Surface Film Formation on Al-V Alloys with Far-From-Equilibrium Microstructure

Abstract

Nanocrystalline supersaturated Al-V alloys produced by high-energy ball milling have been reported to exhibit enhanced corrosion resistance and mechanical properties compared to commercial Al alloys. Corrosion of passive alloys such as Al-V alloy relies on the characteristics of the surface film, which is studied using scanning/transmission electron microscopy and time-of-flight secondary ion mass spectrometry. The effect of microstructure and composition on the surface film has been investigated after different immersion periods (30 min, 2 hours, and 1 day) in 0.1 M NaCl. The surface film was complex and composed of oxidized Al and V. The heterogeneous surface film was observed due to the presence of secondary phases and initiation of localized corrosion. The void formation was observed beneath the surface film that would potentially cause pitting corrosion. The generation of nano-sized voids was dependent on grain orientation. Compared to pure Al, the chloride penetration is suppressed in Al-V alloys. The effect of composition and microstructure on surface film formation and attendant corrosion behavior is discussed herein.

Effect of V Content on Corrosion Behavior of Al-V Alloys Produced by Mechanical Alloying and Subsequent Spark Plasma Sintering

“…This observation is consistent with the authors' previous studies, further evidencing the corrosion initiation in the V-lean phase at the interface between the Al-10V alloy matrix and the Vlean phase after exposing the alloy to 0.1 M NaCl. 36 This corrosion in the V-lean phase could be attributed to a higher electrochemical potential difference between the more noble matrix and the V-lean phase. The area fraction of the corroded V-lean region in Fig.…”

“…It should be noted that the Al-10V alloy E pit value after 30 min of immersion and pure Al electrochemical data are reproduced from the authors' previous publications. 35,36 switched from circuit 1 (Fig. 4a) to circuit 2 (Fig.…”

“…35 Furthermore, the authors showed that the increment of the V content up to 5 at% caused the strong enrichment of V within and underneath the passive film. 36 These enrichments act as a barrier layer for the chloride ion penetration and the prevention of dissolution of the passive film. Therefore, it can be proposed that the V content increment up to 5 at% resulted in the passive film resistance enhancement over the immersion time, as indicated by the R film .…”

“…Representative CPP curves for Al-xV (x-2,5 and 10 at%) as compared with the pure Al control specimens in 0.01 M NaCl after (a) 30 min, and (b) 14 days of immersion. It should be noted that after 30 min of immersion, CPP curves for Al-10V alloy and pure Al CPP curves are reproduced from the authors' previous publications 35,36.…”

Time-Dependent Corrosion Behavior of Aluminum Using Advanced Electrochemical and Characterization Techniques

“…Two regions were defined as surface film and substrate, where the metallic Al intensity became steady, and oxide ions of AlO 2 ‾ and 18 O 2 ‾ signals dropped. 45,46 However, Al 2 ‾ ion count was used to define the surface film/substrate interface as oxide ions of AlO…”