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在Al=44%～49%(原子分数)和Ti/Al原子比为52/48的条件下,以固体与分子经验电子理论为基础,利用键距差法计算并比较合金化前后晶胞价电子结构中的最大共价电子数目,在影响原子间结合力方面对合金元素M的固溶强化作用进行评价。计算结果表明,在M=[0～10]%范围内,V,Nb,Cr,Zr和Hf的添加均可以强化TiAl合金;当合金元素属于同副族、且杂化状态相同时,元素对最大共价电子数目不敏感;当合金元素属于同副族、而不同杂化状态时,元素的成键电子数目较大,则强化作用较强。可见,融入TiAl晶胞形成置换固溶体的合金元素,其强化作用取决于合金元素能够提供的成键电子数目的多少;成键电子数目越多,则成键后键上的最大共价电子数目越大,使得该结构基元的强度越大;大量的该种结构基元可对基体产生明显的强化作用。计算结果与已有实验结果吻合,采用该方法可以为固溶强化TiAl合金的优化设计提供理论参考。
Under the condition of Al = 44% -49% (atomic fraction) and Ti / Al atomic ratio of 52/48, based on the empirical electron theory of solid and molecule, the difference between the unit cell values before and after alloying The maximum number of covalent electrons in the electronic structure is evaluated in terms of the solid solution strengthening effect of the alloying element M in the influence of the binding force between atoms. The calculated results show that the addition of V, Nb, Cr, Zr and Hf can strengthen the TiAl alloy in the range of M = [0 ~ 10]%. When the alloying elements belong to the same subgroup and the hybrid states are the same, The maximum number of covalent electrons is not sensitive; when the alloying elements belonging to the same subgroup, but different hybrid state, the elements of the larger number of bonding electrons, the strengthening effect is stronger. It can be seen that the alloying elements in the TiAl unit cell to form a substitution solid solution depend on the number of bonding electrons that the alloying elements can provide. The larger the number of bonding electrons, the more the maximum number of covalent electrons on the bond after bonding Large, making the strength of the structural elements greater; a large number of such structural elements can have a significant strengthening of the substrate. The calculated results are in good agreement with the existing experimental results. This method can provide theoretical reference for the optimization design of solid solution strengthened TiAl alloy.