The Study Of The Magnetic Property Of The Fe-based Amorphous Alloys

The main work of this thesis focuses on magnetic properties of Fe-based amorphous alloys and mainly includes the following two parts.In the first part,Fe_80-xMo_xP₁₄B₆?x=3,6,9 at.%?bulk metallic glasses?BMGs?are successfully prepared by combining fluxing treatment and J-quenching technique.The effects of Mo substitution for Fe on magnetic properties,glass formation ability?GFA?,thermal stability and mechanical properties of the present FeMoPB BMGs have been investigated systematically.It is found that the present FeMoPB BMGs exhibit good soft magnetic properties,and the saturation magnetization of Fe₇₇Mo₃P₁₄B₆ BMG is 1.27 T at room temperature.The suitable substitution amount of Mo for Fe can enhance the GFA of Fe₈₀P₁₄B₆ alloys,and the critical maximum diameter for fully glass forming reaches 3 mm when the Mo content is 6 at.%.The compression test results show that the proper substitution content of Mo for Fe can obviously enhance the mechanical properties of the present FeMoPB BMGs,and Fe₇₄Mo₆P₁₄B₆ BMG exhibit a compressive strength of 3.6 GPa and a compression plasticity of 24%.In the second part,the effects of the replacement of Fe by Ni or Co on magnetic properties of Fe₈₀P₁₃C₇ BMGs have been studied through experimental and computer simulation methods.The results indicate that the average atomic magnetic moment per magnetic atomic monotonously decreases with the increases of Ni content for Fe_80-xNi_xP₁₃C₇?x=0,5,10,15,20,30 at.%?BMGs.In Fe_80-xCoxP₁₃C₇?x=0,5,10,15,20 at.%?BMGs,the average atomic magnetic moment per magnetic atomic first increases first and then decreases with increasing x from 0 to 20 at.%,and reaches the maximum at x=5,exhibiting the transition behavior from weak ferromagnetism to strong ferromagnetism.Based on magnetic valance theory,the relationship between the average magnetic valance per magnetic atom and the alloy composition in Fe_80-xNi_xP₁₃C₇ and Fe_80-xCoxP₁₃C₇ BMGs can be successfully interpreted.The XPS valance-band spectrum results show that the peak shift to higher binding energy with replacing Fe by Ni in Fe_80-xNi_xP₁₃C₇ BMGs,which may reflect the transition behavior from weak ferromagnetism to strong ferromagnetism and supports the rigid band model and charge transfer model.However,the peak position of XPS valance-band spectrum of Fe_80-xCoxP₁₃C₇ BMGs has no significant change with the Co content,which may result from a lack of accuracy or too small change in the charge of the valance electrons of the alloys.In order to further study the relationship between the saturation magnetization and the alloy composition in Fe_80-xNi_xP₁₃C₇ and Fe_80-xCoxP₁₃C₇ BMGs,we performed ab initio molecular dynamics simulations calculation.The simulation results show that the total density of state?DOS?of the two BMGs have no obvious change with the variation of Ni or Co content,exhibit that both the two BMGs are always weak ferromagnetism throughout the composition range,and the transition from weak ferromagnetism to strong ferromagnetism do not occurs.Thus the simulation results do not support the change transfer models,which is not consistent with the experimental results.It is indicated that there may be some problem in the present simulation calculation and the further research is required.