Hot working magnet

Abstract

The hot-worked magnet contains a rare earth element R, a transition metal element T, and boron. The hot working magnet contains Nd as a rare earth element R. The hot working magnet contains Fe as a transition metal element T. The hot working magnet includes a plurality of main phase particles and a grain boundary phase located between the plurality of main phase particles. The plurality of main phase particles contain a rare earth element R, a transition metal element T, and boron. The grain boundary phase includes a plurality of grains. The plurality of crystal grains are in contact with one or more main phase grains. The ribbon axes of the plurality of crystal grains are oriented in one direction.

Description

Technical Field

[0001] The present disclosure relates to hot working magnets. Background Art

[0002] In recent years, with the popularization of wind power generation and electric vehicles, the demand for neodymium magnets has increased, and there is a demand for improved properties. In order to clarify the expression mechanism of coercive force, which is an important characteristic of neodymium magnets, a lot of research and development has been repeatedly carried out in recent years, and the understanding of the expression mechanism of coercive force has been deepened. (For example, refer to the following patent document 1 and the following non-patent document 1.) The coercive force of neodymium magnets is theoretically determined by the ferromagnetic material (for example, Nd2Fe 14 B) is determined by the crystal anisotropy magnetic field Ha. However, actual neodymium magnets consist of polycrystalline materials and therefore can only exhibit a coercive force of about 20% of the theoretical value.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-009421

[0004] Non-patent document 1: H. Sepehri-Amin et al., Grain boundary and interface chemistry of an Nd-Fe-B-based sintered magnet, Acta Materialia 60 (2012) 819-830, published by Elsevier. Summary of the Invention

[0005] One object of the present disclosure is to provide a hot-processed magnet having high coercive force.

[0006] For example, as described below, one aspect of the present disclosure relates to the hot-worked magnet described in any one of [1] to

[14] .

[0007] [1] A hot deformed magnet comprising a rare earth element R, a transition metal element T, and boron (B), wherein:

[0008] The hot working magnet contains Nd as the rare earth element R,

[0009] The hot working magnet contains Fe as the transition metal element T,

[0010] The hot-working magnet comprises a plurality of main phase grains and a grain boundary phase located between the plurality of main phase grains.

[0011] The plurality of main phase particles contain the rare earth element R, the transition metal element T, and boron,

[0012] The grain boundary phase comprises a plurality of crystal grains.

[0013] A plurality of the crystal grains are in contact with at least one of the main phase particles.

[0014] The crystal zone axes of the plurality of crystal grains are oriented along one direction.

[0015] [2] The hot-worked magnet according to [1], wherein

[0016] The plurality of grains are non-magnetic.

[0017] [3] The hot-worked magnet according to [1] or [2], wherein

[0018] The area fraction of the cross-section of the plurality of crystal grains in the cross-section of the hot-worked magnet is 3% or more and 8% or less,

[0019] The cross section of the hot working magnet is parallel to an easy magnetization axis direction of the hot working magnet.

[0020] [4] The hot-worked magnet according to any one of [1] to [3], wherein

[0021] The plurality of crystal grains contain the rare earth element R and element M, wherein the element M is at least one selected from Cu, Ga, Zn, Ni, and Cr.

[0022] The content of the rare earth element R in the plurality of crystal grains is 50 mass % or more and 98 mass % or less,

[0023] The content of the transition metal element T in the plurality of crystal grains is 0 mass % or more and 50 mass % or less,

[0024] The content of the element M in the plurality of crystal grains is greater than 0 mass % and is 35 mass % or less.

[0025] [5] The hot-worked magnet according to any one of [1] to [4], wherein

[0026] The plurality of crystal grains are respectively cubic crystals, tetragonal crystals, or orthorhombic crystals.

[0027] The crystal zone axis is <100>, <010>, or <001>.

[0028] [6] The hot-worked magnet according to any one of [1] to [4], wherein

[0029] A plurality of the grains contain Nd and Cu,

[0030] The plurality of crystal grains are cubic, tetragonal, or orthorhombic.

[0031] The space group representing the symmetry of the crystal structure of the plurality of the grains is Pnma, I4 / mcm, Fm-3m, or Ia-3.

[0032] [7] The hot-worked magnet according to any one of [1] to [6], wherein

[0033] The width of the grain boundary phase including one or more crystal grains is 4 nm or more and 500 nm or less in the easy magnetization axis direction of the hot-worked magnet.

[0034] [8] The hot-processed magnet according to any one of [1] to [7], wherein

[0035] The one or more main phase grains connected to the one or more crystal grains include at least one of columnar crystals and equiaxed crystals.

[0036] [9] The hot-worked magnet according to any one of [1] to [8], wherein

[0037] The hot working magnet also contains element M,

[0038] The element M is at least one selected from Cu, Ga, Zn, Ni, and Cr,

[0039] The content of the rare earth element R in the hot working magnet is 26.00 mass % or more and 32.00 mass % or less,

[0040] The boron content in the hot working magnet is 0.77 mass % or more and 1.15 mass % or less.

[0041] The content of the element M in the hot-working magnet is 0.67 mass % or more and 7.30 mass % or less.

[0042]

[10] The hot-worked magnet according to any one of [1] to [9], wherein

[0043] The width of each of the plurality of main phase grains in the easy magnetization axis direction of the hot-worked magnet is represented by S.

[0044] When the width of each of the plurality of main phase grains in a direction perpendicular to the easy magnetization axis direction is represented by L,

[0045] The S is smaller than the L,

[0046] L / S is 2 or more and 10 or less,

[0047] The S is greater than or equal to 20 nm and less than or equal to 200 nm.

[0048]

[11] The hot-worked magnet according to any one of [1] to

[10] , wherein

[0049] The angle between the <100> angles of the plurality of crystal grains and the <100> angles of the one or more main phase grains is 0° or more and 10° or less.

[0050]

[12] The hot-processed magnet according to any one of [1] to

[10] , wherein

[0051] The angle between the <010> of the plurality of crystal grains and the <010> of the one or more main phase grains is 0° or more and 10° or less.

[0052]

[13] The hot-processed magnet according to any one of [1] to

[10] , wherein

[0053] The angle between the <001> of the plurality of crystal grains and the <001> of the one or more main phase grains is 0° or more and 10° or less.

[0054]

[14] The hot-processed magnet according to any one of [1] to

[13] , wherein

[0055] The one direction in which the zone axes of the plurality of crystal grains are oriented is parallel to the zone axes of one or more main phase grains in contact with the plurality of crystal grains.

[0056] According to one aspect of the present disclosure, a hot-processed magnet having high coercive force can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1A This is a schematic three-dimensional diagram of a hot-processed magnet. Figure 1B yes Figure 1A Schematic diagram of the cross section of the hot-processed magnet (view in the II line direction of the hot-processed magnet), Figure 1B The cross section shown is parallel to the easy magnetization axis of the hot-worked magnet.

[0058] Figure 2 yes Figure 1B An enlarged view of a detail (region II) of the cross section is shown.

[0059] Figure 3A This is a schematic diagram of the cross section of a secondary grain containing polycrystals among the multiple main phase grains contained in the hot-processed magnet. Figure 3B yes Figure 3A An enlarged view of a detail (region III) of the cross section is shown.

[0060] Figure 4 It is a schematic diagram showing the unit cell and the crystal zone axis of each of an arbitrary pair of crystal grains included in the hot-worked magnet.

[0061] Figure 5 This is a schematic perspective view of a specific example of a mold used in a method for producing a hot-working magnet (hot plastic working step).

[0062] Figure 6 This is a backscattered electron image of the cross section of the hot-processed magnet of Example 1. Figure 6 The cross section shown is parallel to the easy magnetization axis of the hot-worked magnet.

[0063] Figure 7A This is a backscattered electron image of the cross section of the hot-processed magnet of Example 1. Figure 7A The cross section shown is parallel to the easy magnetization axis of the hot-processed magnet. Figure 7B This is a backscattered electron image of the cross section of the hot-processed magnet of Example 1. Figure 7B The cross section shown is parallel to the easy magnetization axis of the hot-processed magnet. Figure 7A and Figure 7B The cross sections shown are relative to each other. Figure 6 The backscattered electron image shown is a backscattered electron image captured at a high magnification.

[0064] Figure 8 This is a TEM image (Transmission Electron Microscope image) of the cross section of the hot-processed magnet of Example 1. Figure 8 The cross section shown is parallel to the easy magnetization axis of the hot-worked magnet.

[0065] Figure 9A It is through Figure 8 The electron beam diffraction pattern obtained by measuring the electron beam incident on the measurement point 1 (crystal grain) in the cross section shown is: Figure 9B It is through Figure 8 The electron beam diffraction pattern obtained by measuring the incident electron beam at the measurement point 2 (crystal grain) in the cross section shown is: Figure 9C It is through Figure 8 The electron beam diffraction pattern obtained by measuring the electron beam incident on the measurement point 3 (crystal grain) in the cross section shown is: Figure 9D It is through Figure 8 The electron beam diffraction pattern is measured by incident electron beam on the measurement point 7 (crystal grain) in the cross section shown.

[0066] Figure 10A It is through Figure 8 The electron beam diffraction pattern obtained by measuring the incident electron beam at the measurement point 4 (NdO) in the cross section shown is: Figure 10B It is through Figure 8 The electron beam diffraction pattern obtained by measuring the electron beam incident on the measurement point 5 (main phase grain) in the cross section shown is: Figure 10C It is through Figure 8 The electron beam diffraction pattern is measured by incident electron beam on the measurement point 6 (main phase grain) in the cross section shown.

[0067] Figure 11 It is a schematic diagram showing the cross section of each of the plurality of crystal grains and the plurality of main phase particles contained in the hot-processed magnet. Figure 11 The cross sections shown are parallel to the easy magnetization axis of the hot-worked magnet.

[0068] Explanation of symbols

[0069] 2…hot-processed magnet, 2cs…cross section of the hot-processed magnet (cross section parallel to the easy magnetization axis), 4…main phase particles, 6…grain boundary phase, 8…grain (non-magnetic phase), C…easy magnetization axis direction, AB…direction perpendicular to the easy magnetization axis direction, cza…zone axis, D…one direction of the zone axis orientation. DETAILED DESCRIPTION

[0070] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, equivalent components are denoted by equivalent reference numerals. The present disclosure is not limited to the following embodiments. Figure 1A The arrow C and the two arrows AB shown represent three mutually orthogonal coordinate axes. Arrow C corresponds to the easy magnetization axis direction C of the hot-worked magnet. The two arrows AB correspond to the AB directions, which are orthogonal to the easy magnetization axis direction C. The easy magnetization axis direction C and the AB directions are the same in each figure.

[0071] (Hot Working Magnet)

[0072] The hot working magnet of this embodiment contains at least a rare earth element R, a transition metal element T, and boron (B).

[0073] Hot working magnets contain at least neodymium (Nd) as a rare earth element R. In addition to Nd, hot working magnets may also contain other rare earth elements R. The other rare earth elements R contained in the hot working magnets may be at least one element selected from scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Hot working magnets do not need to contain heavy rare earth elements (e.g., both Dy and Tb).

[0074] The hot working magnet contains at least iron (Fe) as the transition metal element T. The hot working magnet may contain only Fe as the transition metal element T. The hot working magnet may contain both Fe and cobalt (Co) as the transition metal element T.

[0075] Figure 1A It is a perspective view of the hot-worked magnet 2. Figure 1B This is a schematic diagram of a cross section 2cs of a hot-processed magnet 2. The cross section 2cs of the hot-processed magnet 2 is approximately or completely parallel to the easy magnetization axis direction C of the hot-processed magnet 2. The easy magnetization axis direction C is a direction parallel to a straight line connecting a pair of magnetic poles of the hot-processed magnet 2. In other words, the easy magnetization axis direction C is the direction from the south pole of the hot-processed magnet 2 toward the north pole of the hot-processed magnet 2. The easy magnetization axis direction C can be determined by measuring the magnetic flux distribution of the hot-processed magnet 2. The easy magnetization axis direction C can also be determined by measuring the magnetic flux distribution of an analytical sample separated from the hot-processed magnet 2. As described above, the AB direction is perpendicular to the easy magnetization axis direction C.

[0076] Figure 1A The hot-processed magnet 2 is shown as a rectangular parallelepiped (plate). However, the shape of the hot-processed magnet 2 is not limited to a rectangular parallelepiped. For example, the hot-processed magnet 2 may be in the shape of a cube, a polygonal prism, a circular arc segment, an annular sector, a sphere, a circular plate, a cylinder, a tube, or a ring. For example, the cross-section 2cs of the hot-processed magnet 2 may be in the shape of a polygon, a circular arc (circular chord), an arc, an arch, a C-shape, or a circle.

[0077] Figure 2 yes Figure 1B The enlarged view of a part (region II) of the cross section 2cs is shown. Figure 2As shown, the hot-processed magnet 2 includes a plurality of main phase grains 4 and grain boundary phases 6 located between the plurality of main phase grains 4. In the present disclosure, the grain boundary phase 6 is a collective term for all components other than the plurality of main phase grains 4 (i.e., the remaining components in the hot-processed magnet 2 other than all the main phase grains 4). The hot-processed magnet 2 may include a plurality of grain boundary phases 6 at different locations. For example, the grain boundary phase 6 may exist at a grain boundary surrounded by three or more main phase grains 4 (multiple grain boundary points). For example, the grain boundary phase 6 may also exist at a grain boundary between two main phase grains 4 (two-grain grain boundary).

[0078] The plurality of main phase particles 4 contain at least a rare earth element R, a transition metal element T, and B. The main phase particles 4 contain at least Nd as the rare earth element R. The main phase particles 4 contain at least Fe as the transition metal element T. One main phase particle 4 can be a single crystal grain (i.e., a primary particle). At least a portion or all of the plurality of main phase particles 4 contained in the hot-processed magnet 2 can also be secondary particles containing polycrystals (a plurality of primary particles). The hot-processed magnet 2 can contain a plurality of secondary particles. A single secondary particle can also contain a plurality of main phase particles 4. The main phase particle 4 contains R2T 14 Crystallization of B (single crystal or polycrystalline). R2T 14 B is a three-dimensional intermetallic compound with hard magnetism. 14 The main phase particles 4 of the B crystal are hard magnetic materials. The main phase particles 4 can be composed only of R2T 14 The crystal structure of B. R2T 14 The crystal of B can be tetragonal. 14 The crystal axes of B are represented by the a-axis, the b-axis, and the c-axis. The a-axis, the b-axis, and the c-axis may be orthogonal to each other. 14 The lattice constant of B in the a-axis direction can be compared with R2T 14 The lattice constants of B in the b-axis direction are equal, R2T 14 The lattice constant of B in the c-axis direction may be different from the lattice constants in the a-axis direction and the b-axis direction. 14 The c-axis of B can be approximately or completely parallel to the easy magnetization axis direction C of the hot-working magnet 2. In other words, R2T 14 The (001) plane of the tetragonal crystal of B may be substantially or completely perpendicular to the easy magnetization axis direction C of the hot-worked magnet 2 .

[0079] For example, the R2T of the main phase grain 4 14 B can also be expressed as (Nd 1-x Pr x )2(Fe 1-y Co y ) 14B. x can be greater than 0 and less than 1. y can be greater than 0 and less than 1. As the rare earth element R, in addition to light rare earth elements, the main phase particles 4 can also contain heavy rare earth elements such as Tb and Dy. In addition to containing R, T and B, the main phase particles 4 can also contain other elements. For example, R2T 14 A portion of the B in B may be replaced by another element such as carbon (C). The composition within the main phase grains 4 may be uniform. The composition within the main phase grains 4 may also be non-uniform. For example, the concentration distribution of each of R, T, and B in the main phase grains 4 may have a gradient.

[0080] like Figure 2 As shown, the grain boundary phase 6 includes a plurality of crystal grains 8. The plurality of crystal grains 8 may not be paramagnetic but non-magnetic. Each of the plurality of crystal grains 8 may be single crystal or polycrystalline. Figure 2 and Figure 4 As shown, at least a portion or all of the plurality of crystal grains 8 are in contact with one or more main phase grains 4 .

[0081] Figure 4 The unit cell uc8a shown represents the unit cell of any one crystal grain 8a that is in contact with one or more main phase grains 4 . Figure 4 The other unit cell uc8b shown represents the unit cell of another grain 8b (an arbitrary grain 8 different from the above-mentioned grain 8a) that is connected to one or more main phase particles 4. The three basic translation vectors constituting each unit cell uc8a and unit cell uc8b are represented by vector a, vector b, and vector c. For example, the plurality of grains 8 (grains 8a and grains 8b) can be cubic, tetragonal, or orthorhombic. When vector a, vector b, and vector c are perpendicular to each other and the lengths of vector a, vector b, and vector c are equal, the grain 8a (unit cell uc8a) and the grain 8b (unit cell uc8b) are cubic. When vector a, vector b, and vector c are perpendicular to each other and the lengths of vector a and vector b are equal, and the length of vector c is different from the lengths of vector a and vector b, the grain 8a (unit cell uc8a) and the grain 8b (unit cell uc8b) are tetragonal. When vector a, vector b, and vector c are perpendicular to each other and the lengths of vector a and vector b are different, grain 8a (unit cell uc8a) and grain 8b (unit cell uc8b) are orthorhombic crystals. In the present disclosure, orthorhombic crystals may include rhombic crystals.

[0082] like Figure 4As shown, the zone axes cza of multiple grains 8 (e.g., grains 8a and 8b) that are in contact with one or more primary phase grains 4 are oriented in a single direction (orientation direction D). The zone axes cza of each of the multiple grains 8 that are in contact with the same primary phase grain 4 can be oriented in the same direction (orientation direction D). For example, the angle between the zone axes cza of any two grains 8 in the multiple grains 8 can be 5° or less, or 3° or less. In other words, the angle between the zone axis cza of any one grain 8 and the orientation direction D can be 2.5° or less, or 1.5° or less. The zone axes cza of the multiple grains 8 can also be substantially or completely parallel to each other. In other words, the directions of the zone axes cza of the multiple grains 8 can be the same and can coincide with the orientation direction D. The multiple grains 8 with their zone axes cza oriented in a single direction (orientation direction D) can be contained only partially within a portion of the hot-worked magnet 2. Alternatively, the multiple grains 8 with their zone axes cza oriented in a single direction (orientation direction D) can be present throughout the hot-worked magnet 2.

[0083] [Definition of crystal zone axis]

[0084] Any two non-parallel lattice planes (e.g., the (hkl) plane and the (h'k'l') plane) in any crystal (e.g., grain 8 or main phase grain 4) must intersect. h, k, l, h', k', and l' are Miller indices. When the intersection of the (hkl) plane and the (h'k'l') plane is oriented in the <uvw> direction, the intersection of the (hkl) plane and the (h'k'l') plane is defined as the crystal zone axis expressed as <uvw>. u is equal to kl'-lk', v is equal to lh'-hl', and w is equal to hk'-kh'. The (hkl) plane and the (h'k'l') plane belong to the crystal zone expressed as [uvw]. The zone axis (<uvw>) must be perpendicular to the lattice planes belonging to the zone ([uvw]) (i.e., the (hkl) plane and the (h'k'l') plane). Therefore, the (hkl) plane, the (h'k'l') plane, and the zone axis (<uvw>) satisfy hu + kv + lw = 0 and h'u + k'v + l'w = 0. These equations are called Weiss's zone laws.

[0085] [Orientation of the crystal axis of the grain]

[0086] For example, the zone axis cza of each of the plurality of crystal grains 8 may be <100>, <010>, or <001>.

[0087] For example, the <100> angles of a plurality of crystal grains 8 that are in contact with one or more main phase grains 4 may be oriented along a single direction (orientation direction D). That is, the angle between the <100> angles of any two crystal grains 8 among the plurality of crystal grains 8 may be 5° or less, or 3° or less, and the angle between the <100> angle of any one crystal grain 8 and the orientation direction D may be 2.5° or less, or 1.5° or less.

[0088] For example, the <010> angles of a plurality of crystal grains 8 that are in contact with one or more main phase grains 4 may be oriented along a single direction (orientation direction D). That is, the angle between the <010> angles of any two crystal grains 8 among the plurality of crystal grains 8 may be 5° or less, or 3° or less, and the angle between the <010> angle of any one crystal grain 8 and the orientation direction D may be 2.5° or less, or 1.5° or less.

[0089] For example, the <001> orientations of a plurality of crystal grains 8 that are in contact with one or more main phase grains 4 may be oriented along a single direction (orientation direction D). That is, the angle between the <001> orientations of any two crystal grains 8 among the plurality of crystal grains 8 may be 5° or less, or 3° or less, and the angle between the <001> orientation of any one crystal grain 8 and the orientation direction D may be 2.5° or less, or 1.5° or less.

[0090] [Zone axis of crystal grains and zone axis of main phase particles]

[0091] For example, the crystal zone axis cza' of each of the one or more main phase grains 4 in contact with the plurality of crystal grains 8 may be <100>, <010>, or <001>. The <001> direction of each of the plurality of main phase grains 4 in the hot-worked magnet 2 may be substantially or completely parallel to the easy magnetization axis direction C of the hot-worked magnet 2.

[0092] like Figure 11 As shown, the angle between the zone axis cza of each of the plurality of crystal grains 8 and the zone axis cza′ of each of one or more main phase grains 4 in contact with the plurality of crystal grains 8 can be expressed as an angle θ.

[0093] For example, the angle θ may be the angle between <100> of each of the plurality of crystal grains 8 and <100> of each of one or more main phase grains 4 .

[0094] For example, the angle θ may be the angle between the <010> of each of the plurality of crystal grains 8 and the <010> of each of one or more main phase grains 4 .

[0095] For example, the angle θ may be the angle between the <001> of each of the plurality of crystal grains 8 and the <001> of each of one or more main phase grains 4 .

[0096] For example, the angle θ may be 0° to 19.5°, 0° to 10°, 0° to 9.2°, 1.5° to 19.5°, 1.5° to 10°, or 1.5° to 9.2°. As the angle θ decreases, the crystal structure of each grain 8 in the grain boundary phase 6 and the crystal structure of each main phase grain 4 are more likely to match at the interface therebetween. As a result, the energy barrier at the interface between the grain boundary phase 6 and the main phase grain 4 becomes higher, and the movement of the magnetic wall through the grain boundary phase 6 is more likely to be suppressed. Therefore, when the angle θ is 10° or less, the coercive force and squareness ratio of the hot-worked magnet 2 are more likely to be higher.

[0097] For the same reason, the average value of the angle θ may be 0° to 19.5°, 0° to 10°, 0° to 9.2°, 1.5° to 19.5°, 1.5° to 10°, or 1.5° to 9.2°. For example, the average value of the angle θ may be the average value of the angles θ of 10 or more pairs of crystal grains 8 and main phase grains 4.

[0098] like Figure 11 As shown, the angle between one direction (orientation direction D) in which the zone axes cza of the plurality of crystal grains 8 are oriented and the zone axes cza' of each of the one or more main phase grains 4 in contact with the plurality of crystal grains 8 can be equal to the angle θ, and can be 0° to 19.5°, 0° to 10°, 0° to 9.2°, 1.5° to 19.5°, 1.5° to 10°, or 1.5° to 9.2°. For example, one direction (orientation direction D) in which the zone axes cza of the plurality of crystal grains 8 are oriented can be substantially or completely parallel to the zone axes cza' of each of the one or more main phase grains 4 in contact with the plurality of crystal grains 8.

[0099] Among the plurality of zone axes possessed by each of the plurality of crystal grains 8 in contact with one or more main phase grains 4 , the zone axis oriented in one direction (orientation direction D) can be expressed as cza1 .

[0100] Among the multiple crystal zone axes of the multiple crystal grains 8 respectively connected to one or more main phase grains 4, the crystal zone axis whose angle with the crystal zone axis cza' of each of the one or more main phase grains 4 connected to the multiple crystal grains 8 is greater than or equal to 0° and less than or equal to 10° can be expressed as cza2.

[0101] cza1 and cza2 may be identical or different. That is, the zone axis cza1 of the crystal grain 8 oriented in one direction (orientation direction D) may be identical to or different from the zone axis cza2 of the crystal grain 8 that forms an angle of 0° to 10° with the zone axis cza' of the main phase grain 4.

[0102] [Measurement of the direction of the crystal zone axis]

[0103] The directions of the zone axes cza of the plurality of crystal grains 8 are determined based on the electron beam diffraction patterns of the plurality of crystal grains 8. The electron beam diffraction patterns can be measured by selected area electron diffraction (SAED) using a transmission electron microscope (TEM) or nanobeam electron diffraction (NBED) using a TEM.

[0104] By incidenting an electron beam on the cross section of any one of the crystal grains 8 exposed in the cross section 2cs of the hot-processed magnet 2, an electron beam diffraction pattern of any one of the crystal grains 8 can be obtained. As described above, the cross section 2cs of the hot-processed magnet 2 is approximately or completely parallel to the easy magnetization axis direction C. The electron beam diffraction pattern includes multiple diffraction spots originating from multiple lattice planes in a single crystal grain 8. The spot located at the center of the electron beam diffraction pattern (the central spot indicated as (000)) is a spot where the electron beam is transmitted through the crystal grain 8 without being diffracted by the lattice planes in the crystal grain 8. For example, the direction of the zone axis cza indicated as <uvw> can be the direction of a straight line passing through the center of the diffraction spot originating from the lattice plane indicated as the (uvw) plane and the center of the central spot. The direction of the zone axis cza indicated as <uvw> can also be the direction of a straight line passing through the center of the spot originating from the lattice plane parallel to the (uvw) plane and the center of the central spot.

[0105] The above method can be used to identify the direction of the zone axes cza of each of the multiple grains 8. By comparing the electron beam diffraction patterns of the multiple grains 8, it can be confirmed whether the zone axes cza of the multiple grains 8 are oriented along a single direction (orientation direction D). For example, if the electron beam diffraction patterns of the multiple grains 8 are substantially or completely aligned in terms of the positions of the diffraction spots originating from the respective lattice planes and the directions in which the multiple diffraction spots are arranged, the zone axes cza of the multiple grains 8 are substantially or completely parallel to each other.

[0106] The direction of the zone axis cza' of each of one or more main phase grains 4 in contact with the plurality of crystal grains 8 can also be determined using a method similar to the above. Specifically, the direction of the zone axis cza' of each of one or more main phase grains 4 in contact with the plurality of crystal grains 8 can be determined based on the electron beam diffraction pattern of each main phase grain 4. The electron beam diffraction pattern of any one of the main phase grains 4 exposed in the cross section 2cs of the hot-worked magnet 2 is obtained by incidenting an electron beam on the cross section of the main phase grain 4. The crystal structure of each main phase grain 4 can also be determined based on the electron beam diffraction pattern of each main phase grain 4.

[0107] [Method for measuring angle θ]

[0108] The above-mentioned angle θ can be measured by the following method using TEM.

[0109] A sample (thin slice) is produced by a hot working magnet 2 by milling or other processing methods using a focused ion beam (FIB). The thickness of the sample is adjusted to a thickness suitable for analysis using a TEM (usually 100 nm or less).

[0110] The thickness of the grain boundary phase 6 in the sample is approximately several nanometers, so the TEM is set to the nanobeam diffraction mode.

[0111] By the above-described method, the crystal structure of each crystal grain 8 in the sample and the crystal structure of each main phase grain 4 in contact with each crystal grain 8 in the sample are specified in advance.

[0112] The tilt angle (tilt angle) of the stage on which the sample is set in the TEM is adjusted so that the direction of the electron beam incident on the crystal grain 8 in the sample is parallel to the <uvw> (i.e., the normal to the (uvw) plane) of the crystal grain 8 in the sample. That is, the electron diffraction pattern of the crystal grain 8 is measured in a state where the electron beam is parallel to the <uvw> (crystal zone axis) of the crystal grain 8. For example, the electron diffraction pattern of the crystal grain 8 is measured in a state where the electron beam is parallel to the <001> (i.e., the normal to the (001) plane) of the crystal grain 8 in the sample. Based on this electron beam diffraction pattern, the direction of the <uvw> (e.g., <001>) of the crystal grain 8 in the sample is determined.

[0113] The tilt angle (tilt angle) of the stage on which the sample is mounted in the TEM is adjusted so that the direction of the electron beam incident on the primary phase grains 4 in contact with the crystal grains 8 in the sample is parallel to the <uvw> plane (i.e., the normal to the (uvw) plane) of the primary phase grains 4 in the sample. Specifically, the electron diffraction pattern of the primary phase grains 4 is measured while the electron beam is parallel to the <uvw> plane (the crystal zone axis) of the primary phase grains 4. For example, the electron diffraction pattern of the primary phase grains 4 is measured while the electron beam is parallel to the <001> plane of the primary phase grains 4 in the sample. Based on this electron beam diffraction pattern, the <uvw> direction (e.g., <001>) of the primary phase grains 4 in the sample can be determined.

[0114] The electron diffraction patterns of the crystal grains 8 and the main phase grains 4 can be captured by a digital camera or a CCD camera and analyzed as high-resolution image data.

[0115] The angle θ is determined based on the <uvw> (zone axis) directions of each of the crystal grains 8 and the main phase grains 4 in the sample. For example, a unit vector e1 parallel to the <uvw> of the crystal grain 8 can be determined based on the position of the diffraction spot corresponding to the <uvw> of the crystal grain 8, and a unit vector e2 parallel to the <uvw> of the main phase grain 4 can be determined based on the position of the diffraction spot corresponding to the <uvw> of the main phase grain 4. The angle θ can be calculated using the formula θ = (180° / π) × arccos <e1, e2>. <e1, e2> in the above formula is the inner product of e1 and e2.

[0116] For example, two vectors corresponding to <uvw> of each of the crystal grain 8 and the main phase grain 4 can be visualized based on image data of electron diffraction patterns of each of the crystal grain 8 and the main phase grain 4 , or the angle between the two vectors can be measured using a protractor.

[0117] The hot-worked magnet 2 of the present disclosure can have high coercive force due to the following mechanism.

[0118] In a hot-worked magnet 2 in which the zone axes cza of multiple grains 8 adjoining one or more main phase grains 4 are oriented along a single orientation direction D, the pinning force of the magnetic walls within the grain boundary phase 6 containing the multiple grains 8 is increased compared to a hot-worked magnet in which the zone axes cza of the multiple grains 8 are not oriented. As a result, magnetization reversal caused by the movement of the magnetic walls is suppressed, and each of the multiple main phase grains 4 is more likely to be in a single magnetic domain state, thereby increasing the coercive force (HcJ) of the hot-worked magnet 2. Furthermore, the orientation of the zone axes cza of the multiple grains 8 facilitates magnetic decoupling between the multiple main phase grains 4. This magnetic decoupling maintains a high coercive force and also tends to increase the squareness ratio (Hk / HcJ) of the hot-worked magnet 2. Hk is the strength of the demagnetizing field equivalent to 90% of the residual magnetic flux density in the second quadrant of the magnetization curve of the hot-worked magnet 2.

[0119] In contrast, when the grain boundary phase 6 is ferromagnetic, or when the directions of the crystal axis cza of multiple grains 8 in the grain boundary phase 6 are random, it is easy to produce a multi-magnetic domain state in which the magnetic wall penetrates the main phase particle 4, and it is easy to cause magnetization reversal due to the movement of the magnetic wall, thereby reducing the coercive force.

[0120] Existing research on hot-worked magnets has focused on the macroscopic structure of the main phase grains and grain boundary phases (e.g., the morphology associated with the main phase grains and grain boundary phases). However, the microscopic structure of the grain boundary phase 6 (e.g., the structure and orientation of the crystals in the grain boundary phase) has not been addressed in this current research. The inventors of the present disclosure have discovered for the first time the influence of the orientation of the crystal zone axes cza of the multiple grains 8 in the grain boundary phase 6 on the coercivity and squareness ratio.

[0121] The technical scope of the hot-worked magnet 2 disclosed in the present invention is not limited by the above-mentioned mechanism.

[0122] For example, the coercive force (HcJ) of the hot-worked magnet 2 at 23° C. may be 1313 kA / m or more and 1591 kA / m or less.

[0123] For example, the residual magnetic flux density (Br) of the hot-worked magnet 2 at room temperature may be 1.25 T or more and 1.47 T or less, or 1.25 T or more and 1.46 T or less.

[0124] For example, the squareness ratio (Hk / HcJ) of the hot-worked magnet 2 may be 90.5% or more and 98.5% or less, or 90.5% or more and 98.2% or less.

[0125] The angle between one direction (orientation direction D) in which the crystal zone axes cza of the plurality of crystal grains 8 in contact with one or more main phase particles 4 are oriented and the easy magnetization axis direction C is not particularly limited. For the reason that the coercive force and the squareness ratio are easily increased, the crystal structures of the plurality of crystal grains 8 in contact with one or more main phase particles 4 may be the same. For the same reason, the composition of the plurality of crystal grains 8 in contact with one or more main phase particles 4 may be the same. However, the crystal structures of the plurality of crystal grains 8 in contact with one or more main phase particles 4 may also be different from each other. That is, the crystal zone axes cza of the plurality of crystal grains 8 having different crystal structures may also be oriented along one direction (orientation direction D). The composition of the plurality of crystal grains 8 in contact with one or more main phase particles 4 may also be different from each other. That is, the crystal zone axes cza of the plurality of crystal grains 8 having different compositions may also be oriented along one direction (orientation direction D).

[0126] The composition of the plurality of crystal grains 8 is different from the composition of the plurality of main phase particles 4. For example, the plurality of crystal grains 8 may also contain at least one rare earth element R and at least one element M. The plurality of crystal grains 8 may also contain at least Nd as the rare earth element R. The element M contained in the plurality of crystal grains 8 may be at least one selected from copper (Cu), gallium (Ga), zinc (Zn), nickel (Ni), and chromium (Cr). The element M contained in one crystal grain 8 may also be an element different from the element M contained in other crystal grains 8. The plurality of crystal grains 8 may be composed only of rare earth elements R and element M. For example, in addition to rare earth elements R and element M, the plurality of crystal grains 8 may also contain other elements. For example, the plurality of crystal grains 8 may also contain at least one of Fe and Co as a transition metal element T. The plurality of crystal grains 8 may also be composed only of rare earth elements R, element M, and transition metal element T.

[0127] The plurality of crystal grains 8 may be an intermetallic compound containing a rare earth element R and an element M. For example, Figure 4 As shown, the unit cells of the plurality of crystal grains 8 (unit cells uc8a and unit cells uc8b) may contain a rare earth element R and an element M. For example, a portion of the rare earth element R in the unit cells of the plurality of crystal grains 8 may be replaced by an element other than the transition metal element T. For example, a portion of the element M in the unit cells of the plurality of crystal grains 8 may also be replaced by an element other than the transition metal element T.

[0128] The content (unit: mass %) of the rare earth element R in the plurality of crystal grains 8 can be greater than the content (unit: mass %) of the rare earth element R in the plurality of main phase grains 4. The concentration (unit: atomic %) of the rare earth element R in the plurality of crystal grains 8 can be higher than the concentration (unit: atomic %) of the rare earth element R in the plurality of main phase grains 4. In other words, the rare earth element R can be concentrated in the plurality of crystal grains 8. Due to the concentration of the rare earth element R in the plurality of crystal grains 8, the plurality of crystal grains 8 tends to become a non-magnetic phase. As a result, the plurality of crystal grains 8 tends to cause magnetic decoupling between the main phase grains 4, and the coercivity and squareness ratio tend to increase.

[0129] On the surface of each main phase particle 4 (R2T 14B (001) plane), Nd ions are easily exposed, and therefore the easy magnetization axis direction C is likely to be locally oriented in the in-plane direction of the surface of each main phase grain 4. In other words, the easy magnetization axis direction C is likely to be locally parallel to the surface of each main phase grain 4. As a result, the surface of each main phase grain 4 is likely to become a nucleus for magnetization reversal, and the coercive force is likely to be reduced. However, at the interface between the main phase grain 4 and the crystal grain 8, a portion of the Fe on the surface of the main phase grain 4 is replaced by the element M. As a result, the direction of the crystallographic electric field (anisotropic magnetic field) acting on the 4f electrons of the Nd ions exposed on the surface of the main phase grain 4 is likely to change from the in-plane direction of the surface of each main phase grain 4 to the direction normal to the surface of each main phase grain 4. In other words, due to the element M derived from the multiple crystal grains 8, the easy magnetization axis direction C on the surface of each main phase grain 4 is likely to have the same uniaxial anisotropy as the interior (bulk) of each main phase grain 4. As a result, magnetization reversal caused by the surface of each main phase grain 4 is likely to be suppressed, and the coercive force is likely to be increased.

[0130] The content of the rare earth element R in the plurality of crystal grains 8 may be 50% by mass or more and 98% by mass or less, 60% by mass or more and 80% by mass or less, or 53.40% by mass or more and 96.27% by mass or less. The content of the transition metal element T in the plurality of crystal grains 8 may be 0% by mass or more and 50% by mass or less, 0% by mass or more and 20% by mass or less, 0% by mass or more and 10% by mass or less, or 3.20% by mass or more and 40.93% by mass or less. The content of the element M in the plurality of crystal grains 8 may be greater than 0% by mass and less than 35% by mass, 2% by mass or more and 30% by mass or less, 20% by mass or more and 30% by mass or less, or 0.53% by mass or more and 31.54% by mass or less. The plurality of crystal grains 8 having the above composition are likely to become non-magnetic. The plurality of crystal grains 8 as non-magnetic can be defined as the plurality of crystal grains 8 represented by the following chemical formula 1 or the following chemical formula 2.

[0131] R α T β M γ (1)

[0132] In the above Chemical Formula 1, α is 50 mass% or more and 98 mass% or less, 60 mass% or more and 80 mass% or less, or 53.40 mass% or more and 96.27 mass% or less. In the above Chemical Formula 1, β is 0 mass% or more and 50 mass% or less, 0 mass% or more and 20 mass% or less, 0 mass% or more and 10 mass% or less, or 3.20 mass% or more and 40.93 mass% or less. In the above Chemical Formula 1, γ is greater than 0 mass% and less than 35 mass%, 2 mass% or more and 30 mass% or less, 20 mass% or more and 30 mass% or less, or 0.53 mass% or more and 31.54 mass% or less.

[0133] R A TB M C (2)

[0134] A in the above Chemical Formula 2 is greater than or equal to 40 atomic % and less than or equal to 94 atomic %, or greater than or equal to 31.2 atomic % and less than or equal to 76.6 atomic %, B in the above Chemical Formula 2 is greater than or equal to 0 atomic % and less than or equal to 30 atomic %, or greater than or equal to 6.4 atomic % and less than or equal to 61.7 atomic %, and C in the above Chemical Formula 2 is greater than or equal to 0.9 atomic % and less than or equal to 50 atomic %, or greater than or equal to 0.9 atomic % and less than or equal to 48.3 atomic %.

[0135] R in Chemical Formula 1 and Chemical Formula 2 is the rare earth element R described above, T in Chemical Formula 1 and Chemical Formula 2 is the transition metal element T described above, and M in Chemical Formula 1 and Chemical Formula 2 is the element M described above.

[0136] For the reason that the coercive force and the squareness ratio are easily increased, at least a part or all of the plurality of crystal grains 8 that are in contact with one or more main phase grains 4 may contain Nd and Cu. Figure 4 As shown, the unit cells (unit cells uc8a and unit cells uc8b) of the plurality of crystal grains 8 may contain Nd as the rare earth element R and Cu as the element M. The plurality of crystal grains 8 containing Nd and Cu may also contain a transition metal element T. For the reason that the coercive force and the rectangular ratio are easily increased, the plurality of crystal grains 8 containing Nd and Cu may each be a cubic crystal, a tetragonal crystal, or an orthorhombic crystal. For the reason that the coercive force and the rectangular ratio are easily increased, the space group representing the symmetry of the crystal structure of the plurality of crystal grains 8 containing Nd and Cu may be Pnma, I4 / mcm, Fm-3m, or Ia-3. The notation of the space group is based on the Hermann-Mauguin notation. For the reason that the coercive force and the rectangular ratio are easily increased, as Figure 4 As shown, the <100> orientation of the plurality of crystal grains 8 containing Nd and Cu can be along one direction (orientation direction D). Figure 4 As shown, the (010) planes of the plurality of crystal grains 8 containing Nd and Cu may be substantially or completely parallel to each other.

[0137] The space group representing the crystal structure of each grain 8 and the symmetry of the crystal structure can be determined based on the electron beam diffraction pattern of each grain 8. By referring to a known database related to the crystal structure (for example, the Inorganic Crystal Structure Database (ICSD)), the Miller indices h, k, and l (i.e., the (hkl) plane) corresponding to the multiple points (bright spots) in the electron beam diffraction pattern are determined. The multiple points in the electron beam diffraction pattern are different, and the multiple points are different in brightness. At a specific position, the point disappears. By confirming whether the electron beam diffraction pattern conforms to the known system extinction law and symmetry elements, the candidate for the space group is locked. The electron beam diffraction pattern corresponding to the space group inferred by the above method is reproduced by simulation software (for example, JEMS ElectronMicroscopy Software). The actual space group is determined by making the reproduced electron beam diffraction pattern consistent with the actually measured electron diffraction pattern. That is, the actual space group is determined by repeating the above analysis until the electron beam diffraction pattern reproduced by the simulation software is consistent with the actually measured electron diffraction pattern.

[0138] As mentioned above, the plurality of crystal grains 8 are not limited to orthorhombic crystals containing Nd and Cu. As mentioned above, at least a portion of the plurality of crystal grains 8 may also be cubic crystals or tetragonal crystals. For example, at least a portion of the plurality of crystal grains 8 may also be tetragonal crystals containing Nd and Ga. For example, at least a portion of the plurality of crystal grains 8 may be an Nd-rich phase (e.g., containing Nd6Fe 13 phase of Ga).

[0139] The composition of the plurality of crystal grains 8 can be identified as a composition of components other than the plurality of main phase grains 4 based on the composition. The composition of the plurality of crystal grains 8 can be measured using an energy dispersive X-ray spectroscopy (EDS) device included in a scanning transmission electron microscope (STEM) or a scanning electron microscope (SEM). For example, an image of a cross section of the hot-processed magnet 2 can be captured using a STEM or SEM, and the composition of the plurality of crystal grains 8 can be measured using EDS in the cross-sectional image. Furthermore, through elemental mapping based on EDS, the plurality of crystal grains 8 exposed in the cross section of the hot-processed magnet 2 can be identified as components other than the plurality of main phase grains 4. The composition of components other than the plurality of main phase grains 4 can also be measured using the above-described method. In addition, a sample observed by TEM can be used to observe the same area as the TEM image using STEM. That is, the composition of the area where the crystal zone axis and angle θ were measured by TEM can be measured using STEM-EDS.

[0140] The grain boundary phase 6 may contain an oxide of a rare earth element R. At least a portion or all of the plurality of crystal grains 8 may be an oxide of the rare earth element R. For example, the oxide of the rare earth element R may be at least one of Nd2O3 having a hexagonal structure and NdO having a face-centered cubic structure. The oxide of the rare earth element R may be a type of R-rich phase described below.

[0141] The grain boundary phase 6 may contain metal neodymium (Nd as a single substance) having a hexagonal closest-packed structure. At least a portion or all of the plurality of crystal grains 8 may be metal neodymium having a hexagonal closest-packed structure. The metal neodymium may be a type of R-rich phase described below.

[0142] The plurality of crystal grains 8 containing the rare earth element R and the element M may be one of the following R-rich phases.

[0143] The grain boundary phase 6 may include an R-rich phase. The R-rich phase contains at least the rare earth element R. For example, the R-rich phase may contain Nd as the rare earth element R. The R-rich phase may contain one or more other rare earth elements as the rare earth element R in addition to Nd. The R-rich phase may also contain one or more elements other than the rare earth element R. The R-rich phase may contain at least one of a single substance of the rare earth element R, an alloy containing the rare earth element R, and a metal compound containing the rare earth element R. The concentration (unit: atomic %) of the rare earth element R in the R-rich phase may be higher than the average concentration of the rare earth element R in the main phase grains 4. The concentration of R in the R-rich phase may be higher than the average concentration of the rare earth element R in the cross section 2cs described above. When the hot-worked magnet 2 contains multiple rare earth elements R, the concentration of the rare earth element R may be the sum of the concentrations of the multiple rare earth elements R.

[0144] The grain boundary phase 6 may further include a paramagnetic phase having a greater content of transition metal element T than the plurality of crystal grains 8. For example, the content of transition metal element T in the paramagnetic phase may be 60 mass % to 100 mass %.

[0145] The area fraction AR (phase fraction) of the cross-section of the plurality of crystal grains 8 in the cross-section 2cs of the hot-worked magnet 2 can be 3.0% or more and 8.0% or less. The cross-section 2cs, where the area fraction is measured, is approximately or completely parallel to the easy magnetization axis direction C of the hot-worked magnet 2. When the area fraction AR is 3.0% or more, the coercive force and squareness ratio are likely to increase. When the area fraction AR is 8.0% or less, the coercive force is likely to increase, and the reduction in residual magnetic flux density caused by the plurality of crystal grains 8 is likely to be suppressed. For the reasons that the coercive force and squareness ratio are likely to increase, and the reduction in residual magnetic flux density is likely to be suppressed, the area fraction AR may be 3.2% or more and 6.3% or less.

[0146] The area fraction AR can be expressed as Acr / Acs (unit: %). Acr is the total area of ​​the cross sections of the plurality of crystal grains 8. Acs is the area of ​​the cross section where Acr is measured. The cross section where Acr is measured can be the entire cross section 2cs of the hot-worked magnet 2 or a portion thereof. In other words, Acs can be the entire area of ​​the cross section 2cs of the hot-worked magnet 2 or the area of ​​a portion of the cross section 2cs.

[0147] The total Acr of the cross-sectional areas of the plurality of crystal grains 8 can be measured by the following method.

[0148] An image of the cross section 2cs of the hot-processed magnet 2 is taken using a TEM or SEM. By thresholding (binarizing) the image of the cross section 2cs using image analysis software, a monochrome image is obtained. By adjusting the threshold of the binary processing to an appropriate value, the multiple grains 8 within the monochrome image can be identified as being composed of components other than the multiple main phase particles 4 based on contrast. Furthermore, the image analysis software is used to determine the cross-sectional profiles of each of the multiple grains 8, and the cross-sectional area of ​​each of the multiple grains 8 is measured using the image analysis software. Based on the cross-sectional area of ​​each of the multiple grains 8, the total cross-sectional area Acr of the multiple grains 8 is calculated. Image analysis software such as ImageJ, which is publicly available, or other commercially available image analysis software can be used as the image analysis software.

[0149] For example, the volume ratio of the plurality of main phase grains 4 (the volume ratio of all main phase grains 4 in the hot-worked magnet 2) may be 80 volume % or more and less than 100 volume %, or 92 volume % or more and 97 volume % or less.

[0150] like Figure 2 As shown, the width W (e.g., the average value of the width W) of the grain boundary phase 6, which includes one or more crystal grains 8 connected to one or more main phase grains 4, can be from 4 nm to 500 nm in the easy magnetization axis direction C of the hot-worked magnet 2. In other words, the width W of the grain boundary phase 6, which is located between a pair of main phase grains 4 and includes one or more crystal grains 8, can be from 4 nm to 500 nm in the easy magnetization axis direction C of the hot-worked magnet 2. When the width W of the grain boundary phase 6 is 4 nm or greater, one or more crystal grains 8 (crystalline non-magnetic phases) are easily formed in the grain boundary phase 6, and the coercive force and squareness ratio of the hot-worked magnet 2 are easily increased. When the width W of the grain boundary phase 6 is 500 nm or less, the volume of the grain boundary phase 6, which does not have hard magnetic properties, is appropriately suppressed, and a decrease in the residual magnetic flux density of the hot-worked magnet 2 is easily suppressed. The width W of the grain boundary phase 6 may be 7.1 nm to 27.0 nm, or 7.5 nm to 27.0 nm, for the reasons that the coercive force and the squareness ratio are easily increased and the reduction in residual magnetic flux density is easily suppressed.

[0151] One or more primary phase particles 4 (secondary particles) connected to one or more crystal grains 8 may include at least one of columnar crystals and equiaxed crystals. Figure 3A and Figure 3B As shown, a secondary particle 4b may include a plurality of columnar crystals 4C, a plurality of flat main phase particles 4 (primary particles), and a plurality of equiaxed crystals 4E. The columnar crystals 4C in the secondary particle 4b may extend along the easy magnetization axis direction C. The flat main phase particles 4 (primary particles) in the secondary particle 4b may extend along the AB direction orthogonal to the easy magnetization axis direction C. The equiaxed crystals 4E may be referred to as crystals that are isotropic in shape and crystal orientation. The columnar crystals 4C tend to be located near one surface of the flat secondary particle 4b. The equiaxed crystals 4E tend to be located near the other surface of the flat secondary particle 4b. The flat main phase particles 4 (primary particles) tend to be located between the columnar crystals 4C and the equiaxed crystals 4E. A columnar crystal 4C and an equiaxed crystal 4E may each be a main phase particle (primary particle).

[0152] The columnar crystals 4C and equiaxed crystals 4E can originate from the alloy ribbon that serves as the raw material for the hot-worked magnet 2. In other words, the alloy ribbon can be a precursor to the secondary particles 4b. The alloy ribbon is produced using the rapid cooling and solidification method described below. In the rapid cooling and solidification method, molten metal containing the various elements that constitute the hot-worked magnet 2 contacts the surface of a cooling roller and is cooled. As a result, the molten metal solidifies, forming an alloy ribbon.

[0153] The molten metal is rapidly cooled in the portion (contact portion) that contacts the surface of the cooling roller, which tends to form a chill layer (e.g., a layer containing a plurality of nanoscale microscopic grains) near the surface of the alloy strip. The grains in the chill layer are heated during the hot forming or thermoplastic working process. As a result, the growth of coarse grains originating from the chill layer proceeds rapidly near the surface of the alloy strip, tending to form coarse equiaxed crystals 4E near the surface of the flat secondary particles 4b.

[0154] On the other hand, the portion of the molten metal located behind the contact portion (the non-contact portion) does not contact the cooling roller and is farthest from the surface of the cooling roller. Therefore, the cooling rate of the non-contact portion is lower than that of the rest of the molten metal. Consequently, a temperature gradient of the molten metal is generated along the direction from the non-contact portion toward the contact portion. Due to this temperature gradient, during the solidification and crystallization process of the molten metal, a plurality of columnar crystals 4C extending along the thickness direction of the alloy ribbon are likely to form near the surface of the alloy ribbon (behind the surface where the equiaxed crystals 4E, or the chill layer, are located).

[0155] The cooling rate of the portion between the contact and non-contact portions of the molten metal (the interior of the molten metal) is lower than that of the contact portion and higher than that of the non-contact portion. Consequently, numerous grains with diameters of tens of nanometers (nm) (larger than those in the chilled layer) are likely to form within the molten metal. During the hot plastic working process, these grains form within the molten metal, growing anisotropically along the AB direction, which is perpendicular to the easy magnetization axis direction C, and forming flat main phase grains 4.

[0156] The inventors presume that the numerous fine grains and the numerous coarse grains contained in the alloy ribbon are difficult to orient due to normal grain boundary sliding during the hot plastic working process, and therefore columnar crystals 4C and equiaxed crystals 4E are easily formed.

[0157] A plurality of crystal grains 8 having crystal zone axes cza oriented along one direction (orientation direction D) tend to be present in the vicinity of columnar crystals 4C or equiaxed crystals 4E. That is, the crystal zone axes cza of a plurality of crystal grains 8 connected to one or more columnar crystals 4C or equiaxed crystals 4E may be oriented along one direction (orientation direction D). A grain boundary phase 6 may be present between a plurality of main phase particles 4 contained in a secondary particle 4b. The grain boundary phase 6 within the secondary particle 4b may contain a plurality of crystal grains 8. A plurality of crystal grains 8 within the secondary particle 4b may be connected to one or more main phase particles 4 within the secondary particle 4b. The crystal zone axes cza of a plurality of crystal grains 8 connected to one or more main phase particles 4 within the secondary particle 4b may be oriented along one direction (orientation direction D).

[0158] like Figure 2 As shown, the plurality of main phase grains 4 may be flat when viewed in a cross section 2cs parallel to the easy magnetization axis direction C. In other words, the main phase grains 4 may be plate-shaped when viewed in the cross section 2cs. The plurality of flat main phase grains 4 may be stacked along the easy magnetization axis direction C.

[0159] The width S of each of the plurality of main phase grains 4 (primary particles) in the easy magnetization axis direction C can be smaller than the width L of each of the plurality of main phase grains 4 in the AB direction perpendicular to the easy magnetization axis direction C. In other words, the length (S) of the minor axis of each main phase grain 4 can be smaller than the length (L) of the major axis of each main phase grain 4. The width S of each of the main phase grains 4 in the easy magnetization axis direction C (e.g., the average value of the width S) can be 20 nm to 200 nm, 65 nm to 77 nm, or 66 nm to 75 nm. The width L of each of the main phase grains 4 in the AB direction perpendicular to the easy magnetization axis direction C (e.g., the average value of the width L) can be 100 nm to 1000 nm. For example, the aspect ratio L / S of each of the plurality of main phase grains 4 (e.g., the average value of the aspect ratio L / S) can be 2 to 10. With an aspect ratio L / S of 2 or greater, the c-axis of the main phase grains 4 is more likely to be oriented in the easy magnetization axis direction C, and the coercive force is more likely to increase. 2 or more aspect ratio L / S means that in the thermoplastic processing step described later, the main phase particles 4 (R2T 14 The anisotropic grain growth of the main phase particles 4 in the hot plastic working step has a limit, so the aspect ratio L / S is unlikely to exceed 10.

[0160] The size of each of the plurality of crystal grains 8 may be approximately the same as the size of each of the plurality of main phase grains 4. The size of each of the plurality of crystal grains 8 may also be smaller than the size of each of the plurality of main phase grains 4. The shape of each of the plurality of crystal grains 8 is not limited.

[0161] The shape of the main phase grains 4 in cross section 2cs is not limited to a rectangle. The shape of the main phase grains 4 in cross section 2cs may be deformed. The shape of the main phase grains 4 in cross section 2cs may vary. If the shape of the main phase grains 4 in cross section 2cs is deformed, the shape of the main phase grains 4 may be approximated by the smallest quadrilateral among the quadrilaterals circumscribing the main phase grains 4. The quadrilateral may be a rectangle. The length of the short side of the quadrilateral may be considered the length (S) of the minor axis of the main phase grains 4, and the length of the long side of the quadrilateral may be considered the length (L) of the major axis of the main phase grains 4. The average value of the minor axis lengths of the main phase grains 4 can be calculated based on the measured values ​​of the minor axis lengths of all the main phase grains 4 present in the backscattered electron image of cross section 2cs taken by an SEM. The average value of the major axis lengths of the main phase grains 4 can also be calculated based on the measured values ​​of the major axis lengths of all the main phase grains 4 present in the backscattered electron image. However, the size of the main phase grains 4 revealed in the backscattered electron image is excluded from the calculation of the average value. For example, the maximum value of the size of the backscattered electron image used in the measurement of the length of each of the short axis and the long axis of the main phase particle 4 can be 120 μm in length × 80 μm in width, or 80 μm in length × 120 μm in width. A plurality of representative parts in these backscattered electron images taken at low magnifications can be selected, and backscattered electron images of each part can be taken at high magnifications. Then, the average value of each of the long axis and the short axis can be calculated based on the length of each of the long axis and the short axis of all the main phase particles 4 measured in the backscattered electron image at high magnification. Image analysis software (for example, the above-mentioned ImageJ) can be used to determine the shape (contour line) of the main phase particle 4 and the size of the main phase particle 4 (the quadrilateral circumscribed with the main phase particle 4).

[0162] The main phase grains 4 can be composed of a surface portion and a center portion covered by the surface portion. The surface portion can be alternatively referred to as a shell, and the center portion can be alternatively referred to as a core. The surface portion of the main phase grains 4 can contain at least one heavy rare earth element selected from Tb and Dy. The surface portion of each of the main phase grains 4 can contain at least one heavy rare earth element selected from Tb and Dy. The surface portion of a portion of the main phase grains 4 can also contain at least one heavy rare earth element selected from Tb and Dy. The inclusion of heavy rare earth elements in the surface portion facilitates a local increase in the anisotropic magnetic field near the grain boundaries, making it difficult to generate cores of magnetization reversal near the grain boundaries. As a result, the coercive force of the hot-worked magnet 2 at high temperatures (e.g., 100-200°C) is increased. To easily achieve a balance between the residual magnetic flux density (Br) and the coercive force of the hot-worked magnet 2, the total concentration of the heavy rare earth elements in the surface portion can be higher than the total concentration of the heavy rare earth elements in the center portion.

[0163] For example, the size of the hot-worked magnet 2 in the easy magnetization axis direction C can be several mm to several hundred mm, or several tens of mm to several hundred mm. For example, the size of the hot-worked magnet 2 in the AB direction can be several mm to several hundred mm, or several tens of mm to several hundred mm.

[0164] The following describes the overall composition of the hot-worked magnet 2. However, the composition of the hot-worked magnet 2 is not limited to the following composition. The content of each element in the hot-worked magnet 2 may also be outside the following range.

[0165] The content of the rare earth element R in the hot-worked magnet 2 can be 26.00 mass% or more and 32.00 mass% or 28.00 mass% or more and 32.00 mass% or less. When the rare earth element R content is 26.00 mass% or more, a liquid phase (R-rich phase) is likely to form at the grain boundaries during the production process of the hot-worked magnet 2. This facilitates the orientation of the main phase grains 4 due to grain boundary sliding, and the coercive force of the hot-worked magnet 2 is likely to be increased. On the other hand, when the R content is 32.00 mass% or less, the formation of an excessive liquid phase (R-rich phase) is suppressed, and the volume ratio of the main phase is likely to be increased.

[0166] Because the residual magnetic flux density and coercive force are likely to increase, the total proportion of Nd and Pr in all rare earth elements R may be 80 atomic % or more and 100 atomic % or less, or 95 atomic % or more and 100 atomic % or less.

[0167] The total content of Tb and Dy in the hot-worked magnet 2 can be 0.00 mass% or more and 5.00 mass% or less. By containing at least one heavy rare earth element of Tb and Dy, the magnetic properties of the hot-worked magnet 2 (particularly the coercive force at high temperatures) are likely to be improved. However, the hot-worked magnet 2 does not necessarily need to contain Tb and Dy.

[0168] The content of B in the hot working magnet 2 can be 0.77 mass % or more and 1.15 mass % or less. When the content of B is 0.77 mass % or more, the TbCu7 type R2Fe 17 The formation of a heterogeneous phase increases the coercivity. When the B content is 1.15% by mass or less, the R 1+ε The formation of a different phase such as Fe4B4 (boride) easily increases the coercive force. When the B content is within the above range, the squareness ratio of the hot-worked magnet 2 easily approaches 1.0.

[0169] The hot-worked magnet 2 may further contain element M. Element M may be at least one selected from Cu, Ga, Zn, Ni, and Cr. The content of element M in the hot-worked magnet 2 may be from 0.67 mass% to 7.30 mass%. When the content of element M is 0.67 mass% or more, a plurality of non-magnetic grains 8 are easily formed. Furthermore, when the content of element M is 0.67 mass% or more, a grain boundary phase with a low melting point is easily formed during the hot forming and hot plastic working steps described later, which can reduce the hot forming and hot plastic working temperatures and easily increase the coercive force of the hot-worked magnet 2. When the content of element M is 7.30 mass% or less, the formation of a plurality of non-magnetic grains 8 is appropriately suppressed, the proportion of main phase particles 4 in the hot-worked magnet 2 is increased, and the residual magnetic flux density of the hot-worked magnet 2 is easily increased.

[0170] The Cu content in the hot-worked magnet 2 can be 0.01% to 1.50% by mass, or 0.04% to 0.50% by mass. When the Cu content is within this range, the hot-worked magnet 2 can be easily forged, and the coercive force, corrosion resistance, and temperature characteristics of the hot-worked magnet 2 can be easily improved. However, the hot-worked magnet 2 does not necessarily contain Cu.

[0171] The Ga content in the hot-worked magnet 2 can be between 0.03 mass% and 1.00 mass%, or between 0.20 mass% and 0.80 mass%. When the Ga content is within the above range, the formation of secondary phases (e.g., phases containing R, T, and Ga) is appropriately suppressed, and the residual magnetic flux density and coercive force of the hot-worked magnet 2 are easily increased. However, the hot-worked magnet 2 does not necessarily need to contain Ga.

[0172] The hot-worked magnet 2 may also contain aluminum (Al). For example, the Al content in the hot-worked magnet 2 may be 0.01% to 0.2% by mass, or 0.04% to 0.07% by mass. When the Al content is within this range, the coercive force and corrosion resistance of the hot-worked magnet are easily improved. However, the hot-worked magnet 2 does not necessarily need to contain Al.

[0173] The hot-worked magnet 2 may contain cobalt (Co). For example, the Co content in the hot-worked magnet 2 may be 0.30% to 6.00% by mass, or 0.30% to 4.00% by mass. The inclusion of Co in the hot-worked magnet 2 facilitates raising the Curie temperature of the hot-worked magnet 2. Furthermore, the inclusion of Co in the hot-worked magnet 2 facilitates improving the corrosion resistance of the hot-worked magnet 2. However, the hot-worked magnet 2 does not necessarily need to contain Co.

[0174] The hot working magnet 2 may contain cerium (Ce). For example, the Ce content in the hot working magnet 2 may be 1.42 mass % or more and 14.17 mass % or less. However, the hot working magnet 2 does not necessarily need to contain Ce.

[0175] The remainder of the hot-worked magnet 2 excluding the above-mentioned elements may be Fe alone, or Fe and other elements. In order for the hot-worked magnet 2 to have sufficient magnetic properties, the total content of elements other than Fe in the remainder may be 5% by mass or less relative to the total mass of the hot-worked magnet 2.

[0176] As other elements (e.g., unavoidable impurities), the hot working magnet 2 may contain at least one element selected from the group consisting of silicon (Si), titanium (Ti), Mn (manganese), Zr (zirconium), vanadium (V), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), bismuth (Bi), tin (Sn), calcium (Ca), carbon (C), nitrogen (N), oxygen (O), chlorine (Cl), sulfur (S), and fluorine (F). For example, the total content of the other elements in the hot working magnet 2 may be 0.001% by mass or more and 0.50% by mass.

[0177] For example, the overall composition of the hot-processed magnet 2 can also be analyzed by X-ray fluorescence (XRF) analysis, high-frequency inductively coupled plasma (ICP) emission analysis, inert gas fusion-non-dispersive infrared absorption (NDIR) analysis, combustion in an oxygen flow-infrared absorption analysis, and inert gas fusion-thermal conductivity analysis.

[0178] For example, the hot-processed magnet 2 can be applied to motors, generators, actuators, etc. For example, the hot-processed magnet 2 can be used in various fields such as hybrid vehicles, electric vehicles, hard disk drives, magnetic resonance imaging devices (MRI), smartphones, digital cameras, flat-screen TVs, scanners, air conditioners, heat pumps, refrigerators, vacuum cleaners, washing machines and dryers, elevators, and wind turbines.

[0179] (Method for manufacturing hot-processed magnets)

[0180] The method for manufacturing a hot-worked magnet according to this embodiment includes at least a ribbon forming step, a hot pressing step, a hot defrosting step, and an unloading step. The method for manufacturing a hot-worked magnet may further include other steps, such as a grain boundary diffusion step, following the unloading step. However, the grain boundary diffusion step is not essential.

[0181] To prevent oxidation of the hot-processed magnets and their semi-finished products during the manufacturing process, the hot-processed magnet manufacturing method can be carried out in a non-oxidizing atmosphere. For example, the non-oxidizing atmosphere can be an inert gas such as argon (Ar). In addition to inert gases, the non-oxidizing atmosphere can also contain reducing gases such as hydrogen (H2).

[0182] The ribbon production process uses a super-quench solidification method to produce alloy ribbons from a variety of raw metals. In this method, molten metal within the container is sprayed onto the surface of a cooling roller from a nozzle located at the front end. The molten metal contacts the surface of the cooling roller and is instantly ejected by the high-speed rotating roller, forming multiple long, thin ribbons. Contact with the cooling roller rapidly cools the molten metal and solidifies it, forming multiple long, thin alloy ribbons. A container is positioned in the direction in which the alloy ribbons are ejected by the cooling roller, and the alloy ribbons are recovered within the container.

[0183] The molten metal is a metal containing multiple elements that constitute the hot working magnet (multiple raw metals). The multiple raw metals can include, for example, a single substance (metallic substance) of a rare earth element, an alloy containing a rare earth element, pure iron, a ferroboron alloy, or an alloy containing these. The multiple raw metals can contain the element M described above. The multiple raw metals are weighed to match the composition of the desired hot working magnet.

[0184] The molten metal can be obtained by heating a plurality of raw metals in a container using high-frequency induction heating. The temperature of the molten metal ejected from the nozzle (the ejection temperature) can be, for example, approximately 1400°C. The rate of increase in the temperature of the raw metals to the ejection temperature can be, for example, approximately 20 to 100°C / second.

[0185] The surface of the cooling roller can be made of a metal with high thermal conductivity such as Cu. The surface temperature of the cooling roller can be controlled by a refrigerant flowing through the cooling roller. For example, the surface temperature of the cooling roller can be controlled so that the cooling rate of the molten metal on the surface of the cooling roller is about 10 5 ~10 6 ℃ / second. The higher the cooling rate, the higher the crystallinity (R2T 14B) The finer the particle size, the easier it is to become for the hot-processed magnet to have a higher coercive force. The less the amount of molten metal sprayed onto the surface of the cooling roller per unit time, the thinner the molten metal attached to the surface of the cooling roller, the higher the cooling rate, and the thinner the alloy strip. The higher the circumferential speed of the cooling roller, the thinner the molten metal attached to the surface of the cooling roller, the higher the cooling rate, and the thinner the alloy strip. The thickness of the main phase particles in the direction of the easy magnetization axis (the length of the short axis of the main phase particles) depends on the thickness of the alloy strip (as well as the crushing and classification of the alloy strip). The thinner the alloy strip, the smaller the thickness (particle size) of the main phase particles, and the higher the coercive force of the hot-processed magnet. For example, the thickness of the alloy strip can be greater than 20 μm and less than 60 μm, or greater than 30 μm and less than 50 μm. For example, the width of the alloy strip can be greater than 1.0 mm and less than 5.0 mm.

[0186] A crushing / classification process can be performed after the ribbon production process. The crushing / classification process is a process of crushing the alloy ribbon using a crushing device to produce a coarse powder, and classifying the coarse powder to recover an alloy powder having a specified particle size and aspect ratio. The alloy powder is a precursor of the main phase particles contained in the hot-processed magnet. The shape of each alloy particle constituting the alloy powder can be plate-like or flake-like. The method for crushing the alloy ribbon can be, for example, at least one of a cutting mill and a propeller mill. The device for classifying the coarse powder can be a sieve. The particle size and particle size distribution of the alloy powder obtained by classification can be measured, for example, by a laser diffraction scattering method. The particle size of the alloy powder obtained by classification can be, for example, not less than 60 μm and not more than 2800 μm, or not less than 150 μm and not more than 2800 μm.

[0187] The hot forming process is a process of forming a molded body by heating an alloy strip (alloy powder) while applying pressure. For example, the alloy powder in a mold can be heated while being compressed by the mold. By pressurizing the alloy powder, the gaps between the alloy powders are reduced, and a dense molded body is obtained. In addition, by heating the alloy powder accompanied by pressurization, a liquid phase (R-rich phase such as Nd-rich phase) is formed from the surface of the alloy powder, and the liquid phase fills the gaps (grain boundaries) between the alloy powders. The alloy powder becomes lubricated by the liquid phase, thereby making it easy to compress the alloy powder and easily obtain a dense molded body. A cold forming process can also be performed before the hot forming process. In the cold forming process, a molded body can be formed by pressurizing the alloy powder at room temperature. By heating and pressurizing the molded body obtained by the cold forming process in the hot forming process, the molded body can be densified. For example, the temperature of the alloy powder in the hot forming process (hot forming temperature) can be above 550°C and below 800°C. If the hot forming temperature is too low, a sufficient liquid phase cannot be formed from the surface of the alloy powder, and the compact is difficult to densify. If the hot forming temperature is too high, the crystals (R2T14 B) excessive grain growth, the coercivity of the hot-worked magnet is likely to decrease. For example, the pressure applied to the alloy powder during the hot forming process (hot forming pressure) can be between 50 MPa and 200 MPa. For example, the time (hot forming time) during which the hot forming temperature and hot forming pressure are maintained within the above ranges can be between tens of seconds and hundreds of seconds.

[0188] After the thermoforming step, a thermoplastic processing step is performed. The thermoplastic processing step is to obtain a plurality of main phase particles (R2T 14 B grains). For example, in the thermoplastic processing step, the molded body is extruded from the mold while being heated. In the mold, the grain boundary phase in the heated molded body liquefies to generate a liquid phase (R-rich phase), and stress acts on the molded body in a prescribed direction, and the alloy particles constituting the molded body are deformed. With the generation of the liquid phase and the deformation of the alloy particles, the anisotropic growth of the grains in the direction perpendicular to the c-axis of the grains proceeds. In addition, the liquid phase lubricates the grains and acts on each grain according to the stress. As a result, the grains rotate by grain boundary sliding, and the c-axis of each grain (main phase particle) is oriented roughly parallel to the stress direction. In other words, a plurality of flat main phase particles extending in a direction roughly perpendicular to the c-axis are stacked along the stress direction.

[0189] For example, the temperature of the molded body in the thermoplastic processing step (thermoplastic processing temperature) may be 700°C or higher and lower than 900°C, or 700°C or higher and 850°C or lower.

[0190] If the hot plastic working temperature is too low, it is difficult to form a liquid phase (R-rich phase such as an Nd-rich phase) at the grain boundaries within the molded body, making it difficult for grains to grow and for grain rotation due to grain boundary sliding to occur. As a result, the average length of the minor axis of the main phase particles tends to be less than 20 nm, making it difficult for the c-axis of each main phase particle (grain) to be oriented approximately parallel to the stress direction.

[0191] When the hot plastic working temperature is too high (for example, at 900°C or above), the liquid phase (R-rich phase) excessively seeps out of each alloy particle and segregates toward the surface of each alloy particle and the interfaces between alloy particles, consuming most of the liquid phase during grain growth. This consumption of the liquid phase during grain growth causes abnormal grain growth of the main phase particles (crystals), leading to the formation of coarse main phase particles, with the average minor axis length of the main phase particles often exceeding 200 nm. Coarse main phase particles are less likely to align in the direction of their easy magnetic axis.

[0192] For example, the extrusion speed of the molded body during hot extrusion molding can be 0.01 mm / second or more and 9.9 mm / second or less. When the extrusion speed is too high (for example, when the extrusion speed is 10 mm / second or more), the anisotropic growth of the main phase particles (grains) in the molded body cannot be fully carried out. Therefore, the average value of the length of the minor axis of the main phase particles (primary particles) is easily less than 20 nm. That is, when the extrusion speed is too high, the molded body is extruded from the die before the anisotropic growth of the grains in the molded body is fully carried out. As a result, the c-axis of each main phase particle (grain) is difficult to be oriented parallel to the stress direction.

[0193] For example, the pressure applied to the molded article during the thermoplastic working step (thermoplastic working pressure) can be between 35 MPa and 50 MPa. If the thermoplastic working pressure exceeds 50 MPa, it is difficult to form a plurality of crystal grains 8, and it is difficult for the crystal zones 8 of the plurality of crystal grains 8 to be oriented in a single direction (orientation direction D). For example, the time (thermoplastic working time) during which the thermoplastic working temperature and thermoplastic working pressure are maintained within the above ranges can be tens of seconds.

[0194] For example, Figure 5 As shown, the mold 10 used in the thermoplastic forming process is cylindrical in shape. Specifically, the mold 10 has a pair of circular end faces (the starting end face 10a and the ending end face 10b) and cylindrical side faces. A cavity 12 is formed within the mold 10, extending from the starting end face 10a toward the ending end face 10b and extending through the mold 10. Specifically, the inlet of the cavity 12 (the inlet for the molded body 20) is located on the starting end face 10a, while the outlet of the cavity 12 (the extrusion outlet for the molded body 20) is located on the ending end face 10b. The molded body 20 is introduced into the inlet of the cavity 12 on the starting end face 10a. The thermoforming pressure applied to the molded body 20 by the upper ram of the press causes the molded body 20 to be extruded from the outlet of the cavity 12 on the ending end face 10b. Specifically, the direction from the starting end face 10a toward the ending end face 10b is the extrusion direction Z of the molded body 20, and the direction of the thermoplastic forming pressure is equal to the extrusion direction Z. The starting end face 10 a and the terminal end face 10 b are parallel planes to each other, and the extrusion direction Z is perpendicular to the starting end face 10 a and the terminal end face 10 b.

[0195] The shape of the cavity 12 in the direction perpendicular to the extrusion direction Z (the direction parallel to the starting end face 10a and the terminal end face 10b) is a quadrilateral with all four corners being right angles. A pair of sides facing each other in the quadrilateral is referred to as a first side, and another pair of sides facing each other in the quadrilateral is referred to as a second side.

[0196] The length xa of the first side on the starting end surface 10 a (the entrance of the chamber 12 ) is longer than the length ya of the second side on the starting end surface 10 a (the entrance of the chamber 12 ).

[0197] The length xa of the first side gradually decreases along the extrusion direction Z, ultimately coinciding with the length xb of the first side at the terminal surface 10b (the outlet of the chamber 12). In other words, the length xb of the first side at the terminal surface 10b (the outlet of the chamber 12) is smaller than the length xa of the first side at the starting end surface 10a (the inlet of the chamber 12).

[0198] In contrast, the length ya of the second side gradually increases along the extrusion direction, ultimately coinciding with the length yb of the second side at the terminal surface 10b (the outlet of the chamber 12). In other words, the length yb of the second side at the terminal surface 10b (the extrusion outlet of the chamber 12) is greater than the length ya of the second side at the starting end surface 10a (the inlet of the chamber 12).

[0199] As a result of the decrease in the length xa of the first side along the extrusion direction Z and the increase in the length ya of the second side along the extrusion direction Z, the length xb of the first side at the exit of the cavity 12 becomes smaller than the length yb of the second side at the exit of the cavity 12. Furthermore, due to the changes in the lengths of the first and second sides along the extrusion direction Z, the opening area of ​​the cavity 12 in a direction perpendicular to the extrusion direction Z gradually decreases along the extrusion direction Z. In other words, the opening area of ​​the exit of the cavity 12 on the terminal end surface 10b is smaller than the opening area of ​​the entrance of the cavity 12 on the starting end surface 10a.

[0200] Due to the aforementioned changes in the shape and opening area of ​​cavity 12 along the extrusion direction Z, stress approximately or completely parallel to the first side of cavity 12 acts on molded article 20 passing through cavity 12. The stress exerted by cavity 12 on molded article 20 induces grain boundary sliding and rotation of the main phase grains within molded article 20. As a result, the c-axis of the main phase grains aligns along the stress direction (direction X of the first side). In other words, the easy magnetization axis direction C of the magnet substrate obtained by hot extrusion is approximately or completely aligned with the direction (direction X) of the first side on terminal surface 10b.

[0201] The deloading process subsequent to the thermoplastic processing process includes a first step and a second step subsequent to the first step.

[0202] In the first step, the magnet base material is heated while being pressed with a pressure p.

[0203] In the second step, the magnet base material is naturally cooled while being pressed with a pressure p. After the natural cooling, the pressure p applied to the magnet base material is released.

[0204] In either the first or second step, the magnet substrate is also pressurized by being clamped between a pair of indenters in a two-axis press. The pressure p applied to the magnet substrate is approximately or completely parallel to the easy magnetization axis C of the magnet substrate. In the first step, the temperature of the pair of indenters is maintained at a predetermined temperature (deload temperature t), and the magnet substrate is heated by the pair of indenters.

[0205] The pressure p applied to the magnet substrate during the deloading process may be greater than or equal to 35 MPa and less than or equal to 70 MPa, or greater than or equal to 35 MPa and less than or equal to 50 MPa. When the pressure p exceeds 70 MPa, it is difficult to form a plurality of crystal grains 8, and it is difficult for the crystal axis cza of the plurality of crystal grains 8 to be oriented in one direction (orientation direction D). Even when the deloading process is not performed, it is difficult to form a plurality of crystal grains 8, and it is difficult for the crystal axis cza of the plurality of crystal grains 8 to be oriented in one direction (orientation direction D). For example, the deloading temperature t may be greater than or equal to 25°C and less than or equal to 500°C. The magnet substrate is pressurized with the pressure p, and the time for maintaining the temperature of the magnet substrate at the deloading temperature t may be greater than or equal to 60 seconds and less than or equal to 600 seconds.

[0206] The magnet substrate obtained through the above steps can be a finished product of a hot-worked magnet. The magnet substrate after the grain boundary diffusion step described below can also be a finished product of a hot-worked magnet.

[0207] The following grain boundary diffusion process can also be performed after the deloading process. The grain boundary diffusion process is a process in which a diffusion material containing heavy rare earth elements is attached to the surface of the magnet substrate and the diffusion material and the magnet substrate are heated. By heating the magnet substrate with the diffusion material attached, the heavy rare earth elements in the diffusion material diffuse from the surface of the magnet substrate to the interior of the magnet substrate. Inside the magnet substrate, the heavy rare earth elements diffuse to the vicinity of the surface of the main phase particles via the grain boundaries. Near the surface of the main phase particles, a portion of the light rare earth elements (Nd, etc.) are replaced by heavy rare earth elements. Due to the local presence of heavy rare earth elements near the surface of the main phase particles and at the grain boundaries, the anisotropic magnetic field becomes locally larger near the grain boundaries, making it difficult to generate magnetization reversal nuclei near the grain boundaries. As a result, a hot-worked magnet with high coercive force is obtained.

[0208] For example, the temperature of the diffusion material and the magnet substrate in the grain boundary diffusion step (diffusion temperature) may be 550° C. to 900° C. For example, the time for maintaining the diffusion temperature within the above range (diffusion time) may be 1 minute to 1440 minutes.

[0209] The diffusion material may contain at least one heavy rare earth element selected from Tb and Dy. In addition to the heavy rare earth elements, the diffusion material may also contain at least one light rare earth element selected from Nd and Pr. The diffusion material may be, for example, a metal composed of one of the above elements, a hydride of one of the above elements, an alloy containing multiple elements, or a hydride of the alloy. The diffusion material may be a powder. In the grain boundary diffusion process, a slurry containing the diffusion material and an organic solvent may be applied to the surface of the magnet substrate. In the grain boundary diffusion process, the surface of the magnet substrate may also be covered with a sheet containing the diffusion material and an adhesive. In the grain boundary diffusion process, the surface of the magnet substrate may also be covered with an alloy foil (ribbon) composed of the diffusion material. The diffusion material does not necessarily contain the above-mentioned element M.

[0210] To promote diffusion of the diffusion material, the surface of the magnet substrate may be polished before the grain boundary diffusion step. To remove the diffusion material remaining on the surface of the magnet substrate after the grain boundary diffusion step, the surface of the magnet substrate may be polished after the grain boundary diffusion step.

[0211] The size and shape of the magnet substrate can be adjusted by cutting and grinding the substrate. A passive layer can be formed on the surface of the magnet substrate through oxidation or chemical treatment. The surface of the magnet substrate can also be covered with a protective film such as a resin film. Passive layers or protective films improve the corrosion resistance of hot-processed magnets.

[0212] The present disclosure is not necessarily limited to the above-described embodiment. Various modifications of the present disclosure can be made without departing from the spirit of the present disclosure, and such modifications are also included in the present disclosure.

[0213] [Example]

[0214] The present disclosure is described in detail by the following examples and comparative examples. The present disclosure is not limited to the following examples.

[0215] <Production of Hot-Worked Magnets>

[0216] (Example 1)

[0217] Each step of the following Example 1 was carried out in a non-oxidizing atmosphere (Ar gas).

[0218] In the ribbon production process, alloy powder (alloy ribbon) is produced from a molten metal containing various raw metals through ultra-rapid solidification. The molten metal used in the ribbon production process contains Nd, Fe, Co, Ga, Cu, and B. Ga and Cu correspond to the element M mentioned above.

[0219] The contents of the elements in the molten metal of Example 1 are the values ​​shown in Table 1 below.

[0220] During the hot forming process, the alloy powder in the mold is heated and compressed to produce a compact. The compact is a rectangular parallelepiped with dimensions of 22 mm x 11 mm x 30 mm. The hot forming temperature is 660°C, the hot forming pressure is 100 MPa, and the hot forming time is 240 seconds.

[0221] The thermoplastic processing step following the thermoforming step is performed. In the thermoplastic processing step, the mold 10 ( Figure 5 The magnet substrate was produced by hot extrusion molding of the molded body using the mold 10 shown in FIG. The outline of the hot plastic processing step is as described in the above embodiment.

[0222] The inlet of the cavity 12 of the mold 10 and the outlet of the cavity 12 of the mold 10 are both rectangular.

[0223] The length xa of the first side of the inlet of the chamber 12 is 22.0 mm, and the length ya of the second side of the inlet of the chamber 12 is 11.0 mm.

[0224] The length xb of the first side of the outlet of the chamber 12 is 5.5 mm, and the length yb of the second side of the outlet of the chamber 12 is 30.0 mm.

[0225] The plastic working rate (unit: %) in the hot plastic working step is defined as {(xa-xb) / xa}×100. That is, the plastic working rate is {(22.0-5.5) / 22.0}×100, or 75%.

[0226] The temperature of the die 10 in the hot plastic working step was 750° C. The extrusion speed in the hot extrusion molding was 0.1 mm / sec. The hot plastic working pressure (maximum pressure Pmax) was the value shown in Table 1 below.

[0227] A deloading step is performed following the hot plastic working step. The deloading step is outlined in the above embodiment. The pressure p applied to the magnet substrate during the deloading step is the value shown in Table 1 below. The deloading temperature t is 480°C. The magnet substrate is pressurized at the pressure p and heated at the deloading temperature t for 300 seconds.

[0228] The grain boundary diffusion process using the diffusion material was not performed.

[0229] The hot-worked magnet of Example 1 was produced by the above method.

[0230] (Examples 2 to 9, Comparative Examples 1 to 3)

[0231] The content of each element in the molten metal of each of Examples 2 to 9 and Comparative Examples 1 to 3 is the value shown in the following Table 1. Only the molten metal of Example 4 contains Pr and Dy in addition to Nd, Fe, Co, Ga, Cu, and B.

[0232] The maximum pressure Pmax in the hot plastic working step of each of Examples 2 to 9 and Comparative Examples 1 to 3 is the value shown in Table 1 below.

[0233] The pressure p in the deloading step in each of Examples 2 to 9 and Comparative Example 2 was the value shown in Table 1 below. The deloading step was not performed in Comparative Examples 1 and 3. That is, in Comparative Examples 1 and 3, the magnet substrate was not heated or pressurized after the hot plastic working step, but was naturally cooled.

[0234] Hot-worked magnets of Examples 2 to 9 and Comparative Examples 1 to 3 were produced by the same method as in Example 1 except for the above-mentioned matters.

[0235] <Analysis of Hot-Worked Magnets>

[0236] The backscattered electron image of the cross section of the hot-processed magnet of Example 1 was taken using a scanning electron microscope (SEM). Furthermore, the composition of the cross section of the hot-processed magnet was analyzed using the energy dispersive X-ray spectrometer (SEM-EDS) included in the SEM. The cross section analyzed by SEM and SEM-EDS is parallel to the easy magnetization axis direction C of the hot-processed magnet. In other words, the backscattered electron image of the cross section of the hot-processed magnet is parallel to the easy magnetization axis direction C. The multiple backscattered electron images of Example 1 are shown in FIG. Figure 6 、 Figure 7A ,and Figure 7B Shown in.

[0237] The results of the above-mentioned analyses using SEM have shown that the hot-worked magnet has the following characteristics.

[0238] The composition of the hot-worked magnet is consistent with the composition of the molten metal (the composition shown in Table 1 below).

[0239] Hot-processed magnets contain multiple main phase particles (Nd2T 14 B's grains).

[0240] Hot-processed magnets contain grain boundary phases located between a plurality of main phase particles.

[0241] Each main phase grain contains at least Nd as R and at least Fe as T.

[0242] A number of flat main phase particles were observed in the cross section of the hot-processed magnet.

[0243] The short axis of the flat main phase grains is approximately parallel or completely parallel to the easy magnetization axis direction C.

[0244] The long axis of the flat main phase grains is approximately perpendicular or completely perpendicular to the easy magnetization axis direction C.

[0245] A plurality of flat main phase grains are stacked along the easy magnetization axis direction C.

[0246] like Figure 7A As shown in region 7a of the backscattered electron image, multiple equiaxed crystals (main phase particles) are observed in the cross section of the hot-processed magnet. These equiaxed crystals are surrounded by grain boundary phases. At least some of these equiaxed crystals are in contact with the grains (containing Nd and Cu) described later.

[0247] like Figure 7B As shown in region 7b included in the backscattered electron image of , multiple columnar crystals (main phase grains) extending along the easy magnetization axis direction C are observed in the cross section of the hot-processed magnet. At least some of these columnar crystals are in contact with the grains (grains containing Nd and Cu) described later.

[0248] The following method was used to measure the average width S (minor axis length) of multiple primary phase grains (primary particles) in the direction of the easy magnetization axis C from a backscattered electron image of a cross section of a hot-processed magnet. The longitudinal width (width in the direction of the easy magnetization axis C) of the backscattered electron image, for which the average width S was measured, was 2.54 μm, and the lateral width of the backscattered electron image, for which the average width S was measured, was 1.90 μm. Multiple representative locations within the backscattered electron image were selected and captured at high magnification. The length of the minor axis of each primary phase grain (primary particle) within the high-magnification backscattered electron image was measured. The shape of each primary phase grain was approximated by the smallest rectangle circumscribing the primary phase grain. The length of the long side of this rectangle was considered the length of the major axis of the primary phase grain, and the length of the short side of the rectangle was considered the length of the minor axis of the primary phase grain.

[0249] The average values ​​(unit: nm) of the widths S (length of the minor axis) of the plurality of main phase particles (primary particles) of Example 1 are shown in Table 2 below.

[0250] A TEM image of the cross section of the hot-processed magnet of Example 1 was taken using a transmission electron microscope (TEM). Furthermore, the cross section of the hot-processed magnet (the cross section where the TEM image was taken) was further observed using STEM, and the composition of the cross section was analyzed using the energy dispersive X-ray spectroscopy (STEM-EDS) device included in the STEM. The cross section analyzed by TEM and STEM-EDS is parallel to the easy magnetization axis direction C of the hot-processed magnet. That is, the TEM image of the cross section of the hot-processed magnet is parallel to the easy magnetization axis direction C. The TEM image of Example 1 is Figure 8 Shown in.

[0251] Figure 8 Asterisks (*) with numbers 1 to 7 in between indicate the positions of measurement points 1 to 7. The composition at each of measurement points 1 to 7 was analyzed by STEM-EDS. Electron beam diffraction patterns were measured at each of measurement points 1 to 7 by selected area electron diffraction (SAED).

[0252] The electron beam diffraction pattern at measurement point 1 is Figure 9A Shown.

[0253] The electron beam diffraction pattern at measurement point 2 is Figure 9B Shown.

[0254] The electron beam diffraction pattern at point 3 is Figure 9C Shown.

[0255] The electron beam diffraction pattern at point 4 is Figure 10A Shown.

[0256] The electron beam diffraction pattern at point 5 is measured at Figure 10B Shown.

[0257] The electron beam diffraction pattern at point 6 is measured at Figure 10C Shown.

[0258] The electron beam diffraction pattern at point 7 is measured at Figure 9D Shown.

[0259] The three numerical values ​​recorded at each point in each electron beam diffraction pattern are the orientations (Miller indices) of the lattice planes corresponding to each point.

[0260] The results of the above-mentioned analyses using TEM and STEM have shown that the hot-worked magnet has the following characteristics.

[0261] At each of the measurement points 1 to 3 and 7, grains containing Nd and Cu were detected. That is, a plurality of grains containing Nd and Cu were detected. For example, Nd 44.4 Cu 44.0 Fe 2.1 Co 9.5 The chemical formula of the grains, and Nd 43.7 Cu 44.3 Fe 2.8 Co 9.2 The unit of each numerical value in these chemical formulas is atomic %.

[0262] NdO was detected at measurement point 4.

[0263] Main phase particles were detected at each of measurement points 5 and 6 .

[0264] The concentration of Nd (unit: atomic %) in each crystal grain containing Nd and Cu is higher than the concentration of Nd in each main phase grain.

[0265] Each crystal grain containing Nd and Cu is in contact with one or more main phase grains.

[0266] Each crystal grain containing Nd and Cu is a cubic crystal or an orthorhombic crystal.

[0267] The space group showing the symmetry of the crystal structure of each crystal grain containing Nd and Cu is Pnma.

[0268] The electron diffraction patterns of the measurement points 1 to 3 and 7 derived from a plurality of crystal grains containing Nd and Cu were compared with each other. The results of the comparison are as follows.

[0269] The zone axes (<100>) of the plurality of crystal grains containing Nd and Cu are oriented in one direction. In other words, the zone axes (<100>) of the plurality of crystal grains containing Nd and Cu are substantially or completely parallel to each other.

[0270] The angle between any pair of zone axes (<100>) of a plurality of crystal grains containing Nd and Cu is at most 3°.

[0271] The (010) planes of the plurality of crystal grains containing Nd and Cu are oriented in the same direction. In other words, the (010) planes of the plurality of crystal grains containing Nd and Cu are substantially or completely parallel to each other.

[0272] The area fraction AR of the cross section of multiple grains containing Nd and Cu is measured using a backscattered electron image of the cross section of a hot-processed magnet. The details of the method for measuring the area fraction AR are as described in the above embodiment. Phases located in the grain boundary phase, connected to one or more main phase particles, containing Nd and Cu, and clearly identified as main phase particles and other grain boundary phases under contrast are regarded as grains containing Nd and Cu. The longitudinal width (width in the direction of the easy magnetization axis C) of the backscattered electron image of the area fraction AR was measured to be 12.7 μm, and the lateral width of the backscattered electron image of the area fraction AR was measured to be 9.5 μm. ImageJ, which is a public domain image processing software, was used in the measurement of the area fraction AR.

[0273] The area fraction AR (unit: %) of Example 1 is shown in Table 2 below.

[0274] Electron beam diffraction patterns of each of a pair of mutually contacting crystal grains and main phase grains in the TEM image were measured. Based on these electron beam diffraction patterns, the angle θ between the <001> of the crystal grains and the <001> of the main phase grains was determined.

[0275] The angle θ (unit: °) of Example 1 is shown in Table 2 below.

[0276] Five grain boundary phases containing one or more grains containing Nd and Cu were randomly selected from a TEM image of a cross section of a hot-worked magnet. The width W of each grain boundary phase was measured in the TEM image, and the average value of the width W of the five grain boundary phases was calculated. The width W of the grain boundary phase is the width of the grain boundary phase in the direction of the easy magnetization axis C. The longitudinal width (width in the direction of the easy magnetization axis C) of the grain boundary phase measured in the backscattered electron image was 2.54 μm, and the lateral width (width W) of the grain boundary phase measured in the backscattered electron image was 1.90 μm.

[0277] The average value (unit: nm) of the width W of the grain boundary phase in Example 1 is shown in Table 2 below.

[0278] The coercive force (HcJ), remanent flux density (Br), and squareness ratio (Hk / HcJ) of the hot-worked magnet of Example 1 were measured. The coercive force, remanent flux density, and squareness ratio were measured using a BH tracer. The coercive force was measured at 23°C, and the remanent flux density was measured at room temperature. The squareness ratio was measured at 23°C. The coercive force (unit: kA / m), remanent flux density (unit: T), and squareness ratio (unit: %) of Example 1 are shown in Table 2 below.

[0279] The hot-worked magnets of Examples 2 to 9 and Comparative Examples 1 to 3 were analyzed and measured in the same manner as in Example 1. The results of the analyses and measurements of Examples 2 to 9 and Comparative Examples 1 to 3 are shown in Tables 2 and 3 below.

[0280] In each of Examples 1, 5 to 7, and Comparative Example 1, the crystal grain A was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0281] In Example 2, the crystal grain B was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0282] In Example 3, the crystal grain C was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0283] In Example 4, the crystal grain D was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0284] In Comparative Example 2, the crystal grain E was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0285] In Example 8, the crystal grain F was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0286] In Comparative Example 3, the crystal grain G was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0287] In Example 9, the crystal grain H was detected as one of the plurality of crystal grains in contact with one or more main phase grains.

[0288] The rare earth element R, transition metal element T, and element M contained in each of the crystal grains A, B, C, D, E, F, G, and H are shown in Table 3 below.

[0289] The contents of R, T, and M in each of the crystal grains A, B, C, D, E, F, G, and H (unit: mass %) are shown in Table 3 below.

[0290] The space groups representing the symmetry of the crystal structures of the respective crystal grains A, B, C, D, E, F, G, and H are shown in Table 3 below.

[0291] The crystal structures of each of the grains A, B, C, D, E, F, G, and H are shown in Table 3 below. "fcc" in Table 3 below refers to a face-centered cubic lattice structure (cubic crystal). "tet" in Table 3 below refers to a tetragonal crystal. "bcc" in Table 3 below refers to a body-centered cubic lattice structure (cubic crystal). "ort" in Table 3 below refers to an orthorhombic crystal.

[0292] The term "oriented" listed in the "Zone Axis" column in Table 2 below means that the angle between any pair of zone axes (<100>) of the plurality of crystal grains containing Nd and Cu is 5° or less. In other words, "oriented" means that the zone axes (<100>) of the plurality of crystal grains containing Nd and Cu are oriented in one direction.

[0293] The term "non-oriented" listed in the "Zone Axis" column in Table 2 below means that the angle between any pair of zone axes (<100>) of the plurality of crystal grains containing Nd and Cu is greater than 5°. In other words, "non-oriented" means that the zone axes (<100>) of the plurality of crystal grains containing Nd and Cu are not oriented in one direction.

[0294] The hot-worked magnets of Examples 2 to 9 have the same characteristics as those of Example 1, except for the differences shown in Table 2 and Table 3 below.

[0295] The hot-worked magnets of Comparative Examples 1 and 3 each include multiple crystal grains containing Nd and Cu. However, in Comparative Examples 1 and 3, the crystal zones (<100>) of the multiple crystal grains containing Nd and Cu are not aligned in the same direction. Other than this, the hot-worked magnets of Comparative Examples 1 and 3 have the same characteristics as those of Example 1.

[0296] In the hot-worked magnet of Comparative Example 2, multiple grains containing Nd and Cu were not detected. In the case of Comparative Example 2, multiple amorphous phases containing Nd and Cu were detected in the grain boundary phase. Except for these points, the hot-worked magnet of Comparative Example 2 has the same characteristics as Example 1. For Comparative Example 2 only, the average value of the width W of the grain boundary phase refers to the average value of the width of the grain boundary phase that does not include grains containing Nd and Cu. In other words, for Comparative Example 2 only, the average value of the width W of the grain boundary phase refers to the average value of the width of the grain boundary phase that includes the amorphous phase containing Nd and Cu. For Comparative Example 2 only, the AR described in Table 2 below refers to the area fraction of the cross section of the multiple amorphous phases, not the area fraction of the cross section of the multiple grains.

[0297] The Nd content in the raw material (alloy strip) of Comparative Example 2 is lower than that in Example 1. Therefore, the volume fraction of the Nd-rich phase in the molded body formed from the alloy strip is reduced, and the grain boundary phase is difficult to liquefy during the hot plastic processing step. Therefore, the formation of the grain boundary phase (liquid phase) in the hot plastic processing step is insufficient, which hinders the proper orientation of the main phase particles. As a result, the residual magnetic flux density is reduced. The grain boundary phase of Comparative Example 2 is an oxide of the Nd-rich phase. Therefore, even if the magnet substrate is cooled while maintaining the load (pressure p) in the deloading step after the hot plastic processing step, the crystal axis of the multiple grains in the grain boundary phase cannot be oriented.

[0298] [Table 1]

[0299]

[0300] [Table 2]

[0301]

[0302] [Table 3]

[0303]

[0304] [Industrial Applicability]

[0305] For example, the RTB-based hot-processed magnet according to one aspect of the present disclosure can be suitably used as a material for motors mounted in electric vehicles or hybrid vehicles.

Claims

1. A hot-processed magnet, wherein: The hot working magnet contains rare earth element R, transition metal element T, and boron. The hot working magnet contains Nd as the rare earth element R, The hot working magnet contains Fe as the transition metal element T, The hot-working magnet contains a plurality of main phase particles and a grain boundary phase located between the plurality of main phase particles. The plurality of main phase particles contain the rare earth element R, the transition metal element T, and boron, The grain boundary phase comprises a plurality of grains, A plurality of the crystal grains are in contact with at least one of the main phase particles. The crystal zone axes of the plurality of crystal grains are oriented along one direction.

2. The hot-processed magnet according to claim 1, wherein The plurality of crystal grains are non-magnetic.

3. The hot-processed magnet according to claim 1, wherein The area fraction of the cross-section of the plurality of crystal grains in the cross-section of the hot-worked magnet is 3% or more and 8% or less, The cross section of the hot working magnet is parallel to the easy magnetization axis direction of the hot working magnet.

4. The hot-processed magnet according to claim 1, wherein A plurality of the crystal grains contain the rare earth element R and the element M, The element M is at least one selected from Cu, Ga, Zn, Ni, and Cr, The content of the rare earth element R in the plurality of crystal grains is 50 mass % or more and 98 mass % or less, The content of the transition metal element T in the plurality of crystal grains is 0 mass % or more and 50 mass % or less, The content of the element M in the plurality of crystal grains is greater than 0 mass % and is 35 mass % or less.

5. The hot-processed magnet according to claim 1, wherein The plurality of crystal grains are respectively cubic, tetragonal, or orthorhombic. The crystal zone axis is <100>, <010>, or <001>.

6. The hot-processed magnet according to claim 1, wherein A plurality of the grains contain Nd and Cu, The plurality of crystal grains are respectively cubic, tetragonal, or orthorhombic. The space group representing the symmetry of the crystal structure of the plurality of the grains is Pnma, I4 / mcm, Fm-3m, or Ia-3.

7. The hot-processed magnet according to claim 1, wherein The width of the grain boundary phase including one or more crystal grains is 4 nm or more and 500 nm or less in the easy magnetization axis direction of the hot-worked magnet.

8. The hot-processed magnet according to claim 1, wherein One or more main phase grains in contact with one or more crystal grains include at least one of columnar crystals and equiaxed crystals.

9. The hot-processed magnet according to claim 1, wherein The hot working magnet further contains element M, The element M is at least one selected from Cu, Ga, Zn, Ni, and Cr, The content of the rare earth element R in the hot working magnet is 26.00 mass % or more and 32.00 mass % or less, The boron content in the hot working magnet is 0.77 mass % or more and 1.15 mass % or less. The content of the element M in the hot-working magnet is 0.67 mass % or more and 7.30 mass % or less.

10. The hot-processed magnet according to claim 1, wherein The width of each of the plurality of main phase grains in the easy magnetization axis direction of the hot-worked magnet is represented by S. When the width of each of the plurality of main phase grains in a direction perpendicular to the easy magnetization axis direction is represented by L, The S is smaller than the L, L / S is 2 or more and 10 or less, The S is greater than or equal to 20 nm and less than or equal to 200 nm.

11. The hot-processed magnet according to claim 1, wherein The angle between the <100> angles of the plurality of crystal grains and the <100> angles of the one or more main phase grains is 0° or more and 10° or less.

12. The hot-processed magnet according to claim 1, wherein The angle between the <010> of the plurality of crystal grains and the <010> of the one or more main phase grains is 0° or more and 10° or less.

13. The hot-processed magnet according to claim 1, wherein The angle between the <001> of the plurality of crystal grains and the <001> of the one or more main phase grains is 0° or more and 10° or less.

14. The hot-processed magnet according to claim 1, wherein The one direction in which the zone axes of the plurality of crystal grains are oriented is parallel to the zone axes of one or more main phase grains in contact with the plurality of crystal grains.

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