[This article belongs to Volume - 53, Issue - 06]
Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-12-01-2022-110
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Title : Effect of Zr Addition on Microstructure and Wear Properties of CoCrCuFeMn High-entropy Alloy
MA Mingxing, ZHU Dachuan, WANG Zhixin, LI Shangzhi, DONG Chen,

Abstract :

High entropy alloys break through the traditional alloy design concept with one or two elements as basic elements, and have a simple phase structure and excellent comprehensive performance prepared by equimolar ratio or near equimolar ratio, which is expected to further expand the performance limit and application of metal materials. In order to study the effect of element doping on phase structure, microstructure and wear resistance, CoCrCuFeMn and CoCrCuFeMnZr high entropy alloys with equal molar ratio were prepared by vacuum melting method. The phase structure, microstructure, hardness and wear resistance of CoCrCuFeMn alloy before and after Zr addition were investigated by XRD, OM, SEM, EDS, microhardness tester and friction-wear tester. It was found that after Zr addition, the phase structure of CoCrCuFeMnZr alloy was changed from the original two FCC phases to two HCP phases, and the microstructure was obviously refined. The two alloys were typical dendrite structure. The friction curves of the two alloys showed a trend of first increasing, then decreasing, and then stabilizing. After Zr addition, the friction coefficient and mass loss rate decreased from 0.57 and 4.14% to 0.47 and 0.49% respectively, and the microhardness increased from 219.6 HV to 983.5 HV. The results showed that the HCP transformation of alloy phase structure was mainly related to the formation of a rough solid-liquid interface rich in Zr with large atomic radius and Z-shaped HCP orientation. The reason why Cu is enriched in the interdendrite region is that its melting point is the lowest, its electronegativity is the largest, its atomic radius is second only to Zr, and it has the corresponding largest positive mixing enthalpy with all alloy elements except Zr, so it is enriched in the interdendrite region with the latest solidification. Due to the fact that the melting point of Mn is only higher than that of Cu, Mn has the largest electronegativity difference except Zr, and there is a negative mixing enthalpy between Mn and Co or Zr and the largest positive mixing enthalpy between Mn and Cu, which is not conducive to its long-range diffusion and entering into the lattice site of the leading phase, the segregation coefficient of Mn is the smallest. The increase of hardness and wear resistance of the alloy with Zr element is due to fine grain strengthening, solid solution strengthening and phase structure transformation.