Ti在bcc Fe晶界中的作用

EFFECT OF TITANIUM ON bcc Fe GRAIN BOUNDARY COHESION

在密度泛函理论框架下，用第一原理 ＤＭｏｌ团簇方法，基于 Ｒｉｃｅ－Ｗａｎｇ热力学模型研究了合金化元素 Ｔｉ对 ｂｃｃＦｅ∑３［１１０］（１１１）晶界结合的影响 结果表明：合金化元素Ｔｉ在晶界和自由表面的偏聚能之差为－０．３７２ｅＶ，Ｔｉ增强晶界结合，为韧性掺杂元素．Ｔｉ的化学效应起主要作用，贡献为－０．７１３ ｅＶ，表现为较强的增强晶界结合作用．力学效应即掺杂引起的局域畸变贡献为＋０．３４１ ｅＶ，表现为减弱晶界结合的作用．同时分析了Ｔｉ对晶界键合的影响，当 Ｔｉ原子占据晶界时，Ｔｉ使得距它较近的跨越晶界的键合加强，反映了Ｔｉ强化晶界的作用．

First-principles DMol method within the framework of density functional theory is used to study the effect of Ti on bcc Fe Sigma3 [1 (1) over bar0](111) grain boundary cohesion. The difference of segregation energies of a Ti atom at the grain boundary and at the free surface equals to -0.372 eV indicating that Ti is a cohesion enhancer. Further analyses show that the chemical and mechanical effects equal to -0.713 eV and +0.341 eV, respectively. The chemical effect plays a major role but mechanical effect can not be neglected in the computation. At the same time, the effect of Ti on bond is also analyzed. When Ti segregates on grain boundary, it can make the bonds across grain boundary stronger than that of clean grain boundary, that reflects the strenghthening action of Ti.