Nb Additional Effection On Nd₉Fe_81xTi₄C₂B_xNb₄（x=11,13,15） Alloys Prepared By Copper Mold Suction

In this paper, the thickness of0.7mm Nd9Fe81-xTi4C2BxNb4(x=11,13,15) alloys were preparedby copper mold suction casting, the phase composition, crystallization behavior and magneticproperties were studied. The influence of B content on the microstructure of the as-castedNd9Fe81-xTi4C2BxNb4(x=11,13,15) alloys, as well as the influence of Nb addition on the phasecomposition, crystallization behavior of the as-casted alloys was discussed. The phase composition,microstructure and magnetic properties under different annealing conditions (annealingtemperature and annealing time) were studied.The results showed that: Compared the phase composition of Nd9Fe81-xTi4C2BxNb4(x=11,13,15) alloys with Nd9Fe83-xTi4C4Bx(x=11,13,15) alloys, Nb substitution could not onlysuppress the formation of the Nd2Fe23B3、Nd1.1Fe4B4and an unknown phase, leading to thepresence of the large amount of Nd2Fe14B and α–Fe phase, but also promote the formation ofcrystal phase in the solidification process. With the increasing of B content, the volume fraction ofthe Nd2Fe14B phase increased gradually, the volume fraction of the α–Fe phase decreased, at thesame time the grain size became finer.The influence of Nb addition on the magnetic properties of theNd9Fe81-xTi4C2BxNb4(x=11,13,15) alloys was studied. With the addition of Nb, the Hciof the as-cast alloys increased. Optimal magnetic properties, i.e. Br=0.32T， Hci=116.66kA/m，(BH)max=6.59kJ/m3were achieved for Nd9Fe66Ti4C2B15Nb4as-cast alloy. Whether adding Nb ornot, the Hciincreased with the increase of B contents.The influence of Nb addition on the crystallization behavior of theNd9Fe81-xTi4C2BxNb4(x=11,13,15) alloys was studied. With the addition of Nb， thecrystallization process of the alloys changed from one step to two steps, and the GFA wasreduced. Nb addition changed the influence of B content on the stability of amorphous. With theincrease of B content, the stability of no Nb contained amorphous increased first, thendecreased;on the contrary, the stability of Nb contained amorphous decreased first, then increased,with the increase of B content.Nd9Fe81-xTi4C2BxNb4(x=11,13,15) alloys annealed under different annealing conditions.Optimal magnetic properties, Hci=203.13kA/m，(BH)max=11.86kJ/m3，Br=0.39T，were achieved for Nd9Fe70Ti4C2B11Nb4alloy annealed at973K for10min. The best annealing temperature was63K higher than the initial crystallization temperature of the second exothermic peak. Optimalmagnetic properties, Hci=279.19kA/m，(BH)max=15.49kJ/m3，Br=0.43T，were achieved forNd9Fe66Ti4C2B15Nb4alloy annealed at988K for10min. The best annealing temperature was60Khigher than the initial crystallization temperature of the second exothermic peak. Optimal magneticproperties, Hci=155.11kA/m，(BH)max=18.73kJ/m3， Br=0.63T， were achieved forNd9Fe68Ti4C2B13Nb4alloy annealed at983K for10min. The best annealing temperature was41Khigher than the initial crystallization temperature of the second exothermic peak. We compared thebest annealing condition of the experimental results with the best annealing condition ofNd9Fe83-xTi4C4Bx(x=10~15) alloy prepared by the copper mold suction, the best annealingtemperature of the former was higher than the latter, the best annealing time of the former waslonger than the latter.