Study on Microstructure Evolution and Mechanical Properties of CoCrFeNiTiAl_x High Entropy Alloys

CoCrFeNiTiAl_x high entropy alloys(x=0,0.25,0.5,0.75,1,1.5,2,x is the mole ratio)were prepared by vacuum arc melting.The effects of Al content on the phase structure and mechanical properties of CoCrFeNiTiAl_x high entropy alloys were studied.The results show that Co Cr FeNiTi alloy exhibits FCC crystal structure.With the increase of Al content,the crystal structure transfers to BCC crystal structure.The microstructure of CoCrFeNiTiAl_x alloy is dendritic structure.The dendritic region is rich in Co,Ni,Ti and Al,and the interdendritic region is rich in Cr and Fe.CoCrFeNiTiAl_x shows excellent mechanical properties at room temperature,when x=0.5,the properties of the aloy are the best one,then,the microhardness of the dendritic region reaches 829 HV,the interdendritic microhardness is 952 HV,the compressive strength is 2.023 GPa,and the elastic modulus is 21.29 GPa.