Effect of Cu-doping on the microstructure and magnetic properties of low-cost MM-Fe-B melt spun ribbons

In this paper, MM-Fe-B ribbons with different MM contents were prepared by melt spun technique at a fixed copper roll speed of 25 m/s. The maximum magnetic energy product of the MM₁₅Fe₇₈B₇ ribbon is 9.22 MGOe and the coercivity is 6005 Oe. With the increase of MM contents, the coercivity of the magnet was increased, and the highest coercivity reached 9352 Oe in MM₁₈Fe₇₅B₇. In addition, the microstructure and magnetic properties of Cu-doped MM₁₅Fe_78-xB₇Cu_x (x = 0, 0.4, 0.6, 1 at.%) ribbons were systematically investigated. The results show that the introduction of Cu can suppress the formation of α-Fe soft magnetic phase in the melt spun ribbons. When the Cu content is 0.4 at.%, the grain size decreased from 61 nm to 44 nm, and the coercivity was improved from 6005 Oe to 8527 Oe, which is an increment of about 42 %, whereas the remanence and the magnetic energy product can remain basically unchanged. The addition of Cu element can not only refine the grain size, but also facilitate the enhancement of the homogeneity of the microstructure of the ribbons.