Diffusion behavior of aluminum in the surface layer of iron processed by shot peening

Abstract: An ultrafine-grained surface layer was fabricated on a pure Fe plate by the shot peening process. The average grain size within the surface layer of 10μm thick is about 28nm. The diffusion kinetics of Al was measured by secondary ion mass spectrometry within a temperature range of 300–380°C. The diffusion coefficient of Al in the nanocrystalline layer is about 4 orders of magnitude higher than that in coarse-grained Fe. The activation energy of Al diffusion in nanocrystalline layer is 1.38eV, which is much smaller than that reported for Al diffusion in the conventional Fe. The enhanced diffusivity of Al may originate from a considerable amount of nonequilibrium grain boundaries and a high density of dislocations in the surface layer processed by shot peening. [Copyright &y& Elsevier]