TiAl基合金中γ/γ界面关系的定量分析

Quantitative Analyses of γ/γ Interfacial Relations of TiAl-based Alloy

γ/γ界面对于(γ+α2)双相TiAl基合金的力学性能具有重要影响。本工作利用汇聚束电子衍射技术对一种含有Mn,Nb合金元素的(γ+α2)TiAl基合金中具有六种不同晶体学取向的γ相及γ/γ界面关系进行了实验唯一测定。结果表明,仅利用一套〈334〉高阶劳厄带花样就可以完全决定该合金中γ层片的晶体学取向。该合金中γ/γ界面有四种,即绕〈111〉旋转120°、旋转180°呈镜面对称真孪晶、旋转60°呈镜面对称的伪孪晶和反相畴界面。统计分析表明,真孪晶γ/γ界面的比例最高,伪孪晶γ/γ界面和旋转120°γ/γ界面较少。TiAl合金中偶尔也会出现γ/γ反相畴界。

The γ/γ lamellar interfaces play a critical role in the mechanical properties of (γ + α2) two phase TiAl-based alloys. An umambiguous experimental determination of all six domain orientations in lamellar structure and the interface types between neighboring γ laths in a (γ + α2) two-phase TiAl alloy containing Mn and Nb were analysed by means of convergent-beam electron diffraction. The results show that a single High-Order-Laue-Zone (HOLZ) line pattern is adequate to uniquely describe the γ lath orientation, and four types of interfaces, i.e., 120° rotational interfaces, true-twin interfaces, pseudo-twin interfaces and antiphase boundaries occurred in the present alloy. The statistical analysis shows that among the possible interface types, true-twin related interfaces are observed most frequently, while the pseudo-twin interfaces and the 120° rotational interfaces are less. The occurrence of antiphase boundaries in this alloy is rather low.