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Aluminum Σ3 grain boundary sliding enhanced by vacancy diffusion / Ningning Du in Acta materialia, Vol. 58 N° 12 (Juillet 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 12 (Juillet 2010) . - pp. 4245–4252 Titre : Aluminum Σ3 grain boundary sliding enhanced by vacancy diffusion Type de document : texte imprimé Auteurs : Ningning Du, Auteur ; Yue Qi, Auteur ; Paul E. Krajewski, Auteur Année de publication : 2011 Article en page(s) : pp. 4245–4252 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Molecular  dynamics  Grain  boundary  sliding  Aluminum  Superplasticity  Grain  boundary  structure Résumé : Grain boundary sliding is an important deformation mechanism for elevated temperature forming processes. Molecular dynamics simulations are used to investigate the effect of vacancies in the grain boundary vicinity on the sliding of Al bi-crystals at 750 K. The threshold stress for grain boundary sliding was computed for a variety of grain boundaries with different structures and energies. These structures included one symmetrical tilt grain boundary and five asymmetrical tilt grain boundaries. Without vacancies, low energy Σ3 grain boundaries exhibited significantly less sliding than other high energy grain boundaries. The addition of vacancies to Σ3 grain boundaries decreased the threshold stress for grain boundary sliding by increasing the grain boundary diffusivity. A higher concentration of vacancies enhanced this effect. The influence of vacancies on grain boundary diffusivity and grain boundary sliding was negligible for high energy grain boundaries, due to the already high atom mobility in these boundaries. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410002326 [article] Aluminum Σ3 grain boundary sliding enhanced by vacancy diffusion [texte imprimé] / Ningning Du, Auteur ; Yue Qi, Auteur ; Paul E. Krajewski, Auteur . - 2011 . - pp. 4245–4252. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 12 (Juillet 2010) . - pp. 4245–4252 Mots-clés : Molecular  dynamics  Grain  boundary  sliding  Aluminum  Superplasticity  Grain  boundary  structure Résumé : Grain boundary sliding is an important deformation mechanism for elevated temperature forming processes. Molecular dynamics simulations are used to investigate the effect of vacancies in the grain boundary vicinity on the sliding of Al bi-crystals at 750 K. The threshold stress for grain boundary sliding was computed for a variety of grain boundaries with different structures and energies. These structures included one symmetrical tilt grain boundary and five asymmetrical tilt grain boundaries. Without vacancies, low energy Σ3 grain boundaries exhibited significantly less sliding than other high energy grain boundaries. The addition of vacancies to Σ3 grain boundaries decreased the threshold stress for grain boundary sliding by increasing the grain boundary diffusivity. A higher concentration of vacancies enhanced this effect. The influence of vacancies on grain boundary diffusivity and grain boundary sliding was negligible for high energy grain boundaries, due to the already high atom mobility in these boundaries. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410002326

Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys / Paul E. Krajewski in Acta materialia, Vol. 58 N° 3 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 3 (Fevrier 2010) . - pp. 1074-1086 Titre : Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys Type de document : texte imprimé Auteurs : Paul E. Krajewski, Auteur ; Louis G. Hector, Auteur ; Ningning Du, Auteur Article en page(s) : pp. 1074-1086 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Aluminum  alloys  Creep  Superplasticity  Grain  boundaries  Micromechanical  modeling Index. décimale : 669 Métallurgie Résumé : A multiscale model for predicting elevated temperature deformation in Al–Mg alloys is presented. Constitutive models are generated from a theoretical methodology and used to investigate the effects of grain size on formability. Flow data are computed with a polycrystalline, microstructure-based model which accounts for grain boundary sliding, stress-induced diffusion, and dislocation creep. Favorable agreement is found between the computed flow data and elevated temperature tensile measurements. A creep constitutive model is then fit to the computed flow data and used in finite-element simulations of two simple gas pressure forming processes, where favorable results are observed. These results are fully consistent with gas pressure forming experiments, and suggest a greater role for constitutive models, derived largely from theoretical methodologies, in the design of Al alloys with enhanced elevated temperature formability. The methodology detailed herein provides a framework for incorporation of results from atomistic-scale models of dislocation creep and diffusion. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...] [article] Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys [texte imprimé] / Paul E. Krajewski, Auteur ; Louis G. Hector, Auteur ; Ningning Du, Auteur . - pp. 1074-1086. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 3 (Fevrier 2010) . - pp. 1074-1086 Mots-clés : Aluminum  alloys  Creep  Superplasticity  Grain  boundaries  Micromechanical  modeling Index. décimale : 669 Métallurgie Résumé : A multiscale model for predicting elevated temperature deformation in Al–Mg alloys is presented. Constitutive models are generated from a theoretical methodology and used to investigate the effects of grain size on formability. Flow data are computed with a polycrystalline, microstructure-based model which accounts for grain boundary sliding, stress-induced diffusion, and dislocation creep. Favorable agreement is found between the computed flow data and elevated temperature tensile measurements. A creep constitutive model is then fit to the computed flow data and used in finite-element simulations of two simple gas pressure forming processes, where favorable results are observed. These results are fully consistent with gas pressure forming experiments, and suggest a greater role for constitutive models, derived largely from theoretical methodologies, in the design of Al alloys with enhanced elevated temperature formability. The methodology detailed herein provides a framework for incorporation of results from atomistic-scale models of dislocation creep and diffusion. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...]

Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys / Paul E. Krajewski in Acta materialia, Vol. 58 N° 3 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 3 (Fevrier 2010) . - pp. 1074–1086 Titre : Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys Type de document : texte imprimé Auteurs : Paul E. Krajewski, Auteur ; Louis G. Hector Jr., Auteur ; Ningning Du, Auteur Année de publication : 2011 Article en page(s) : pp. 1074–1086 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Aluminum  alloys  Creep  Superplasticity  Grain  boundaries  Micromechanical  modeling Résumé : A multiscale model for predicting elevated temperature deformation in Al–Mg alloys is presented. Constitutive models are generated from a theoretical methodology and used to investigate the effects of grain size on formability. Flow data are computed with a polycrystalline, microstructure-based model which accounts for grain boundary sliding, stress-induced diffusion, and dislocation creep. Favorable agreement is found between the computed flow data and elevated temperature tensile measurements. A creep constitutive model is then fit to the computed flow data and used in finite-element simulations of two simple gas pressure forming processes, where favorable results are observed. These results are fully consistent with gas pressure forming experiments, and suggest a greater role for constitutive models, derived largely from theoretical methodologies, in the design of Al alloys with enhanced elevated temperature formability. The methodology detailed herein provides a framework for incorporation of results from atomistic-scale models of dislocation creep and diffusion. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007125 [article] Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys [texte imprimé] / Paul E. Krajewski, Auteur ; Louis G. Hector Jr., Auteur ; Ningning Du, Auteur . - 2011 . - pp. 1074–1086. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 3 (Fevrier 2010) . - pp. 1074–1086 Mots-clés : Aluminum  alloys  Creep  Superplasticity  Grain  boundaries  Micromechanical  modeling Résumé : A multiscale model for predicting elevated temperature deformation in Al–Mg alloys is presented. Constitutive models are generated from a theoretical methodology and used to investigate the effects of grain size on formability. Flow data are computed with a polycrystalline, microstructure-based model which accounts for grain boundary sliding, stress-induced diffusion, and dislocation creep. Favorable agreement is found between the computed flow data and elevated temperature tensile measurements. A creep constitutive model is then fit to the computed flow data and used in finite-element simulations of two simple gas pressure forming processes, where favorable results are observed. These results are fully consistent with gas pressure forming experiments, and suggest a greater role for constitutive models, derived largely from theoretical methodologies, in the design of Al alloys with enhanced elevated temperature formability. The methodology detailed herein provides a framework for incorporation of results from atomistic-scale models of dislocation creep and diffusion. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007125