Effect of Mo on microstructure, mechanical and corrosion properties of FeCrNiMnMox high-entropy alloys
Xuewei Xing, Jinkang Hu, Ying Liu, Wei Li
Abstract
Four FeCrNiMnMo x ( x =0, 0.1, 0.3, 0.5, in molar ratio) high-entropy alloys (HEAs) were synthesized by vacuum arc melting to explore the potential impact of Mo on the microstructure, mechanical properties, and passivation and electrochemical behaviors in 0.5 M H 2 SO 4 solution. The results display that the FeCrNiMn alloy exhibits a single face-centered cubic (FCC) structure while the microstructures of the FeCrNiMnMo 0.1 , FeCrNiMnMo 0.3 , and FeCrNiMnMo 0.5 alloys consist of the FCC and σ phase. The appear of the σ phase ascribed to the addition of Mo enhances the hardness and yield strength with the sacrifice of plasticity. The FeCrNiMnMo x HEAs achieve the maximum hardness of 414 HV 0.2 and the highest compressive yield strength of 830 MPa when x =0.5, but compressive fracture strain is lowered to 10.8%. X-ray photoelectron spectroscopy (XPS) and electrochemical analysis show that the passivation film in FeCrNiMnMo x alloy mainly consists of chromium oxides and molybdenum oxides. Mo has a beneficial effect on the corrosion resistance of the FeCrNiMnMo x HEAs in a 0.5 M H 2 SO 4 solution by increasing the corrosion potential ( E corr ) and decreasing the corrosion current density ( I corr ) and passivation current density ( I pass ). The FeCrNiMnMo 0.1 alloy shows the best corrosion resistance, mainly due to its passivation film consisting of a large proportion of chromium oxide (Cr 2 O 3 ). More Mo additions promote the formation of the precipitate of a phase and the matrix regions depleted Cr and Mo elements adverse to the resistance to preferential localized corrosion.