Calculation of impurity diffusivities in α-Fe using first-principles methods

✍ Scribed by Shenyan Huang; Daniel L. Worthington; Mark Asta; Vidvuds Ozolins; Gautam Ghosh; Peter K. Liaw

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 465 KB
• Volume: 58
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2009.11.041

✦ Synopsis

Self-and impurity diffusivities in body-centered-cubic (bcc) iron have been calculated within the formalisms of harmonic transitionstate theory and the Le Claire nine-frequency model for vacancy-mediated diffusion. The approach combines first-principles calculations of vacancy formation, migration, and solute-binding enthalpies and entropies in the ferromagnetic phase, with an empirical relationship for the effect of magnetic disorder on diffusion activation energies. Calculated Fe self-diffusion and Mo and W impurity-diffusion coefficients are shown to agree within a factor of five with the most recent experimental measurements in both the ferromagnetic and paramagnetic phases. Calculated diffusion coefficients for Mo and W impurities are comparable to or larger than that for Fe self-diffusion at all temperatures below the a-c phase transition. Calculated activation energies for Ta and Hf impurities suggest that these solutes should also display impurity-diffusion coefficients larger than that for self-diffusion in body-centered cubic Fe.