晶界添加Ho63.3Fe36.7 对NdFeB再生磁体组织与性能的影响

Effect of Adding Ho63.3Fe36.7 to Grain Boundaries on Structure and Properties of Regenerated NdFeB Magnets

摘要:

采用一种高效、绿色的物理方法对NdFeB废旧磁体表面进行清理并回收利用。通过晶界添加低熔点Ho_63.3Fe_36.7合金制备NdFeB再生磁体。在未添加Ho_63.3Fe_36.7的磁体中，没有足够的富Nd相隔离Nd₂Fe₁₄B相，从而导致磁体性能较差；随着Ho_63.3Fe_36.7合金的加入，晶界相变得清晰且连续。在质量分数2%Ho_63.3Fe_36.7添加量下，钕铁硼再生磁体获得最佳磁性能[(BH)_max+H_cj=1756.07]。此时矫顽力增加123 kA/m（约提高9.1%），磁体的最大能积由290.94 kJ/m³下降到281.07 kJ/m³，而剩磁少量下降。通过对再生磁体显微组织和成分的分析可知，磁体晶界处形成了(Nd, Pr, Ho)₂Fe₁₄B壳层，这能够提高磁体的矫顽力。而X射线衍射分析表明，磁体I₍₀₀₆₎/I₍₁₀₅₎的衍射峰强度比从0.92提高到1.32。这说明磁体取向度提高，可以减弱对剩磁的影响，从而使得再生磁体在保持剩磁的同时提高磁体的矫顽力。

Abstract:

A high-efficiency and green physical method was proposed to clean the surface of NdFeB waste magnets for recycling. NdFeB regenerated magnets were fabricated by adding low-melting point Ho_63.3Fe_36.7 alloy to grain boundaries. Results show that in magnets without Ho_63.3Fe_36.7, there are insufficient Nd-rich phases to isolate the Nd₂Fe₁₄B phase, leading to poor magnet performance. With the addition of Ho_63.3Fe_36.7 alloy, the grain boundary phases become clear and concatenated. Optimal magnetic energy [(BH) _max+H_cj=1756.07] can be obtained by adding 2wt% Ho_63.3Fe_36.7 to the magnet. Further, the coercivity increases by 123 kA/m (approximately 9.1%), the maximum magnetic energy product decreases from 290.94 kJ/m³ to 281.07 kJ/m³, and remanence decreases slightly. Through analysis of the microstructure and composition, it can be seen that the (Nd, Pr, Ho)₂Fe₁₄B shell layers form at the grain boundary, which enhances the coercivity of the magnet. X-ray diffraction analysis suggests that the diffraction peak intensity ratio of magnet I₍₀₀₆₎/I₍₁₀₅₎ increases from 0.92 to 1.32, which indicates that the alignment degree is improved and the influence on remanence is weakened. Therefore, regenerated magnets can possess improved coercivity while maintaining magnetic remanence.