Microstructure and corrosion resistance of sintered NdFeB magnet modified by intergranular additions

• 作 者: 莫文剑 张澜庭 刘琼珍 单爱党 吴建生 Komuro Matahiro 沈丽萍
• 机 构: School of Materials Science and Engineering Shanghai Jiao Tong University,School of Materials Scien
• 出 处: Journal of Rare Earths
• 发表日期: 2008年02期
• 关键词: NdFeB sintered magnet coercivity additives additions anodic refined steam additi

Microstructure and corrosion resistance of sintered Nd15Dy1.2Fe77Al0.8B6 and Nd22Fe71B7 magnets modified by intergranular addi- tion of MgO and ZnO were investigated. Both the remanence and sintering density of the magnets increased slightly with intergranular addi- tions of MgO and ZnO. There was a remarkable increase in coercivity of Nd22Fe71B7 after addition. Besides, the effects on magnetic proper- ties and an improved corrosion resistance were observed. Compared with the native magnets without addition, corrosion potential of the magnets with MgO and ZnO additives was more positive and the current density in the anodic branch of the polarization curve was reduced. Corrosion resistance resulting from autoclave testing (2×105 Pa of steam pressure, 120 °C) showed that the corrosion rate of NdFeB magnets reduced with the increase of additive amount. Microstructure observation revealed that MgO and ZnO additives were incorporated into the intergranular phases in the magnets. With the introduction of MgO and ZnO, more intergranular phase with high oxygen content was formed while keeping the volume fraction of all the intergranular phases almost unchanged, which may contribute to improved corrosion resistance. Furthermore, addition of MgO and ZnO refined the grain size of Nd22Fe71B7.

Microstructure and corrosion resistance of sintered Nd15Dy1.2Fe77Al0.8B6 and Nd22Fe71B7 magnets modified by intergranular addi- tion of MgO and ZnO were investigated. Both the remanence and sintering density of the magnets increased slightly with intergranular addi- tions of MgO and ZnO. There was Compared with the native magnets without addition, corrosion potential of the magnets with MgO and ZnO additives was more positive and the Corrosion resistance caused from autoclave testing (2 × 105 Pa of steam pressure, 120 ° C) showed that the corrosion rate of NdFeB magnets reduced with the increase of additive amount. Microstructure observation revealed that MgO and ZnO additives were incorporated into the intergranular phases in the magnets. With the introduction of MgO and ZnO, more intergranular phase with high oxygen content was formed while keeping the volume fraction of all the intergranular phases almost unchanged, which may contribute to improved corrosion resistance.