CaH_2-TiO_2-Al体系制备TiAl合金反应机制的探讨

Discussion on Reaction Mechanism of TiAl Alloy Prepared in CaH_2-TiO_2-Al System

通过热力学计算可知,在CaH2-TiO2-Al体系中用还原扩散法制备TiAl合金是可能的。该反应为一级反应,采用液-固未反应核模型探讨其反应机制。结果表明,TiO2还原成纯金属Ti非常迅速,不是反应的控制步骤,界面化学反应为反应的控制环节。反应的表观活化能为76.84kJ·mol-1。当CaH2的量为理论计算量的1.5倍时反应充分;Al粉的粒度对反应没有影响;反应温度为1423K、反应时间为8h时,TiAl合金的转化率接近100%。

It is possible on thermodynamics to prepare TiAl alloy in CaH2-TiO2-Al system by Reduction-Diffusion method. It is a first-class reaction, whose mechanism was discussed by liquid-solid contracting core model. Results show that TiO2 is reduced to Ti rapidly, which is not the rate-controlling step of the reaction. The interfacial chemical reaction is the rate-controlling step of the reaction. The apparent activation energy of the reduction-diffusion reaction is 76.84 kJ/mol. There is sufficient reaction when the entering quantity of Call2 is 1.5 times of theoretic quantity. Al powder granularity doesn＇t influence the reaction. The transformation efficiency of TiAI alloy is about 100% when the reaction temperature is 1423 K and the reaction time is 8 h.