Influence of Fiber Size and Interface Morphology on the Electrochemical Corrosion Resistance of Directionally Solidified NiAl-9Mo Eutectic Alloy

As the solidified microstructures have a significant influence on the corrosion behavior, the present work is thereby aimed to derive the optimum microstructures and electrochemical conditions for producing Mo nanowires. Eutectic microstructures showing coupling growth of NiAl phase and Mo fibers were obtained at growth rates from 10 µm/s to 40 µm/s. The fiber size varies from 800 nm to 300 nm, and decreases with the increase of solidification rate. The results of potentiodynamic polarization studies indicate that NiAl-Mo alloy at a growth rate of 20 µm/s has a better corrosion resistance in 0.1 mol/L HCl solution at room temperature. The electrochemical corrosion behavior of directionally solidified NiAl-Mo alloys not only depends on fiber size, but also relates to the interface morphology. To further analyze the influence of interface morphology on the corrosion behavior, velocity sudden change experiments were carried out. The microstructure of directionally solidified NiAl-Mo alloy transforms from planar to cellular and dendritic structures as the value of V/V₁ increases. The results of potentiodynamic polarization curves reveal that the planar structure has the highest corrosion resistance compared to other morphologies with the same fiber size of Mo-nanowires.