| Rare earth giant magnetostrictive materials have attracted much interest because of theirgiant magnetostriction, high energy density and quick response at room temperature. They areregarded as important functional materials used in transducers and actuators.Sm-Nd-Fe alloyspossess the large negative saturation magnetostriction and contain no heavy-rare-earth elementswhich make it a candidate as new type giant negative magnetostrictive material. In the presentwork, the microstructure, structureand magnetostriction of Sm-Nd-Fe alloys have been studied.The magnetostriction of Sm1-xNdxFe2alloys has been improved by annealing and magneticannealing. In addition, the effects of different temperatures and pressures on magnetic propertieshave been investigated. Main results are summarized as follows:The Sm1-xNdxFe2magnetostrictive materials were prepared by vacuum arc furnace.(Sm,Nd)2Fe17phase,(Sm,Nd)Fe3phase and (Sm,Nd)Fe2phase are produced through peritecticreaction during solidification when x<0.5. The main phase of alloys is cubic Laves phase, andsmall amount of phases,(Sm,Nd)Fe3and (Sm,Nd), exist in the alloys. The magnetostriction ofSm0.88Nd0.12Fe2alloy is quite large and it can reach-800x10-6when magnetic field is700kA/m.A small amount of (Sm,Nd)Fe3and (Sm,Nd) phase in the as-cast Sm0.88Nd0.12Fe2alloy willreduce magnetostriction of alloy. After the as-cast Sm0.88Nd0.12Fe2alloy is heated to650℃andfor7days, the magnetostriction of annealed alloy is improved and it is as2.2times as that ofas-cast Sm0.88Nd0.12Fe2alloy.Magnetic annealing could improve the distribution state of initial domain in alloys. Themagetic filed direction, intensity, temperature, and time during the magnetic annealing haveaffected the magnetostriction. After the Sm0.88Nd0.12Fe2alloy is annealed at300℃for10min, inthe magnetic field of200kA/m, perpendicular to the axis direction of sample, themagnetostriction of alloy increases from-800ppm to-1600ppm. The magnetic properties of alloy change differently in different temperature and pressureconditions. The magnetic moments of alloy become small with temperature increases, and,therefore, the magnetostriction and magnetic induction intensity of alloy decreases withtemperature increases. The magnetostriction and magnetic induction intensity of alloy isobviously small at80℃. However, the magnetostriction and magnetic induction intensity ofalloy can be improved with increasing the pressure. The magnetostriction of alloy can obviourlybe improved under the pressure of10MPa. |
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