Reaction products of Al/TiC composites fabricated by the pressureless infiltration technique

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MANY types of ceramic phases have been added to Al matrix composites as reinforcement: particles, whiskers, and fibers of the oxides (Al2O3, MgO, TiO2, etc.), carbides (SiC, TiC, B4C, etc.), nitrides (AlN, BN, Si3N4, etc.), and borides (TiB2, etc.). Recently, the Al-Ti-C system has become of great interest in the grain refining industry, because it may be a viable alternative to the Al-Ti-B system.[1,2,3] Therefore, the Al-Ti-C system has been studied by a number of researchers. More recently there has been a growing interest in the development of technologies for Al composites reinforced with TiC particles because of good wettability with Al, high hardness, high temperature stability, and low weight. Accordingly, there were many reports about Al/TiC composites fabricated by various methods including XD process, powder metallurgy (P/M) and casting route, etc.[4–30] Because the interfacial reaction in Al composites reinforced with ceramic phases depends on several fabrication parameters (e.g., temperature, holding time, atmosphere, and chemical composition of both the Al matrix and the reinforcements), the characteristics of composites fabricated will be changed, depending on the fabricating procedure and composite system.[31] While there are several binary (Al3Ti, TiAl, and Al4C3) and ternary (Ti2AlC and Ti3AlC) carbides that have been reported in Al-Ti-C systems, their results do not agree with each other. Thus, the disagreement in phases reported could possibly be related to the difference in fabrication methods. Prasad et al.[28] and Pandey et al.[25] have observed Al3Ti and Al4C3 phases as reaction products in Al/TiC composite, which was fabricated by the conventional P/M route, whereas Mitra et al.[6] have reported Al3Ti, Al4C3, Ti2AlC, and TiAl phases in Al/TiC composite, which was fabricated by the XD process. The interfacial reaction between Al matrix and reinforcement in Al composites is very important, because it can K.B. LEE, Assistant Professor, H.S. SIM, Doctoral Course Student, and H. KWON, Professor, are with the School of Advanced Materials Engineering, Kookmin University, Seoul 136-702, Korea. Contact e-mail: [email protected] Manuscript submitted October 7, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A

affect the way that the load is transferred at the interface and then can affect the mechanical properties of the composites.[29] In addition, the interfacial reaction can change the composition of the matrix and reinforcement. Although limited interfacial reactions may enhance the load bearing capabilities of composites, extensive interfacial reaction will form to the detriment of composites. Therefore, in order to obtain optimum mechanical properties, it is important to achieve good bonding between the Al matrix and the ceramic reinforcements via appropriate interfacial reaction. In the case of the Al/TiC composites, however, the interfacial reaction between Al matrix and TiC reinforcement is not clearly established, as mentioned previously. In addition, no data are available