Preparation And Soft Magnetic Properties Of Fe-Si-B-(Ni/Co) Amorphous Nanocrystals

Iron-based amorphous nanocrystalline alloys have excellent soft magnetic properties,mechanical properties,and low cost,so they are used for many components,such as transformers,sensors and others.In this thesis,Fe-Si-B alloy was chosen as the matrix to study the effects of Ni and Co substitution of Fe on the microstructure,thermodynamic behavior and soft magnetic properties of Fe-based amorphous nanocrystals.The microstructure of the strips was observed by X-ray diffractometry and transmission electron microscopy.The differential scanning calorimeter was used to measure the thermal properties of the strips,and the soft magnetic properties of the strips were characterized by a vibrating sample magnetometer and a coercivity tester.On the basis of Fe-Si-B,Fe_82-xNi_xB₁₂Si₆?x=4,8,12?,Fe_82-xNi_xB₁₄Si₄?x=4,8,12?Fe_84-xNi_xB₁₄Si₂?x=6,10,14?,and Fe_84-xNi_xB₁₂Si₄?x=6,10,14?series of alloys were prepared by melt quenching method with appropriate composition of Ni.By controlling the surface speed of the copper roller could be directly produced the quenching of the amorphous matrix containing nanocrystalline bands,after X-ray diffractometry and transmission electron microscopy analysis,the grain size was less than 40 nm.The method of preparing amorphous nanocrystals in suit reduced the energy consumption and brittleness of materials in the process of amorphous annealing crystallization.Through further research,it was found that with the increase of Ni content,the nanocrystalline grain size of the alloy decreased to some extent,the saturation magnetization gradually increased,and the coercive force gradually decreased,indicating that the addition of Ni played an effective role in the soft magnetic properties of the alloy.Used Co replaces Fe preparation Fe_84-xCo_xB₁₂Si₄?x=4,6,8?,Fe_84-xCo_xB₁₄Si₂?x=4,6,8?alloy,copper roll surface line was prepared velocity was 45 m/s.It was found that the microstructure of the alloy quenched strips was changed from amorphous to nanocrystalline with the increase of Co content,demonstrating that the capability of these alloys for forming amorphous was reduced.After testing its soft magnetic properties,it was found that the saturation magnetization of the prepared alloy increased and the coercivity decreased with the increase of Co content.After annealing,coercivity of the alloy strips reduced to different degrees in comparison to the prepared state.The results showed that the proper addition of Ni and Co in Fe-Si-B could precipitate nanocrystals in situ by a suitable preparation process,and the obtained iron-based amorphous nanocrystals has better soft magnetic properties.At the same time,this method improved the annealing process,which in turn reduced the energy consumption of annealing.