High Temperature Oxidation Resistance And Corrosion Resistance Of Cu_xCrFeNiTi High Entropy Alloy

High entropy alloys are a kind of new type alloy which different from the traditional design concept,the alloys composed of 5¹3 metals or non-metallic elements,and each component in equimolar or near equimolar concentrations formed alloys by mixing method,and the content of each component is between 5%³5%.Because of containing a variety of main elements in high entropy alloys,the high entropy effect produced between each element results in the crystal to form a simple structure solid solution easier,such as body centered structure solid solution and face centered structure solid solution,and probably accompanied by the formation of inter-crystalline compounds or nano-crystals,which can reach the solid solution strengthening,precipitation strengthening,precipitation strengthening and dispersion strengthening effect.By reasonable composition designing,high entropy alloys can show more excellent performance than traditional alloy,for example,high hardness,high strength,good high temperature oxidation resistance and excellent corrosion resistance,etc.In this paper,CuxCrFeNiTi?x=0.1,0.25,0.5,0.75,1??denoted as Cux in the following section? high entropy alloys are prepared by using the method of vacuum arc melting.Phase structure,microstructure and composition of Cux high entropy alloys are analyzed by using X-ray diffraction,scanning electron microscope and energy spectrometer.In addition,microhardness,high temperature oxidation resistance and corrosion resistance of these high entropy alloys are investigated,and the investigated result is analyzed and discussed.The results show that the as-cast Cu_x?x=0.1,0.25,0.5,0.75,1? high entropy alloys are mainly composed of FCC solid solution,BCC solid solution and Fe₂Ti Laves phase,and form typical dentrite microstructure.All the studied HEAs have high microhardness owing to the solid solution strengthening by multi elements;With the increase of Cu content,the microhardness of alloys is continuous decreasing from834 HV to 657 HV,which is mainly attributed to the decreasing volume fraction of Fe₂Ti Laves phase with the increase of Cu content.The oxidation experiment of Cu_x?x=0.25,0.5,0.75,1? high entropy alloys are examined at 600?,700?and 800?in air atmosphere.The results show that Cux?x=0.25,0.5,0.75,1?high entropy alloys can better conform to the parabolic law at600?and 700?.And the oxidation rate constant rise with the increase of temperature.When the temperature rise to 800?,the surface oxidation film of CuxCrFeNiTi high entropy alloys show severe cracking and peeling phenomenon,oxidation kinetics curve of these alloys no longer follow the rules of parabola;Cux?x=0.25,0.5,0.75,1?high entropy alloys form a variety of oxidation products in the process of oxidation,and the oxidation products mainly are TiO₂ and Cr₂O₃,In addition,there are a small amount of Fe₃O₄,Fe₂O₃,Fe₅CuO₈ and spinel oxides?mainly CuFe₂O₄,FeCr₂O₄ and NiFe₂O₄?.Cux?x=0.1,0.25,0.5,0.75,1? high entropy alloys possess good corrosion resistance with relative high Ecorr,low icorr and corrosion rate as whole.The corrosion resistance of the alloy decreases with the increase of the Cu content,and the interdendritic regions containing Cu-Ni-Ti-rich FCC phase is corroded in priority,the reason is that existing obvious positive and negative potential difference between Cu element of rich copper interdendritic regions and Cr element lean copper dendritic regions,which formed the galvanic corrosion,current leads to rich Cu interdendritic corrode in priority.