TiC-Ni金属陶瓷自蔓延高温合成中的显微组织演变

用燃烧波淬熄法研究了TiC-Ni金属陶瓷自蔓延高温合成(SHS)中的组织演变,淬熄试样中保留了未反应区、反应区和已反应区.用扫描电子显微镜观察了燃烧反应中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和燃烧波蔓延速度,并用XRD分析了反应产物的相组成.结果表明,TiC-Ni金属陶瓷自蔓延高温合成(SHS)的机理为溶解-析出机制,镍粉与钛粉的固态扩散导致低熔点Ti-Ni溶液形成,Ti、Ni、C粉粒逐渐向Ti-Ni溶液中溶解,当Ti-Ni-C溶液中的Ti和C浓度饱和时,从中析出TiC颗粒,同时形成粘结TiC颗粒的Ni3Ti基体.分析结果表明,该体系的燃烧合成具有不完全性,最终产物中残留少量Ni3Ti2 NiTi共晶体,这种反应的不完全性是由于使用了较粗的Ti粉和Ni粉.

Microstructural evolution during self-propagating high-temperature synthesis of TiC-Ni cermet

In the study of microstructural evolution during self-propagating high-temperature synthesis of Ti_2AlC machinable ceramics from Ti-Al-C powders, a propagating combustion wave in the sample was quenched, and the microstructural evolution was observed with scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The combustion temperature was measured, and the phase constituent of the synthesized product was inspected by X-ray diffraction (XRD). The results show that the combustion reaction is preceded by melting of the Al particle, and it proceeds in a dissolving-precipitating-melting-crystallizing mechanism. In addition, the reaction is incomplete, this is because the coarser Ti and Al powders are used in the experiment.