| Amorphous alloys posseses the unique of atomic structure and performance that is beyond the traditional crystal material,in which Iron-based amorphous alloy known as soft magnetic properties is one of the most mature and widely applying.In this article,we choose the amorphous alloy with Fe64Ni1Al4.5Cu0.5Ga2P9.65B9.6Si3C5.75 as the research object and pretreated by pulsed magnetic field under condition of different parameters,then samples were crystallized partially.The influence of Fe-based amorphous with pulsed magnetic field on structure,crystallization kinetics and magnetic properties after crystallization were studied through XRD,DSC,VSM and other methods of detection.According to comparison of the X-ray diffraction analysis between the alloys treated by pulsed magnetic field and the quenched sample,it is found that the structure of samples with treatment presents more intense peak fluctuation,a certain number of atomic clusters and micro-nuclei are formed in the alloy,however,it still maintains the amorphous state.As the times of pulsed magnetic field on samples increasing,structural changes become more and more significant,and variety of magnetic field intensity doesn’t bring obvious distinction for amorphous strcture.Result of differential scanning calorimetry reflects firstly that crystallization process of amorphous alloy has remarkable dynamic characteristics and effect of energy compensation makes the crystallization temperature of the samples after treatment of pulsed magnetic field decayed to quenched state.Meanwhiles,augment of pulse number lead to continuous descent of Tx and Tp,the degree of decline is obviously greater than that of strength of magnetic field.Next,crystallization activation energy of specimens Z and A,B,C,D,E are calculated by the Ozawa method,the initial activation energy Ex are 405.5kJ/mol,430.7kJ/mol,453.1kJ/mol,475.5kJ/mol,481.1kJ/mol,484.3kJ/mol and the peak activation energy Eg are 458.7kJ/mol,485.2kJ/mol,509.7kJ/mol,530.2kJ/mol,535.1kJ/mol,539kJ/mol respectively,which is found that the growth of crystal grains is more difficult than nucleation for amorphous crystallization and magnetic pulsed treatment enhance stability of amorphous phase.When magnetic pulsed number is taken as variable,increment of Ex and Ep is larger,on the contrary,increment is much smaller as the variable is strength.Last,the Avrami factor mx and mp in the crystallization process of specimen is calculated based on the JMA model.The crystallization process of amorphous alloys is the transition from the overall crystallization to the surface crystallization and rate of reaction is accelerated by treatment of pulsed magnetic field.Simultaneously,both mx and mp are positively correlated with the number and intensity,which variation of mx is at the time of change of magnetic field intensity,the mp value-added of two cases is closer.In the light of the XRD analysis of the crystallized samples,it is discovered that magnetic pulsed processing can effectively improve the diffusion ability of small size atoms.When intensity is 6T,this action is enhanced with increasing of number,while,strength has weak impaction for it at the moment of pulse number being 700 times.Besides,it indicates pulsed magnetic field plays a role in grain refinement that the grain size of samples Z and A,B,C,D,E are namely 31.8nm,30.1nm,28.8nm,27.9nm,25.0nm,24.5nm.Addition of the number and intensity is provided with stimulation for aggrandizement of crystallization ratio,and magnetic pulsed treatment raises the amount of nucleation.The VSM test shows that treatment of magnetic field optimizes comprehensive soft magnetic properties of the samples after crystallization,but the magnetic coercivity appears enhencement accompanied by increasement of times and intensity.It clearly states that the substantial addition in the number and strength of magnetic pulses is not an absolute benefit to the improvement of the soft magnetic properties for amorphous nanocrystalline materials. |
