Liquid phase sintering of rare earth–iron (Dy0.7Tb0.3Fe2) magnetostrictive materials

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Abstract
A liquid phase powder metallurgy method has been evaluated for the production of dense, thermally stable Dy0.7Tb0.3Fe2 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. Dy0.7Tb0.3Fex alloys ranging in composition from x=1.65 to stoichiometric were ground, aligned, compacted and then sintered between 1130 and 1190 °C. 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 Dy0.7Tb0.3Fe2, 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 °C, the magnetoelastic properties of the liquid phase sintered materials were as stable as cast polycrystalline alloy.

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