Coarsening of a multimodal nickel-base superalloy / James Coakley in Acta materialia, Vol. 58 N° 11 (Juin 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 11 (Juin 2010) . - pp. 4019–4028 Titre : Coarsening of a multimodal nickel-base superalloy Type de document : texte imprimé Auteurs : James Coakley, Auteur ; Hector Basoalto, Auteur ; David Dye, Auteur Année de publication : 2011 Article en page(s) : pp. 4019–4028 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Nickel alloys Coarsening Diffusion Modelling Résumé : The coarsening of γ′-Ni3Al precipitates in the nickel superalloy Ni115 has been examined and compared to the results of a numerical model based on LSW coarsening theory. Ni115 has a γ′ fraction of around 60%, and at the coarsening temperatures of interest the γ′ distribution is bimodal, with two populations ∼5 nm and ∼90 nm in radius. It is found that during the initial transient (around 2000 h at 800 °C), the fine γ′ dissolve, leading to a rapid increase in the mean radius followed by a plateau. At long times, the expected steady-state unimodal t1/3 coarsening is observed. The model reproduces these features in form and approximately in magnitude, a first for LSW model-experiment comparisons in nickel superalloys. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964541000162X [article] Coarsening of a multimodal nickel-base superalloy [texte imprimé] / James Coakley, Auteur ; Hector Basoalto, Auteur ; David Dye, Auteur . - 2011 . - pp. 4019–4028. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 11 (Juin 2010) . - pp. 4019–4028 Mots-clés : Nickel alloys Coarsening Diffusion Modelling Résumé : The coarsening of γ′-Ni3Al precipitates in the nickel superalloy Ni115 has been examined and compared to the results of a numerical model based on LSW coarsening theory. Ni115 has a γ′ fraction of around 60%, and at the coarsening temperatures of interest the γ′ distribution is bimodal, with two populations ∼5 nm and ∼90 nm in radius. It is found that during the initial transient (around 2000 h at 800 °C), the fine γ′ dissolve, leading to a rapid increase in the mean radius followed by a plateau. At long times, the expected steady-state unimodal t1/3 coarsening is observed. The model reproduces these features in form and approximately in magnitude, a first for LSW model-experiment comparisons in nickel superalloys. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964541000162X

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The role of microtexture on the faceted fracture morphology in Ti–6Al–4V subjected to high-cycle fatigue / Ioannis Bantounas in Acta materialia, Vol. 58 N° 11 (Juin 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 11 (Juin 2010) . - pp. 3908–3918 Titre : The role of microtexture on the faceted fracture morphology in Ti–6Al–4V subjected to high-cycle fatigue Type de document : texte imprimé Auteurs : Ioannis Bantounas, Auteur ; David Dye, Auteur ; Trevor C Lindley, Auteur Année de publication : 2011 Article en page(s) : pp. 3908–3918 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Titanium alloys Fatigue Texture Electron backscattered diffraction (EBSD) Transmission electron microscopy (TEM) Résumé : Microtextured regions (or macrozones) are commonly reported in titanium alloys and are believed to be related to fatigue life. Here, fractographic investigations are conducted on bimodal Ti–6Al–4V plate, including transmission electron microscopy to determine the mechanism of fatigue facet formation and electron backscattered diffraction to examine the underlying macrozone structures. It is found that macrozones oriented with their c-axis close to the loading direction are responsible for facet formation, and that the facets are associated with basal slip. Microtextured regions with c-axis orientations near-perpendicular to the loading direction are believed to act as barriers to faceted crack growth, based on the change in crack morphology as the crack crosses a macrozone boundary. The variant selection occurring during the transformation of the retained beta appears to favour a common orientation with the surrounding primary alpha grains, contributing to the size of the macrozones and therefore to the extent of the observed faceted regions. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001916 [article] The role of microtexture on the faceted fracture morphology in Ti–6Al–4V subjected to high-cycle fatigue [texte imprimé] / Ioannis Bantounas, Auteur ; David Dye, Auteur ; Trevor C Lindley, Auteur . - 2011 . - pp. 3908–3918. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 11 (Juin 2010) . - pp. 3908–3918 Mots-clés : Titanium alloys Fatigue Texture Electron backscattered diffraction (EBSD) Transmission electron microscopy (TEM) Résumé : Microtextured regions (or macrozones) are commonly reported in titanium alloys and are believed to be related to fatigue life. Here, fractographic investigations are conducted on bimodal Ti–6Al–4V plate, including transmission electron microscopy to determine the mechanism of fatigue facet formation and electron backscattered diffraction to examine the underlying macrozone structures. It is found that macrozones oriented with their c-axis close to the loading direction are responsible for facet formation, and that the facets are associated with basal slip. Microtextured regions with c-axis orientations near-perpendicular to the loading direction are believed to act as barriers to faceted crack growth, based on the change in crack morphology as the crack crosses a macrozone boundary. The variant selection occurring during the transformation of the retained beta appears to favour a common orientation with the surrounding primary alpha grains, contributing to the size of the macrozones and therefore to the extent of the observed faceted regions. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001916

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