晶界添加Dy80Fe13Ga7对烧结钕铁硼热稳定性和耐腐蚀性的影响

Thermal Stability and Corrosion Resistance of Sintered Nd-Fe-B Magnets with Intergranular Addition of Dy80Fe13Ga7

采用晶界添加法制备烧结Nd-Fe-B磁体,通过添加Dy80Fe13Ga7合金研究了磁体的磁性能、热稳定性能和耐腐蚀性能。结果表明,磁体的矫顽力在添加Dy80Fe13Ga7合金后显著增加,添加量为4%(质量分数)Dy80Fe13Ga7合金磁体的矫顽力从1036增加到1539 kA·m^-1。扫描电镜(SEM)图显示,在添加Dy80Fe13Ga7合金后,富稀土晶界相数量明显增多,主相晶粒间的去磁交换耦合作用增强,使得矫顽力显著提高。磁体剩磁温度系数从-0.1268%·K^-1优化到-0.1073%·K^-1,矫顽力温度系数从-0.6473%·K^-1优化到-0.6344%·K^-1,不可逆磁通损失率从76.5%优化到50.1%,说明添加Dy80Fe13Ga7合金可以改善磁体的热稳定性。然而,加速腐蚀试验(HAST)和电化学分析表明,添加Dy80Fe13Ga7合金后,磁体内部的富稀土相增加,腐蚀扩散通道增多,而富稀土相的腐蚀电位相对于主相更低,导致磁体的耐腐蚀性能降低。

Sintered Nd-Fe-B magnets were prepared by intergranular addition. The magnetic property, thermal stability and corrosion resistance of the magnets with Dy80Fe13Ga7 intergranular addition were investigated. The results showed that the coercivity was improved greatly by adding Dy80Fe13Ga7 alloys, which increased from 1036 to 1539 kA·m^-1 when the Dy80Fe13Ga7 addition amount was 4%(mass fraction). The scanning electron microscopy(SEM) image showed that the amount of Nd-rich phase and grain boundary increased obviously with the addition of Dy80Fe13Ga7 alloys, and the demagnetizing exchange coupling between the main phase grains were enhanced, which made the coercivity increase significantly. In addition, the temperature coefficient of remanence and coercivity increased from-0.1268 %·K^-1 to-0.1073 %·K^-1 and from-0.6473 %·K^-1 to-0.6344 %·K^-1, respectively. The irreversible loss of magnetic flux was optimized from 76.5% to 50.1%. It suggested that the thermal stability of the magnets could be improved by adding Dy80Fe13Ga7 alloys. However, the highly accelerated stress test(HAST) and electrochemical analysis showed that the corrosion resistance of the magnets reduced with the increase of the amount of Dy80Fe13Ga7 alloys. This was because that more rare earth-rich(RE-rich) phases could provide more corrosion diffusion channels, and the corrosion potential of the RE-rich phases was much lower than that of the main phases.