Abstract
Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiCnp on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiCnp in the anodic film.
Highlights
Hard ceramic particle-reinforced aluminum matrix composites (Al-metal matrix composite (MMCs)) have received great interest due to their mechanical and physical properties; as a result, they are widely used to fabricate diverse components for the automotive and aerospace industries [1,2]
The literature is quite extensive on studying the system aluminum matrix reinforced with silicon carbide particles (Al/SiCp), in order to characterize its mechanical [8,9,10], wear [11,12], corrosion [13,14] and tribocorrosion [15,16] behavior, showing that the fraction volume and/or particle size of SiCp play an important role in the composite behavior
He et al [34] studied the effect of the size of reinforcement particles on the thickness of the anodic layers on Al(2024)/SiC-MMC, showing that the anodic layers are thicker for bigger particles, with an average diameter of 10 μm, and, they have a lack of uniformity in thickness more remarkable than those fabricated on MMC with SiCp of a smaller diameter, 3.5 μm
Summary
Hard ceramic particle-reinforced aluminum matrix composites (Al-MMCs) have received great interest due to their mechanical and physical properties; as a result, they are widely used to fabricate diverse components for the automotive and aerospace industries [1,2]. The poor corrosion resistance of the anodic films fabricated on Al/MMC is due to their discontinuity and non-uniform thickness [24,28,29] He et al [34] studied the effect of the size of reinforcement particles on the thickness of the anodic layers on Al(2024)/SiC-MMC, showing that the anodic layers are thicker for bigger particles, with an average diameter of 10 μm, and, they have a lack of uniformity in thickness more remarkable than those fabricated on MMC with SiCp of a smaller diameter, 3.5 μm. The influence of different volume fractions of nanosized SiC reinforcement particles on the morphology, composition and thickness of the anodic film grown on Al/SiCnp-MMCs substrates is discussed
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