| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
To synthesize titanium carbide-boride composites by solid-state displacement reaction method, method the reaction mechanism between B_4C and Ti in the solid state was examined at temperatures of 1000 to 1300ﾟC, In the early stage of the reaction, TiC_X and TiB formed. The TiC_X formed was nonstoichiometric, the composition of which was that in equilibrium with Ti. As the reaction proceeded, TiB_2 began to form with reducing TiB and increasing carbon contents in TiC_X. These results were well explained by the following reaction mechanism : as the first step, the reaction B_4C+(4+l/x)Ti4TiB+1/xTiC_x proceeded, and as the second step, the reaction yB_4C+4TiB+1/xTiC*(2+ 2y)TiB_2+(2+2y)TiC+(2-2y+l/x)Tic_<(y+1)(2-2y+1/x)> followed.
To obtain dense sintered bodies of B_4C and Ti composites, a reactive spark plasma sintering method was applied to densification from B_4C and Ti powders. The most suitable sintering temperature and holding time were first surveyed and determined by measuring their relative densities. Sintered bodies were then examined metallographically and mechanical properties were measured for Young's modulus, Vickers hardness and fracture toughness. When mixtures of B_4C and Ti powders were sintered above 1400ﾟC, in the early stage TiB, TiB_2, Ti_3B_4 and TiC_X were produced and finally they were entirely transformed into TiB_2 and TiC_X. Composites with relative densities higher than 99 % was obtained at 1800ﾟC and above. The composites sintered at 1800ﾟC and below had unique microstructure : TiB_2 phases formed networks surrounding TiC phases. The network structure disappeared at higher temperatures. The composites with relative densities higher than 99 % had mechanical properties of Young's modulus 514 GPa, Poisson's ratio 0.178, Vickers hardness 2090 and fracture toughness 3.8 MPam^<0.5>.
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