EFFECT OF ADDITIONS OF NB TO SM2FE17-BASED CAST ALLOYS

The microstructures of niobium free and niobium containing Sm2F17 cast alloys were investigated by X-ray diffraction, image analysis, quanti tative electron probe microanalysis and thermomagnetic analysis. A cas t ingot consisting of the Sm2Fe17 phase and paramagnetic NbFe2 Laves p hase was produced at different Sm-Fe-Nb compositions. An addition of 4 at.%Nb was found to be sufficient to produce an as cast alloy without alpha-Fe phase. The aim of the present work is to study the effect of niobium addition upon the microstructure and the Sm2Fe17 phase. X-ray diffraction showed that the lattice spacings were dependent upon the n iobium concentration in the alloy and this indicated some solid solubi lity of Nb in the Sm2Fe17 phase which was confirmed by electron probe microanalysis. Thermomagnetic analysis was carried out to support the X-ray diffraction results. Some enhancement in Curie temperature was f ound to be associated with the volume expansion of the Sm2Fe17 phase d ue to the solid solubility of Nb in the Sm2Fe17 phase.