Solidified Structure And Mechanical Performance Research Of CoCrFeNiSi_x And CrFeNi₂Si_x High-entropy Alloys

High-entropy alloys(HEAs)or multi-principal element alloys(MPEAs)have many unique properties,such as high hardness,excellent temper softening resistance,good wear resistance,unique oxidation resistance,corrosion resistance and soft magnetic properties characteristic.These characteristics have caused widespread concern.High-entropy alloy materials have developed rapidly in recent years due to their excellent mechanical properties,especially the design of alloy components to achieve their specific properties has become a research hotspot.In this paper,a high-entropy alloy block smelted in a vacuum arc melting furnace is used to study the effect of different Si content on the microstructure and properties of CoCrFeNiSi_x(x=0,0.2,0.4,0.6,0.8,1)and CrFeNi₂Si_x(x=0,0.2,0.4,0.6,0.8,1)high-entropy alloys.The influence of Si content on the phase composition and microstructure of the two groups of alloys was analyzed by XRD,SEM,EDS,simulation calculation and other methods.and the mechanical properties and hardness of the alloys were tested at the same time.Study the feasibility of Ni substituting Co to reduce alloy costWith the increase of Si content,the CoCrFeNiSi_x high-entropy alloy and CrFeNi₂Si_x high-entropy alloy transform from a single FCC phase to FCC+silicide.When x=1,the FCC phase in the CoCrFeNiSi and CrFeNi₂Si alloys disappears,and there is a silicide grain boundary structure.The alloy microstructure is composed of silicide+silicide grain boundary structure.The increase of Si element causes lattice distortion of the alloy,and the lattice constant of the FCC phase increases.There is a slight difference between the simulated analysis and the experimental results in the element distribution,which may be caused by the delayed diffusion and solid solution phenomenon under non-equilibrium solidification.As the Si content increases,the strength and hardness of the two groups of high-entropy alloys increase,and the compression rate decreases.The increase in alloy strength and hardness may be caused by the solid solution strengthening of Si element and the second phase strengthening of silicide.When x=1,both CoCrFeNiSi and CrFeNi₂Si high-entropy alloys exhibit extremely strong brittleness,and the strength and hardness of the alloys are reduced.The addition of high content of Si element will cause the CoCrFeNiSi_x and CrFeNi₂Si_x high-entropy alloys to lose the FCC phase and greatly reduce the alloy properties.Comparing the mechanical properties of the two groups of high-entropy alloys,when x=0.6,CoCrFeNiSi_0.6 alloy and CrFeNi₂Si_0.6 high-entropy alloy have relatively excellent comprehensive properties.The yield strength,compressive strength,and hardness of CoCrFeNiSi_0.6 alloy are slightly higher than CrFeNi₂Si_0.6 high-entropy alloy,and the compressibility of CoCrFeNiSi_0.6 high-entropy alloy is slightly lower than that of CrFeNi₂Si_0.6high-entropy alloy.The experimental results show that it is feasible to replace Co with Ni in the CoCrFeNiSi_x series high-entropy alloys.