Preparation And Properties Of AlCrFeX High Entropy Alloys

High entropy alloy(HEA)is one of new alloys,which breaks though the concept of traditional alloys.It usually includes four or more elements as the main components,and takes equal mole ratio or approximate mole ratio as the design principle.It is prepared by ball milling or arc melting and so on.High entropy alloys have many advantages,such as high strength,high hardness,strong corrosion resistance,excellent radiation tolerance.It has a good application prospect in unclear material field.In this paper,six kinds of cast HEAs,AlCrFeMo,AlCrFeZr,AlCrFeNb,AlCrFeSi,AlCrFeMoSi and AlCrFeMoZr,were produced.The microstructure of thess HEAs were analyzed by means of OM,XRD,SEM and EDS.The hardness of the HEAs was measured and the oxidation resistance of the HEAs was also analyzed.The following conclusions are obtained:(1)The phase formation of high entropy alloy is predicted by thermodynamic simulation and XRD analysis.AlCrFeMo alloy is made of a single phase BCC solid solution.AlCrFeZr is Zr rich HCP phase and BCC phase,AlCrFeNb generates BCC and Laves phase,AlCrFeSi generates BCC phase and Cr5Si3 phase,AlCrFeMoSi generates BCC phase and Mo5Si3 phase,AlCrFeMoZr alloy generates BCC phase and Cr2Zr phase.(2)The hardness of six groups of alloys were measured.The hardness of AlCrFeMo is 679 HV,hardness of AlCrFeZr is 804 HV,hardness of AlCrFeNb is 771 HV,hardness of AlCrFeSi is 986 HV,hardness of AlCrFeMoSi is 784 HV,hardness of AlCrFeMoZr is 925 HV.(3)The high temperature oxidation experiments showed that after high temperature oxidation,the outer oxidation layer of of AlCrFeMo alloy is MoO3,Fe2O3,Fe3O4 and Al2O3;For AlCrFeNb alloy,the oxiadtion layer is(Al0.9Cr0.1)2O3,Fe(Cr,Al)2O4 and NbCrO4;For AlCrFeSi alloy,the oxiadtion layer is Al2O3 and SiO2;For AlCrFeMoSi alloy,the oxiadtion layer is Al2O3;For AlCrFeMoZr alloy,the oxiadtion layer is MoO3,Fe2O3 and AlxZr1-xOy(x=0?1,y=1.74?2).The thickness of the outer oxide layer of AlCrFeMoZr alloy can reach 6.2 ?m,the intermediate oxide layer is about 6?m,the inner oxide layer thickness is about 4 ?m;The thickness of outer oxide layer of AlCrFeMo alloy is about 10 ?m,the inner oxide layer thickness is about 2.5 ?m;oxidation layer thickness of AlCrFeSi alloy and AlCrFeMoSi alloy is 5.4 ?m and 3.6 ?m,the outer oxide layer of AlCrFeNb alloy is about 2 ?m,the inner oxide layer is about 5 ?m.The thicker the oxide layer is,the worse its property is.We can find out that AlCrFeMoSi alloy has the best oxidation resistance,followed by AlCrFeSi alloy,both alloys generated Al2O3.The oxidation resistance of AlCrFeNb alloy is poorer than these two alloys,total thickness of oxide layer is about 7 ?m.AlCrFeMo alloy and AlCrFeMoZr alloy has the worst oxidation resistance.