Effects of Ti Content on Microstructure and Mechanical Properties of High Entropy Alloys Fe_1.4Co_0.8Ni_0.8CrTi_x

Fe_1.4Co_0.8Ni_0.8CrTi_x(x=0, 0.1, 0.2, 0.25, 0.3) high entropy alloys with different Ti contents were synthesized by vacuum induction melting. The effects of Ti content on the microstructure and mechanical properties of Fe_1.4Co_0.8Ni_0.8CrTi_x high entropy alloys were investigated. The results show that Fe_1.4Co_0.8Ni_0.8CrTi_x high entropy alloys with different Ti contents are FCC single-phase solid solution. The microstructure displays typical dendrite and interdendritic structure. As Ti content increases, the precipitated phase rich in Ti increases obviously. The ultimate tensile strength first increases and then decreases,while the percent elongation gradually decreases. The fracture pattern transits from the ductile to cleavage fracture. When Ti is not added, the ultimate tensile strength of Fe_1.4Co_0.8Ni_0.8Cr is 523 MPa. When x increases to 0.25, the ultimate tensile strength of Fe_1.4Co_0.8Ni_0.8CrTi_0.25 gradually increases to 957 MPa, and the percent elongation is 30.7%, showing a ductile fracture. When x further increases to 0.3, the ultimate tensile strength is basically unchanged, the percent elongation reduces to 18%, and the fracture generates a cleavage fracture.