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为提高Fe-Ti二元系外推到三元或多元体系的能力,应用CALPHAD方法重新优化了该二元系。与前人的优化工作相比,重点放在对两个二元金属间化合物Fe2Ti和FeTi的热力学描述上。因目前普遍采用双亚点阵模型来描述C14_Laves相,所以采用双亚点阵模型来描述Fe2Ti相。通过检验包含Fe-Ti二元系的三元体系Fe-Ti边界上Fe2Ti相的均匀化范围进一步证实了Fe2Ti相的相边界。FeTi相具有BCC_B2晶体结构,因而将其处理成为BCC_A2相的有序相,并且用统一的Gibbs 能函数来描述有序和无序相。另外一个特别关注的方面就是重现这两个化合物的实测热容。计算结果与有关相图和热力学性质实验结果的广泛对比显示两者符合得很好,从而证明了所得热力学描述的有效性。
In order to improve the ability of Fe-Ti binary system to extrapolate to ternary or multicomponent system, CALPHAD method was used to re-optimize the binary system. Compared with the previous optimization work, the emphasis is placed on the thermodynamic description of two binary intermetallic compounds Fe2Ti and FeTi. Because of the dual sub-lattice model commonly used to describe the C14_Laves phase, the dual sub-lattice model is used to describe the Fe2Ti phase. The phase boundary of the Fe2Ti phase was further confirmed by examining the homogenization range of Fe2Ti phase on the Fe-Ti boundary of the ternary system containing Fe-Ti binary system. The FeTi phase has the BCC_B2 crystal structure and thus is processed into an ordered phase of the BCC_A2 phase and a uniform Gibbs energy function is used to describe the ordered and disordered phases. Another area of particular concern is to reproduce the measured heat capacities of the two compounds. The extensive comparisons of the calculated results with experimental results on phase diagrams and thermodynamic properties show that the two agree well and prove the validity of the thermodynamic description obtained.