高温900 ℃回火在烧结NdFeB制备中的作用

Effect of High Temperature 900 oC Tempering on Magnetic Properties of NdFeB

摘要:

高温回火处理对烧结钕铁硼磁体性能影响研究表明：经不同高温T1回火处理后再低温T2=600 ℃回火处理，磁体剩磁Br和矫顽力iHc随T1温度升高而增大，在900 ℃时有最佳值，进一步升高T1磁体的Br和iHc下降。在相同T2回火条件?下，经历高温回火的磁体比未经高温回火的iHc明显更高，但Br较低。而且无论磁体是否经过高温回火，T2从450升到600 ℃时，Br、最大磁能积(BH)m缓慢增大，iHc显著提高，T2在600 ℃时磁性能达到最佳。磁体显微组织分析表明：经高温900 ℃回火可使烧结态的磁体主相内部大量分散的不均匀非晶相消失，而且使晶粒边界变得清晰、均匀，能较好的抑制硬磁性相间交换耦合作用，磁体矫顽力大幅提高。

Abstract:

Effect of high temperature (T1) tempering on sintered NdFeB magnets was investigated. With increased T1 tempering of magnets, both Br and iHc are improved after low temperature T2 tempering at 600 oC, and optimum T1 is 900 oC. As T1 increases further, Br and iHc begin to decrease. Magnets experiencing T1 tempering own higher iHc but lower Br compared with magnets of free T1 tempering. Whether the magnets experience T1 tempering or not, both Br and (BH)m increase gradually while iHc increases greatly when low temperature T2 tempering increases. The optimum T2 is 600 oC. Microstructure analysis shows that there is a large amount of non-uniform phases in the main phase of sintered magnets, and they act as nuclear centers of reversal magnetism and result in iHc decreasing. After T1 tempering, the non-uniform phases disappear in the main phase and the grain boundary becomes clear and smooth, inhabiting the interaction between Nd2Fe14B grains. So the value of iHc for the tempered magnets is improved a lot.