燃焼合成による微細TiC粒子分散Ti-Al-C三元系複合材の作製と微細組織観察

抄録

Ti-Al-C ternary composites were produced by combustion synthesis using titanium, aluminum and graphite powders. Microstructure observations, X-ray diffraction experiments and micro Vickers hardness test were performed for the obtained porous specimens. With low carbon contents, a few intermetallic compounds of titanium and aluminum were obtained. Ti₄Al₂C₂ and TiC phases were produced as the carbon content increased. It is considered that formation of these phases depends on the quantity of heat generated during combustion synthesis. It was suggested that Ti₄Al₂C₂ phase was formed by direct reaction between TiC and Ti-Al system intermetallic compounds. Ti₄Al₂C₂ phase indicated the same hardness value (about 4.5GPa) as γ-TiAl phase. As the carbon content increased, the hardness value increased remarkably because of dispersion strengthening by TiC particles. The maximum hardness was about 8.6GPa. Microstructure observations for low carbon contents showed that large TiAl₃ particles were covered with γ-TiAl particles with a grain size of approximately 1μm. On the other hand, for high carbon contents, it was found that microcomposites which TiC particles with a grain size of approximately 1μm were dispersed homogeneously in the Ti₄Al₂C₂ phase with rod-like structures. This microcomposite will be expected to have more excellent elevated temperature strength than that of TiAl intermetallic compounds.