Effect of cobalt substitution on magnetic properties and microstructure of nanocrystalline (NdDyTb)12.3(FeZrNbCu)81.7B6.0 ribbons

Effect of Co substitution and annealing treatment on the formation, magnetic properties and microstructure of (NdDyTb)(12.3)(FeZrNbCu)(81.7-x)CoxB6(x=0-15) ribbons prepared by rapid quenching and subsequent annealing was systematically investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and vibrating sample magnetometer (VSM). Phase analysis revealed single-phase material. The remanence polarization J(r), and maximum energy product (BH)(max) increased with increasing x from 0 to 12 and then decreased for x=15. The intrinsic coercivity H-ci of (NdDyTb)(12.3) (FeZrNbCu)(81.7-x)CoxB6 ribbons optimally processed decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15. Optimum magnetic properties with J(r)=1.041 T, H-ci=944.9 kA/m and (BH)(max)=155.1 kJ/m(3) were achieved by annealing melt-spun ribbon (x=12) at 675 degrees C for 10 min. There was no significant influence of Co substitution on microstructure.