Metal-matrix composites copper

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. 

The composition of the codeposition bath is defined not only by the concentration and type of electrolyte used for depositing the matrix metal, but also by the particle loading in suspension, the pH, the temperature, and the additives used. A variety of electrolytes have been used for the electrocodeposition process including simple metal sulfate or acidic metal sulfate baths to form a metal matrix of copper, iron, nickel, cobalt, or chromium, or their alloys. Deposition of a nickel matrix has also been conducted using a Watts bath which consists of nickel sulfate, nickel chloride and boric acid, and electrolyte baths based on nickel fluoborate or nickel sulfamate. Although many of the bath chemistries used provide high current efficiency, the effect of hydrogen evolution on electrocodeposition is not discussed in the literature. 

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. 

Metal-matrix composites using TiC as the reinforcing phase have also been used as tool materials for copper alloys (Ref 26). Both sintered TiC Ni W and hipped TiC Ni Mo alloys were used to friction stir copper alloys. However, both TiC-containing alloys produced brittle tools that fractured during the tool plunge. 

Recent advances further enhance their commercial potential in metal matrix composites such as aluminum, nickel, and copper ceramic matrix composites, such as alumina, zirconia and silicon nitride and glass ceramic matrix composites such as lithium aluminosilicate. Silicon carbide whiskers increase strength, reduce crack propagation, and add structural reliability in ceramic matrix composites. Structural applications include cutting tool inserts, wear parts, and heat engine parts. They increase strength and stiffness of a metal, and support the design of metal matrix composites with thinner cross sections than those of the metal parts they replace, but with equal properties in applications such as turbine blades, boilers and reactors. 

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 ... 

Sun, H., Orth, J. E., and Wheat, H. G., "Corrosion Behavior of Copper-Based Metal-Matrix Composites, Journal of Metals, September 1993, pp. 36-41. 

Sintered Materials or Cermets. Heavy weights and high landing speeds of modem aircraft or high speed trains require friction materials that ate extremely stable thermally. Organic or semimetallic friction matenals ate frequendy unsatisfactory for these appHcations. Cermet friction materials ate metal-bonded ceramic compositions (see Composite materials) (12—14). The metal matrix may be copper or iron (15). 

The first reports on the incorporation of molybdenum disulphide in a metal matrix were those mentioned previously which were published by Bowden in 1950. He reported a coefficient of friction of 0.13 for a composite in sintered copper. In his other metallic composite the molybdenum disulphide was formed in situ by hydrogen sulphide in sintered molybdenum and had a coefficient of friction of 0.06. At about the same time R L Johnson et al at NACA studied the effect of molybdenum disulphide concentration in silver with 5% of copper. They reported coefficients of friction as low as 0.17 and found that the friction decreased with increasing concentration of molybdenum disulphide. Their wear rates were high, around 10 mm /Nm, but this work was the fore-runner of many studies using the same components. 

The thermal characteristics of NR-metal composites are close to the properties of metals, whereas the mechanical properties and the processing methods are typical of polymers.Thermally conducting, but electrically insulating, polymer-matrix composites are increasingly important for electronic packaging because the heat dissipation ability limits the reliability, performance and miniaturization of electronics.Thermal properties such as thermal conductivity, thermal dilfusivity and specific heat of metal (copper, zinc, Fe and bronze) powder-filled polymer composites are investigated experimentally in the range of filler content 0-24% by volume. ... 

In recent years metallic particles have also been considered as fillers to increase the electrical and thermal conductivities of epoxy systems. The electrical and thermal conductivities of epoxy systems filled with metal (i.e. copper and nickel) powders have been studied (Mamunya et al., 2002). In this work it was shown that the composite preparation conditions allow the formation of a random distribution of metallic particles in the polymer matrix. The percolation theory equation holds true for systems with a random distribution of dispersed filler, while in contrast to the electrical conductivity, the dependence of thermal conductivity on concentration shows no jump in the percolation threshold region. 

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