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Interfacial diffusion in Cu with a gradient nanostructured surface layer / Z.B. Wang in Acta materialia, Vol. 58 N° 7 (Avril 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 7 (Avril 2010) . - pp. 2376–2386 Titre : Interfacial diffusion in Cu with a gradient nanostructured surface layer Type de document : texte imprimé Auteurs : Z.B. Wang, Auteur ; K. Lu, Auteur ; G. Wilde, Auteur Année de publication : 2011 Article en page(s) : pp. 2376–2386 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Nanostructured  material  Surface  mechanical  attrition  treatment  Diffusion  Grain  boundaries  Twin  boundaries Résumé : A graded microstructure was produced in the surface layer of a pure Cu sample by means of surface mechanical attrition treatment (SMAT) [Wang K, Tao NR, Liu G, Lu J, Lu K. Acta Mater 2006;54:5281.]. The diffusion behavior of 63Ni in such a surface layer was investigated by the radiotracer technique at temperatures <438 K. It is shown that the effective diffusivity in the top 10 μm surface layer is more than 2 orders of magnitude higher than that along conventional high-angle grain boundaries (HAGB) in Cu of similar purity. The diffusion rate increases gradually with increasing depth up to 30–50 μm, and then decreases with further increasing depth. The enhanced diffusivities reveal higher-energy states of various interfaces in the SMAT surface layer. The excess free energy of HAGB in this layer is estimated to be ∼30% higher than that of conventional grain boundaries. An apparent retardation of the effective diffusion rate in the top 25 μm surface layer is induced by tracer leakage into numerous twin-boundary-like interfaces, while the gradual decrease in interface excess free energy correlates with the observed decrease in diffusivity in the subsurface layer at depths exceeding 50 μm. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008702 [article] Interfacial diffusion in Cu with a gradient nanostructured surface layer [texte imprimé] / Z.B. Wang, Auteur ; K. Lu, Auteur ; G. Wilde, Auteur . - 2011 . - pp. 2376–2386. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 7 (Avril 2010) . - pp. 2376–2386 Mots-clés : Nanostructured  material  Surface  mechanical  attrition  treatment  Diffusion  Grain  boundaries  Twin  boundaries Résumé : A graded microstructure was produced in the surface layer of a pure Cu sample by means of surface mechanical attrition treatment (SMAT) [Wang K, Tao NR, Liu G, Lu J, Lu K. Acta Mater 2006;54:5281.]. The diffusion behavior of 63Ni in such a surface layer was investigated by the radiotracer technique at temperatures <438 K. It is shown that the effective diffusivity in the top 10 μm surface layer is more than 2 orders of magnitude higher than that along conventional high-angle grain boundaries (HAGB) in Cu of similar purity. The diffusion rate increases gradually with increasing depth up to 30–50 μm, and then decreases with further increasing depth. The enhanced diffusivities reveal higher-energy states of various interfaces in the SMAT surface layer. The excess free energy of HAGB in this layer is estimated to be ∼30% higher than that of conventional grain boundaries. An apparent retardation of the effective diffusion rate in the top 25 μm surface layer is induced by tracer leakage into numerous twin-boundary-like interfaces, while the gradual decrease in interface excess free energy correlates with the observed decrease in diffusivity in the subsurface layer at depths exceeding 50 μm. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409008702