Documents disponibles écrits par cet auteur

Effect of solid solution elements on nanoindentation hardness, rate dependence, and incipient plasticity in fine grained magnesium alloys / Hidetoshi Somekawa in Acta materialia, Vol. 59 N° 20 (Décembre 2011) 

Public ISBD [article]  in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7554–7563 Titre : Effect of solid solution elements on nanoindentation hardness, rate dependence, and incipient plasticity in fine grained magnesium alloys Type de document : texte imprimé Auteurs : Hidetoshi Somekawa, Auteur ; Christopher A. Schuh, Auteur Année de publication : 2012 Article en page(s) : pp. 7554–7563 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Nanoindentation  Magnesium  Activation  volume  Pop-in  behavior  Deformation  mechanism Résumé : The effect of solid solution alloying elements on the plastic deformation of fine grained Mg alloys was studied in five binary systems: Mg–0.3 at.% X (X = Al, Ca, Li, Y or Zn). All the alloys were produced by extrusion and had an average grain size of ∼2–3 μm. Solid solution strengthening is observed for all of the alloys subjected to hardness tests with a scale much larger than the grain size, and the efficacy of the various solutes is in line with expectations based on recent solution strengthening models. The different alloying elements also have an impact on the rate dependence of deformation, with activation volumes ranging between 20 b3 and 80 b3 being consistent with cross-slip as a rate limiting mechanism. For nanoscale indentations the yield point is identified by a pop-in event, and this event is found to have a dramatically different rate dependence and activation volume than does global plasticity. Specifically, the dislocation generation mechanism associated with pop-in has an activation volume of scale ∼0.2–1 b3, and is far less affected by solute content than is global plasticity. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006240 [article] Effect of solid solution elements on nanoindentation hardness, rate dependence, and incipient plasticity in fine grained magnesium alloys [texte imprimé] / Hidetoshi Somekawa, Auteur ; Christopher A. Schuh, Auteur . - 2012 . - pp. 7554–7563. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7554–7563 Mots-clés : Nanoindentation  Magnesium  Activation  volume  Pop-in  behavior  Deformation  mechanism Résumé : The effect of solid solution alloying elements on the plastic deformation of fine grained Mg alloys was studied in five binary systems: Mg–0.3 at.% X (X = Al, Ca, Li, Y or Zn). All the alloys were produced by extrusion and had an average grain size of ∼2–3 μm. Solid solution strengthening is observed for all of the alloys subjected to hardness tests with a scale much larger than the grain size, and the efficacy of the various solutes is in line with expectations based on recent solution strengthening models. The different alloying elements also have an impact on the rate dependence of deformation, with activation volumes ranging between 20 b3 and 80 b3 being consistent with cross-slip as a rate limiting mechanism. For nanoscale indentations the yield point is identified by a pop-in event, and this event is found to have a dramatically different rate dependence and activation volume than does global plasticity. Specifically, the dislocation generation mechanism associated with pop-in has an activation volume of scale ∼0.2–1 b3, and is far less affected by solute content than is global plasticity. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006240

Sliding wear of nanocrystalline Ni–W / Timothy J. Rupert in Acta materialia, Vol. 58 N° 12 (Juillet 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 12 (Juillet 2010) . - pp. 4137–4148 Titre : Sliding wear of nanocrystalline Ni–W : Structural evolution and the apparent breakdown of Archard scaling Type de document : texte imprimé Auteurs : Timothy J. Rupert, Auteur ; Christopher A. Schuh, Auteur Année de publication : 2011 Article en page(s) : pp. 4137–4148 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Nanocrystalline  materials  Wear  Mechanical  properties  Ni–W  alloys  Grain  boundary  migration Résumé : Sliding wear of nanocrystalline Ni–W alloys with grain sizes of 3–47 nm, a range which spans the transition in deformation mechanisms from intra- to inter-granular, has been studied through pin-on-disk wear testing. The extreme conditions produced during sliding wear are found to result in structural evolution and a deviation from Archard scaling for the finest grain sizes; in the finest nanocrystalline materials wear resistance is higher than would be expected based on hardness alone. The repetitive sliding load is found to lead to a modest amount of grain growth and grain boundary relaxation, which in turn leads to local hardening in the wear track. Analysis of the dynamic microstructure suggests that it is produced primarily as a result of local plasticity and is not principally due to frictional heating. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410002119 [article] Sliding wear of nanocrystalline Ni–W : Structural evolution and the apparent breakdown of Archard scaling [texte imprimé] / Timothy J. Rupert, Auteur ; Christopher A. Schuh, Auteur . - 2011 . - pp. 4137–4148. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 12 (Juillet 2010) . - pp. 4137–4148 Mots-clés : Nanocrystalline  materials  Wear  Mechanical  properties  Ni–W  alloys  Grain  boundary  migration Résumé : Sliding wear of nanocrystalline Ni–W alloys with grain sizes of 3–47 nm, a range which spans the transition in deformation mechanisms from intra- to inter-granular, has been studied through pin-on-disk wear testing. The extreme conditions produced during sliding wear are found to result in structural evolution and a deviation from Archard scaling for the finest grain sizes; in the finest nanocrystalline materials wear resistance is higher than would be expected based on hardness alone. The repetitive sliding load is found to lead to a modest amount of grain growth and grain boundary relaxation, which in turn leads to local hardening in the wear track. Analysis of the dynamic microstructure suggests that it is produced primarily as a result of local plasticity and is not principally due to frictional heating. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410002119