Effect of annealing temperature on microstructure and magnetic properties of NdFeB magnets

doi:10.13251/j.issn.0254-6051.2024.12.009

Abstract

Abstract: To investigate the effect of annealing treatment on the microstructure and magnetic properties of NdFeB magnets, powder sintered NdFeB magnets were annealed at 500-600 ℃. XRD, SEM and magnetic performance measuring instruments were used to analyze and characterize the NdFeB magnets. The results show that the annealing treatment has little effect on the structure of the main phase Nd₂Fe₁₄B of the NdFeB magnets, but mainly affects the distribution and composition of the rich-Nd phase. After annealing treatment, the coercivity of the NdFeB magnets is improved to varying degrees. After annealing at 550 ℃, the rich Nd phase is continuous and uniformly distributed along the grain boundaries of the Nd₂Fe₁₄B main phase, and the content of Nd in the rich-Nd phase increases while the content of Fe decreases, and the coercivity of the magnets has the best improvement effect, increasing from 1135 kA/m to 1434 kA/m, correspondingly increased by 26.3%. After annealing treatment, the residual magnetism of the magnets doesn't change significantly, but the maximum magnetic energy product decreases to varying degrees.

Key words: NdFeB magnets, annealing temperature, microstructure, coercivity, residual magnetism, maximum magnetic energy product

CLC Number:

TG146.454

Li Huan, Wang Junbo, Liu Jiangnan, Si fang, Wu Shujie, Dong Yi. Effect of annealing temperature on microstructure and magnetic properties of NdFeB magnets[J]. Heat Treatment of Metals, 2024, 49(12): 57-61.

References

[1]Zhou Q, Li W, Hong Y, et al. Microstructure improvement related coercivity enhancement for sintered NdFeB magnets after optimized additional heat treatment[J]. Journal of Rare Earths, 2018, 36(4): 379-384.
[2]Liao X F, Zhao L Z, Zhang J S, et al. Clarifying the basic phase structure and magnetic behavior of directly quenched (Ce, La)₂Fe₁₄B alloys with various Ce/La ratios[J]. Current Applied Physics, 2019, 19(6): 733-738.
[3]王憨鹰, 王兆华, 晋宏营, 等. 热处理对NdFeB磁性材料表面化学镀Ni-Cu-P合金性能影响[J]. 金属热处理, 2017, 42(9): 53-56.
Wang Hanying, Wang Zhaohua, Jin Hongying, et al. Effect of heat treatment on performance of electroless Ni-Cu-P deposits on NdFeB permanent magnets materials[J]. Heat Treatment of Metals, 2017, 42(9): 53-56.
[4]Hugonnet B, Missiaen J M, Martin C L, et al. Effect of contact alignment on shrinkage anisotropy during sintering: Stereological model, discrete element model and experiments on NdFeB compacts[J]. Materials and Design, 2020, 191: 108575.
[5]Tang M H, Bao X Q, Zhang X J, et al. Tailoring the mechanical anisotropy of sintered NdFeB magnets by Pr-Cu grain boundary reconstruction[J]. Journal of Rare Earths, 2019, 37(4): 393-397.
[6]孙绪新, 包小倩, 高学绪, 等. 热处理对双合金钕铁硼烧结磁体边界结构与磁性能的影响[J]. 材料热处理学报, 2008, 29(5): 101-105.
Sun Xuxin, Bao Xiaoqian, Gao Xuexu, et al. Effect of heat treatment on grain boundary and magnetic properties of Nd-Fe-B magnets prepared by a binary powder blending technique[J]. Transactions of Materials and Heat Treatment, 2008, 29(5): 101-105.
[7]王誉, 刘小芳, 宇根康裕, 等. 细化晶粒法提高烧结钕铁硼磁体矫顽力的研究[J]. 稀土信息, 2020(4): 8-12.
[8]Hono K, Sepehri-Amin H. Strategy for high-coercivity Nd-Fe-B magnets[J]. Scripta Materialia, 2012, 67(6): 530-535.
[9]刘卫强, 查善顺, 岳明, 等. 高矫顽力烧结钕铁硼永磁研究进展[J]. 北京工业大学学报, 2017, 43(10): 1569-1581.
Liu Weiqiang, Cha Shanshun, Yue Ming, et al. Research progress of sintered Nd-Fe-B permanent magnets with high coercivity[J]. Journal of Beijing University of Technology, 2017, 43(10): 1569-1581
[10]Ma T Y, Wu B, Zhang Y J, et al. Enhanced coercivity of Nd-Ce-Fe-B sintered magnets by adding (Nd, Pr)-H powders[J]. Journal of Alloys and Compounds, 2017, 721: S0925838817318741.
[11]Chen K, Guo S, Fan X D, et al. Coercivity enhancement of Ce-Fe-B sintered magnets by low-melting point intergranular additive[J]. Journal of Rare Earths, 2017, 35(2): 158-163.
[12]刘路军, 刘政. 回火工艺对烧结(CePrNd)-Fe-B磁体内禀矫顽力的影响[J]. 中国有色金属学报, 2019, 29(12): 2785-2792.
Liu Lujun, Liu Zheng. Effect of annealing technology on coercivity and thermal stability in(CePrNd)-Fe-B sintered magnet[J]. The Chinese Journal of Nonferrous Metals, 2019, 29(12): 2785-2792.
[13]郭诚君, 陈金水, 李家节, 等. 回火工艺对热扩渗PrZn合金烧结态磁体组织和磁性能的影响[J]. 金属热处理, 2017, 42(5): 108-111.
Guo Chengjun, Chen Jinshui, Li Jiajie, et al. Liu WuJie. Effect of tempering on magnetic properties and microstructure of Pr Zn-coated NdFeB magnet[J]. Heat Treatment of Metals, 2017, 42(5): 108-111.
[14]李志杰, 李旭, 李嘉, 等. 回火工艺对快淬钕铁硼永磁材料磁性能的影响[J]. 材料保护, 2014, 47(S1): 140-142.
Li Zhijie, Li Xu, Li Jia, et al. Effect of annealing on magnetic properties of rapid quenching Nd-Fe-B magnets[J]. Materials Protection, 2014, 47(S1): 140-142.
[15]Li W F, Ohkubo T, Hono K. Effect of post-sinter annealing on the coercivity and microstructure of Nd-Fe-B permanent magnets[J]. Acta Materialia, 2009, 57: 1337-1346.
[16]Dong X, Yang J, Zhang L, et al. An investigation of the microstructure in the grain boundary region of Nd-Fe-B sintered magnet during post-sintering annealing[J]. Scripta Materialia, 2013, 68(9): 687-690.
[17]Sepehri-Amina H, Ohkubo T, Shima T, et al. Grain boundary and interface chemistry of an Nd-Fe-B-basedsintered magnet[J]. Acta Materialia, 2012, 60: 819-830.
[18]彭光怀, 杜西龙, 贾小武, 等. 回火热处理对烧结NdFeB磁体组织与性能的影响[J]. 热加工工艺, 2015, 44(6): 206-208, 211.
Peng Guanghuai, Du Xilong, Jia Xiaowu, et al. Effect of tempering heat-treatment on microstructure and properties of sintered NdFeB permanent magnet materials[J]. Hot Working Technology, 2015, 44(6): 206-208, 211
[19]王伟, 罗伟, 文玉华, 等. 二级回火对(NdDy)FeCoCuB磁体磁性能和微结构的影响[J]. 稀有金属材料与工程, 2005, 34(10): 125-128.
Wang Wei, Luo Wei, Wen Yuhua, et al. Effect ofsecond annealing on magnetic properties and microstructure of (NdDy)FeCoCuB magnets[J]. Rare Metal Materials and Engineering, 2005, 34(10): 125-128.
[20]郑华均, 黄建国, 马淳安, 等. 退火处理对烧结钕铁硼永磁体磁性能的影响[J]. 金属热处理, 2003, 28(11): 19-22.
Zheng Huajun, Huang Jianguo, Ma Chun'an, et al. Effect of annealing on the magnetism of the sintered NdFeB magnet[J]. Heat Treatment of Metals, 2003, 28(11): 19-22.