GRAIN BOUNDARY DIFFUSION METHOD FOR BULK RARE EARTH PERMANENT MAGNETIC MATERIAL

Abstract

A grain boundary diffusion method for a bulk rare earth permanent magnetic material includes the following steps: (1) fabricating an initial magnet by a sintering, hot pressing, or hot deformation process; (2) loading a grain boundary diffusion alloy source on a surface of the magnet through electrodeposition, chemical vapor deposition (CVD), physical vapor deposition (PVD), direct physical contact, or adhesive bonding; and (3) placing the initial magnet loaded with the grain boundary diffusion alloy source in a SPS device, and heating to obtain a final magnet. The current, plasma, and pressure in an SPS process can be controlled to significantly improve elemental diffusion coefficient and enhance the diffusion depth. The bulk rare earth permanent magnetic material undergoing grain boundary diffusion fabricated in the present disclosure has a significant increase in magnetic properties that catering to commercial demands for industrial production.

Claims

1. A grain boundary diffusion method for a bulk rare earth permanent magnetic material, comprising the following steps: (1) fabricating an initial magnet by a sintering, hot pressing, or hot deformation process, wherein the initial magnet has a composition of (R′.sub.aA′.sub.1-a).sub.bQ′.sub.balM′.sub.cB.sub.d, wherein R′ is one or more selected from the group consisting of high-abundance rare earth elements La, Ce, and Y; A′ is one or more selected from the group consisting of lanthanide rare earth elements other than La, Ce, and Y; Q′ is one or more selected from the group consisting of Fe, Co, and Ni; M′ is one or more selected from the group consisting of Al, Cr, Cu, Zn, Ga, Ge, Mn, Mo, Nb, P, Pb, Si, Ta, Ti, V, Zr, O, F, N, C, S, and H; B is boron; and a, b, c, and d satisfy the following relationships: 0<a<0.8, 23≤b≤33, 0.5≤c≤8, and 0.9≤d≤1.4; (2) loading a grain boundary diffusion alloy source on a surface of the initial magnet, wherein the grain boundary diffusion alloy source has a composition of R″.sub.uM″.sub.1-u, wherein R″ is one or two selected from the group consisting of light rare earth elements Nd and Pr; M″ is one or more selected from the group consisting of Fe, Co, Ni, Al, Cr, Cu, Zn, Ga, Ge, Mn, Mo, Si, Ti, O, F, and H; and u satisfies the following relationship: 0<u<1; (3) placing the initial magnet loaded with the grain boundary diffusion alloy source in a spark plasma sintering (SPS) device, and heating the initial magnet loaded with the grain boundary diffusion alloy source at a heating rate of 20° C./min to 400° C./min in the SPS device to allow a grain boundary diffusion for 20 min to 180 min at a diffusion temperature of 400° C. to 900° C., a pressure of 2 MPa to 50 MPa, and a vacuum degree of less than 10.sup.−3 Pa to obtain a final magnet.

2. The grain boundary diffusion method according to claim 1, wherein in step (2), loading the grain boundary diffusion alloy source is achieved by an electrodeposition, a chemical vapor deposition (CVD), a physical vapor deposition (PVD), a direct physical contact, or an adhesive bonding.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] The present disclosure will be further described below in conjunction with specific examples, but the present disclosure is not limited to the following examples.

Example 1

[0016] An initial magnet (Pr.sub.0.12Nd.sub.0.48Ce.sub.0.4).sub.30.8Fe.sub.balCu.sub.0.3Al.sub.0.2Ga.sub.0.2Zr.sub.0.3B.sub.1.05 with a height of 25 mm was fabricated by a sintering process; a grain boundary diffusion alloy powder Nd.sub.80Al.sub.20 was loaded on a surface of the initial magnet through direct contact; and the initial magnet was placed in a SPS device and then heated at a heating rate of 400° C./min to allow grain boundary diffusion for 40 min at a diffusion temperature of 700° C. and a pressure of 20 MPa to obtain a final magnet with the following magnetic properties: B.sub.r=12.4 kG, h.sub.cj=15.5 kOe, and (BH).sub.max=36.6 MGOe.

Example 2

[0017] An initial magnet (Nd.sub.0.4La.sub.0.2Ce.sub.0.4).sub.32Fe.sub.balNb.sub.0.3Ti.sub.0.2Ga.sub.0.5Co.sub.0.3B.sub.0.9 with a height of 20 mm was fabricated by a sintering process; a grain boundary diffusion alloy powder NdH.sub.3 was loaded on a surface of the initial magnet through polyvinylpyrrolidone (PVP) adhesive bonding; and the initial magnet was placed in an SPS device and then heated at a heating rate of 20° C./min to allow grain boundary diffusion for 100 min at a diffusion temperature of 900° C. and a pressure of 50 MPa to obtain a final magnet with the following magnetic properties: B.sub.r=12.2 kG, h.sub.cj=12.5 kOe, and (BH).sub.max=33.4 MGOe.

Example 3

[0018] An initial magnet (Nd.sub.0.5Y.sub.0.1Ce.sub.0.4).sub.30Fe.sub.balZr.sub.0.15Cu.sub.0.3Co.sub.0.5Al.sub.0.2B.sub.1.01 with a height of 10 mm was fabricated by a hot deformation process; a grain boundary diffusion alloy powder Nd.sub.70Cu.sub.30 was loaded on a surface of the initial magnet through PVP adhesive bonding; and the initial magnet was placed in an SPS device and then heated at a heating rate of 400° C./min to allow grain boundary diffusion for 60 min at a diffusion temperature of 600° C. and a pressure of 2 MPa to obtain a final magnet with the following magnetic properties: B.sub.r=11.3 kG, H.sub.cj=16.5 kOe, and (BH).sub.max=28.2 MGOe.

Example 4

[0019] An initial magnet (Pr.sub.0.18Nd.sub.0.72Ce.sub.0.1).sub.36Fe.sub.balMo.sub.0.15Al.sub.0.15Cu.sub.0.2Zr.sub.0.2B.sub.0.95 with a height of 18 mm was fabricated by a sintering process; a grain boundary diffusion alloy source Dy.sub.20Pr.sub.60Al.sub.20 was loaded on a surface of the initial magnet through magnetron sputtering; and the initial magnet was placed in an SPS device and then heated at a heating rate of 400° C./min to allow grain boundary diffusion for 180 min at a diffusion temperature of 800° C. and a pressure of 25 MPa to obtain a final magnet with the following magnetic properties: B.sub.r=12.5 kG, H.sub.cj=25.4 kOe, and (BH).sub.max=39.2 MGOe.

Example 5

[0020] An initial magnet (Nd.sub.0.2Ce.sub.0.8).sub.26Fe.sub.balZr.sub.0.1Cu.sub.0.2Co.sub.0.5Al.sub.0.3Si.sub.0.1B.sub.1.0 with a height of 8 mm was fabricated by a hot deformation process; a grain boundary diffusion alloy powder Pr.sub.70Cu.sub.30 was loaded on a surface of the initial magnet through magnetron sputtering; and the initial magnet was placed in an SPS device and then heated at a heating rate of 100° C./min to allow grain boundary diffusion for 20 min at a diffusion temperature of 650° C. and a pressure of 5 MPa to obtain a final magnet with the following magnetic properties: B.sub.r=10.1 kG, H.sub.cj=11.2 kOe, and (BH).sub.max=20.3 MGOe.

Example 6

[0021] An initial magnet (Pr.sub.0.14Nd.sub.0.56La.sub.0.1Ce.sub.0.2).sub.36Fe.sub.balGa.sub.0.35Al.sub.0.25Cu.sub.0.2Zr.sub.0.15B.sub.0.93 with a height of 60 mm was fabricated by a sintering process; a grain boundary diffusion alloy source Pr.sub.80Al.sub.20 was loaded on a surface of the initial magnet through magnetron sputtering; and the initial magnet was placed in an SPS device and then heated at a heating rate of 400° C./min to allow grain boundary diffusion for 180 min at a diffusion temperature of 700° C. and a pressure of 25 MPa to obtain a final magnet with the following magnetic properties: B.sub.r=12.6 kG, H.sub.cj=18.2 kOe, and (BH).sub.max=38.2 MGOe.