Intrinsic properties, phase constitution and microstructure of novel RE-Fe-B strip-casting alloys based on misch metal

In order to reduce the RE-Fe-B material cost and balance the utilization of rare earth sources, misch metal substitution for Nd in the sintered magnet becomes of many interests. Under the process of fabricating high magnetic properties magnet, the strip-casting (SC) technique plays a key role, a series of rapidly solidified [(PrNd)_1-xMM_x]_13.8Fe_balCo_0.5Cu_0.1Al_0.6Ga_0.07B_5.9 (x = 0 ~ 1.00) (MM, Misch Metal) strips were manufactured. Subsequently, the phase constitution, microstructure and the intrinsic magnetic properties were measured. There are always stable RE₂Fe₁₄B phase in the strips with MM, which is similar to Nd-Fe-B strip. Whereas, when x ≥ 0.50, there exists REFe₂ phase inevitably, and the amount of REFe₂ phase gradually increases with increasing MM content. Magnetic measurements indicated that intrinsic magnetic properties, such as the saturation magnetization M_s and magneto-anisotropy field H_A, deteriorate gradually by substituting PrNd with MM except for x = 0.35. For x = 0.35, the abnormal phenomenon is ascribed to Ce valence shifting toward +3 that is caused by lattice expanding. In addition, when x ≥ 0.50, La and Ce is prior to aggregate in the RE-rich phase clusters, and the content of Fe rises with the increase of MM, moreover, the interfaces between of RE₂Fe₁₄B phase and RE-rich phase become indistinct.