Abstract
Composite peening offers the opportunity to introduce ceramic blasting particles into metallic base material. By embedding Al2O3 particles, mechanical properties of aluminum can be improved. However, those surface modifications might negatively impact corrosion resistance and thus shorten the lifetime of components. This study analyzes corrosion properties of peened aluminum in chloride solution via immersion, scanning electron microscopy and polarization. The data of observed microstructures indicate that peening accelerates corrosion and that intergranular corrosion is the main force of degradation in contrast with pitting corrosion of monolithic aluminum.
Highlights
Micro shot peening modifies surfaces by introducing residual compressive stress in near-surface regions
Surfaces of composite peened and unpeened aluminum are analyzed by scanning electron microscopy and by potentiometry in corrosive solution, as it is generally known that monolithic aluminum alloys suffer from pitting corrosion in chloride solutions (Ref 21, 22)
This study examined the previously uncharacterized corrosion behavior of composite peened aluminum
Summary
Micro shot peening modifies surfaces by introducing residual compressive stress in near-surface regions. Control of the penetration depth is important as embedded particles may act as reinforcement of the surface regions. Underneath the composite peened surface of alumina is a thin layer of magnesium aluminate MgAl2O4 (spinel), which is formed during the peening process (Ref 4). This spinel formation has been observed on other interfaces of Al and Al2O3 (Ref 6, 7), and spinel seems to be responsible for chemical bonding of alumina to the aluminum matrix, according to Levi et al (Ref 8)
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