Preparation Of Rare Earth Iron-based Alloy By Mechanical Alloying Milling And Magnetic Properties Study

RE-Fe rare earth iron-based alloy is a kind of magnetic material with excellent performance.It has the characteristics of low coercivity,low magnetic loss and high saturation magnetization.It is widely used in transformers,electromagnetic switches,sensors,magnetic refrigeration and magnetic fluids.Especially in the study of magnetic fluid,the particle size and magnetocaloric properties need to be fully considered.Mechanical alloying method can better realize metal alloying and achieve the purpose of grain refinement,and the operation is simple,the reaction process is safe and environmentally friendly.In this paper,rare earth Fe-based alloys were prepared by mechanical alloying.The specific contents are as follows: RE2Fe17 alloy was prepared by mechanical alloying,RE2Fe17 alloy was prepared by mechanical alloying assisted powder metallurgy,and Fe82RE12B6 and Fe75RE12Nb7B6 alloys were prepared by adding B and Nb elements,where RE = Sc,La,Nd,Sm,Gd,Dy,Ho and Yb.The phase composition,micromorphology,thermal properties and magnetic properties of rare earth iron-based alloys were investigated by Xray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),differential thermal analysis(DTA)and physical property measurement system(PPMS).The key findings are as follows:(1)The relationship between milling time and magnetic properties was studied by preparing RE2Fe17 rare earth iron-based alloy powders with different milling time.The diffraction peak intensity of α-Fe phase in RE2Fe17-M sample decreases,but no other crystal phases are precipitated.The samples have typical soft magnetic properties,and the saturation magnetization decreases with the increase of ball milling time.Among them,the Sc2Fe17-M sample changes the most,and the saturation magnetization decreases by 9 % after ball milling for 60 h.The coercivity increases with the increase of milling time.In addition,the results of magnetocaloric properties show that all samples can maintain good stability in the range of 220-400 K after ball milling for different time.The Curie point of Sm2Fe17-M sample is978 K.(2)The RE2Fe17 system rare earth iron-based alloy powder was prepared by mechanical alloying combined with powder metallurgy.The XRD results show that the system is dominated by the α-Fe phase,with a small amount of Sm2Fe17 phase present in the Sm2Fe17-BM sample,and that both crystalline and amorphous structures are present.The saturation magnetization is lower than that of the same component alloy samples prepared by mechanical alloying.The presence of Sm2Fe17 phase makes the coercivity of Sm2Fe17-BM and SF5-BM samples higher.Increasing Sm content can improve the sensitivity of magnetization to temperature.In the study of magnetocaloric properties,the magnetization of Sm2Fe17-BM and SF5-BM samples is sensitive to temperature,and the Curie temperature is 988 K and863 K,respectively.In addition,due to the presence of Sm2Fe17 phase and SmFe5 phase,the sample exhibits a magnetic transition at 420 K.(3)The effects of B and Nb on the amorphization and magnetic properties of Fe82RE12B6 and Fe75RE12Nb7B6 rare earth iron-based alloy powders were studied by mechanical alloying.The XRD patterns show that the addition of B element can greatly improve the glass forming ability of the alloy,and the peak shape of the diffraction peak is obviously broadened,only the α-Fe phase is observed.The Fe82Sc12B6 sample has the highest saturation magnetization of 165 emu/g.In the study of magnetocaloric properties,all samples have excellent stability.The substitution of Nb for Fe further improves the amorphization ability,and the Fe75Gd12Nb7B6 alloy has a typical steamed bread amorphous peak.The particle size distribution is relatively uniform and irregular polygon.The magnetic properties decrease with the decrease of Fe,while the coercivity increases.In the study of magnetocaloric properties,the addition of Nb improves the temperature sensitivity of magnetism,and the magnetocaloric coefficient of Fe75Gd12Nb7B6 alloy increases from 0.02 emu/(gK)to 0.21 emu/(gK).