Effects Of Annealing And Remelting On Corrosion Resistance Of AlCoCuFeNiCr_x High Entropy Alloy In NaCl Solution

As a new material with high hardness and strength,excellent wear and corrosion resistance,high entropy alloys(HEAs)exhibit many superb properties.Based on their properties,HEAs have wide prospects in application.Therefore,it has great significance to study the formation and transformation of their phases,microstructure and corrosion resistance.The cast Al CoCuFeNiCr_x(x=0,0.25,0.5,1)HEA was prepared by vacuum arc furnace melting and sheet metal specimens with size of 2 mm × 10 mm × 85 mm were manufactured by copper mold suction casting method.X-ray diffraction,metallographic microscope and energy dispersive system(EDS)were used to study phase composition and microstructure of the cast AlCoCuFeNiCr_x(x=0,0.25,0.5,1)HEA.It was found that all the cast HEA was composed with BCC(body-centered cubic)and FCC(face-centered cubic)phases,and phase composition has not changed with the increasing Cr,metallographic structure was the typical dendrite structures.Corrosion resistance was tested by immersion test,polarization test and scanning electron microscope(SEM),the results showed that corrosion resistance of the cast HEA increased with the increasing Cr.Then the specimens were annealed in a chamber electric furnace,phase composition has not changed with the increasing Cr,which were still BCC and FCC phases.But the dendrite grew larger compared with that of the cast specimens.Corrosion resistance of the annealed specimens increased with the increasing Cr and showed better corrosion resistance than the cast ones.AlFeNiCoCuCr HEA with the best corrosion resistance of the cast and the annealed specimens was chosen to be remelted,intending to study and compare the microstructure and their corrosion resistance among the three conditions.It was discovered that the AlFeNiCoCuCr HEA was still composed with BCC and FCC phases after remelting,size of its dendrite was between that of the cast and the annealed HEAs.Corrosion resistance of the remelted HEA was better than that of the cast HEA,but remelting had less effect on corrosion resistance compared with annealing.In summary,corrosion resistance was enhanced with the increasing Cr.Moreover,annealing and remelting both have positive influences on microstructure and corrosionresistance of Al FeNi CoCuCr HEA,but the influence of remelting is relatively smaller than the influence of annealing.