Study On Microstructure And Properties Of Nd₂fe₁₄b/α-fe Nanocomposite Magnets With P Element

Nanocomposite permanent magnet materials have both high saturation magnetization of soft magnetic phase and high coercivity of hard magnetic phase.The maximum magnetic energy product predicted by theory can exceed 100 MGOe,which has high research value.The nanocomposite magnets have the advantages of low cost and good corrosion resistance due to their low rare earth content.The corrosion resistance of a magnet has a great influence on its service life,but there are few reports on the corrosion resistance of nanocomposite magnets.In this paper,the microstructure and magnetic properties of nanocomposite magnets were improved by adding P element,and the effects of P element on its corrosion resistance was studied.The Nd₉Fe₈₅B_6-xP_x（x=0,0.1,0.2,0.3）alloy ribbons were prepared by melt rapid quenching at copper roller speed of 18 m/s,and the effects of P element on its microstructure and magnetic properties was studied.The results show that with the increase of P element,the average grain size of soft and hard magnetic phase grains in the magnet first decreases and then increases.When the content of P element is 0.1at.%,the average grain sizes of soft magnetic phase and hard magnetic phase are 24nm and 28 nm respectively,which is 20.5%and 19.7%lower than that of Nd₉Fe₈₅B₆alloy ribbons.This is due to the obstruction of grain growth by P element segregated at the grain boundary.The maximum magnetic energy product（BH）_max of the Nd₉Fe₈₅B_5.9P_0.1 alloy ribbon is 18.5 MGOe,which is 12%higher than that of the Nd₉Fe₈₅B₆alloy ribbon.The microstructure and magnetic properties of Nd₉Fe₈₅B_5.9P_0.1 alloy ribbons were optimized by adjusting the melt rapid quenching rate.With the increase of rapid quenching speed,the average grain sizes of soft and hard magnetic phase decreases until amorphous is produced.When the rapid quenching speed is 19 m/s,the average grain sizes of soft and hard magnetic phases of Nd₉Fe₈₅B_5.9P_0.1 alloy ribbon are about24 nm and 21 nm respectively,and there is a small amount of interface amorphous phase.The maximum magnetic energy product（BH）_max is 19.8 MGOe,which is 11.9%higher than that of Nd₉Fe₈₅B₆ alloy ribbons at the same rapid quenching speed.Zahner-Zenium E electrochemical workstation was used to study the effects of P element on the corrosion resistance of nanocomposite magnet.The addition of a small amount of P element significantly improves the corrosion resistance of the alloy ribbon,which is due to the aggregation of P element at the grain boundary filling the loose atomic interface,enhancing the compactness of the grain boundary and reducing the corrosion channel;When P element is added continuously,the volume fraction of hard magnetic phase increases,which is not conducive to the improvement of corrosion resistance.By adjusting the rapid quenching speed of the melt,the Nd₉Fe₈₅B_5.9P_0.1 alloy ribbon containing a small amount of interfacial amorphous phase was prepared,and its I_corr was 14.1μA/cm²,which was 50.9%lower than that of the Nd₉Fe₈₅B₆ alloy ribbon at the same quenching rate.