| Summary: | 碩士 === 中國文化大學 === 化學工程與材料工程學系奈米材料碩士班 === 106 === The purpose of this thesis is to study the microstructure and electrochemical properties of Cr19Fe22Co21Ni25Mo13 and Cr27Fe24Co18Ni26Nb5 high entropy alloys. The compositions of these two alloys were selected from the FCC phases in the CrFeCoNiMo and CrFeCoNiNb equlmolar alloys to develop the alloys with good corrosion resistance and workability. In this case, the polarization curves of Cr19Fe22Co21Ni25Mo13 and Cr27Fe24Co18Ni26Nb5 alloys in 0.5M sulfuric acid, 1M hydrochloric acid, 1M nitric acid, and 1M sodium chloride solution at 30, 40, 50, and 60 degrees Celsius were measured by a constant current/potentiometric potentiometer. The corrosion potential, corrosion current density, and passivation potential are compared with each other and finally compared with 304 stainless steel. These two alloys generated passivation zone in deaerated 0.5M sulfuric acid, 1M hydrochloric acid, 1M nitric acid, and 1M sodium chloride solutions. However, the passivation zone disappeared because the test temperature increased. This would also cause corrosion potential Ecorr and corrosion current icorr unstable. In addition, we investigated the microstructures and hardness of these alloys after annealing. Annealing had no effect on the Cr27Fe24Co18Ni26Nb5 alloy, but some precipitates were found in Cr19Fe22Co21Ni25Mo13 alloy.
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