Degradation processes in Al/SiC_p/MgAl₂O₄ composites prepared from recycled aluminum with fly ash and rice hull ash

Abstract

The degradation characteristics of Al/SiC p /spinel composites prepared with fly ash (FA) and rice hull ash (RHA) under environmental conditions were investigated. Composite specimens were prepared with recycled aluminum via reactive infiltration in the temperature range 1050-1150 8C for 50-70 min and, in argon atmosphere at a pressure slightly above that of the atmospheric pressure. Results reveal that although both FA and RHA help in preventing SiC p dissolution and the subsequent chemical degradation of the composites, due to the interaction of native carbon in FA with liquid aluminum, FA-composites are susceptible to corrosion via Al 4 C 3 . Moreover, this phase accelerates the degradation process and increases the damage severity. The primary corrosion mechanism in both types of composites is attributed to microgalvanic coupling between the intermetallic Mg 2 Si and the matrix. Accordingly, an appropriate control of the Si/(Si þ Mg) molar ratio in the aluminum alloy hinders the Mg 2 Si corrosion mechanism in both types of composites and a proper FA calcination prevents chemical degradation in FA composites.

Corrosion characteristics of Al‐Si‐Mg/SiCp composites with varying Si/Mg molar ratio in neutral chloride solutions

“…The other common method is the use of SiO 2 , either by intentional oxidation of SiC [3,8], by the presence of a native SiO 2 layer on commercial SiC particles [9] or even by the use of SiO 2 particles into the SiC performs [10]. Fly ash (FA) and rice hull ash (RHA) contain SiO 2 and, as we reported recently in this journal [11], they represent an interesting alternative for incorporating Si to the infiltration process. Their addition helps not only in preventing the formation of Al 4 C 3 , but also in abating fabrication costs and promoting in situ growth of thermodynamically stable phases (MgO and MgAl 2 O 4 ) that may act as reinforcements.…”

“…Our recent contribution includes results of an investigation in which matrix alloying was combined with the inclusion of FA or RHA during the infiltration process [11]. Two different alloys were used for the fabrication of the composites, containing a fixed amount of Mg (15 wt%) and variable Si (3 and 8 wt%).…”

Conservation of waste melon shell and fly ash utilized as reinforcements for aluminum alloy matrix in terrestrial ecosystem acquired green hybrid composites

“…Effectively utilizing agricultural waste can reduce fabrication costs and form a protective layer against pollution. Organic waste has been utilized to replace ceramic (inorganic) material and gained similar mechanical and tribological characteristics (Pech‐Canul et al., 2007). The waste fly ash reinforced steel concrete structure increased compressive strength and corrosion resistance for commercial building applications (Ali et al., 2022).…”

Applicability of Industrial Wastes in Metal Matrix Composites Production – A Review

“…These constituents are different from one another in terms of both chemical composition and morphology/geometry (such as platelets, fibers, flakes, particles etc.) [11].…”