Metal matrix composite material

Advanced Structural and Heating Materials. Molybdenum siHcide [12136-78-6] and composites of MoSi2 and siHcon carbide, SiC, have properties that allow use as high temperature stmctural materials that are stable in oxidizing environments (see Composite materials Metal-matrix composites). Molybdenum disiHcide also finds use in resistance heating elements (87,88). 

Two approaches have been taken to produce metal-matrix composites (qv) incorporation of fibers into a matrix by mechanical means and in situ preparation of a two-phase fibrous or lamellar material by controlled solidification or heat treatment. The principles of strengthening for alloys prepared by the former technique are well estabUshed (24), primarily because yielding and even fracture of these materials occurs while the reinforcing phase is elastically deformed. Under these conditions both strength and modulus increase linearly with volume fraction of reinforcement. However, the deformation of in situ, ie, eutectic, eutectoid, peritectic, or peritectoid, composites usually involves some plastic deformation of the reinforcing phase, and this presents many complexities in analysis and prediction of properties. 

Metal-Matrix Composites. A metal-matrix composite (MMC) is comprised of a metal ahoy, less than 50% by volume that is reinforced by one or more constituents with a significantly higher elastic modulus. Reinforcement materials include carbides, oxides, graphite, borides, intermetahics or even polymeric products. These materials can be used in the form of whiskers, continuous or discontinuous fibers, or particles. Matrices can be made from metal ahoys of Mg, Al, Ti, Cu, Ni or Fe. In addition, intermetahic compounds such as titanium and nickel aluminides, Ti Al and Ni Al, respectively, are also used as a matrix material (58,59). P/M MMC can be formed by a variety of full-density hot consolidation processes, including hot pressing, hot isostatic pressing, extmsion, or forging. 

A composite material (1) is a material consisting of two or more physically and/or chemically distinct, suitably arranged or distributed phases, generally having characteristics different from those of any components in isolation. Usually one component acts as a matrix in which the reinforcing phase is distributed. When the continuous phase or matrix is a metal, the composite is a metal-matrix composite (MMC). The reinforcement can be in the form of particles, whiskers, short fibers, or continuous fibers (see Composite materials). 

Developments in metal-matrix composites technology has resulted in aluminum matrix materials filled with siUcon carbide [409-21 -2] SiC, (see Carbides, silicon carbide) particles (15 to 60 vol %) that provide the possibihty of weight reduction for brakes (20). These composite materials are being tested and evaluated. 

Other Matrix Materials. Advanced materials, eg, stmctural components, in aerospace vehicles also employ ceramics and metals as composite matrices (see Composite materials, ceramic-matrix Metal-matrix composites). 

Applied Sciences, Inc. has, in the past few years, used the fixed catalyst fiber to fabricate and analyze VGCF-reinforced composites which could be candidate materials for thermal management substrates in high density, high power electronic devices and space power system radiator fins and high performance applications such as plasma facing components in experimental nuclear fusion reactors. These composites include carbon/carbon (CC) composites, polymer matrix composites, and metal matrix composites (MMC). Measurements have been made of thermal conductivity, coefficient of thermal expansion (CTE), tensile strength, and tensile modulus. Representative results are described below. 

Metallic Particles in Metallic Matrix Composite Materials... 

Let s address the issue of nonlinear material behavior, i.e., nonlinear stress-strain behavior. Where does this nonlinear material behavior come from Generally, any of the matrix-dominated properties will exhibit some degree of material nonlinearity because a matrix material is generally a plastic material, such as a resin or even a metal in a metal-matrix composite. For example, in a boron-aluminum composite material, recognize that the aluminum matrix is a metal with an inherently nonlinear stress-strain curve. Thus, the matrix-dominated properties, 3 and Gj2i generally have some level of nonlinear stress-strain curve. 

M. Mabuchi, J. Koike, H. Iwasaki, K. Higashi, and T.G. Langdon, "Processing and Development of Superplastic Metals Matrix Composites," in Materials Science Forum Vols. 170-172, pp. 503-512, T.G. Langdon ed., Trans Tech Publications, Switzerland, (1994). 

An., Continuous Silicon Carbide Metal Matrix Composites, Technical Brochure, Textron Specialty Materials, Lowell, MA... 

Applications. Boron fibers are used as unidirectional reinforcement for epoxy composites in the form of preimpregnated tape. The material is used extensively, mostly in fixed and rotary wing military aircrafts for horizontal and vertical stabilizers, mdders, longerons, wing doublers, and rotors. They are also used in sporting goods. Another application is as reinforcement for metal matrix composites, in the form of an array of fibers pressed between metal foils, the metal being aluminum in most applications. 

Lanxide A process for making composites of metals with oxides. A molten metal reacts with an adjacent oxidant and is progressively drawn through its own oxidation product so as to yield a ceramic/metal composite. Fibres or other reinforcing materials can be placed in the path of the oxidation reaction and so incorporated in the final product. The Lanxide Corporation was founded in 1983 in Newark, DE, to exploit this invention. In 1990 it formed a joint venture with Du Pont to make electronic components by this process. Variations are Dimox (directed metal oxidation), for making ceramic metal composites, and Primex (pressureless infiltration by metal), for making metal matrix composites. 

Metcalfe, A.G. (1974). Physical-chemical aspects of the interface. In Interfaces in Metal Matrix Composites, Composite Materials. Vol. 1. (A.G. Metcalfe ed.). New York, Academic Press, pp. 65-... 

Castle, J.E. and Watts, J.F. (1988). The study of interfaces in composite materials by surface analytical techniques. In Interfaces in Polymer, Ceramic and Metal Matrix Composites (Proc. ICCI-II) (H. Ishida ed ), Elsevier Seienee, New York, pp. 57-71. 

Rapidly solidified in-situ metal matrix composites. A design project for alloys based on the Fe-Cr-Mo-Ni-B system, and produced by rapid solidification, was undertaken by Pan (1992). During processing a mixture of borides is formed inside a ductile Fe-based matrix which makes the alloys extremely hard with high moduli. These alloys provide a good example of how phase-diagram calculations were able to provide predictions which firstly helped to identify unexpected boride formation (Saunders et al. 1992) and were ultimately used in the optimisation of the modulus of a shaft material for gas turbines (Pan 1992). 

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. ... 

Most fiber-matrix composites (FMCs) are named according to the type of matrix involved. Metal-matrix composites (MMCs), ceramic-matrix composites (CMCs), and polymer-matrix composites (PMCs) have completely different structures and completely different applications. Oftentimes the temperatnre at which the composite mnst operate dictates which type of matrix material is to be nsed. The maximum operating temperatures of the three types of FMCs are listed in Table 1.27. 

Zweben, C. "Metal Matrix Composites," Advanced Materials 4t Pmcesses. 25... 

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. 

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