Strain-Mediated Defect Engineering toward Rapid Atomic Migration in Fe-Al Diffusion Couples.

ABSTRACT

In the pursuit of rapid atomic migration in lightweight Fe-Al diffusion couples, rationally designing short-circuit diffusion paths has become paramount. Herein, a strain-mediated defect engineering strategy was proposed for reducing the vacancy activation energy and enhancing diffusion behaviors along dislocations (DLs) and grain boundaries (GBs). Combining the modified Arrhenius-type relationship, an interfacial apparent activation energy of 139 kJ mol-1 was acquired utilizing defect engineering, which was decreased by about 49%. This was closely related to high-density vacancies, DLs, and GBs formed in strained Fe and Al materials, which provided more low activation energy paths for atomic migration. First-principles calculations indicated that the lattice diffusion barrier mediated by monovacancy was reduced with strain incorporation, attributed to the weakened atom-vacancy bond as a consequence of less electron transport. The synergistic effect of abnormal electron-charge distribution in the bulk and strong attraction force at the Al/Fe interface radically resulted in rapid atomic migration, collectively regulating the "breaking-forming bond" process.