Y Content On FeCoNiAl_0.2Y_x High Entropy Alloy Performance Study

Among all metallic elements,iron,cobalt,and nickel are the three elements with stronger ferromagnetic properties.Fe Co Ni alloy is considered as the foundation for the design of all soft magnetic alloys in order to design complex magnetic alloys.In this thesis,FeCoNiAl_0.2Y_xhigh-entropy alloys were prepared by vacuum arc melting,aiming to study the properties of the alloy through XRD,SEM,SQUID,hardness test,and electrochemical measurement on the basis of the Fe Co Ni-based high-entropy alloy with good properties,and to investigate the mechanism that affects the magnetic and electrochemical properties by adjusting the Y element content.（1）The as-cast FeCoNiAl_0.2Y_xalloys are dendritic structures,including secondary dendrites and long dendrites,consisting of Fe Ni phases.FeCoNiAl_0.2Y_0.05,FeCoNiAl_0.2Y_0.1,and FeCoNiAl_0.2Y_0.2high-entropy alloys consist of Fe Ni phases and Co_5.95Fe_13.25Y₂phases.A new phase of Co_3.25Fe_5.15Y₂appears in FeCoNiAl_0.2Y_0.3.The hardness of FeCoNiAl_0.2Y₀high-entropy alloy is the lowest,at 146HV_0.2,and FeCoNiAl_0.2Y_0.3has the highest hardness,at 687HV_0.2.（2）The annealed alloy structure still exhibits dendritic structure,with finer dendritic structure,equiaxed dendrites,and parallel dendrites within the substrate.The microstructure of Y-containing alloys includes long dendrites and secondary dendrites,in addition to equiaxed columnar dendrites.Fe and Co are enriched in dendrites,while Ni,Al,and Y are enriched in interdendritic regions.EDS analysis shows that Y is mostly enriched in the interdendritic regions.The Y-free alloy consists of Al Ni₃phase.Fe₃Co₄phases appear after the addition of Y elements.The hardness of FeCoNiAl_0.2Y₀alloy is the lowest,at 146.8HV_0.2,and FeCoNiAl_0.2Y_0.3alloy has the highest hardness,at 554.4HV_0.2.（3）The saturation magnetization of FeCoNiAl_0.2Y₀alloy is 129.54emu/g,with a coercivity of 0.74Oe.The FeCoNiAl_0.2Y_0.1sample exhibits the highest saturation magnetization of 139.25emu/g,with a coercivity of 5.8Oe,reaching the maximum saturation magnetization and highest coercivity.The FeCoNiAl_0.2Y_0.3sample shows the lowest saturation magnetization at 115.78emu/g.After annealing,the saturation magnetization of the substrate increases from 129.54 emu/g to 140.61 emu/g,while the coercivity increases from 0.74Oe to 4.52Oe.The hysteresis loop area of the annealed alloy remains small and close to zero.（4）The corrosion potential of the as-cast alloy FeCoNiAl0.2Y0 increased from-1.072V to-1.081V for FeCoNiAl_0.2Y_0.05and then decreased to-1.042V for FeCoNiAl_0.2Y_0.3,while the corrosion current density decreased from 5.52×10^-5A/cm²for FeCoNiAl_0.2Y₀to 1.714×10^-5A/cm²for FeCoNiAl_0.2Y_0.2.The as-cast FeCoNiAl_0.2Y_0.1had the most positive corrosion potential and the lowest corrosion current density,while the as-cast FeCoNiAl_0.2Y_0.05had the most negative corrosion potential and the highest corrosion current density among the samples with added Y element,indicating the worst corrosion resistance.The self-corrosion potential of the annealed FeCoNiAl_0.2Y_xalloys decreased in the order of FeCoNiAl_0.2Y_0.05>FeCoNiAl_0.2Y₀>FeCoNiAl_0.2Y_0.1>FeCoNiAl_0.2Y_0.2>FeCoNiAl_0.2Y_0.3,while the self-corrosion current density decreased in the order of FeCoNiAl_0.2Y₀>FeCoNiAl_0.2Y_0.05>FeCoNiAl_0.2Y_0.2>FeCoNiAl_0.2Y_0.3>FeCoNiAl_0.2Y_0.1.FeCoNiAl_0.2Y_0.1also had a lower self-corrosion current density and corrosion voltage.The high-entropy alloy FeCoNiAl_0.2Y_xstill had an obvious passive region,and FeCoNiAl_0.2Y_0.1had the widest passive region,the densest dendrites,the smallest grain size,and the weakest intergranular corrosion tendency.The annealed FeCoNiAl_0.2Y_xhigh-entropy alloys had little change in corrosion potential,but the corrosion current density increased significantly,resulting in lower corrosion resistance than the as-cast alloys.Figure[28]table[14]reference[90]...