Research On GFA, Thermal Stability And Magnetic Performances Of Mult-elemental Fe-based Bulk Amorphous Alloys

Fe-based amorphous alloys have attracted attention of scholar more and more, owing to its'excellent physical,chemical and mechanical performance,specially it's soft magnetic nature will be applied extensively.Has used the ordinary casting method since 1989 to obtain the bulk amorphous alloy for the first time successly,the research of new bulk amorphous alloys developed extremely rapid and also the achievement are countless in the short ten years.Fe-based bulk metallic glasses plates with 0.5mm thickness were prepared by copper mould injection method in this paper.Alloy elements,such as B,Sn,Co and P were added into Fe-based alloys with proper quantities,and the effects on glass-forming ability(GFA),thermal stability,internal structure and magnetic performance of the alloys were investigated by X-ray diffraction(XRD),differential scanning calorimeter (DSC),Scaning Electron Microscope(SEM)and vibrating sample magnetometer(VSM).Research work showed:proper addition of element B was helpful to alloys'GFA, the melting point of alloy fell down accompany with addition of B,the alloys exhibit typical amorphous alloy morphology with 8.6%and 9.6%B addition(atom percentage).Meanwhile the amorphous clusters conformation were concervered by analyzing the SEM images of amorphous alloys and compared to other three parameters,γ(γ=Tx/(Tg+Tl))was a good one to measure GFA of Fe-based amorphous alloys by discussing the GFA of alloys.The experiments also showed that single Co or Sn cannot enhance the GFA of primitive component(Fe₆₄Ni₁Al₅Ga₂P_9.65B_9.6Si₃C_5.75),but simultaneously joins them has the tremendous influence to the internal structure.The alloys' GFA were effectively improved by adding 0.5%Co and 0.5%Sn and continuously enhanced along with the addition,but rapidly reduced when Co surpassed 3.5at%or Sn surpassed 0.5%.It was also found that based alloy's GFA increased and then decreased with the decrease of P and finally it formed the complex tissue including crystal phases and amorphous phases.Using the Kissinger equation,alloys' activation energy of crystallization initial temperature Ex and crystallization peak value temperature Ep were calculated to analyze the thermal stability.The analysis results indicated that the Fe₆₅Ni₁Al₅Ga₂P_8.65B_9.6Si₃C_5.75alloy had the best thermal stability.We also discussed the GFA from the difference of the atomic size,electrongativity and thermodynamics perspective and believed that reasonable atomic size difference will play a positive role on the GFA and the increase of electrongativity not only increases the interaction between alloying elements,but also conducive to the formation and stability of amorphous phases.Speaking from thermodynamics:the mixing enthalpy (â–³H)is smaller and the mixing entropy(â–³S)is greater,the free energy(â–³G)will reduce, which more favor forms the formation of amorphous alloy,but smallerâ–³G is by no means better,but has the certain variation range.Magnetic analysis shows that the coerciveforce size and the amorphous alloys' interior microscopic structure has a direct relationship.The more meticulous internal dusters were,the smaller coercivity was.The saturation magnetization is response to the intrinsic nature and Medium-range ordered structure will affect the existence of alloys' magnetic performance.