Titanium metal-matrix composites

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. 

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. 

C. G. Rhodes, and R. A. Spurting, Fiber/matrix interface reactions in SIC reinforced titanium alloys, in Developments in Ceramic and Metal-Matrix Composites, K. Upadhya, ed.. The Minerals, Metals and Materials Society, Warendale, PA, 99-113 (1991). 

Ferro-Tic, Titanium carbide metal matrix composites, Alloy Technology International, Inc. 

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 ... 

Eyl86] Eylon, D., Cooke, C.M., and Froes, F.H., Production of Metal Matrix Composites from Rapidly Solidified Titanium Alloy Foils, in Titanium Rapid Solidification Tkchnology, F.H. Froes and D. Eylon, Ed., The Metallurgical Society, 1986, p. 311-322... 

Bouix, J., Vincent, H., Boubehira, M., and Viala, J. C., Titanium Diboride-Coated Boron Fibre for Aluminum Matrix Composites, J. Less Common Metals, 117(l-2) 83-89 (Mar. 1986)... 

Other than in polymer matrix composites, the chemical reaction between elements of constituents takes place in different ways. Reaction occurs to form a new compound(s) at the interface region in MMCs, particularly those manufactured by a molten metal infiltration process. Reaction involves transfer of atoms from one or both of the constituents to the reaction site near the interface and these transfer processes are diffusion controlled. Depending on the composite constituents, the atoms of the fiber surface diffuse through the reaction site, (for example, in the boron fiber-titanium matrix system, this causes a significant volume contraction due to void formation in the center of the fiber or at the fiber-compound interface (Blackburn et al., 1966)), or the matrix atoms diffuse through the reaction product. Continued reaction to form a new compound at the interface region is generally harmful to the mechanical properties of composites. 

As noted above, the range of fibers employed does not precisely overlap with those employed for organic composites. Because the formation of the MMCs generally requires melting of the metal-matrix, the fibers need to have some stability to relatively high temperatures. Such fibers include graphite, silicon carbide, boron, alumina-silica, and alumina fibers. Most of these are available as continuous and discontinuous fibers. It also includes a number of thin metal wires made from tungsten, titanium, molybdenum, and beryllium. 

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. 

The principal theme of this section is concerned with the involvement of ESCA or XPS in various metal matrix-based composite systems. This section will be devoted to boron-, nitrogen-, aluminum-, and titanium-based composite systems and some of the ESCA results have been published elsewhere by the authors. 

Carbides and nitrides of transition metals are usually hard and some of them are used as hard materials. Tungsten carbide, which was briefly described above, is a major component of cutting tools and wear-resistant materials. Titanium carbide. Tie, and nitride, TiN, are two other major hard materials that are widely used in tools. They also find application as hard coatings (in particular, TiN [177]) and components of ceramic matrix composites [178]. Both TiC and TiN show a very... 

Examples of stab resistant body armour are often quite different in constractional character. For example, some comprise a matrix of overlapping metal or composite plates located between fabric layers (based on para-aramid or UHMW polyethylene), others are based on more flexible aramid woven textiles which have been coated with silicon carbide particles to blunt the knife point and others incorporate fine tungsten wire within a knitted fabric matrix. Copying the ancient chain mail concept, similar fine mail constructed from stainless steel or titanium wire may be included as a layer. Obviously the overall weight and thickness of the resulting armour is of crucial importance for the comfort of the wearer but this will be determined largely by the magnitude of the threat. 

G. Das, Interfacial reactions in SiC-reinforced titanium alloy and titanium aluminkJe composites, in Metal and Ceramic Matrix Composites, R.B. Bhagat, A.H. Clauer, P. Kumar and A.M. Ritter, eds., The Minerals, Metals and Materials Soc., Warrendale, PA, 413- 2 (1990). 

First, a few studies on metal-filled composite bipolar plates are briefly described. At Los Alamos National Laboratory (LANL) composite bipolar plates filled with porous graphite and stainless steel and bonded with polycarbonate (Hermann, 2005) has been developed. Kuo (2006) investigated in composite bipolar plates based on austenitic chromium-nickel-steel (SS316L) incorporated in a matrix of PA 6. Their results showed that these bipolar plates are chemically stable. Furthermore, Bin et al. (2006) reported a metal-filled bipolar plate using polyvinylidene fluorid (PVDF) as the matrix and titanium silicon carbide (TijSiCj) as the conductive filler and obtained an electrical conductivity of 29 S cm" with 80 wt% filling content. 

---