Enhancement of magnetic properties in spark plasma sintered Nd-Fe-B magnets via controlled microstructure of melt-spun ribbons

In this work, we investigated the formation of columnar grain microstructure of melt - spun Nd28.5Fe66.5Dy4B1 (wt.%) (Nd-Fe-B) alloy and concurrently, studied their effect on the magnetic properties of the spark plasma sintered (SPS) Nd-Fe-B bulk. The melt spinning was performed at different wheel speeds in the range of 15 to 30 m/s. The formation of columnar grains perpendicular to the plane of the ribbons were examined through SEM and the XRD result reveals the strong (00 l) crystal texture. The mechanism behind the formation of columnar grains in melt-spun ribbon and the magnetic properties of the sintered Nd-Fe-B bulks were deeply discussed. The obtained Nd-Fe-B magnet realizes enhanced magnetic properties through the controlled microstructure of meltspun ribbons including columnar grain regions along with equiaxed grain regions. Eventually, it shows an improved coercivity of 17.3 kOe and remanence at 7.2 kG, which is 22% and 6%, respectively, larger than the magnet containing isotropic grains alone.