Liquid phase sintering of rare earth--iron (Dy/sub 0.7/Tb/sub 0.3/Fe2) magnetostrictive materials

A liquid phase powder metallurgy method has been evaluated for the production of dense, thermally stable Dy/sub 0.7/Tb/sub 0.3/Fe2 compacts. The method involved the use of a rare earth rich alloy which forms the RFe2 phase and a RFe2-R eutectic. The latter is molten at the sintering temperature employed. Dy/sub 0.7/Tb/sub 0.3/Fe/sub x/ alloys ranging in composition from x=1.65 to stoichiometric were ground, aligned, compacted and then sintered between 1130 and 1190 0C. Densities as high as 98% were achieved for compositions between x=1.65 and 1.8. Densities were markedly lower for compositions beyond x=1.8. Although the magnetostriction of the compacts were lower than those found for cast polycrystalline Dy/sub 0.7/Tb/sub 0.3/Fe2, the magnetomechanical coupling coefficients (k33) of a number of the sintered compacts appeared to be as much as 50% higher than for the cast materials. Suprisingly, the highest coupling was found for samples with 5 to 15% porosity. When aged in air at 150 0C, the magnetoelastic properties of the liquid phase sintered materials were as stable as cast polycrystalline alloy