Study On The Microstructure And Properties Of (Nd_0.4Pr_0.6)₉Fe_85-xTa_xB₆ Nanocomposite Magnets

Nd2Fe14B-based nanocomposite permanent magnetic materials have been widely concerned by scholars at home and abroad because of their ultra-high theoretical energy product under the premise of low rare earth content.However,due to the fact that the microstructure of the actually prepared magnet cannot meet the requirements of the theoretical model,the values of magnetic parameters such as energy product,coercivity,etc.are far below their theoretical limits.Therefore,how to further control its microstructure to prepare nanocomposite magnets with excellent comprehensive magnetic properties has become a topic of general concern.Based on the above research background,this paper systematically studies the effect of Ta element addition on the microstructure,magnetic properties and coercivity mechanism of(Nd,Pr)2Fe14B/α-Fe nanocomposite permanent magnets using melt spinning technique,with a view to providing some reference for the preparation of nanocomposite permanent magnets with high coercivity,high energy product and better thermal stability.The specific research analysis is as follows.The(Nd0.4Pr0.6)9Fe85-xTaxB6(0≤x≤2)nanocomposite permanent magnets were prepared by melt spinning technique,and the effects of Ta content on the microstructure and magnetic properties of the composite magnet at room temperature and high temperature were investigated.The study found that Ta elements could inhibit the formation of α-Fe soft magnetic phase and promote the increase of 2:14:1 hard magnetic phase.When the x increases from 0 to 2,the volume fraction of α-Fe decreases from 26.2%to 17.5%,and the volume fraction of 2:14:1 increases from 73.4%to 82.5%.Ta elements can refine the grain size of soft and hard magnetic phases.The grain sizes of the soft and hard magnetic phases are 12.3 nm and 17.4 nm atx=2,which were significantly smaller than the dα-Fe=22 nm and d2:14:1=34.3 nm at x=0.As the Ta content increases,the coercivity increases monotonically,its value increases from 6.1 kOe at x=0 to 10.4 kOe at x=2,an increase of up to 70%.The remanence increases slightly at x=0.5 and then decreases with the further increase of Ta content.Therefore,the optimum magnetic properties were obtained at x=1,Hci=7.5 kOe,(BH)max=23.4 MGOe.The addition of Ta elements can enhance the thermal stability of the magnet.In the temperature range of 27-175℃,the temperature coefficient of coercivity of the magnet is increased from-0.350%℃-1 at x=0 to-0.329%℃-1 at x=2.The coercivity mechanism of three different components(Nd0.4Pr0.6)9Fe85-xTaxB6(x=0,1,2)nanocomposite permanent magnets prepared by melt spinning technique was investigated by testing the initial magnetization curves,minor hysteresis curves and Henkel curves.The results show that the coercivity mechanism of the three components magnets is pinning mechanism,but it is different from the ideal pinning model,which is an inhomogeneous domain wall pinning mechanism.The addition of Ta element is beneficial to the enhancement of the pinning field.The magnitude of the coercivity of the composite magnet is determined by the pinning field of the magnet.