Microstructure And Magnetic Properties Of Rare Earth (TbDyHo)-Fe Giant Magnetostrictive Materials

The giant magnetostrictive material TbDyFe alloy with a giant magnetostriction, highenergy density, good reliability and fast response characteristics, has a broad applicationprospects in aerospace, sonar, robotics and other fields. It is one of the key materials,known as the development of high and new technology in the new century. The Ho elementis added on the basis of TbDyFe alloy, hoping to obtain large magneto-striction or smallhysteresis, and change the properties of the alloy through heat treatment of hightemperature and magnetic heat treatment. By means of X-ray diffraction, scanning electronmicroscope, differential thermal analysis, magnetic testing system of multi-parameter andvibrating sample magnetometer, we can exam on microstructure, phase transformation andmagnetic properties of samples.The x(Tb0.15Ho0.85Fey)+(1-x)(Tb0.3Dy0.7Fey)(y=1.85,1.9,2.0) samples were melted byvacuum arc furnace, and annealed at1000℃for1days and950℃for5days. The matrixof The x(Tb0.15Ho0.85Fe2)+(1-x)(Tb0.3Dy0.7Fe2) is REFe2phase and the structure containssmall amount of REFe3phase. Heat treatment can reduce the amount of REFe3phase andwas benefit to get the single-phase alloy. The peritectic temperature of the heat-treatedsamples was determined by differential thermal analysis. The magnetostriction λ∥slowlydecreases with increasing x in the range of0≤x≤0.1, and quickly does in the range of0.1≤x≤0.3. The magnetostrictive λ∥approaches saturation after the magnetic field of320kA/m. The magnetostriction is725×10-6at320kA/m for x=0.1. The magnetostrictiondecreased with the increase of Ho content.For the x(Tb0.15Ho0.85Fe1.9)+(1-x)(Tb0.3Dy0.7Fe1.9) alloys, the magnetostriction λ∥is750×10-6at320kA/m for x=0.3, and the saturation magnetostriction is810×10-6. Themagnetostrictive properties can be improved by means of magnetic heat treatment andpressure. The microstructure and magnetostriction of x(Tb0.15Ho0.85Fe1.85)+(1-x)(Tb0.3Dy0.7Fe1.85) alloys have been investigated, and there is some RE-rich phase,but no REFe3phase.It is found that Tb0.26Dy0.49Ho0.25Fe1.9alloy exhibits a good magnetostrictive property.Therefore, the atomic ratio should be selected as0.26to Tb, above0.25to Ho,1.9to Fe.The magnetostriction can reach800×10-6, and the hysteresis width is less than5kA/m.