Boron diffusion in bcc-Fe studied by first-principles calculations

• Published in: Chinese physics B Vol. 25; no. 3; pp. 307 - 313
• Main Author: 李向龙 吴平 杨锐杰 闫丹 陈森 张师平 陈宁
• Format: Journal Article
• Language: English
• Published: 01.03.2016
• Subjects: bcc; Body centered cubic lattice; Boron; Diffusion; Diffusion coefficient; Ferrous alloys; Interstitials; Mathematical analysis; Segregations; 扩散机制; 扩散机理; 硼扩散; 第一原理计算; 质扩散系数; 非平衡偏聚
• ISSN: 1674-1056; 2058-3834; 1741-4199
• DOI: 10.1088/1674-1056/25/3/036601

The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is DO = 1.05 x l0-7 exp （-0.75 eV/kT） m2. s-1, while the diffusion coefficients of the B-monovacancy and the B-divacancy complex mechanisms are D1 =1.22 x 10-6fl exp （-2.27 eV/kT） mE. s-1 and D2 - 8.36 x 10-6 exp （-4.81 eV/kT） m2. s-l, re- spectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe-3%Si-B alloy （bcc structure）. Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.