Study On The Microstructure And Corrosion Properties Of ?CuFeMnNi?_1-xCr_x?x=0-0.25? High Entropy Alloys

High entropy alloys adopt multi-principle design concept,which makes it have different microstructure and performance from traditional alloys and has been widely studied by researchers.CuCrFeMnNi series high entropy alloys are expected to be used in extreme conditions due to their excellent corrosion resistance and resistance to temper softening.This paper takes(CuFeMnNi)1-x,Crx(x=0-0.25)as the research object by means of X-ray diffraction,scanning electron microscopy,energy dispersive spectroscopy,differential thermal analyzer and electrochemical workstation as research methods.The effect of Cr content on the microstructure and corrosion resistance of the system were investigated systematically in order to provide reliable data for engineering applications.The main conclusions of the paper are as follows:Microstructure of as-cast(CuFeMnNi)1-xCrx(x = 0,0.05,and 0.1)alloys are composed of(Fe,Ni and Cr)-rich FCC1 and(Cu,Mn)-rich FCC2.However,as-cast(CuFeMnNi)1-xCrx(x=0.15,0.2 and 0.25)alloys contain FCC1,FCC2 and(Cr,Fe)-rich BCC phases.Annealed at 850? for 1440 hours,the microstructures of(CuFeMnNi)1-xCrx(x=0,0.05 and 0.1)alloys are composed of FCC1 and FCC2 phases as the same as the as-cast alloy structure,the dendrite size did not change significantly.The microstructure of the(CuFeMnNi)1-xCrx(x = 0.15,0.2,and 0.25)alloys turn to the FCC1,FCC2 and p phases,which is consistent with the conclusions of the phase prediction empirical formula.Annealed at 1100? for 320 hours,The compositional phase of(CuFeMnNi)1-xCrx(x = 0,0.05 and 0.1)alloys are composed of liquid phase and FCC1 phase,(CuFeMnNi)1-xCrx(x = 0.15,0.2 and 0.25)alloys are consist of liquid phase,FCC1 and BCC phase composition.The annealing experiment results show that the p phase is an unstable phase and disappears after high temperature.In addition,the hardness of as-cast and 850 ? annealed(CuFeMnNi)1-xCrx alloys increases with the increasing of Cr content.The hardness of(CuFeMnNi)1-xCrx(x = 0,0.05,and 0.1)as-cast alloys are relatively higher than that of the corresponding 850? annealed alloys.The corrosion of as-cast(CuFeMnNi)1-xCrx(x=0-0.25)alloys in the experimental acid,alkali and salt solutions mainly occurs between dendrites,due to the segregation of Cu elements,With the increasing of Cr content,the corrosion current density decreases and the corrosion rate gradually reduces,it shows that the corrosion resistance of(CuFeMnNi)1-xCrx,(x=0-0.25)high entropy alloys is improved.The alloy only undergoes an active dissolution process in 2 wt.%nitric acid solution and 3.5 wt.%sodium chloride solution,and no significant passivation behavior occurs.but the(CuFeMnNi)1-xCrx(x = 0.15,0.2 and 0.25)alloys show obvious passivation reactions in 4 wt.%sodium hydroxide solution.Corrosion experiments show that the corrosion resistance of as-cast(CuFeMnNi)1-x,Crx(x=0-0.25)alloy in 4 wt.%sodium hydroxide solution is obviously better than that of 2 wt.%nitric acid solution and 3.5 wt.%chlorination sodium solution.