钛合金中原子迁移性质的第一原理研究

钛合金作为一种重要的航空材料,具有比强度高,耐蚀性好等优异性能,并具有一定的高温蠕变抗力。但是在更高温度下,有限的蠕变抗力限制了钛合金的进一步应用。实验研究表明,钛合金稳态蠕变过程蠕变激活能与合金的表观扩散激活能非常接近,说明原子的扩散与蠕变过程密切相关。本文采用第一性原理的方法,计算了钛合金中常见的杂质及合金原子的迁移能垒。结果表明,对以空位机制扩散的合金原子,其在基面内迁移的能垒从高到低为Al、V、Ti、Sn、Ta、Mo、Nb、Zr,面间原子迁移由难到易为Al、Sn、V、Ti、Ta、Mo、Nb、Zr。以间隙机制迁移的Co、Fe、Ni迁移能垒较低,与实验观测到的这些原子为快扩散原子相符。

First-principles investigations of atom migration in a-titanium

Titanium alloysfind wide applications in aerospace industry for its high specific strength and good corrosion resistance. However, limited creep resistance may restrict their applications at high temperature. Experiments have demonstrated that the steady creep activation energy is close to the effective diffusion activation energy, indicating that the atomic diffusiontakesan important effect on the creep resistance. In the present work, a first-principles method is employed to study the migration energy of various alloying atoms ina-titanium. We show that, for the atoms migrating through vacancy mechanism, the in-basal-plane migration energy decreases in the order of Al, V, Ti,Sn, Ta, Mo,Nb,Zr, whereas the out-plane migration energy decreases in the order of Al, Sn, V, Ti, Ta, Mo,Nb,Zr. For the atoms (Fe, Co, Ni) migrating through interstitial mechanism, the migration energies are quite low.