJ ) are shown in Table 24. As shown in Table 24, even if the distribution amount of the R2-Ga-Cu-based alloy is as small as 0.25 mass parts, a high H cJ which exceeds 1590 kA / m and a high B r , which exceeds 1.37T, was achieved in Samples Nos. 8-2 to 8-5, which satisfied the condition [T1] / [X]≥13.0 for the R1-T1-X-based sintered compact, resulting in magnets with very good performance. On the other hand, high H was not observed in Sample No. 8-1. cJwhich does not satisfy the condition [T1] / [X]≥13.0 for the R1-T1-X based sintered compact. [Table 24] Sample No. Manufacturing conditions B r (T) A cJ (kA / m) Notes R1-T1-X based sintered alloy compact R2-Ga-Cu-based alloy Distribution quantity [*] Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 8-1 8-A 31.0 12.9 8-a 76.0 0.5 0.25 parts by mass 500°C×4h 1.40 900 Comparison example 8-2 8-B 31.0 14.9 8-a 76.0 0.5 0.25 parts by mass 500°C×4h 1.37 1640 Example of the invention 8-3 8-C 30.0 14.1 8-b 75.8 0.5 0.25 parts by mass 500°C×4h 1.37 1690 Example of the invention 8-4 8-C 30.0 14.1 8-c 75.7 0.5 0.25 parts by mass 500°C×4h 1.37 1750 Example of the invention 8-5 8-C 30.0 14.1 8-d 75.9 0.5 0.25 parts by mass 500°C×4h 1.37 1590 Example of the invention [*] A distribution amount of an R2-Ga-Cu alloy based on 100 parts by mass of an R1-T1-X based sintered alloy compact. Experimental Example 9[Providing an R1-T1-X-based sintered alloy compact]

[0105] An R1-T1-X-based sintered alloy compact was prepared by a method similar to that of Experimental Example 1, except that the composition (without considering Al, Si, and Mn) of a sintered compact was adjusted to obtain the composition according to Label 9-A shown in Table 25. [Table 25] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Ga Al Si Mn B C 9-A 30.7 0.55 66.5 0.20 0.08 0.05 0.02 0.87 0.05 31.3 14.2 [Providing an R2-Ga-Cu-based alloy]

[0106] An R2-Ga-Cu-based alloy was prepared by a method similar to that of Experimental Example 1, so that the alloy composition was the composition according to Label 9-a shown in Table 26. [Table 26] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu 9-a 75 12.5 12.5 75 0.5

[0107] The R1-T1-X-based sintered alloy compact according to Label 9-A in Table 25 was divided and cut into a 11.0 mm x 10.0 mm x 4.4 mm (orientation direction) rectangular body. Next, the R2-Ga-Cu-based alloy according to Label 9-a, shown in Table 26, was prepared as shown in Fig.2, arranged above and below the corresponding R1-T1-X-based sintered alloy compact according to label 9-A so that mainly a surface (which in this experimental example was an 11.0 mm x 10.0 mm surface) perpendicular to the orientation direction (ie, the direction shown by arrows in the figure) of the R1-T1-X-based sintered alloy compact 1 came into contact with the R2-Ga-Cu-based alloy 2.

[0108] Subsequently, it was maintained at 540°C for 4 hours in argon controlled at a reduced pressure of 200 Pa using a tubular flow furnace. The temperature was then reduced to 500°C at -10°C / minute, where it was maintained for 1 hour, followed by cooling. It was then machined using an outer blade cutter and a surface grinder to obtain a 4.0 mm × 4.0 mm × 4.0 mm cube-shaped sample (sintered RTB-based magnet). [Evaluation of samples]

[0109] After the resulting sample was magnetized in a pulsed magnetic field of 3.2 MA / m, its magnetic properties were measured at room temperature and at 140°C using a BH tracer. A coercivity value (H cJ) as obtained from the resulting hysteresis curve is shown in Table 27. From Table 27, it can be seen that when the molar ratio of [T1] / [X] in the R1-T1-X based sintered alloy compact is 13.0 or more, a high H cJ at room temperature. It can also be seen that a temperature coefficient β, which consists of H cJ at room temperature and H cJ at 140°C is better than that of a conventional sintered RTB-based magnet at room temperature (β≒-0.50[% / °C]) with a similar H cJ , to which Dy has been added. Note that the previously mentioned β is obtained as β = (H cJ (140°C) - H cJ (23°C)) / (140 - 23) / H cJ (23°C)×100. [Table 27] Sample No. Manufacturing conditions A cJ (kA / m) @23°C A cJ (kA / m) @140°C β (23°C-140°C) Notes Composition of R1-T1-X-based sintered alloy compact Composition of the R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 9-1 9-A 31.1 14.2 9-a 75 0.5 540°C × 4h +500°C × 1h 1887 823 -0.48 Example of the invention

[0110] A cross-section of the resulting sample was obtained using a scanning electron microscope (SEM: JSM-7800F, manufactured by JEOL, Ltd.). Fig. Figure 5 shows a backscattered electron image of a cross section near the surface of the resulting sample and Fig. Figure 6 shows a backscattered electron image of a cross-section of a central region of the resulting sample. Thick intergranular grain boundaries of 100 nm or more were formed between the magnet surface region and the central region of the magnet. The composition of each phase with different contrast in each of these views was analyzed by energy-dispersive X-ray spectroscopy (EDX: JED-2300 SD30, manufactured by JEOL, Ltd.), which detected Ga and Cu in the grain boundary phase, a part of which, based on its constituents, was classified as an R6T. 13 Z phase, which contains Ga and Cu, was identified. Experimental Example 10[Providing an R1-T1-X-based sintered alloy compact]

[0111] The respective elements were sized to obtain R1-T1-X-based sintered alloy compacts with compositions according to labels 10-A to 10-F shown in Table 28 (without considering Si and Mn), and alloys were prepared by a strip casting technique. Each resulting alloy was coarsely pulverized by a hydrogen pulverization method to obtain a coarsely pulverized powder. Each coarsely pulverized powder was finely pulverized in a jet mill, producing a finely pulverized powder with a particle size D50 (volume average as obtained by a laser diffraction method using an air-flow dispersion technique) of 4 μm. In the finely pulverized powder, 0.05 parts by mass of zinc stearate was added as a solvent, based on 100 parts by mass of the finely pulverized powder; after mixing, it was pressed in a magnetic field to obtain a compact.A so-called orthogonal magnetic field press (transverse magnetic field press), in which the direction of the applied magnetic field is orthogonal to the pressing direction, was used as the pressing device. Each resulting compact was sintered by holding it at 1020°C to 1060°C, depending on the composition, for 4 hours in a vacuum, followed by cooling, to obtain an R1-T1-X-based sintered alloy compact. The R1-T1-X-based sintered alloy compact had a density of 7.5 Mg / m³. 3or more. The component analysis results of these R1-T1-X-based sintered alloy compacts are shown in Table 28. The respective components in Table 28 were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES). C (carbon content) was measured using a gas analyzer based on a combustion infrared absorption method. The oxygen content in each sintered compact was measured by a gas fusion infrared absorption method, and each had a value around 0.1 mass percent.In Table 28, "[T1] / [X]" denotes a ratio (a / b) between: (a) a sum of values obtained by dividing an analytical value (mass percent) of each element constituting T1 (including unavoidable impurities, which in this experimental example are Si and Mn) by the atomic weight of that element; and (b) a sum of values obtained by dividing analytical values (mass percent) of B and C by the atomic weights of these elements. The same applies to all subsequent tables. Note that each composition in Table 28 does not sum to 100 mass percent. This is because, as described above, a different analytical method is used for each component, and further because components other than those entered in Table 28 are present. [Table 28] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Al Si Mn B C 10-A 29.8 0.18 68.3 0.02 0.06 0.02 0.88 0.10 30.0 13.8 10-B 29.3 0.19 68.8 0.02 0.06 0.02 0.89 0.09 29.5 13.8 10-C 28.5 0.19 69.9 0.04 0.05 0.02 0.90 0.07 28.7 14.1 10-D 27.7 0.16 70.6 0.05 0.05 0.02 0.92 0.08 27.9 13.8 10-E 26.0 0.15 72.4 0.04 0.05 0.02 0.93 0.08 26.2 14.0 10-F 25.0 0.16 73.2 0.04 0.05 0.03 0.93 0.08 25.2 14.1 [Providing an R2-Ga-Cu-based alloy]

[0112] An R2-Ga-Cu-based alloy was prepared by a method similar to that of Experimental Example 1, so that the alloy composition was the composition according to Label 10-a shown in Table 29. [Table 29] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu 10-a 75 12.5 12.5 75 0.5

[0113] The R1-T1-X-based sintered alloy compacts according to labels 10-A to 10-F in Table 28 were divided and cut into 11.0 mm × 10.0 mm × 4.4 mm (orientation direction) rectangular bodies. Next, the R2-Ga-Cu-based alloy according to label 10-a, shown in Table 29, was processed as in Fig.2, in a processing container 3 made of niobium foils above and below each of the R1-T1-X-based sintered alloy compacts according to labels 10-A to 10-F, mainly a surface (which in this experimental example was an 11.0 mm x 10.0 mm surface) perpendicular to the orientation direction (i.e., the direction shown by arrows in the figure) of the R1-T1-X-based sintered alloy compact 1 came into contact with the R2-Ga-Cu-based alloy 2.

[0114] Subsequently, heat treatment was performed in argon controlled at a reduced pressure of 200 Pa at the heat treatment temperature shown in Table 30 using a tubular flow furnace, followed by cooling. They were then machined using an outer sheet cutter and a surface grinder, resulting in samples each in the shape of a 4.0 mm × 4.0 mm × 4.0 mm cube (sintered RTB-based magnet). [Evaluation of samples]

[0115] After each resulting sample was magnetized in a pulsed magnetic field of 3.2 MA / m, its magnetic properties were measured using a BH tracer. Coercivity (H cJ ), as obtained from the resulting hysteresis curves, are shown in Table 30. From Table 30 it can be seen that a high H cJis obtained when R1 is 27 mass % or more and further the molar ratio of [T1] / [X] in the R1-T1-X based sintered alloy compact is 13.0 or more. [Table 30] Sample No. Manufacturing conditions A cJ (kA / m) Notes Composition of R1-T1-X-based sintered alloy compact Composition of the R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 10-1 10-A 30.0 13.8 10-a 75 0.5 480°C×8h 1967 Example of the invention 10-2 10-B 29.5 13.8 10-a 75 0.5 480°C×8h 2036 Example of the invention 10-3 10-C 28.7 14.1 10-a 75 0.5 480°C×8h 2002 Example of the invention 10-4 10-D 27.9 13.8 10-a 75 0.5 480°C×8h 1976 Example of the invention 10-5 10-E 26.2 14.0 10-a 75 0.5 480°C×8h 321 Comparison example 10-6 10-F 25.2 14.1 10-a 75 0.5 480°C×8h 112 Comparison example Experimental Example 11[Providing an R1-T1-X-based sintered alloy compact]

[0116] An R1-T1-X-based sintered alloy compact was prepared by a method similar to that of Experimental Example 1, except that the composition (without considering Al, Si, and Mn) of a sintered compact was adjusted to obtain the composition according to Label 11-A shown in Table 31. [Table 31] Label Composition of R1-T1-X-based sintered alloy compact (mass percent) R1 (mass percent) [T1] / [X] R1 T1 X Nd Pr Fe Al Si Mn B C 11-A 30.6 0.06 67.3 0.05 0.04 0.03 0.87 0.08 31.2 13.9 [Providing an R2-Ga-Cu-based alloy]

[0117] Using a Pr metal, a Ga metal, a Cu metal, and an Fe metal (each metal having a purity of 99% or more), the composition of an alloy was adjusted to result in the compositions according to labels 11-a to 11-c shown in Table 32. These raw materials were dissolved; thus, an alloy in ribbon or chip form was obtained by a single-roll rapid quenching process (a melt spinning process). Using a mortar, the resulting alloy was pulverized in an argon atmosphere and then passed through a sieve with an opening of 425 µm, thereby providing an R2-Ga-Cu-based alloy. The composition of the resulting R2-Ga-Cu-based alloy is shown in Table 32. [Table 32] Label Composition of the R2-Ga-Cu-based alloy (mol%) R2 (mol%) [Cu] / ([Ga]+[Cu]) Pr Ga Cu Fe 11-a 73.9 12.3 12.3 1.5 73.9 0.5 11-b 71.3 11.9 11.9 5.0 71.3 0.5 11-c 67.5 11.3 11.3 10.0 67.5 0.5 [Heat treatment]

[0118] The R1-T1-X-based sintered alloy compact according to Label 11-A in Table 31 was divided and cut into a 4.4 mm × 4.4 mm × 4.4 mm cube. Next, as shown in Fig. 2, the R2-Ga-Cu-based alloys according to labels 11-a to 11-c shown in Table 32 were arranged in a processing container 3 made of niobium foils above and below the corresponding R1-T1-X-based sintered alloy compact according to label 11-A such that mainly a surface perpendicular to the orientation direction of the R1-T1-X-based sintered alloy compact 1 (i.e., the direction shown by arrows in the figure) came into contact with the R2-Ga-Cu-based alloy 2.

[0119] Subsequently, heat treatment was performed in argon controlled at a reduced pressure of 200 Pa at the heat treatment temperature shown in Table 33 using a tubular flow furnace, followed by cooling. To remove a thickened portion in the R2-Ga-Cu-based alloy present in the surface area of each sample after heat treatment, a surface grinder was used to cut off the entire surface of each sample, thereby obtaining samples each in the shape of a 4.0 mm × 4.0 mm × 4.0 mm cube (sintered RTB-based magnet). [Evaluation of samples]

[0120] The resulting samples were placed in a vibrating sample magnetometer (VSM:VSM-5SC-10HF, manufactured by TOEI INDUSTRY CO., LIMITED) with a superconducting coil. After applying a magnetic field of up to 4 MA / m, the magnetic hysteresis curve of the sintered compacts was measured in the orientation direction while the magnetic field was changed to -4 MA / m. Coercivity (Hc) values J ) obtained from the resulting hysteresis curves are shown in Table 33. From Table 33 it can be seen that a high Hc J is obtained even when Fe is contained in the R2-Ga-Cu-based alloy. Furthermore, as shown by Sample Nos. 11-1 to 11-4, an even higher H cJ can be achieved if the heat treatment temperature is in the range of not less than 480°C and not more than 540°C. [Table 33] Sample No. Manufacturing conditions A cJ (kA / m) Notes Composition of R1-T1-X-based sintered alloy compact Composition of the R2-Ga-Cu-based alloy Heat treatment Label R1 (mass percent) [T1] / [X] Label R2 (mol%) [Cu] / ([Ga]+[Cu]) 11-1 11-A 31.2 13.9 11-a 73.9 0.5 460°C×8h 1784 Example of the invention 11-2 11-A 31.2 13.9 11-a 73.9 0.5 480°C×8h 1915 Example of the invention 11-3 11-A 31.2 13.9 11-a 73.9 0.5 520°C×8h 2031 Example of the invention 11-4 11-A 31.2 13.9 11-a 73.9 0.5 540°C×8h 1944 Example of the invention 11-5 11-A 31.2 13.9 11-b 71.3 0.5 520°C×8h 2020 Example of the invention 11-6 11-A 31.2 13.9 11-c 67.5 0.5 520°C×8h 2010 Example of the invention

[0121] In the specification of Japanese Patent Application No. 2015-150586 as filed (filing date: July 30, 2015), which forms the basis for priority, C (carbon content) in 1-F to 1-I of Table 1, 4-A to 4-D of Table 10, 5-A to 5-D of Table 13, and 6-A of Table 16 were target values; however, these were corrected to measured values. INDUSTRIAL APPLICABILITY

[0122] A sintered RTB-based magnet as obtained according to the present invention can be suitably used in voice coil motors (VCM) of hard disk drives, various types of motors, for example, motors for electric vehicles (EV, HV, PHV, etc.), and motors for industrial devices, home use products, and the like. LIST OF REFERENCE SYMBOLS 1 R1-T1-X-based sintered alloy compact 2 R2-Ga-Cu-based alloy 3 processing containers

Claims

[1] A method for producing a sintered RTB-based magnet, wherein R is at least one rare earth element which always includes Nd, T is at least one transition metal element which always includes Fe and B is partially replaceable by C, wherein the RTB-based magnet consists of a main phase which consists essentially of an R2T 14 B substance, and a grain boundary phase which lies at grain boundaries of the main phase, the method comprising: a step of providing an R1-T1-X-based sintered alloy compact, wherein R1 is at least one rare earth element which always includes Nd, the R1-T1-X-based sintered alloy compact containing R1 in a proportion of not less than 27 mass % and not more than 35 mass %; wherein T1 is Fe or Fe and M, wherein M is at least one element selected from the group consisting of Ga, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, and Ag, wherein X is B, wherein B is partially replaceable with C, and wherein a molar ratio of [T1] / [X] is not less than 13.0, the R1-T1-X-based sintered alloy compact being formed by sintering particles each having a size of not less than 1 µm and not more than 10 µm; a step of providing an R2-Ga-Cu-based alloy, wherein R2 is at least one rare earth element which always includes Pr, wherein Pr accounts for 50 mol% or more of R2, wherein the R2-Ga-Cu-based alloy contains R2 in a proportion of not less than 65 mol% and not more than 95 mol%, and wherein a molar ratio of [Cu] / ([Ga]+[Cu]) is not less than 0.1 and not more than 0.9; and while allowing at least a part of the R2-Ga-Cu-based alloy to come into contact with at least a part of a surface of the R1-T1-X-based sintered alloy compact, a step of performing a heat treatment at a temperature of not lower than 450°C and not higher than 600°C in a vacuum or an inert gas environment. [2] A method for producing a sintered RTB-based magnet according to claim 1, wherein T1 in R1-T1-X comprises Fe and M, where M is at least one element selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, and Ag. [3] A method for producing a sintered RTB-based magnet according to claim 1 or 2, wherein a molar ratio of [T1] / [X] in the sintered R1-T1-X-based alloy compact is 13.6 or more. [4] A method for producing a sintered RTB-based magnet according to any one of claims 1 to 3, wherein a molar ratio of [T1] / [X] in the sintered R1-T1-X-based alloy compact is 14 or more. [5] A method for producing a sintered RTB-based magnet according to any one of claims 1 to 4, wherein any heavy rare earth element accounts for 1 mass % or less of the sintered R1-T1-X-based alloy compact. [6] A method for producing a sintered RTB-based magnet according to any one of claims 1 to 5, wherein the step of providing an R1-T1-X-based sintered alloy compact comprises: pulverizing a raw material alloy to a size of not less than 1 µm and not more than 10 µm, then pressing the pulverized raw material alloy in a magnetic field and sintering. [7] A method of manufacturing a sintered RTB-based magnet according to claim 6, wherein the step of providing an R1-T1-X-based sintered alloy compact after sintering comprises: performing a high-temperature heat treatment at a temperature which is above 600°C and below a sintering temperature. [8] A method for producing a sintered RTB-based magnet according to any one of claims 1 to 7, wherein the R2-Ga-Cu-based alloy does not contain a heavy rare earth element. [9] A method of manufacturing a sintered RTB-based magnet according to claim 8, wherein R2 in the R2-Ga-Cu-based alloy consists only of Pr except for unavoidable impurities. [10] A method of manufacturing a sintered RTB-based magnet according to any one of claims 1 to 8, wherein R2 in the R2-Ga-Cu-based alloy further comprises Nd. [11] A method for producing a sintered RTB-based magnet according to any one of claims 1 to 7, wherein a part of R2 in the R2-Ga-Cu-based alloy is a heavy rare earth element, the heavy rare earth element being contained at 10 mol% or less of the entire R2-Ga-Cu-based alloy. [12] A method for producing a sintered RTB-based magnet according to claim 11, wherein a part of R2 in the R2-Ga-Cu-based alloy is a heavy rare earth element, the heavy rare earth element being contained at 5 mol% or less of the entire R2-Ga-Cu-based alloy. [13] A method of manufacturing a sintered RTB-based magnet according to claim 11 or 12, wherein a part of R2 in the R2-Ga-Cu-based alloy is a heavy rare earth element, and Pr constitutes all of R2 except the heavy rare earth element and apart from unavoidable impurities. [14] A method for producing a sintered RTB-based magnet according to any one of claims 1 to 13, wherein the temperature in the step of performing a heat treatment is not less than 480°C and not more than 540°C. [15] A method of manufacturing a sintered RTB-based magnet according to any one of claims 1 to 14, wherein, in the step of performing a heat treatment, a R12T1 14 X phase in the R1-T1-X-based sintered alloy compact reacts with a liquid phase originating from the R2-Ga-Cu-based alloy, so that a R6T 13 Z phase, where Z always comprises Ga and / or Cu, is generated at least partially within the sintered magnet. [16] A method for producing a sintered RTB-based magnet according to any one of claims 1 to 15, wherein the step of performing a heat treatment comprises: applying and / or spreading a powder of the R2-Ga-Cu-based alloy on at least a part of the surface of the R1-T1-X-based sintered alloy compact so that the R2-Ga-Cu-based alloy comes into contact with at least a part of the surface of the R1-T1-X-based sintered alloy compact. [17] The method for producing a sintered RTB-based magnet according to claim 16, wherein the powder of the R2-Ga-Cu-based alloy to be dispersed and / or coated on the surface of the R1-T1-X-based sintered alloy compact has not less than 0.2 part by mass and not more than 0.5 part by mass with respect to 100 parts by mass of the R1-T1-X-based sintered alloy compact.

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