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采用基于密度泛函理论(DFT)的第一性原理,研究了稀土La对含铌钢中NbC在铁素体区析出行为的影响。计算了α-Fe中La原子和Nb原子与空位之间,以及La原子和Nb原子之间的点缺陷结合能;此外,讨论了La在α-Fe中与Nb扩散激活能的关系。在此基础上,分析了稀土加入对铌析出行为的影响。结果表明:La原子与空位之间有较强的相互吸引作用,而与Nb原子之间则为相互排斥,这种结合能的差异会造成Nb的扩散迁移能有所升高。同时,La的加入使Nb原子近邻的空位形成能显著降低,从而促进α-Fe中Nb原子近邻空位的形成。迁移能与空位形成能变化的计算结果显示,La能够使α-Fe中Nb的扩散激活能显著降低,从而促进了铁素体区NbC的析出。
The first principle based on density functional theory (DFT) was used to study the effect of rare earth La on the precipitation behavior of NbC in ferrite zone in Nb-bearing steels. The binding energies of La, Nb and vacancies in α-Fe, as well as the point defects of La atoms and Nb atoms, were calculated. In addition, the relationship between La and Nb diffusion activation energy in α-Fe was also discussed. On this basis, the effect of rare earth addition on the precipitation behavior of niobium was analyzed. The results show that there is a strong mutual attraction between La atoms and vacancies and mutual exclusion with Nb atoms. The difference in the binding energy results in the increase of diffusion and migration of Nb. At the same time, the formation of vacancy of Nb atom in α-Fe can be promoted by the addition of La. The calculated results of the change of migration energy and vacancy formation show that La can significantly decrease the diffusion activation energy of Nb in α-Fe and promote the precipitation of NbC in the ferrite region.