Researches On Preparation And LaCe-doping Of FeGa Magnetostrictive Alloy

FeGa alloy has the advantages of responding to magnetic field rapidly,the price is cheap,and it can be machined easily,so it was considered as a promising magnetostrictive materials for practical application.But it should be noted that the magnetostricitive coefficient of FeGa alloy is lower than TbDyFe giant magnetostrictive materials.And for the best performance of FeGa alloy is single crystal which oriented to <100> plane.However,for the preparation method of FeGa alloy,polycrystalline is obtained easily than single crystal.In order to improve the saturation magnetostricition coefficient of FeGa polycrystalline alloy,researches were carried out from two aspects in this paper.One is the preparation technology of FeGa alloy.Fe₈₁Ga₁₉ alloy was prepared with vacuum melting and mechanical alloying methods.The as-cast alloy was homogenized and heat treated at different temperatures.The powders,prepared by mechanical alloy,were sintered at 1100 for 3 hours ?after compression molding process.The other one is the composition of FeGa alloy was the focus of research.Ce and LaCe were dopped into Fe₈₁Ga₁₉ alloy to obtain some phase and microstructure which could lead to higher magnetostricitive coefficient.After analyzing the Fe₈₁Ga₁₉ alloy which prepared by vacuum melting and heat treatment method,the results showed that heat treatment process can disappeare the intragranular subgrain boundary and the grain size grow up.When the heat temperature was 800?,the <100> preferred orientation was obtained,and the saturation magnetostricitive coefficient was 95 ppm under the magnetic field of 50 KA/m.So the heat treatment process was an effective way to improve the magnetostricitive coefficient of Fe₈₁Ga₁₉ polycrystalline alloy.After Ce and LaCe doping into Fe₈₁Ga₁₉ alloy,due to the solubility of Ce and LaCe in Fe is low,the rare earth can not be dissolved completely.It can form new compounds with other elements.These compounds can turn into heterogeneous nucleation and prevent the grain growth process during heat treatment.There are some other phases were detected after doping.For example,the L12 phase,ordering D03 phase and disorder D03 phase,all of these phases effect the magnetostricitive coefficient of FeGa alloys.Among all the doped samples,the largest magnetostrictive coefficient was about 80 ppm.So the Fe₈₁Ga₁₉ alloy which use rare earth doping method to improve magnetostricitive coefficient should be reseached more deeply.For the Fe₈₁Ga₁₉ alloy which prepared by mechanical alloying method,the results showed that the sintered density were low,and some phases which could reduce magnetostricitive coefficient appeared.All of these reasons above result in low magnetostricitive coefficient?the best performance only 22 ppm?.According to this paper,the best heat treatment process for Fe₈₁Ga₁₉ polycrystalline alloy is homogenizing at 1100? for 1 h,and then heat treating at 800? for 3 h.For the alloy which doped rare earth,the best performance sample when the heat treatment was 800?,Ce and LaCe contents was 0.3% and 1.4% respectively.