Metal-matrix composites corrosion resistance

Aerosol spray delivery, 23 196 Aerosol sprays, 7 773-774 Aerospace applications aluminum alloys, 2 340 artificial graphite in, 72 740-741 for high performance fibers, 13 397-398 of liquid-crystal polymers, 20 85 metal-matrix composites in, 16 191 polyimide matrix composites in, 20 284 Aerospace bearings, corrosion resistance of, 74 452... 

Besides these developments, which are directed at specific applications, NijAl alloys are used for the development of inter-metallic matrix composites which contain reinforcing particles or fibers of borides, carbides, oxides or carbon (Fuchs, 1989 Lee et al., 1990 Tortorelli et al., 1990 Al-man and Stoloff, 1991 Kumar, 1991 McKamey and Carmichael, 1991 Muk-herjee and Khanra, 1991 Brennan etal., 1992). Apart from the mechanical properties and the necessary corrosion resistance, the chemical compatibility of the used phases is of primary importance with respect to the long-term stability. It was found that SiC, B4C, and TiBj react extensively with Nij Al alloys, whereas very little reaction has been observed with AljOj or Tie in NijAl (Fuchs, 1989 Lee etal., 1990 Brennan etal., 1992). It should be noted that NijAl alloys are used not only as the matrix material, but also as a reinforcing phase in, e.g. an Al alloy to form a metal-matrix composite (Metelnick and Varin, 1991). 

Shimizu, Y., Nishimura, T., and Matsushima, L, "Corrosion Resistance of Al-Based Metal Matrix Composites, Materials Science and Engineering A, Vol. 198, 1995, pp. 113-118. 

The requirement for a strip rollable alloy suitable for high-temperature use in metal matrix composites (MMC s) led to the development of TIMETAL-21S (Beta 2IS). The alloy has creep resistance equivalent to Ti-6A1-4V combined with the advantages of a strip rollable, cold formable p alloy. It is finding many uses where its corrosion and oxidation resistance at elevated temperatiire are more important than the ability to withstand high stresses at elevated temperature. Applications up to 600 °C are anticipated. The alloy s oxidation resistance and mod-... 

Abstract Electrodeposition is a weU-known conventional surface modification method to improve the surface characteristics, decorative and functional, of a wide variety of materials. Now, electrodeposition is emerging as an accepted versatile technique for the preparation of nanomaterials. Work done in this direction is discussed in this chapter. The basics of electrodeposition are introduced, then the electrodeposition of nanomaterials using special techniques for reducing grain size. Methods such as pulse and pulse reverse current deposition, template-assisted deposition and use of additives and grain refiners are explained with suitable examples. Deposition of nanostructured metals, alloys, metal matrix composites, multilayers and biocompatible materials reported in the literature are discussed. Finally, there is a discussion of the improved corrosion resistance of electrodeposited nanostructured materials, quoting results reported in Uterature. 

Electrodeposition is a versatile technique for the production of nanostructured materials with lower capital investment, higher production rates and few shape and size limitations. Electrodeposited nanomaterials such as nanostractured metals, alloys and metal matrix composites have proven successful in providing superior corrosion resistance of substrate materials compared with the corresponding microstmctured materials. 

One of the fastest growing areas today is composites. Composites offer good strength, corrosion resistance, and lightweight so they are continually replacing metals. As the cost of fuel continues to increase, much of the replacement of metals is due to desired weight reductions. Composites are generally composed of two phases the continuous or matrix phase, which surrounds the discontinuous or dispersed phase. 

As discussed before, hard metal-like composites can be prepared by pressureless sintering of ternary borides with Fe, Ni, or Co melts. Materials with x-phase (M21M2 Bg, where = Fe, Ni, or Co, and M = Zr, Hf, Nb, Ta, or W with M as the matrix phase) have not been developed for technical use but Ni-based alloys with x are in applications as wear- and corrosion-resistant coatings on steels [355]. The x phase is also used for the improvement of the creep resistance of Ni-based superalloys. 

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