Al-Co Alloys Prepared by Vacuum Arc Melting: Correlating Microstructure Evolution and Aqueous Corrosion Behavior with Co Content

Lekatou, Angeliki, Sfikas, Athanasios, Petsa, Christina and Karantzalis, Alexandros (2016) Al-Co Alloys Prepared by Vacuum Arc Melting: Correlating Microstructure Evolution and Aqueous Corrosion Behavior with Co Content. Metals, 6 (3). p. 46. ISSN 2075-4701

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Official URL: https://doi.org/10.3390/met6030046

Abstract

Hypereutectic Al-Co alloys of various Co contents (7–20 weight % (wt.%) Co) were prepared by vacuum arc melting, aiming at investigating the influence of the cobalt content on the microstructure and corrosion behavior. Quite uniform and directional microstructures were attained. The obtained microstructures depended on the Co content, ranging from fully eutectic growth (7 wt.% and 10 wt.% Co) to coarse primary Al9Co2 predominance (20 wt.% Co). Co dissolution in Al far exceeded the negligible equilibrium solubility of Co in Al; however, it was hardly uniform. By increasing the cobalt content, the fraction and coarseness of Al9Co2, the content of Co dissolved in the Al matrix, and the hardness and porosity of the alloy increased. All alloys exhibited similar corrosion behavior in 3.5 wt.% NaCl with high resistance to localized corrosion. Al-7 wt.% Co showed slightly superior corrosion resistance than the other compositions in terms of relatively low corrosion rate, relatively low passivation current density and scarcity of stress corrosion cracking indications. All Al-Co compositions demonstrated substantially higher resistance to localized corrosion than commercially pure Al produced by casting, cold rolling and arc melting. A corrosion mechanism was formulated. Surface films were identified.

Item Type: Article
Uncontrolled Keywords: Al-Co alloys; hypereutectic; Al9Co2; complex metallic alloys; vacuum arc melting; directional growth; aqueous corrosion; reverse polarization; pseudo-passivation; Raman spectroscopy
Subjects: H300 Mechanical Engineering
H800 Chemical, Process and Energy Engineering
H900 Others in Engineering
Department: Faculties > Engineering and Environment > Mechanical and Construction Engineering
Depositing User: Rachel Branson
Date Deposited: 02 Mar 2021 15:00
Last Modified: 02 Mar 2021 15:00
URI: http://nrl.northumbria.ac.uk/id/eprint/45587

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