The effects of Ho substitution for Nd on the microstructure, corrosion resistance and thermal stability of the Nd-Fe-B magnets were investigated. The（Nd,Ho）-O phase was formed with increasing Ho substitution. The re...The effects of Ho substitution for Nd on the microstructure, corrosion resistance and thermal stability of the Nd-Fe-B magnets were investigated. The（Nd,Ho）-O phase was formed with increasing Ho substitution. The results of potentiodynamic polarization and highly accelerated stress test show improved corrosion resistance with increasing Ho substitution. The optimum mass loss 0.29 mg/cm^2 is achieved.Moreover, the average temperature coefficients for remanence and coercivity in the range of 25-150℃are both closer to zero, indicating improved thermal stability. The mechanisms for the improved corrosion resistance and thermal stability are discussed in relation to the microstructure featuring the（Nd,Ho）-O phase.展开更多
Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets.Firstly,rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precu...Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets.Firstly,rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precursors using the hot-pressing process.The prepared isotropic precursors are then hot-deformed to produce high-anisotropy uniaxial bulk rare earth permanent magnets and a highly textured structure is produced via this process.The resulting magnets possess many advantages such as near-net-shape,outstanding corrosion resistance,and ultrafine-grain structure.The influence of the preparation parameters utilized in the hot-pressing and deformation processes on the magnetic properties and microstructure of the permanent magnets are systemically summarized in this report.As a near-net-shape technique,the hot deformation process has notable advantages with regard to the production of irregular shapes,especially for radially oriented ringshaped magnets with high length-diameter ratios or thin walls.The difficulties associated with the fabrication of crack-free,homogeneous,and non-decentered ring-shaped magnets are substantially resolved through an emphasis on mold design,adjustment of deformation parameters,and application of theoretical simulation.Considering the characteristics of hotdeformed magnets which include grain shape and size,anisotropic distribution of intergranular phases,etc.,investigation and improvement of the mechanical and electric properties,in addition to thermal stability,with the objective of improving the application of hot-deformed magnets or ring-shaped magnets,is of practical significance.展开更多
基金Project supported by the Ningbo Major Technology Innovation Projects(2017B10005)Ningbo Natural Science Foundation(2015A610011)Guangxi Science and Technology Project(2016AD05041)
文摘The effects of Ho substitution for Nd on the microstructure, corrosion resistance and thermal stability of the Nd-Fe-B magnets were investigated. The（Nd,Ho）-O phase was formed with increasing Ho substitution. The results of potentiodynamic polarization and highly accelerated stress test show improved corrosion resistance with increasing Ho substitution. The optimum mass loss 0.29 mg/cm^2 is achieved.Moreover, the average temperature coefficients for remanence and coercivity in the range of 25-150℃are both closer to zero, indicating improved thermal stability. The mechanisms for the improved corrosion resistance and thermal stability are discussed in relation to the microstructure featuring the（Nd,Ho）-O phase.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0700902)the National Natural Science Foundation of China(Grant Nos.51671207,51601207,and 51501213)
文摘Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets.Firstly,rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precursors using the hot-pressing process.The prepared isotropic precursors are then hot-deformed to produce high-anisotropy uniaxial bulk rare earth permanent magnets and a highly textured structure is produced via this process.The resulting magnets possess many advantages such as near-net-shape,outstanding corrosion resistance,and ultrafine-grain structure.The influence of the preparation parameters utilized in the hot-pressing and deformation processes on the magnetic properties and microstructure of the permanent magnets are systemically summarized in this report.As a near-net-shape technique,the hot deformation process has notable advantages with regard to the production of irregular shapes,especially for radially oriented ringshaped magnets with high length-diameter ratios or thin walls.The difficulties associated with the fabrication of crack-free,homogeneous,and non-decentered ring-shaped magnets are substantially resolved through an emphasis on mold design,adjustment of deformation parameters,and application of theoretical simulation.Considering the characteristics of hotdeformed magnets which include grain shape and size,anisotropic distribution of intergranular phases,etc.,investigation and improvement of the mechanical and electric properties,in addition to thermal stability,with the objective of improving the application of hot-deformed magnets or ring-shaped magnets,is of practical significance.
