Effect of DyF3 on temperature stability and corrosion resistance of sandwich structure hot-deformed NdFeB magnets
In order to improve the temperature stability and corrosion resistance of hot-deformed NdFeB mag-nets,a sandwich structure magnet with DyF3 additives was designed.By adding different contents of DyF3 pow-ders to the upper and lower near-ends of the magnet,the phase composition,structure and composition of the grain boundary phase in the upper and lower near-ends of the magnet were regulated,and the corrosion resist-ance of the magnet was improved.On the other hand,Dy element partially diffused into the main phase,form-ing(Nd,Dy)2Fe14B phase to improve the magnetocrystalline anisotropy field of the magnet and optimize the tem-perature stability.The magnetic properties of the sandwich structure hot-deformed magnet were measured by PFM,and the coercivity up to 2.16T was obtained.The polarization curve of the sandwich structure hot-de-formed magnet was measured by an electrochemical workstation.The corrosion current rate was one order mag-nitude smaller than that of the substrate.For the sandwich structure magnet,the near-ends with 5wt％DyF3 addition showed a much smaller weight loss per unit surface area(0.061mg/cm2)compared with the matrix sur-face(1.172 mg/cm2)after a 168-hour PCT test.The microstructure analysis showed that NdF3 and Dy2O3 com-pounds were formed by Nd-rich phase and F,O and Dy elements,respectively.XRD analysis showed that the texture of sandwich structure hot-deformed magnet was deteriorated after DyF3 addition.This study provides a new way to improve the temperature stability and corrosion resistance of hot-deformed NdFeB magnet.
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