Improved magnetic properties and optimized preparation process of (MM)-Fe-B magnets

Substitution of Nd element with misch metal (MM) element in the RE-Fe-B magnets has been set off as an effective method to decrease the cost of RE-Fe-B materials and ensure a more balanced utilization of rare-earth elements. In the present work, the composition of MM_xFe_94-xB₆ (x = 14 and 16) alloys are fabricated by the melt-spinning method with wheel speeds of 20 and 25 m s^-1, respectively. It is demonstrated that with increasing wheel speed and MM content, can effectively suppress the formation of α-Fe soft phase and refine grain size. The maximum energy product (BH)_max of 10.03 MGOe is obtained for the MM16-V25 alloy, which is a result of its higher intrinsic coercivity H_cj (H_cj : 9.15 kOe) and squareness H_k/H_cj (H_k/H_cj : 0.49). Meanwhile, the analysis of Henkel plots δM(H) and microstructure show that the MM16-V25 alloy obtains the strongest exchange coupling effect and more uniform microstructure with fine grain size. In addition, the compositions of 2:14:1 grain and grain boundary from energy dispersive spectroscopy for the MM16-V25 alloy are also discussed in detail. (author)