Al-Ti-CaC_2体系自蔓延反应及其热力学分析

Self-propagating High Temperature Synthesis and Thermodynamic Analysis of Al-Ti-CaC_2 System

对Al-Ti-CaC2体系自蔓延反应过程中有关反应的Gibbs自由能ΔG及最高热力学温度进行了一系列计算,并对Al(50%,质量分数,下同)、Ti(30%)、CaC2(20%)混合粉末进行了压制,并将压制试样在氩气保护下进行了加热烧结试验。结果表明,TiC、CaAl2、TiAl3、Al4C3具有较好的热力学稳定性,在1200K以上时,由TiAl3、Al4C3反应,合成TiC;Al-Ti-CaC2体系的最高热力学温度随预热温度提高而增加;在体系中Al含量为50%、预热温度为1000K条件下,计算的最高热力学温度大于2400K,自蔓延反应易于发生;试验时压制试样加热到963K时发生剧烈反应。X射线衍射分析表明反应产物中含有TiC、CaAl2、TiAl3,TiAl3为不完全反应产物。试验与热力学分析结果基本符合。

A series of calculations were performed to the self-propagating reaction process of Al-Ti-CaC2 system about the Gibbs free energy change and adiabatic temperature,and the mixed powder of Al,Ti and CaC2 was pressed and the pressed samples were heated and sintered under the protection of argon atmosphere.The results show that TiC,TiAl3,CaAl2 and Al4C3 phases exhibit desirable thermodynamical stability,and TiC can be generated by the reaction of TiAl3 and Al4C3 under high temperature above 1200 K.The adiabatic temperature of the Al-Ti-CaC2 system can be improved with increasing in the preheating temperature.The calculated adiabatic temperature is more than 2400 K when Al content in the system reaches 50% with preheating at 1000K,leading to the easier self-propagating synthesis.Sharp reaction can be observed when the pressed samples are heated above 963K,and the reaction products are mainly composed of TiC,CaC2 and TiAl3,in which TiAl3 phase is the intermediate reaction product.The experimental results are well in agreement with thermodynamic analysis.