Influence of Si and B on Structure and Corrosion Properties of Quasi-Crystalline Al–Cu–Fe Alloys in Solutions of Salts

О. V. Sukhova, V. А. Polonskyy, K. V. Ustinоvа

Oles Honchar Dnipro National University, 72 Gagarin Ave., UA-49010 Dnipro, Ukraine

Received: 12.04.2018. Download: PDF

Structure of quasi-crystal Al–Cu–Fe alloys doped with silicon or/and boron is investigated in this work using metallographic, x-ray fluorescent and x-ray analyses. Influence of alloying elements on relative phase content of the structure is determined. The highest amount of icosahedral quasi-crystalline $\psi$-phase is revealed to be reached in the Al$_{55}$Cu$_{25}$Fe$_{12}$Si$_7$В$_1$ alloy structure. Alloying with silicon and boron favours the decrease in the content of iron-rich phases of the alloys’ structure. Corrosion behaviour in aqueous solutions of NaCl and Na$_2$SO$_4$ (pH = 7.0) is studied by the gravimetric and potentiodynamic methods. The alloys’ surfaces affected by solutions of salts are investigated using scanning electron microscopy. The most negative value of stationary potential is revealed for non-doped Al$_{63}$Cu$_{25}$Fe$_{12}$ alloy. With increasing concentration of both the silicon and the boron in the alloys, the values of stationary potentials steadily shift towards the more positive values. It is shown the prevailing influence of silicon compared to that of boron on the decrease in chemical activity of the alloys. As revealed, the investigated alloys corrode in solutions of salts as provided by electrochemical mechanism with oxygen depolarization. The alloys fail because of selective corrosion of iron within the Al–Cu–Fe alloys. As a result, the corrosion resistance increases with the decrease in the content of iron-rich phases of the doped alloys. The positive influence of silicon and boron on corrosion resistance of the alloys is confirmed by the investigations of the alloys’ surfaces affected by solutions of salts. The quantity and size of the corroded pits appearing mostly near iron-rich phases and phase interfaces are established to decrease.

Key words: quasi-crystalline alloys, alloying elements, structure, salt solutions, corrosion tests, stationary potential.



PACS: 61.44.Br, 68.35.Fx, 68.35.Np, 68.37.Hk, 81.05.Je, 81.65.Kn, 82.45.Bb

Citation: О. V. Sukhova, V. А. Polonskyy, and K. V. Ustinоvа, Influence of Si and B on Structure and Corrosion Properties of Quasi-Crystalline Al–Cu–Fe Alloys in Solutions of Salts, Metallofiz. Noveishie Tekhnol., 40, No. 11: 1475—1487 (2018) (in Ukrainian)

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