Denise M. Aylor

Bio: Denise M. Aylor is an academic researcher. The author has contributed to research in topics: Corrosion & Pitting corrosion. The author has an hindex of 3, co-authored 3 publications receiving 147 citations.

Effect of Reinforcement on the Pitting Behavior of Aluminum‐Base Metal Matrix Composites

Abstract: This paper examines the effect of graphite and silicon carbide reinforcements on the pitting behavior of graphite/aluminum (Gr/Al) and silicon carbide/aluminum (SiC/Al) metal matrix composites. Electrochemical corrosion tests were performed on both Gr/Al and SiC/Al composite specimens. Identical tests were completed on powder metallurgy processed aluminum and wrought aluminum of the same composition. The electrochemical behavio of the SiC/Al composites was essentially identical to that of the powder processed and wrought aluminum alloys; however, the pitting attack on the SiC/Al composites was distributed more uniformly across the surface, and the pits penetrated to significantly less depths. The presence of graphite in the Gr/Al composites did not cause an electropositive shift in corrosion potential as anticipated, but caused a substantial decrease in resistance to passive film breakdown. This effect is the predominant reason for the poor performance of Gr/Al composites in marine environments.

The influence of incubation time on the passive film breakdown of aluminum alloys in sea water

Abstract: : Potential-controlled electrochemical methods were used to characterize the pitting behavior of 6061 alloy aluminum in synthetic ocean water. Irreproducible breakdown potentials (E sub bd) and reproducible repassivation potentials (E sub rp) were determined from cyclic anodic polarization (CAP). Reproducible breakdown and repassivation potentials were found from the quasi-stationary anodic polarization method; however, the breakdown potential values were shifted in the electronegative direction relative to the CAP method due to the allowance of a longer incubation time. These results support the theory that with sufficient incubation time, pit initiation and propagation will occur at potentials at or slightly above the repassivation potential, and that the repassivation potential value is the only characteristic potential for aluminum. The quasi-stationary anodic polarization method used for E sub rp determination provides a reproducible electrochemical method for obtaining E sub rp after minimal pit growth or surface damage. Cyclic anodic polarization can also be used for determining a representative potential if surface damage subsequent to pit initiation is minimized.

Metal Matrix Composites

Abstract: Metal matrix composites consist of a metal or an alloy as the continuous matrix and a reinforcement that can be particle, short fiber or whisker, or continuous fiber. In this chapter, we first describe important techniques to process metal matrix composites, then we describe the interface region and its characteristics, properties of different metal matrix composites, and finally, we summarize different applications of metal matrix composites.

Corrosion of metal matrix composites

Abstract: The corrosion of metal matrix composites (MMCs) is reviewed with emphasis on relating MMC corrosion behaviour to the electrochemical and chemical properties of MMC constituents. Galvanic corrosion between the reinforcement constituent and the metal matrix governs the corrosion behaviour of many MMCs. Other factors such as residual contaminants of MMC processing and the formation of interphases between reinforcement and matrix can also have pronounced effects on MMC corrosion behaviour. The lack of inherent resistance to corrosion of some MMCs requires that they be coated with organic or inorganic coatings for protection. Although the ultimate goal is to engineer and design MMCs to have good inherent resistance to corrosion (while maintaining excellent mechanical properties), no significant breakthroughs have been achieved in this area for MMCs that are typically prone to corrosion (e.g. graphite-aluminium MMCs). In this review, aluminium, magnesium, lead, depleted uranium, and stainless steel MMCs...

Discontinuously-reinforced aluminum matrix composites

Abstract: This article reviews the literature relating to aluminum matrix composites reinforced by ceramic particles, short fibers or whiskers. The main reinforcements which have been used are presented with respect to their nature, morphology and mechanical behavior. The influence of matrix alloying elements on ceramic-metal compatibility is discussed. Most fabrication techniques which have been proposed are described and particular attention is paid to the methods suitable for large scale production. The mechanical characteristics of this kind of composite are reported and compared in relation to processing parameters. Finally, models giving a rough prediction of the mechanical behavior of the composites are discussed.

Microstructural and corrosion behavior of Al/SiC metal matrix composites

Abstract: Several Al/SiC MMCs having several volume fractions up to 15 vol.% and different SiC particulates average sizes, typically, 11, 6 and 3 μm were fabricated using conventional powder metallurgy (PM) route. The effect of the size and volume fraction of SiC particulates on the microstructural and corrosion behavior of Al/SiC metal matrix composites (MMCs) were studied. The results revealed that the Al/SiC MMCs exhibited higher density than pure Al matrix. The static immersion corrosion tests of Al/SiC MMCs in 3.5 wt.% NaCl aqueous solution at several temperatures showed that, at ambient temperature, the Al/SiC MMCs have better corrosion resistance than the pure Al matrix. Reducing the SiC particles size and/or increasing the volume fraction of the SiC particulates reduce(s) the corrosion rate of the Al/SiC MMCs. In contrast, the Al/SiC composites exhibited higher corrosion rates at 50 °C and 75 °C than the pure Al matrix.