TL;DR: In this paper, 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.
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...
TL;DR: There remains growing interest in magnesium (Mg) and its alloys, as they are the lightest structural metallic materials Mg alloys have the potential to enable design of lighter engineered systems, including positive implications for reduced energy consumption as mentioned in this paper.
TL;DR: It is shown that a graphene coating can, on the contrary, accelerate long-term oxidation of an underlying copper substrate in ambient atmosphere at room temperature.
Abstract: This paper reports the enhancement of long-term oxidation of copper at room temperature by a graphene coating. Previous studies showed that graphene is an effective anticorrosion barrier against short-term thermal and electrochemical oxidation of metals. Here, we show that a graphene coating can, on the contrary, accelerate long-term oxidation of an underlying copper substrate in ambient atmosphere at room temperature. After 6 months of exposure in air, both Raman spectroscopy and energy-dispersive X-ray spectroscopy indicated that graphene-coated copper foil had a higher degree of oxidation than uncoated foil, although X-ray photoelectron spectroscopy showed that the surface concentration of Cu(2+) was higher for the uncoated sample. In addition, we observed that the oxidation of graphene-coated copper foil was not homogeneous and occurred within micrometer-sized domains. The corrosion enhancement effect of graphene was attributed to its ability to promote electrochemical corrosion of copper.
•02 Aug 1972
TL;DR: In this article, important techniques to process metal matrix composites are described, then the interface region and its characteristics, properties of different metal matrix composite composites, and finally, the authors summarize different applications of metal matrices 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.
TL;DR: In this paper, the authors used optical emission spectroscopy (OES) in the visible and near ultraviolet (NUV) band (285 nm-800 nm) to characterize the PEO plasma and found that the plasma discharge behavior significantly influenced the microstructure and morphology of the oxide coatings and hence the corrosion resistance.
Abstract: Magnesium alloys are increasingly being used as lightweight materials in the automotive, defense, electronics, biomaterial and aerospace industries. However, their inherently poor corrosion and wear resistance have, so far, limited their application. Plasma electrolytic oxidation (PEO) in an environmentally friendly aluminates electrolyte has been used to produce oxide coatings with thicknesses of similar to 80 mu m on an AJ62 magnesium alloy. Optical emission spectroscopy (OES) in the visible and near ultraviolet (NUV) band (285 nm-800 nm) was employed to characterize the PEO plasma. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the coated materials, and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution were used to determine the corrosion behavior. It was found that the plasma discharge behavior significantly influenced the microstructure and the morphology of the oxide coatings and, hence the corrosion resistance. The corrosion resistance of the coated alloy was increased by changing the current mode from unipolar to bipolar, where the strong plasma discharges had been reduced or eliminated. (C) 2011 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the influence of various alloying elements on the mechanical properties of magnesium is reviewed and the broad classification of Mg alloys and their behavioral trends are detailed, and the manufacturing techniques of magnesium alloys along with the secondary techniques are also covered.