Formation And Magnetic Properties Of FeCoNi-based High-entropy Amorphous Alloy

High-entropy alloy based on the concept of entropy is a new type of multi-component alloy.Due to its typical four core effects:the high entropy effect,the lattice distortion effect,the sluggish diffusion effect and cocktail effect,it presents a variety of excellent performance.However,so far,its mechanical properties have attracted researcheres'attention,while the magnetic properties of Fe Co Ni-based high-entropy alloys with ferromagnetic elements is still less researched.In particular,considering the isotropic magnetic structure of amorphous alloys and the characteristics of good magnetic properties,the combination of the structural characteristics of high-entropy alloys and amorphous alloys in order to give full play to the overall performance of the both,the development of high-entropy amorphous alloys has caused researcheres`interest.Therefore,in this paper,a series of high-entropy amorphous alloys Fe-Co-Ni-Si-B and Fe-Co-Ni-Si-B-Cu-Nb-V were perpared by the copper wheel spin quenching method.And,its amorphous forming ability,thermodynamic parameters,crystallization behavior and magnetic properties have been investigated.A series of(Fe-Co-Ni)₈₀Si₉B₁₁ high-entropy amorphous alloys were prepared by the copper roller spin quenching method,and the phase formation and magnetic properties were studied by XRD,TEM,DSC,VSM and other characterization methods.By comparing the structure of different alloys,it can be judged that Fe element has greatest amorphous forming ability,followed by Co,while Ni is the worst.The DSC curve shows that the most alloys have two-stage exothermic characteristics during crystalline.And,a rare endothermic transformation appears in Fe_26.67Co_26.67Ni_26.66Si₉B₁₁ with the highest entropy,when heating continues after the alloy is crystallized.The result of its crystalline phase shows that this process has undergone the transition from BCC to FCC.Through further investigation and research,it is found that the phase transformation process of Fe-Co-Ni-Si-B alloy system is determined by its components and composition.And,This is the result of the multi-component"cocktail"effect of the high-entropy alloy.The competition between the FCC tendency of Ni and the BCC tendency of Fe should play a important role.In addition,it can be seen from the activation energy fitting results that the primary crystalline phase of the alloy is easy to nucleate but difficult to grow,while the second crystalline phase has the highest stability.On the thermomagnetic curve,it can be seen that the more strong ferromagnetic elements alloys contain,the better the thermomagnetic stability alloys have,which means the ability to resist the decrease of the magnetic moment with the increase of temperature.Among Fe,Co and Ni,the thermomagnetic stability is Fe?Co>Ni.In the prepared Fe_24.5Co_24.5Ni_24.5Si_13.5B₉Cu₁Nb_xV_(3-x)(x=1-3 at%)alloy,a completely amorphous structure was obtained with the copper roll spin quenching method.And the endothermic process also occured in the alloy after complete crystallization,and it can be proved to be the transition from BCC to FCC.There is no obvious difference in the activation energy fitted by Kissinger or Ozawa,but the addition of Nb can significantly increase the apparent activation energy of the primary crystal phase of the alloy.With proper annealing method,a soft magnetic alloy has magnetic saturation greater than 0.7T and coercivity lower than 3A/m.