Effects Of Dc Joule Heating On Corrosion Resistance And Magnetic Anisotropy Of Fe₇₈Si₉B₁₃ Amorphous Alloys

In this thesis,we present a technique of DC joule heating to fabricate a Fe-based amorphous ribbon with excellent corrosion resistance and magnetization property.The microstructure of the amorphous ribbons has been characterized by X-ray diffraction(XRD),differential scanning calorimetry(DSC),thermal dilatometer(DIL),scanning electron microscope(SEM),transmission electron microscope(TEM).DC Joule heated samples are tested by electrochemistry corrosion in neutral and alkaline resultion.The result showed that corrosion potential is increasing and corrosion current is decreasing.the immersion corrosion results showed that with the current density of DC Joule heating increasing,corrosion current density decreasing.It shows that the effect of DC Joule heating on Fe78Si9B13 metallic glass is positive.From the result of the scanning electron microscopy we can found that the more DC Joule heating corrosion current density,the less corrosion particles in the sample surface.With the DC Joule heating current density increasing,the diameter and the number of pitting corrosion pit decreasing.From the result of the scanning transmission electron microscope,there are nanocrystalline in the C2,C3.The nanocrystalline develop the corrosion resisstance of Fe78Si9B13 amorphous ribbons.With increasing direct current density iDC from 0 to 2.7×105 A/cm2,the structure of Fe78Si9B13 ribbons is in amorphous state,their characteristic distance ?c and saturated magnetization Ms increase,but their electric resistivity p and coercivity Hc decrease;with increasing iDC from 3×105 to 3.3×105 A/cm2,the samples experience crystallization and their Ms and p decrease,but their Hc increases drastically.Moreover,the Ms of samples after DCH in longitudinal direction is higher than the samples in transverse direction,and their ?c,and p are on the contrary.The Fe78Si9B13 sample after DCH in longitudinal direction with iDc = 2.5×105 A/cm2 has excellent comprehensive soft magnetic properties of Ms=179.0 emu/g and Hc=1.8 A/m.The Fe78Si9B13 sample has a larger negative thermal expansion(NTE)degree in transverse direction than in longitudinal direction.The larger improvement of magnetic properties for Fe78Si9B13 glasses after DCH in longitudinal direction with respect to transverse direction can be explained from the viewpoint of the anisotropy in negative expansion and magnetization of ribbons.The anisotropic information of Fe-based glasses is helpful to fully explore the potential in their magnetic properties.