NITRIDING OF MELT-SPUN ND-FE-MO ALLOYS

The hard magnetic properties of nitrided melt-spun Nd-Fe-Mo ribbons have been investigated as functions of composition, quench rate, and nitriding time. Ingots having the compositions Nd1Fe10Mo2, Nd1.15Fe10Mo2, Nd1.3Fe10Mo2, and Nd1.45Fe10Mo2 were melt spun over a range of quench rates specified by substrate wheel velocities upsilon(s) in the 5 m/s less-than-or-equal-to upsilon(s) less-than-or-equal-to 40 m/s interval. Ribbons prepared with upsilon(s) less-than-or-equal-to 17.5 m/s from the Nd1.15Fe10Mo2 alloy consist only of stoichiometric NdFe10Mo2 with the ThMn12 crystal structure; at higher quench rates the ThMn12 structure is suppressed. It is found that all ribbons prior to nitriding are characterized by intrinsic coercivity H(ci)<0.4 kOe. For ribbons direct quenched at wheel speeds between 12.5 and 17.5 m/s, nitriding produces technologically significant coercivity (H(ci) approximately 6 kOe). The maxima in the technical magnetic properties as functions of upsilon(s) resemble those observed in direct-quenched Nd-Fe-B ribbons.