Study On Compression And Corrosion Resistance Of VCrNbMoW High Entropy Alloy Prepared By Mechanical Alloying

The composition design of high entropy alloy is multi principal element,which breaks away from the traditional alloy design framework of single principal element.High entropy alloy has many effects,such as high entropy effect in thermodynamics,slow diffusion effect in dynamics,lattice distortion effect in structure and"cocktail effect"in performance,so it can usually show many excellent properties,such as high strength,high hardness,high wear resistance,high oxidation resistance,high corrosion resistance and so on.Among them,refractory high entropy alloy has higher room temperature strength and high temperature softening resistance,which has a broad application prospect in the field of high temperature structural materials.In order to develop new refractory materials,VCrNbMoW high entropy alloy was prepared by mechanical alloying method and powder metallurgy method based on the existing theory and design concept of high entropy alloy.Firstly,the alloying sequence and microstructure of the main components in VCrNbMoW high entropy alloy,as well as the relationship between the grain size and the milling time were studied by means of X-ray diffraction analysis and transmission electron diffraction pattern analysis.It is found that with the increase of mechanical alloying time,the order of solid solution generation among the main elements in VCrNbMoW high entropy alloy is Cr-V-Nb-Mo-W.The main phase structure is Bcc solid solution.The relationship between grain size and milling time is=12.54+107.46/1+(x/2.68)~3.According to the change rule,the average grain size is stable at about 13nm after the ball milling time is extended to 20h or longer.Secondly,the compression properties of VCrNbMoW high entropy alloy were measured by universal mechanical testing machine,and the fracture morphology and fracture mechanism were analyzed by SEM.VCrNbMoW high entropy alloy has very high compression strength,prolonging the mechanical alloying time,the compressive strength of the material is obviously improved,the toughness and brittleness are optimized,and the material type changes from hard and brittle type to hard and strong type.The room temperature compressive strength of the VCrNbMoW high entropy alloy milled for 5h,10h,20h and 40H is 553.62mpa,1663.87mpa,3376.39mpa and3880.13mpa,respectively.After milling for 40H,the stress-strain curve of the alloy shows obvious yield point and plastic deformation before fracture.With the extension of mechanical alloying time,the fracture type of VCrNbMoW high entropy alloy changed from brittle cleavage with cleavage step pattern to quasi cleavage with partial dimple and tear ridge.Finally,the corrosion resistance of VCrNbMoW high entropy alloy in 1mol/L HCl solution,3.5%NaCl solution and 1mol/L NaOH solution and the effect of mechanical alloying time on its corrosion resistance were studied by electrochemical workstation.It is found that VCrNbMoW high entropy alloy has good corrosion resistance in 1mol/L HCl solution and 3.5%NaCl solution,but poor corrosion resistance in 1mol/L NaOH solution.