Influences of alloying elements and dendritic spacing on the corrosion behavior of Al-Si-Ag alloys

Author(s)

Gomes, Leonardo Fernandes ^[1] ; Kugelmeier, Cristie Luis ^{[1, 2]} ; Garcia, Amauri ^[3] ; Della Rovere, Carlos Alberto ^{[4, 1, 2]} ; Spinelli, Jose Eduardo ^{[4, 1]}

Affiliation

^[1] Univ Fed Sao Carlos, Grad Program Mat Sci & Engn, BR-13565905 Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Carlos, Munir Rachid Corros Lab, Dept Mat Engn, BR-13565905 Sao Carlos, SP - Brazil

^[3] Univ Estadual Campinas, Dept Mfg & Mat Engn, BR-13083860 Campinas, SP - Brazil

^[4] Fed Univ Sao Carlos UFSCar, Dept Mat Engn, BR-13565905 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T; v. 15, p. 5880-5893, NOV-DEC 2021.
• Web of Science Citations: 0

Abstract

The most important commercial casting alloys are those based on Al-Si. Their technical characteristics are highly connected to their as-cast microstructure, which is translated by the secondary dendrite arm spacing (SDAS). The alloy microstructure has been demonstrated to be changed by the adding of certain alloying elements, in the sense of boosting the desired properties and features. Search has been intensified to provide a positive balance of several properties, such as: high yield strength, high electrical conductivity, and high corrosion resistance, besides maintaining the ability for the alloy to be conventionally solidified. Under such context, both addition of Ag and the control of the fineness of the dendritic structure can be alternatives seeking better properties for Al-Si alloys. In addition to the possibility of application in current studies contributing to the growing development needs as engine materials, Al-Si-Ag alloys can emerge as an alternative to the manufacture of parts for electric vehicles, such as rotors and inverters, where high mechanical strength, corrosion resistance and electrical conductivity are required. Corrosion findings of Al-Si-Ag specimens having quite different SDAS of five alloys are presented here: Al-5wt.% Si, Al-5wt.% Si-0.1wt.% Ag, Al-10wt.% Si-0.1wt.% Ag, Al-5wt.% Si-2wt.% Ag, Al-10wt.%Si-2wt.%Ag alloys. A complete set of characterization with potentiodynamic polarization, electrochemical impedance spectroscopy, immersion tests, optical microscopy and scanning electron microscopy (SEM) was developed for these alloys. It has been demonstrated that increase in the alloy Si content diminishes corrosion resistance, and that increase in Ag content, considering Al-10% Si alloys, reduces corrosion resistance as well, despite creating thicker passive films. Furthermore, the alloys with the lowest Ag content (0.1 wt.%) had the greatest corrosion performance among the Ag-containing alloys, while the microstructure refinement tends to enhance the nobility of the samples. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). (AU)

• FAPESP's process: 19/23673-7 - Evaluation of alloys for thermal interface contact and for additive manufacturing
• Grantee: José Eduardo Spinelli
• Support Opportunities: Regular Research Grants