Structure, Thermal Stability And Magnetic Property Of Fe-based Sotf Magnetic Alloys

Fe₇₉Zr₉B₁₂, Fe₇₆Zr₉B₁₅, Fe₇₉Zr₈W₁B₁₂, Fe₇₉Zr₈Ti₁B₁₂, Fe79Zr8Mo1B12, Fe₅₇Co₁₉Zr₉B₁₅,Fe₃₈Co₃₈Zr₉B₁₅and Fe₄₀Co₄₀Zr₇V₂B₉Ta₂alloys were prepared by melt-spinning method in thispaper. The Thermal properties, structures and magnetic properties of the samples were studiedusing differential thermal analysis （DTA）, X-ray diffraction （XRD）, scanning electronmicroscope （SEM） and vibrating sample magnetometer （VSM）. The main results are asfollows:（1） The XRD results show that the α-Mn type and α-Fe phases are observed in theFe₇₉Zr₉B₁₂alloy in the initial crystallization stage. The Fe₂₃B₆type and α-Fe phases areobserved in Fe₇₆Zr₉B₁₅alloy. The change trends of coercivity （Hc） of two alloys afterannealing are different. Hcof Fe₇₉Zr₉B₁₂alloy increases suddenly at600℃and then softens.Hcof Fe₇₆Zr₉B₁₅alloy increases with increasing annealing temperature.（2） On the basis of Fe₇₉Zr₉B₁₂alloy, adding M （M=W、Ti、Mo） elements, Fe₇₉Zr₈M₁B₁₂alloys were prepared. The addition of Mo element increases the crystallization peaktemperature. The addition of W element increases the thermal stability. The addition of Tielement increases the hardness.（3） On the basis of Fe₇₆Zr₉B₁₅alloy,(Fe_1-xCo_x)₇₆Zr₉B₁₅（x=0,0.25,0.5） alloys wereprepared. The increase of Co content increases the thermal stability and changes thecrystallization process. The crystallization processes of (Fe_1-xCo_x)₇₆Zr₉B₁₅（x=0,0.25,0.5）alloys are: amorphous→amorphous+α-Fe+Fe₂₃B₆type→Fe2B+Fe3B+α-Fe; amorphous→amorphous+α-FeCo+α-Mn type→α-FeCo→ZrCo₃B₂+α-FeCo; amorphous→amorphous+α-FeCo→ZrCo₃B₂+α-FeCo. Hcof Fe₇₆Zr₉B₁₅and Fe₅₇Co₁₉Zr₉B₁₅alloys increases gradually.Hcof Fe₃₈Co₃₈Zr₉B₁₅alloy first increases and then decreases with increasing annealingtemperature.（4） The crystallization process of Fe₄₀Co₄₀Zr₇V₂B₉Ta₂alloy is: amorphous→amorphous+α-FeCo→α-FeCo+ZrCo₃B₂+ZCo₂₃Zr₆+ZrB. The results of SEM show the appearance ofthe cross section. In the Fe₄₀Co₄₀Zr₇V₂B₉Ta₂alloy as-quenched and annealed at300℃, thefree area shows mesh structure and the contact area shows dendritic structure. With theincrease of annealing temperature, the granular structure instead of the mesh structure of the free area and the dendritic structure of the contact area. After annealing at550℃,HcofFe₄₀Co₄₀Zr₇V₂B₉Ta₂alloy reaches minimum, then increases with increasing annealingtemperature.