MAGNETIC-PROPERTIES AND MICROSTRUCTURE OF SM2FE17-XTAX COMPOUNDS

The magnetic properties and microstructure of cast and annealed Sm-2 F e-17-x Ta-x (0 less than or equal to x less than or equal to 2) alloys were investigated by means of microstructural, X-ray diffraction and thermomagnetic analysis. A process for obtaining the Sm-2 Fe-17 phase nearly free of lion in the as-cast state is described. The method cons ists of adding 5 at% of Ta to the melt. By this addition of Ta to the basic alloy, a two phase structure of the as-cast ingots consisting of Sm-2 Fe-17 phase and a Pauli paramagnetic hexagonal Laves phase - TaF e2, can be obtained. X-ray diffraction showed an increase of the latti ce spacing dependent upon the tantalum concentration in the alloy, whi ch indicated some solid solubility of Ta in the Sm-2 Fe-17 phase. Quan titative electron probe microanalysis confirmed the solid solubility o f tantalum in the Sm-2 Fe-17 phase of up to 2.3 (+/- 0.5) at%. This re sulted in an increase of the Curie temperature of the Sm-2 Fe-17-x pha se, which was determined by means of thermomagnetic analysis.