原位自生碳化物增强 CoCrFeNi 高熵合金的显微组织与力学性能

In order to strengthen FCC-type high-entropy alloy (HEA), Ti and C were added to FCC single-phase CoCrFeNi HEA to realize the strengthening effect. (CoCrFeNi)_100-x(TiC)_x(x=0, 2, 4, 6, 8(atomic fraction,%)) was prepared by vacuum arc melting. Effects of different contents of Ti and C on the microstructure and mechanical properties of CoCrFeNi HEA were studied. The results show that after adding Ti and C, the microstructure of (CoCrFeNi)_100-x(TiC)_x changes from single FCC phase to FCC matrix phase and in-situ Ti-rich carbides. The formation of Ti-rich carbides does not change the type of matrix phase. Ti-rich carbides solidify along the interdendrite, which is lamellar and connected with each other to form a network structure. With the increase of Ti and C content, the content of FCC matrix phase gradually decreases, and the volume fraction of Ti-rich carbides gradually increases to 12%. The tensile test results show that with the increase of Ti-rich carbides content, the yield strength and tensile strength of the alloy increase continuously, while the elongation decreases; with x =8, the tensile strength can be increased from 409 MPa (x=0) to 618 MPa, with the applicable plasticity maintained, and the elongation can still reach 15. 7%. The hardness test results show that the hardness of the alloy increases with the increase of Ti rich carbides content; with x=8, the hardness value is 253HV₀ 2. The second phase strengthening of in-situ Ti-rich carbides, solid solution strengthening and the synergistic effect of dendritic lamellar and network structure improve the strength of the alloy and ensures its good plasticity.