自蔓延高温合成层状Ti3SiC2陶瓷的显微组织演变

本文采用燃烧波前沿淬熄法研究了层状Ti3SiC2陶瓷在自蔓延高温合成(SHS)过程中的显微组织转变过程。用扫描电子显微镜观察了SHS反应中其显微组织的转变过程,用能谱仪分析了各微区的成分变化,测量了燃烧温度TC,并通过XRD分析了燃烧产物的相组成。研究结果表明,层状Ti3SiC2陶瓷自蔓延高温合成(SHS)的反应机理为溶解—析出机制,Ti粉与Si粉的固态扩散导致低熔点Ti-Si溶液形成,Ti、Si、C粉粒逐渐向Ti-Si溶液中溶解,当溶液中的Ti、Si、C浓度饱和时,从中析出TiC、SiC颗粒。最后TiC和SiC与剩余的熔融Ti通过固—液反应转化生成最终产物Ti3SiC2。

MICROSTUCTURAL EVOLUTION DURING SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS OF Ti3SiC2 CERAMICS

The microstructural evolution during self-propagating high-temperature synthesis (SHS) of Ti3SiC2 ceramic was studied by means of the combustion front quenching method. The process of microstructure conversion in the quenched sample was observed using a scanning electron microscope (SEM), a compositional change in each micro-region of the microstructure was studied by energy depressive X-ray (EDX), the temperature was measured, and investigated by X-ray diffraction (XRD) of samples sintered at different temperatures. The results show that the mechananism of combustion synthesis of Ti3SiC2 ceramic composition can be described as dissolution-precipitation. Ti-Si melt is formed through sold diffusion between titanium and nickel powders, then the atoms of Ti, C and Si gradually dissolve into the Ti-Si melt, and TiC, SiC particles will precipitate from the Ti-Si-C melt as the Ti-Si-C melt is saturated. At last the final productio(nTi3SiC2) is resulted by the solid-liquid reaction between TiC , SiC and remanent melted Ti.