Metal-matrix composites magnesium

Reinforcement for metal-matrix composites with such metals as titanium, titanium aluminide, aluminum, magnesium, and copper. Applications are found mostly in advanced aerospace programs and include fan blades, drive shafts, and other components. 

Ceramic matrix composites are produced by one of several methods. Short fibers and whiskers can be mixed with a ceramic powder before the body is sintered. Long fibers and yams can be impregiated with a slurry of ceramic particles and, after drying, be sintered. Metals (e.g., aluminum, magnesium, and titanium) are frequently used as matrixes for ceramic composites as well. Ceramic metal-matrix composites are fabricated by infiltrating arrays of fibers with molten metal so that a chemical reaction between the fiber and the metal can take place in a thin layer surrounding the fiber. 

Often there is a borrowing of terms between metal-intense materials science and polymer-intense materials science where there is actually little relationship between the two. This is not the case with metal-matrix composites (MMCs). Although the materials are often different, there are a number of similarities. For polymer-intense composites, the matrix materials are organic polymers. For MMCs, the matrix materials are typically a metal or less likely an alloy. Popular metals include aluminum, copper, copper-alloys, magnesium, titanium, and superalloys. ... 

Metals and ceramics (claylike materials) are also used as matrices in advanced composites. In most cases, metal matrix composites consist of aluminum, magnesium, copper, or titanium alloys of these metals or intermetallic compounds, such as TiAl and NiAl. The reinforcement is usually a ceramic material such as boron carbide (B4C), silicon carbide (SiC), aluminum oxide (A1203), aluminum nitride (AlN), or boron nitride (BN). Metals have also been used as reinforcements in metal matrices. For example, the physical characteristics of some types of steel have been improved by the addition of aluminum fibers. The reinforcement is usually added in the form of particles, whiskers, plates, or fibers. 

N. Wang, Z. Wang, and G. C. Weatherly, Formation of Magnesium Aluminate (Spinel) in Cast SiC Particulate-Reinforced A1 (A356) Metal Matrix Composites, Metall. Trans., 23A[5], 1423-1430 (1992). 

These concepts can be applied to many metallic materials and metal-matrix composites, but they have maximum impact on aluminum and magnesium alloys and components. 

Description and General Properties. Metal matrix composites (MMCs) consist of a metal or an alloy matrix with a reinforcement material (e.g., particulates, monofilaments, or whiskers). The matrix alloy, the reinforcement material, the volume and shape of the reinforcement, the location of the reinforcement, and the fabrication method can all be varied to achieve required properties. Most of the metal-matrix composites are made of an aluminum matrix. But aluminum-matrix composites must not be considered as a single material but as a family of materials whose stiffness, strength, density, and thermal and electrical properties can be tailored. Moreover a growing number of applications require improved matrix properties and therefore, metal matrices of magnesium, titanium, superalloys, copper, or even iron are now available commercially. Compared to bulk metals and their alloys, MMCs offer a number of advantages such as ... 

Bakkar A and Neubert V (2009), Corrosion behaviour of carbon fibres/magnesium metal matrix composite and electrochemical response of its constituents , Electrochimica Acta, 54(5), 1597-1606. 

Hall I W (1987), Corrosion of carbon/magnesium metal matrix composites , Scripta Metallurgica, 21, 1717-1721. 

Hihara L H and Kondepudi P K (1994), Galvanic corrosion between SiC monofilament and magnesium in NaCl, Na2S04 and NaN03 solutions for application to metal-matrix composites . Corrosion Science, 36, 1585-1595. 

M.A. Gonzalez-Nunez, C.A. Nunez-Lopez, P. Skeldon, G.E. Thompson, H. Karimzadeh, P. Lyon and T.E. Wilks, A non-chromate conversion coating for magnesium alloys and magnesium-based metal matrix composites . Corrosion Science, 37, (1995), 1763-1772. 

Ratna Sunil, B., Kumar, T.S.S., Chakkingal, U., Nandakumar, V., Doble, M., 2014. Nanohydroxyapatite reinforced AZ31 magnesium alloy by friction stir processing a solid state processing for biodegradable metal matrix composites. Journal of Materials Science. Materials in Medicine 25, 975-988. 

At very low surface areas (about 5 m /g) and constant conversion (70%), the contaminant selectivities are dominated by the matrix composition (Table I). Rare earth and magnesium-containing microspheres were prepared to examine the effects of these metal oxides on catalyst selectivities in the presence of nickel and vanadium. These oxides were chosen because the literature (3,5,10-15) has shown them to be effective at reducing the deleterious effects of vanadium in cracking catalysts. 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

Closer in concept to the DMO process is the infiltration of aluminum alloys in nitrogen to yield Al-AIN composites. Low temperatures (<1000°C) and high magnesium or strontium eontent promote the spontaneous infiltration of liquid metal with a small concurrent nitridation to yield dispersions of AIN [34]. Similar alloys may be infiltrated at higher temperatures, resulting in nitride contents that increase with temperature to yield AlN-matrix composites [35-38]. This process can result in particulate loadings of up to 75%. The mechanical properties of these aluminum nitride composites have been extensively characterized [39]. 

Chen Y, Zhang GD, Wu F, Zhu J, Study of the C/Mg interface in magnesium matrix composites reinforced by carbon (graphite) fiber, Rare Metal Mater Eng, 26(3), 20-25, 1997. 

At present, Chinese researchers have considerable knowledge and experience in the synthesis of aluminum borate whiskers, reinforcing and toughening composites, and industrialization. Before long, aluminum borate whiskers will be used widely in reinforced metal matrixes (aluminum base, magnesium base), ceramic matrix, plastic, glass, fiber, and coatings. ... 

Zhao-hui, W., Xu-dong, W., Zhaou-xin, W., Wen-bo, D., 2010. SiC nanoparticles reinforced magnesium matrix composites fabricated by ultrasonic method. Transactions of Nonferrous Metals Society of China 20, 1029—1032. 

The superalloys, as well as alloys of aluminum, magnesium, titanium, and copper, are used as matrix materials. The reinforcement may be in the form of particulates, both continuous and discontinuous fibers, and whiskers concentrations normally range between 10 and 60 vol%. Continuous-fiber materials include carbon, silicon carbide, boron, aluminum oxide, and the refractory metals. However, discontinuous reinforcements consist primarily of silicon carbide whiskers, chopped fibers of aluminum oxide and carbon, or particulates of silicon carbide and aluminum oxide. In a sense, the cermets (Section 16.2) fall within this MMC scheme. Table 16.9 presents the properties of several common metal-matrix, continuous and aligned fiber-reinforced composites. 

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