| High-entropy alloys(HEAs)are new types of alloys developed in recent years,usually consisting of five or more major elements with approximately equimolar ratios.High-entropy alloys are easy to form simple face-centered cubic(FCC),body-centered cubic(BCC),and close-packed hexagonal(HCP)structural solid solutions.Because of its excellent properties,such as high ductility,high strength,excellent wear resistance,excellent corrosion resistance and excellent high temperature stability,it has become one of the hot materials.This article takes CoCrFeMnNi high-entropy alloy as the research object,preparesCoCrFeMnNi high entropy alloy powder by one-step gas atomization method,and then uses VHPS to prepare CoCrFeMnNi,Al powder and TiC reinforced CoCrFeMnNi high-entropy alloy block.material.With the help of XRD,SEM,ICP,the microstructure and chemical composition characterization was performed,the Vickers hardness of the sample was tested by a micro Vickers hardness tester,the Tafel curve and electrochemical impedance spectrum of the sample were tested by an electrochemical workstation to study its corrosion resistance.In this study,a spherical CoCrFeMnNi high-entropy alloy powder was first prepared by a one-step gas atomization method.The powder has an FCC single-phase structure,and each element is uniformly distributed on the entire powder surface and section,with an average particle size of about 34?m.Then,the CoCrFeMnNi high-entropy alloy bulks was successfully prepared by the VHPS method,and the influence of sintering temperature on the microstructure and properties was studied.Analysis of the microstructure and chemical composition shows that the CoCrFeMnNi high-entropy alloy block is mainly composed of the FCC phase and contains a small amount of precipitated phases.Co,Fe,Mn,and Ni are mainly distributed in the FCC phase,and Cr is mainly distributed in the precipitated phase.And each element is uniformly distributed in the two phases,as the sintering temperature is increased from 900?to 1100?,the size of the precipitated phase becomes smaller,the distribution is more uniform,and the structure is denser.The hardness test results show that with the increase of the sintering temperature,the hardness increases from 151.4 HV at 900?to 248.4 HV.Electrochemical tests show that as the sintering temperature increases,CoCrFeMnNi high-entropy alloy blocks sintered at 1100?have the smallest corrosion current in 3.5%Na Cl solution,0.05 mol/L HCl solution and 0.5 mol/L H2SO4,respectively it was 2.256×10-6A/cm2,4.180×10-6A/cm2and 2.836×10-5A/cm2.Next,CoCrFeMnNi high-entropy alloy blocks with different Al powder contents were prepared,and the microstructure control and performance enhancement of CoCrFeMnNi high-entropy alloys were studied with Al content.The analysis of microstructure and chemical composition shows that the crystal structure of CoCrFeMnNi high-entropy alloys with different Al contents is composed of FCC and BCC dual phases.Cr,Mn,and Al are mainly concentrated in the BCC phase region,and Co,Fe,and Ni are mainly concentrated in the FCC phase.Zone,and each element is distributed in both phases;as the Al content increases,the BCC phase content increases.The hardness test results show that as the Al content increases,the hardness first increases and then decreases.The hardness is the highest when the Al content is5wt.%,Reaching 508.3 HV,and then the hardness is reduced to 396.0 HV when the Al content is increased to 7wt.%.Electrochemical tests show that the CoCrFeMnNi high-entropy alloy block with 5wt.%Al content has the smallest corrosion current in3.5%Na Cl solution,0.05 mol/L HCl solution and 0.5 mol/L H2SO4solution,respectively it was 2.878×10-7A/cm2,2.633×10-6A/cm2and 2.476×10-6A/cm2.Finally,Al0.55CoCrFeMnNi high-entropy alloys with different TiC contents were prepared.The microstructure control and performance enhancement of Al0.55CoCrFeMnNi high-entropy alloys were studied by TiC.The analysis of microstructure and chemical composition shows that the crystal structure of Al0.55CoCrFeMnNi high-entropy alloy with different TiC content is composed of FCC,BCC and TiC phases,each element in Al0.55CoCrFeMnNi high-entropy alloy with two kinds of TiC is in addition to Ti,the two phases are uniformly distributed,Cr and Mn are mainly concentrated in the BCC phase region,Co,Fe,Ni,and Al are mainly concentrated in the FCC phase region.Ti agglomeration in Al0.55CoCrFeMnNi high-entropy alloy containing TiC(0.8?m)more serious,the distribution of Al0.55CoCrFeMnNi high entropy alloy with TiC(3?m)is more uniform.The hardness test shows that the Al0.55CoCrFeMnNi high entropy alloy containing TiC(3?m)has a higher hardness.As the TiC content increases,the hardness increases first and then decreases.When the TiC content is 5wt.%,The hardness is the highest,reaching622.5 HV.When the TiC content was increased to 7wt.%,The hardness decreased to591.3 HV.Electrochemical tests show that the Al0.55CoCrFeMnNi high-entropy alloy containing 5wt.%TiC(3?m)has the smallest corrosion current in 3.5%Na Cl solution,0.05 mol/L HCl solution and 0.5mol/L H2SO4solution,respectively it was 1.565×10-7A/cm2,1.642×10-6A/cm2and 1.876×10-6A/cm2. |
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