Microstructure And Properties Of(AlFeCoNiC_xTi_y)_100-zBi_z High Entropy Alloy

AlFeCoNi alloy has the advantages of high hardness and high strength because of its single BCC phase,but its self-lubricating property is poor.Therefore,in order to further improve the friction wear properties of the alloy,this paper uses AlFeCoNi alloy as the matrix,through in-situ reaction to generate lubrication phase-graphite and hard particle phase-TiC by adding C,Ti elements,and the element Bi is added to adjust the content and shape of graphite of the alloy.In this paper,A series of(AlFeCoNiCxTiy)100-zBiz high-entropy alloys were prepared by vacuum arc melting.The effects of C,Ti and Bi on the wear resistance and the wear mechanism of the alloy were studied,by analyzing the microstructure,the hardness,the friction and wear properties,and the antioxidant of the alloy.The results show that:1)The phase structure of AlFeCoNiCxTiy alloy consists of BCC,FCC,graphite and TiC.With the increase of the content of C and Ti,the wear mechanism of the alloy gradually changes from oxidation wear to oxidation wear and plastic deformation.When x=0.5 and y=0.1,the maximum hardness and minimum wear rate are 48.8 HRC and 6.0×101-5mm3·N-1·m-1 respectively,which are increased by 36.3%and 25%respectively,compared with AlFeCoNi alloy.2)The phase structure of(AlFeCoNiC0.5)100-zBiz alloy consists of BCC,FCCl,FCC2 and graphite.With the increase of the content of Bi,the graphite content firstly increases and then decreases,and the morphology of graphite also changes.When z=1.27,the morphology of graphite is vermicular and chunky,the content of graphite is reduced by 9.8%compared with Bi0 alloy.The maximum hardness and minimum wear rate of Bi1.27 alloy are 43.8 HRC and 3.3×10-5mm3·N-1·m-1 respectively,which are increased by 24.4%and 83.5%compared with Bi0 alloy.The wear mechanism of the alloy changes from oxidation wear and delamination wear to oxidation wear and plastic deformation.3)The phase structure of(AlFeCoNiC0.5Ti0.1)98.73Bi1.27 alloy consists of BCC,FCC,graphite and TiC.As the temperature rises,the wear mechanism of the alloy changes from delamination wear to oxidation wear,the lowest friction coefficient and wear rate of the alloy are 0.35 and 7.1×10-6mm3·N-1·m-1-1 at 800?.The oxides formed during oxidation wear are AlO3,CoFe2O4 and CoO,respectively.4)When (AlFeCoNiC0.5Ti0.1)98.73Bi1.27 alloy is oxidized at different temperatures,the oxides are planar Al2O3,polygonal CoFe2O4 and honeycomb CoO,respectively.With the increase of temperature and time,the oxidation rates of CoFe2O4 and CoO are higher than that of Al2O3?At the same time,the oxidation resistance of the alloy is excellent?...