Iron-based Amorphous Properties By Content Tuning And Isothermal Treatment

In this work,Element-specific positron annihilation spectroscopy was applied to study the local atomic structure and the correlation between amorphous-forming ability?AFA?and atomic packing state in(Fe_71.2B₂₄Y_4.8)_100-xNb_x?x=3,4,5,6?bulk metallic glasses?BMGs?.It was found that the changing tendency of the intrinsic positron lifetime was not correlated with AFA for Fe-B-Y-Nb BMG,which was attributed to that Nb atoms were not able to diffuse among the Bernal interstitial space.The findings help us to understand the relationship between the local atomic structure and the AFA.We also have developed a series of amorphous alloy ribbons of Fe₇₅Co₄B₁₃Y₄Nb_4-xNi_x?x=0,0.5,1,2,3 and 4?which were prepared by industrial purity alloy.Besides,the effects of Ni substitution and isothermal annealing on the saturation magnetization?M_s?and intrinsic coercive force?jH_c?were systematically investigated.The SQUID-VSM data pointed out the M_s has been increased by Ni content addition with largest enhanced by 57%from 114 emu/g to 180 emu/g.After quickly annealing at the optimal temperature,the M_s reached 199 emu/g and jH_c decreased from 50 Oe to33 Oe.DSC?Differential Scanning calorimeter?measurements displayed that this system has a multi-step crystallization in the heating process.Under the premise of maintaining the excellent amorphous forming ability?AFA?,the gap between the two crystallization peaks was broadened with Ni addition,which is good to the forming of?-Fe phase at the annealing treatment.And this was also consistent with the X-ray diffractometer?XRD?results.The annealing temperature and time can not only affect the precipitation of nano-crystalline,but also control the grain size.Hence,an appropriate annealing process is very important to improve the properties of these iron-based nanocrystalline magnetic materials.In conclusion,the results will help us to understand the influence of Ni elements and isothermal annealing on the microstructure and magnetic of Fe₇₅Co₄B₁₃Y₄Nb_4-xNi_x amorphous alloys.