Transformation of the crystalline and electron structures of the NdFeB alloys modified with Titanium

摘要

Rapid quenched ribbons of the Nd_yFe_((86-x-y))B_(14)Ti_x(x = 0, 4; y = 7, 8) alloys were annealed at 953K for 20 minutes. The best properties(_JH_c =648kA/m, J_r=972mT, (BH)_(max)=143kJ/m~3) were obtained for the alloy composition Nd_8Fe_(74)B_(14)Ti_4. The magnetically hard phase Nd_2Fe_(14)B dominates in the ternary alloy (x=0). It transforms into the Nd_2Fe_(12.6)BTi_(1.4) phase with the addition of Ti to the alloy. Titanium replaces the iron atoms in the elementary cell of the Nd_2Fe_(14)B in a continuous manner, which results in a variable content of this element in individual grains. The presence of α-Fe, Nd_2Fe_(23)B_3, Fe_2B and Nd_(1.1)Fe_4B_4 was identified. These phases are also enriched in Ti. The proportion of the phases varies depending on the percentage of the elements in the investigated alloys. X-Ray absorption spectrum for Nd and Fe showed that in samples without Ti there is a charge transfer from Nd to Fe while Nd concentration increases from 7 to 8 at. %. It was found that Ti addition promotes modifications of the electronic structures of Nd and Fe sub-bands.