METHOD FOR IMPROVING MAGNETIC PROPERTIES OF CERIUM-YTTRIUM-RICH RARE EARTH PERMANENT MAGNET

Abstract

A method for improving magnetic properties of a Ce—Y-rich rare earth permanent magnet is provided, and the Ce—Y-rich rare earth permanent magnet is subjected to pressurized heat treatment to improve magnetic properties. The method includes: preparing a pristine magnet through a sintering process; and placing the pristine magnet into a pressurized heat treatment device and performing pressurized heat treatment under the protection of an argon atmosphere. By regulating parameters such as pressure, temperature and holding time in the heat treatment process, element diffusion in the Ce—Y-rich permanent magnet is promoted, and coercivity, remanence, magnetic energy product and temperature stability of the Ce—Y-rich permanent magnet are improved. The method has advantages of a simple process with low energy consumption, a substitution amount of rare earths Ce—Y up to 90 wt % while having excellent magnetic performance, so that a way for efficient utilization of high-abundance rare earths Ce and Y is provided.

Claims

1. A method for improving magnetic properties of a cerium-yttrium-rich (Ce—Y-rich) rare earth permanent magnet, comprising: preparing a pristine magnet through a sintering process, wherein the pristine magnet is rich in high-abundance rare earths Ce—Y and comprises components, in mass percent, of [(Y.sub.aCe.sub.1-a).sub.bRE.sub.1-b].sub.cFe.sub.100-c-d-eM.sub.dB.sub.c, where Y is yttrium element, Ce is cerium element, RE is one or more selected from the group consisting of neodymium (Nd), praseodymium (Pr), gadolinium (Gd) and holmium (Ho), Fe is iron element, M is one or more selected from the group consisting of aluminum (Al), cobalt (Co), chromium (Cr), copper (Cu), gallium (Ga), manganese (Mn), molybdenum (Mo), niobium (Nb), nickel (Ni), silicon (Si), tantalum (Ta), titanium (Ti), vanadium (V) and zirconium (Zr), B is boron element, and a, b, c, d, e satisfy relationships that 0.3≤a≤0.7, 0.4≤b≤0.9, 26≤c≤34, 0.5≤d≤2, and 0.85≤e≤1.15; placing the pristine magnet into a pressurized heat treatment device, vacuumizing to a vacuum degree less than 10.sup.−3 Pa, introducing argon gas for protection and performing pressurized heat treatment with a heat treatment temperature in a range of 400˜800 degrees Celsius (° C.), an applied pressure in a range of 0.5˜10 MPa and a heat preservation time in a range of 3˜10 hours (h), to obtain a resultant magnet.

2. The method as claimed in claim 1, wherein the high-abundance rare earths Ce—Y are 40%˜90% in mass percent of total rare earths in the pristine magnet.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

[0016] The present disclosure will be further described in combination with concrete embodiments, but the present disclosure is not limited to the following embodiments.

Embodiment 1

[0017] A pristine magnet of [Y.sub.0.3Ce.sub.0.7).sub.0.5Nd.sub.0.5].sub.30.5Fe.sub.67.11Co.sub.1.1Al.sub.0.2Zr.sub.0.09B.sub.1 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 800° C., the applied pressure is 0.5 MPa, and the heat preservation time is 8 h. For the resultant magnet, magnetic properties are B.sub.r=12.9 kG, H.sub.cj=11.4 kOe, (BH).sub.max=38.3 MGOe.

Comparative Embodiment 1

[0018] A pristine magnet of [(Y.sub.0.3Ce.sub.0.7).sub.0.5Nd.sub.0.5].sub.30.5Fe.sub.67.11Co.sub.1.1Al.sub.0.2Zr.sub.0.09B.sub.1 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a normal pressure heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform normal pressure heat treatment to obtain a resultant magnet. The heat treatment temperature is 800° C., and the heat preservation time is 8 h. For the resultant magnet, magnetic properties are B.sub.r=12.6 kG, H.sub.cj=8.9 kOe, (BH).sub.max=36.1 MGOe.

Embodiment 2

[0019] A pristine magnet of [(Y.sub.0.4Ce.sub.0.6).sub.0.5Nd.sub.0.5].sub.30.5Fe.sub.67.11Co.sub.0.8Cu.sub.0.2Al.sub.0.25Zr.sub.0.14B.sub.1 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 500° C., the applied pressure is 3 MPa, and the heat preservation time is 4 h. For the resultant magnet, magnetic properties are B.sub.r=13.1kG, H.sub.cj=11.6 kOe, (BH).sub.max=41.1 MGOe.

Comparative Embodiment 2

[0020] A pristine magnet of [(Y.sub.0.4Ce.sub.0.6).sub.0.5Nd.sub.0.5].sub.30.5Fe.sub.67.11Co.sub.0.8Cu.sub.0.2Al.sub.0.25Zr.sub.0.14B.sub.1 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a normal pressure heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform normal pressure heat treatment to obtain a resultant magnet. The heat treatment temperature is 500° C., and the heat preservation time is 4 h. For the resultant magnet, magnetic properties are B.sub.r=12.8 kG, H.sub.cj=9.0 kOe, (BH).sub.max=38.3 MGOe.

Embodiment 3

[0021] A pristine magnet of [(Y.sub.0.4Ce.sub.0.6).sub.0.7Nd.sub.0.3].sub.31Fe.sub.66.45Co.sub.0.8Al.sub.0.2Ga.sub.0.25Cu.sub.0.25Nb.sub.0.1B.sub.0.95 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 400° C., the applied pressure is 0.8 MPa, and the heat preservation time is 10 h. For the resultant magnet, magnetic properties are B.sub.r=12.3 kG, H.sub.cj=9.1 kOe, (BH).sub.max=35.8 MGOe.

Comparative Embodiment 3

[0022] A pristine magnet of (Ce.sub.0.7Nd.sub.0.3).sub.31Fe.sub.66.45Co.sub.0.8Al.sub.0.2Ga.sub.0.25Cu.sub.0.25Nb.sub.0.1B.sub.0.95 rich in Ce is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 400° C., the applied pressure is 0.8 MPa, and the heat preservation time is 10 h. For the resultant magnet, magnetic properties are B.sub.r=12.0 kG, H.sub.cj=6.7 kOe, (BH).sub.max=32.9 MGOe.

Embodiment 4

[0023] A pristine magnet of [Y.sub.0.7Ce.sub.0.3).sub.0.4Nd.sub.0.43Pr.sub.0.12Gd.sub.0.05].sub.31.0Fe.sub.67.01Co.sub.0.39Cu.sub.0.15Al.sub.0.15Ga.sub.0.2Nb.sub.0.1B.sub.1 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 650° C., the applied pressure is 10 MPa, and the heat preservation time is 3 h. For the resultant magnet, magnetic properties are B.sub.r=13.4 kG, H.sub.cj=12.8 kOe, (BH).sub.max=43.5 MGOe.

Comparative Embodiment 4

[0024] A pristine magnet of [(Y.sub.0.2Ce.sub.0.8).sub.0.4Nd.sub.0.43Pr.sub.0.12Gd.sub.0.05].sub.31.0Fe.sub.67.01Co.sub.0.39Cu.sub.0.15Al.sub.0.15Ga.sub.0.2Nb.sub.0.1B.sub.1 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 650° C., the applied pressure is 10 MPa, and the heat preservation time is 3 h. For the resultant magnet, magnetic properties are B.sub.r=13.0 kG, H.sub.cj=10.8 kOe, (BH).sub.max=41.3 MGOe.

Embodiment 5

[0025] A pristine magnet of [(Y.sub.0.3Ce.sub.0.7).sub.0.9Pr.sub.0.1].sub.31Fe.sub.66.39Co.sub.0.5Zr.sub.0.15Al.sub.0.3Ga.sub.0.5Cu.sub.0.25B.sub.0.91 rich in Ce—Y is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 480° C., the applied pressure is 3 MPa, and the heat preservation time is 3.5 h. For the resultant magnet, magnetic properties are that B.sub.r=11.6 kG, H.sub.cj=6.1 kOe, (BH).sub.max=30.1 MGOe.

Comparative Embodiment 5

[0026] A pristine magnet of (Ce.sub.0.9Pr.sub.0.1).sub.31Fe.sub.66.39Co.sub.0.5Zr.sub.0.15Al.sub.0.3Ga.sub.0.5Cu.sub.0.25B.sub.0.91 rich in Ce is prepared by a sintering process, and subsequently the pristine magnet is placed into a pressurized heat treatment device. It is vacuumized to a vacuum degree less than 10.sup.−3 Pa, and then argon is introduced as a protective gas to perform pressurized heat treatment to obtain a resultant magnet. The heat treatment temperature is 480° C., the applied pressure is 3 MPa, and the heat preservation time is 3.5 h. For the resultant magnet, magnetic properties are B.sub.r=11.3 kG, H.sub.cj=5.1 kOe, (BH).sub.max=27.1 MGOe.

[0027] As seen from the above embodiments and comparative embodiments, it can be found that by the pressurized heat treatment on the Ce—Y-rich rare earth permanent magnet, the synergistic diffusion effect of rare earth elements such as Ce, Y and Nd in the pressurized heat treatment process can be fully exploited, so that a method for improving remanence, coercivity and magnetic energy product is realized, which is creative invention of the inventors obtained by summarization and theoretical calculation after a large number of experiments. The conditions associated with the present disclosure are that: the ratio of Ce to Y meets a composition range of 7:3˜3:7, the mass percentage of Ce—Y in the total rare earths is required to be 40%˜90%, the applied pressure in the heat treatment process is in a range of 0.5˜10 MPa, and cooperating with the heat treatment temperature, the holding time and the composition, to realize the goal of improving magnetic properties. The properties of the prepared magnet are much better than that of the Ce—Y-rich magnet which meets the composition range but is subject to the normal pressure heat treatment, and also better than that of the magnet which meets the pressurized heat treatment process conditions but does not match the composition range. The technical features and effects of the present disclosure are apparently different from that of traditional Ce—Y-rich sintered, hot-pressed or hot-deformed magnets, and thus substantial innovation and progress are achieved.