Structure And Properties Of CrMoNbTaVZr System High Entropy Alloy Prepared By Molten Casting

High entropy alloys(HEAs),the alloys composed of at least five principal elements in equimolar or near equimolar ratios by melting or sintering methods etc.,which can facilitate the formation of simple solid solutions during solidification,breaking the traditional alloy concept.Recently,HEAs become a new research hotspot in the material science because it shows a lot of excellent performance such as good plasticity,high strength,high microhardness,good thermal stability and good corrosion resistance and has a very broad application prospect.In this present study,three sets of high entropy alloys CrMoNbTaV,CrMoNbTiZr and MoNbTaTiVZr are prepared by using the method of vacuum arc melting,microstructure,phase structure and composition of three as-cast alloy are analyzed by using scanning electron microscope,energy spectrometer and X-ray diffraction.In addition,micromicrohardness,high temperature oxidation resistance and corrosion resistance of these high entropy alloys are investigated.The present work mainly gains following results:The results show that the as-cast CrMoNbTaV alloy is mainly composed of BCC phase and a small amount of Laves phase V2Ta,and forms typical crystal structure which has composition segregation between intracrystalline and crystalline.The as-cast CrMoNbTiZr alloy is mainly composed of BCC phase,HCP phase and a small amount of Laves phase Ti4Cr,and formed typical crystal structure which has composition segregation between intracrystalline and crystalline.The as-cast MoNbTaTiVZr alloy is mainly composed of BCC phase and HCP phase,and forms typical crystal structure.The CrMoNbTaV alloy has a very high microhardness with the value of 923 HV,and the microhardness of interdendrites(950 HV)is significantly higher than the microhardness of dendrites(896 HV)because of composition segregation;The CrMoNbTiZr alloy has a microhardness value with 689 HV,and the microhardness of interdendrites(710 HV)is significantly higher than the microhardness of dendrites(668 HV)because of composition segregation;The MoNbTaTiVZr alloy has a relatively low microhardness with the value of 923 HV.The CrMoNbTaV alloy has poor oxidation properties at high temperature.With the increasing of oxidation time,the oxidation products rise at the temperature of 900 ?,1000 ? and 1100 ?.At last,there is a thick oxide layer is formed on the surface of the alloy,and the oxidation products mainly are Nb2O5,NbO2,CrTaO4,CrNbO4,Ta9VO25,Nb9VO25 and TaO.The three sets of high entropy alloy CrMoNbTaV,CrMoNbTiZr and MoNbTaTiVZr all show a good corrosion resistance.The corrosion rates of high entropy alloy CrMoNbTaV and CrMoNbTiZr are very small and decrease with the increasing of corrosion time.There is no obvious change on the surface morphology of CrMoNbTaV alloy after 96 h corroded in 3.5%NaCl solution,but there is pitting phenomenon appeared on the surface morphology of CrMoNbTaV alloy after 96 h corroded in 5%,15%,30%HNO3 solution.There is no obvious change on the surface morphology of CrMoNbTiZr alloy after 96 h corroded in 3.5%NaCl and 5%,15%and 30%HNO3 solution.The electrochemical corrosion results show that CrMoNbTaV and CrMoNbTiZr high entropy alloys have obvious passivation transition and passivation process in 3.5%NaCl and 5%,15%and 30%HNO3 solution.The comprehensive corrosion resistance of the MoNbTaTiVZr alloy is the most outstanding among the three sets of high entropy alloys.