Variation of microstructures and properties of Co0.2CrAlNi high entropy alloy doped Si

The effects of Si on the microstructures and various properties of Co0.2CrAlSixNi (in mole ratio, x = 0, 0.1, 0.3, 0.5, and 0.7) multi-component high entropy alloys were investigated. Co0.2CrAlNi was selected as the matrix, and Si was doped as the reinforcement. Microstructure analysis revealed that the Co0.2CrAlSixNi high entropy alloys consisted of two body-centered cubic (BCC) phases, the Cr-rich phase and nano-scale Ni-Al phase. With the addition of Si, the new Cr3Si phase was precipitated, and the crystallite size decreased to some extent in the alloys. Hardness test indicated that the alloys had high hardness with the maximum value of 973 at x = 0.5. The crystallite size and Cr3Si phase content were two key factors significantly affecting the hardness of Co0.2CrAlSixNi HEAs. Electrochemical test results indicated that Si affected the formation of the passivation film, the corrosion potential of Co0.2CrAlSi0.1Ni was - 0.37 V and the self -corrosion current density was 1.15 x 10-6 A/cm2, respectively. The main contribution in which Si doping affected the corrosion resistance of HEA was reduced oxidized Cr3+ and Ni2+ on the alloy surface. This study is of great significance to develop light and hard engineering materials for practical applications.(c) 2022 Elsevier B.V. All rights reserved