CaH2-TiO2-Al体系制备TiAl合金反应机制的探讨

通过热力学计算可知,在CaH_2-TiO_2-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,TiO_2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76.84 kJ·mol~(-1).当CaH_2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1423 K、反应时间为8 h时,TiAl合金的转化率接近100%.

Discussion on Reaction Mechanism of TiAl Alloy Prepared in CaH2-TiO2-Al System

It is possible on thermodynamics to prepare TiAl alloy in CaH_2-TiO_2-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 TiO_2 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 CaH_2 is 1.5 times of theoretic quantity. Al powder granularity doesn't influence the reaction. The transformation efficiency of TiAl alloy is about 100% when the reaction temperature is 1423 K and the reaction time is 8 h.