Dépouillements

Atomistic modeling of interfaces and their impact on microstructure and properties / Y. Mishin in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1117–1151 Titre : Atomistic modeling of interfaces and their impact on microstructure and properties Type de document : texte imprimé Auteurs : Y. Mishin, Auteur ; M. Asta, Auteur ; Ju Li, Auteur Année de publication : 2011 Article en page(s) : pp. 1117–1151 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Atomistic  modeling  Interatomic  potentials  First-principles  methods  Molecular  dynamics  Interfaces Résumé : Atomic-level modeling of materials provides fundamental insights into phase stability, structure and properties of crystalline defects, and to physical mechanisms of many processes ranging from atomic diffusion to interface migration. This knowledge often serves as a guide for the development of mesoscopic and macroscopic continuum models, with input parameters provided by atomistic models. This paper gives an overview of the most recent developments in the area of atomistic modeling with emphasis on interfaces and their impact on microstructure and properties of materials. Modern computer simulation methodologies are discussed and illustrated by several applications related to thermodynamic, kinetic and mechanical properties of materials. Existing challenges and future research directions in this field are outlined. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007526 [article] Atomistic modeling of interfaces and their impact on microstructure and properties [texte imprimé] / Y. Mishin, Auteur ; M. Asta, Auteur ; Ju Li, Auteur . - 2011 . - pp. 1117–1151. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1117–1151 Mots-clés : Atomistic  modeling  Interatomic  potentials  First-principles  methods  Molecular  dynamics  Interfaces Résumé : Atomic-level modeling of materials provides fundamental insights into phase stability, structure and properties of crystalline defects, and to physical mechanisms of many processes ranging from atomic diffusion to interface migration. This knowledge often serves as a guide for the development of mesoscopic and macroscopic continuum models, with input parameters provided by atomistic models. This paper gives an overview of the most recent developments in the area of atomistic modeling with emphasis on interfaces and their impact on microstructure and properties of materials. Modern computer simulation methodologies are discussed and illustrated by several applications related to thermodynamic, kinetic and mechanical properties of materials. Existing challenges and future research directions in this field are outlined. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007526

Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling / F. Roters in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1152–1211 Titre : Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling : Theory, experiments, applications Type de document : texte imprimé Auteurs : F. Roters, Auteur ; P. Eisenlohr, Auteur ; L. Hantcherli, Auteur Année de publication : 2011 Article en page(s) : pp. 1152–1211 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Crystal  plasticity  Twinning  Indentation  Multiphase  steel  Anisotropy Résumé : This article reviews continuum-based variational formulations for describing the elastic–plastic deformation of anisotropic heterogeneous crystalline matter. These approaches, commonly referred to as crystal plasticity finite-element models, are important both for basic microstructure-based mechanical predictions as well as for engineering design and performance simulations involving anisotropic media. Besides the discussion of the constitutive laws, kinematics, homogenization schemes and multiscale approaches behind these methods, we also present some examples, including, in particular, comparisons of the predictions with experiments. The applications stem from such diverse fields as orientation stability, microbeam bending, single-crystal and bicrystal deformation, nanoindentation, recrystallization, multiphase steel (TRIP) deformation, and damage prediction for the microscopic and mesoscopic scales and multiscale predictions of rolling textures, cup drawing, Lankfort (r) values and stamping simulations for the macroscopic scale. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007617 [article] Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling : Theory, experiments, applications [texte imprimé] / F. Roters, Auteur ; P. Eisenlohr, Auteur ; L. Hantcherli, Auteur . - 2011 . - pp. 1152–1211. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1152–1211 Mots-clés : Crystal  plasticity  Twinning  Indentation  Multiphase  steel  Anisotropy Résumé : This article reviews continuum-based variational formulations for describing the elastic–plastic deformation of anisotropic heterogeneous crystalline matter. These approaches, commonly referred to as crystal plasticity finite-element models, are important both for basic microstructure-based mechanical predictions as well as for engineering design and performance simulations involving anisotropic media. Besides the discussion of the constitutive laws, kinematics, homogenization schemes and multiscale approaches behind these methods, we also present some examples, including, in particular, comparisons of the predictions with experiments. The applications stem from such diverse fields as orientation stability, microbeam bending, single-crystal and bicrystal deformation, nanoindentation, recrystallization, multiphase steel (TRIP) deformation, and damage prediction for the microscopic and mesoscopic scales and multiscale predictions of rolling textures, cup drawing, Lankfort (r) values and stamping simulations for the macroscopic scale. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007617

Phase field modeling of defects and deformation / Yunzhi Wang in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1212–1235 Titre : Phase field modeling of defects and deformation Type de document : texte imprimé Auteurs : Yunzhi Wang, Auteur ; Ju Li, Auteur Année de publication : 2011 Article en page(s) : pp. 1212–1235 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Dislocation  Twinning  Martensitic  transformation  Plasticity  Fracture Résumé : New perspectives on the phase field approach in modeling deformation and fracture at the fundamental defect level are reviewed. When applied at sub-angstrom length scales the phase field crystal (PFC) model is able to describe thermally averaged atomic configurations of defects and defect processes on diffusional timescales. When applied at individual defect levels the microscopic phase field (MPF) model is a superset of the Cahn–Hilliard description of chemical inhomogeneities and the Peierls (cohesive zone) description of displacive inhomogeneities. A unique feature associated with the MPF model is its ability to predict fundamental properties of individual defects such as size, formation energy, saddle point configuration and activation energy of defect nuclei, and the micromechanisms of their mutual interactions, directly using ab initio calculations as model inputs. When applied at the mesoscopic level the coarse grained phase field (CGPF) models have the ability to predict the evolution of microstructures consisting of a large assembly of both chemically and mechanically interacting defects through coupled displacive and diffusional mechanisms. It is noted that the purpose of the MPF model is fundamentally different from that of the CGPF models. The latter have been used primarily to study microstructural evolution with user-supplied linear response rate laws, defect energies and mobilities. Combined phase field simulations hold great promise in modeling deformation and fracture with complex microstructural and chemical interactions. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007447 [article] Phase field modeling of defects and deformation [texte imprimé] / Yunzhi Wang, Auteur ; Ju Li, Auteur . - 2011 . - pp. 1212–1235. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1212–1235 Mots-clés : Dislocation  Twinning  Martensitic  transformation  Plasticity  Fracture Résumé : New perspectives on the phase field approach in modeling deformation and fracture at the fundamental defect level are reviewed. When applied at sub-angstrom length scales the phase field crystal (PFC) model is able to describe thermally averaged atomic configurations of defects and defect processes on diffusional timescales. When applied at individual defect levels the microscopic phase field (MPF) model is a superset of the Cahn–Hilliard description of chemical inhomogeneities and the Peierls (cohesive zone) description of displacive inhomogeneities. A unique feature associated with the MPF model is its ability to predict fundamental properties of individual defects such as size, formation energy, saddle point configuration and activation energy of defect nuclei, and the micromechanisms of their mutual interactions, directly using ab initio calculations as model inputs. When applied at the mesoscopic level the coarse grained phase field (CGPF) models have the ability to predict the evolution of microstructures consisting of a large assembly of both chemically and mechanically interacting defects through coupled displacive and diffusional mechanisms. It is noted that the purpose of the MPF model is fundamentally different from that of the CGPF models. The latter have been used primarily to study microstructural evolution with user-supplied linear response rate laws, defect energies and mobilities. Combined phase field simulations hold great promise in modeling deformation and fracture with complex microstructural and chemical interactions. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007447

Effect of MeV ion irradiation on the coefficient of thermal expansion of Fe–Ni Invar alloys / Xuan Zheng in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1236–1241 Titre : Effect of MeV ion irradiation on the coefficient of thermal expansion of Fe–Ni Invar alloys : A combinatorial study Type de document : texte imprimé Auteurs : Xuan Zheng, Auteur ; David G. Cahill, Auteur ; Ji-Cheng Zhao, Auteur Année de publication : 2011 Article en page(s) : pp. 1236–1241 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Coefficient  of  thermal  expansion  Invar  effect  Ion  irradiation  Combinatorial  study Résumé : The effect of low-dose MeV ion irradiation on the thermal conductivity and coefficient of thermal expansion (CTE) of Fe–Ni alloys has been studied over the entire composition range using a combinatorial method. With our experimental precision of ±5%, the thermal conductivity of Fe–Ni alloys is unchanged by View the MathML source irradiation at a fluence of View the MathML source. The CTE of Fe–Ni Invar alloys with Ni concentrations between 30 and 37 at.% increases significantly upon View the MathML source irradiation. At the Invar composition of Fe65Ni35, the CTE increases from View the MathML source before ion irradiation to View the MathML source after irradiation for an ion fluence of View the MathML source or, equivalently, 0.1 displacements per atom. We attribute this increase in CTE to changes in atomic short-range order created by ion irradiation. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007137 [article] Effect of MeV ion irradiation on the coefficient of thermal expansion of Fe–Ni Invar alloys : A combinatorial study [texte imprimé] / Xuan Zheng, Auteur ; David G. Cahill, Auteur ; Ji-Cheng Zhao, Auteur . - 2011 . - pp. 1236–1241. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1236–1241 Mots-clés : Coefficient  of  thermal  expansion  Invar  effect  Ion  irradiation  Combinatorial  study Résumé : The effect of low-dose MeV ion irradiation on the thermal conductivity and coefficient of thermal expansion (CTE) of Fe–Ni alloys has been studied over the entire composition range using a combinatorial method. With our experimental precision of ±5%, the thermal conductivity of Fe–Ni alloys is unchanged by View the MathML source irradiation at a fluence of View the MathML source. The CTE of Fe–Ni Invar alloys with Ni concentrations between 30 and 37 at.% increases significantly upon View the MathML source irradiation. At the Invar composition of Fe65Ni35, the CTE increases from View the MathML source before ion irradiation to View the MathML source after irradiation for an ion fluence of View the MathML source or, equivalently, 0.1 displacements per atom. We attribute this increase in CTE to changes in atomic short-range order created by ion irradiation. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007137

Effects of breakaway oxidation on local stresses in thermal barrier coatings / E. P. Busso in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1242–1251 Titre : Effects of breakaway oxidation on local stresses in thermal barrier coatings Type de document : texte imprimé Auteurs : E. P. Busso, Auteur ; H. E. Evans, Auteur ; Z.Q. Qian, Auteur Année de publication : 2011 Article en page(s) : pp. 1242–1251 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Thermal  barrier  coatings  Finite-element  modelling  Breakaway  oxidation  Stress  development Résumé : It is known that fast-growing non-alumina scales in thermal barrier coating (TBC) systems tend to form at features where aluminium depletion is enhanced due to a high surface-area to volume ratio, a phenomenon known as breakaway oxidation. In this work, the influence of breakaway oxidation around protuberances in an MCrAlY bond coat in a TBC system during isothermal oxidation and after cooling is quantified numerically. A finite element approach is used which incorporates elastic, plastic and creep deformation of the bond coat and thermally grown oxide (TGO) and, importantly, the volumetric strains associated with oxide formation during the isothermal exposure. It is shown how volumetric strains which develop during breakaway oxidation can result in the formation of significant (>0.5 GPa) out-of-plane tensile stresses within the yttria-stabilized zirconia top coat at the oxidation temperature. These stresses are located along the flanks of the bond coat protuberances in locations where sub-critical cracks have previously been reported. The magnitude of the stresses increases with bond coat surface roughness, after the initiation of breakaway oxidation and after cooling. Results are also presented for the normal tractions across both TGO interfaces, and the influence of breakaway oxidation on these is discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007228 [article] Effects of breakaway oxidation on local stresses in thermal barrier coatings [texte imprimé] / E. P. Busso, Auteur ; H. E. Evans, Auteur ; Z.Q. Qian, Auteur . - 2011 . - pp. 1242–1251. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1242–1251 Mots-clés : Thermal  barrier  coatings  Finite-element  modelling  Breakaway  oxidation  Stress  development Résumé : It is known that fast-growing non-alumina scales in thermal barrier coating (TBC) systems tend to form at features where aluminium depletion is enhanced due to a high surface-area to volume ratio, a phenomenon known as breakaway oxidation. In this work, the influence of breakaway oxidation around protuberances in an MCrAlY bond coat in a TBC system during isothermal oxidation and after cooling is quantified numerically. A finite element approach is used which incorporates elastic, plastic and creep deformation of the bond coat and thermally grown oxide (TGO) and, importantly, the volumetric strains associated with oxide formation during the isothermal exposure. It is shown how volumetric strains which develop during breakaway oxidation can result in the formation of significant (>0.5 GPa) out-of-plane tensile stresses within the yttria-stabilized zirconia top coat at the oxidation temperature. These stresses are located along the flanks of the bond coat protuberances in locations where sub-critical cracks have previously been reported. The magnitude of the stresses increases with bond coat surface roughness, after the initiation of breakaway oxidation and after cooling. Results are also presented for the normal tractions across both TGO interfaces, and the influence of breakaway oxidation on these is discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007228

Brazing copper to alumina using reactive CuAgTi alloys / O. Kozlova in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1252–1260 Titre : Brazing copper to alumina using reactive CuAgTi alloys Type de document : texte imprimé Auteurs : O. Kozlova, Auteur ; M. Braccini, Auteur ; R. Voytovych, Auteur Année de publication : 2011 Article en page(s) : pp. 1252–1260 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Brazing  Joining  Interfaces  Mechanical  properties  Alumina Résumé : The purpose of this work was to describe and discuss the fundamental issues involved in reactive brazing of alumina to copper by CuAgTi alloys. The method used to bring the Ti to the CuAg braze enabled the Ti concentration in the braze to be varied to a large extent (from 0.8 to 6 wt.%). It was then possible to study the effects of this parameter on the interfacial chemistry and joint microstructure, as well as on the mechanical performance of the brazing joints, characterized by tensile tests. The mechanical strength of metal/alumina joints processed by reactive brazing was also compared with data obtained using a standard metallization process. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900723X [article] Brazing copper to alumina using reactive CuAgTi alloys [texte imprimé] / O. Kozlova, Auteur ; M. Braccini, Auteur ; R. Voytovych, Auteur . - 2011 . - pp. 1252–1260. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1252–1260 Mots-clés : Brazing  Joining  Interfaces  Mechanical  properties  Alumina Résumé : The purpose of this work was to describe and discuss the fundamental issues involved in reactive brazing of alumina to copper by CuAgTi alloys. The method used to bring the Ti to the CuAg braze enabled the Ti concentration in the braze to be varied to a large extent (from 0.8 to 6 wt.%). It was then possible to study the effects of this parameter on the interfacial chemistry and joint microstructure, as well as on the mechanical performance of the brazing joints, characterized by tensile tests. The mechanical strength of metal/alumina joints processed by reactive brazing was also compared with data obtained using a standard metallization process. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900723X

Splitting phenomenon in the precipitation evolution in an Fe–Ni–Al–Ti–Cr stainless steel / H. Leitner in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1261–1269 Titre : Splitting phenomenon in the precipitation evolution in an Fe–Ni–Al–Ti–Cr stainless steel Type de document : texte imprimé Auteurs : H. Leitner, Auteur ; M. Schober, Auteur ; R. Schnitzer, Auteur Année de publication : 2011 Article en page(s) : pp. 1261–1269 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Maraging  steel  Atom  probe  tomography  Precipitates Résumé : The evolution of precipitation and mechanical properties of an Fe–Ni–Al–Ti–Cr stainless steel was studied during ageing at 525 °C. Atom probe tomography and transmission electron microscopy were applied to follow the microstructural evolution. An initial hardening reaction, which is remarkable in terms of extent, is reported to be caused by the formation of complex multi-component clusters. They are composed mainly of Ni, Al and Ti. After ageing to peak hardness (3 h), splitting of these clusters into spherical and elongated particles was observed. Based on the chemical composition, the spherical precipitates were identified to be of type NiAl B2, and the elongated particles were associated with the η-phase (Ni3(Ti, Al)). Βoth types of precipitates contribute to the strength of the material. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007241 [article] Splitting phenomenon in the precipitation evolution in an Fe–Ni–Al–Ti–Cr stainless steel [texte imprimé] / H. Leitner, Auteur ; M. Schober, Auteur ; R. Schnitzer, Auteur . - 2011 . - pp. 1261–1269. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1261–1269 Mots-clés : Maraging  steel  Atom  probe  tomography  Precipitates Résumé : The evolution of precipitation and mechanical properties of an Fe–Ni–Al–Ti–Cr stainless steel was studied during ageing at 525 °C. Atom probe tomography and transmission electron microscopy were applied to follow the microstructural evolution. An initial hardening reaction, which is remarkable in terms of extent, is reported to be caused by the formation of complex multi-component clusters. They are composed mainly of Ni, Al and Ti. After ageing to peak hardness (3 h), splitting of these clusters into spherical and elongated particles was observed. Based on the chemical composition, the spherical precipitates were identified to be of type NiAl B2, and the elongated particles were associated with the η-phase (Ni3(Ti, Al)). Βoth types of precipitates contribute to the strength of the material. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007241

Wavelength-tunable blue photoluminescence of <2 nm Si nanocrystal synthesized by ultra-low-flow-density PECVD / Chung-Hsiang Chang in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1270–1275 Titre : Wavelength-tunable blue photoluminescence of <2 nm Si nanocrystal synthesized by ultra-low-flow-density PECVD Type de document : texte imprimé Auteurs : Chung-Hsiang Chang, Auteur ; Yi-Hao Pai, Auteur ; Jr-Hau He, Auteur Année de publication : 2011 Article en page(s) : pp. 1270–1275 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Photoluminescence  Si  nanocrystal  PECVD  HRTEM Résumé : Strong blue photoluminescence (PL) spectra from Si nanocrystals (Si-ncs) embedded in Si-rich SiOx grown by PECVD at ultra-low N2O flow density and N2O/SiH4 flow ratios are characterized. The N2O flow density is kept as low as 25 sccm to restrict oxygen desorption and to completely facilitate SiH4 decomposition, thus minimizing the oxygen adsorption and suppressing the hydrogen-passivation on dangling bonds at the Si-nc surface. In contrast to the as-grown SiOx, the blue-shifted PL of the annealed SiOx is attributed to the small-size Si-ncs rather than to oxygen vacancy defects. High-resolution transmission electron microscopy analysis reveals dense Si-ncs with diameters of 1.7 ± 0.2 nm in annealed SiOx, contributing to a minimum PL wavelength of 370 nm. X-ray photoelectron spectroscopy indicates a critical O/Si composition ratio of >1.44 for precipitating small Si-ncs with significant Si–Si binding energy peak at 99.0 eV. The weakened hydrogen-passivation effect for precisely manipulating the Si-nc size blue PL is confirmed by Fourier transform infrared spectroscopy. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007253 [article] Wavelength-tunable blue photoluminescence of <2 nm Si nanocrystal synthesized by ultra-low-flow-density PECVD [texte imprimé] / Chung-Hsiang Chang, Auteur ; Yi-Hao Pai, Auteur ; Jr-Hau He, Auteur . - 2011 . - pp. 1270–1275. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1270–1275 Mots-clés : Photoluminescence  Si  nanocrystal  PECVD  HRTEM Résumé : Strong blue photoluminescence (PL) spectra from Si nanocrystals (Si-ncs) embedded in Si-rich SiOx grown by PECVD at ultra-low N2O flow density and N2O/SiH4 flow ratios are characterized. The N2O flow density is kept as low as 25 sccm to restrict oxygen desorption and to completely facilitate SiH4 decomposition, thus minimizing the oxygen adsorption and suppressing the hydrogen-passivation on dangling bonds at the Si-nc surface. In contrast to the as-grown SiOx, the blue-shifted PL of the annealed SiOx is attributed to the small-size Si-ncs rather than to oxygen vacancy defects. High-resolution transmission electron microscopy analysis reveals dense Si-ncs with diameters of 1.7 ± 0.2 nm in annealed SiOx, contributing to a minimum PL wavelength of 370 nm. X-ray photoelectron spectroscopy indicates a critical O/Si composition ratio of >1.44 for precipitating small Si-ncs with significant Si–Si binding energy peak at 99.0 eV. The weakened hydrogen-passivation effect for precisely manipulating the Si-nc size blue PL is confirmed by Fourier transform infrared spectroscopy. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007253

Effect of pre-existing shear bands on the tensile mechanical properties of a bulk metallic glass / Q. P. Cao in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1276–1292 Titre : Effect of pre-existing shear bands on the tensile mechanical properties of a bulk metallic glass Type de document : texte imprimé Auteurs : Q. P. Cao, Auteur ; J.W. Liu, Auteur ; K.J. Yang, Auteur Année de publication : 2011 Article en page(s) : pp. 1276–1292 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Metallic  glasses  Rolling  Shear  bands  Tension  test  In  situ  SEM Résumé : Bulk Zr64.13Cu15.75Ni10.12Al10 metallic glass has been rolled at room temperature in two different directions, and the dependences of microstructure and tensile mechanical property on the degree of deformation and rolling directions have been investigated. No deformation-induced crystallization occurs except for shear bands. Shear band formation in conjugated directions is achieved in the specimen rolled in two directions, while rolling in one direction induces shear band formation only in a single direction. Pre-existing properly spaced soft inhomogeneities can stabilize shear bands and lead to tensile plastic strain, and the efficient intersection of shear bands in conjugated directions results in work-hardening behavior, which is further confirmed by in situ tensile scanning electron microscopic observation. Based on the experimental results obtained in two different specimen geometries and finite element analysis, it is deduced that a normal-stress-modified maximum shear stress criterion rather than a shear plane criterion can describe the conditions for the formation of shear bands in uniaxial tension. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007265 [article] Effect of pre-existing shear bands on the tensile mechanical properties of a bulk metallic glass [texte imprimé] / Q. P. Cao, Auteur ; J.W. Liu, Auteur ; K.J. Yang, Auteur . - 2011 . - pp. 1276–1292. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1276–1292 Mots-clés : Metallic  glasses  Rolling  Shear  bands  Tension  test  In  situ  SEM Résumé : Bulk Zr64.13Cu15.75Ni10.12Al10 metallic glass has been rolled at room temperature in two different directions, and the dependences of microstructure and tensile mechanical property on the degree of deformation and rolling directions have been investigated. No deformation-induced crystallization occurs except for shear bands. Shear band formation in conjugated directions is achieved in the specimen rolled in two directions, while rolling in one direction induces shear band formation only in a single direction. Pre-existing properly spaced soft inhomogeneities can stabilize shear bands and lead to tensile plastic strain, and the efficient intersection of shear bands in conjugated directions results in work-hardening behavior, which is further confirmed by in situ tensile scanning electron microscopic observation. Based on the experimental results obtained in two different specimen geometries and finite element analysis, it is deduced that a normal-stress-modified maximum shear stress criterion rather than a shear plane criterion can describe the conditions for the formation of shear bands in uniaxial tension. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007265

HRTEM studies of cobalt-filled carbon nanotubes / V. D. Blank in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1293–1298 Titre : HRTEM studies of cobalt-filled carbon nanotubes Type de document : texte imprimé Auteurs : V. D. Blank, Auteur ; B.A. Kulnitskiy, Auteur ; I.A. Perezhogin, Auteur Année de publication : 2011 Article en page(s) : pp. 1293–1298 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Transmission  electron  microscopy  Carbon  Graphite  Nanocrystalline  materials  Deformation  structure Résumé : Cobalt-filled carbon nanotubes were synthesized at high temperature and high gas pressure. A high-resolution transmission electron microscopy study demonstrates that the product of the synthesis contains cylindrical carbon nanotubes whose cores are filled with cobalt nanoparticles or nanorods. It is shown that cobalt appears inside the nanotubes in three basic modifications: face-centered cubic (fcc) lattice, hexagonal close-packed (hcp) lattice and disordered polytypic structure. The fcc lattice is often twinned, with two or more non-parallel twinning planes being observed. The orientations of the fcc and hcp cobalt particles with respect to the nanotubes were investigated. The authors believe that the variety of cobalt modifications inside the nanotubes is due to the process of segregation of the closely packed structures from the melt. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007277 [article] HRTEM studies of cobalt-filled carbon nanotubes [texte imprimé] / V. D. Blank, Auteur ; B.A. Kulnitskiy, Auteur ; I.A. Perezhogin, Auteur . - 2011 . - pp. 1293–1298. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1293–1298 Mots-clés : Transmission  electron  microscopy  Carbon  Graphite  Nanocrystalline  materials  Deformation  structure Résumé : Cobalt-filled carbon nanotubes were synthesized at high temperature and high gas pressure. A high-resolution transmission electron microscopy study demonstrates that the product of the synthesis contains cylindrical carbon nanotubes whose cores are filled with cobalt nanoparticles or nanorods. It is shown that cobalt appears inside the nanotubes in three basic modifications: face-centered cubic (fcc) lattice, hexagonal close-packed (hcp) lattice and disordered polytypic structure. The fcc lattice is often twinned, with two or more non-parallel twinning planes being observed. The orientations of the fcc and hcp cobalt particles with respect to the nanotubes were investigated. The authors believe that the variety of cobalt modifications inside the nanotubes is due to the process of segregation of the closely packed structures from the melt. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007277

Characterization and properties of an advanced composite substrate for YBCO-coated conductors / Mangmang Gao in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1299–1308 Titre : Characterization and properties of an advanced composite substrate for YBCO-coated conductors Type de document : texte imprimé Auteurs : Mangmang Gao, Auteur ; Hongli Suo, Auteur ; Yue Zhao, Auteur Année de publication : 2011 Article en page(s) : pp. 1299–1308 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Composite  substrate  Coated  conductors  Cubic  texture  In  situ  EBSD  tensile  test  Texture  stability Résumé : Thin, biaxially textured Ni5W/Ni12W/Ni5W composite substrates for coated conductor applications have been fabricated. The particularity of this three-layer composite configuration resides in the elemental diffusion between the outer layer and the core layer. Due to the migration of elemental W, the diffusion layer in the as-annealed substrate becomes broader than that of the as-rolled substrate. The obtained tape has a sharp cubic texture on the Ni5W outer layers, and the volume fraction of cubic grains exceeds 98.8% (<10°) at the outer surfaces. In situ electron backscatter diffraction strain–stress analysis shows that the high-quality cubic texture was stable until elongations as high as 2%. The yield strength of the composite substrate approaches 240 MPa and its saturation magnetization at 77 K has been strongly reduced with respect to pure Ni and Ni5W substrates. The present results demonstrate that this advanced three-layer substrate is suitable for the epitaxial growth of the LZO buffer layers. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007289 [article] Characterization and properties of an advanced composite substrate for YBCO-coated conductors [texte imprimé] / Mangmang Gao, Auteur ; Hongli Suo, Auteur ; Yue Zhao, Auteur . - 2011 . - pp. 1299–1308. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1299–1308 Mots-clés : Composite  substrate  Coated  conductors  Cubic  texture  In  situ  EBSD  tensile  test  Texture  stability Résumé : Thin, biaxially textured Ni5W/Ni12W/Ni5W composite substrates for coated conductor applications have been fabricated. The particularity of this three-layer composite configuration resides in the elemental diffusion between the outer layer and the core layer. Due to the migration of elemental W, the diffusion layer in the as-annealed substrate becomes broader than that of the as-rolled substrate. The obtained tape has a sharp cubic texture on the Ni5W outer layers, and the volume fraction of cubic grains exceeds 98.8% (<10°) at the outer surfaces. In situ electron backscatter diffraction strain–stress analysis shows that the high-quality cubic texture was stable until elongations as high as 2%. The yield strength of the composite substrate approaches 240 MPa and its saturation magnetization at 77 K has been strongly reduced with respect to pure Ni and Ni5W substrates. The present results demonstrate that this advanced three-layer substrate is suitable for the epitaxial growth of the LZO buffer layers. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007289

Effect of Ga addition on the microstructure and magnetic properties of hydrogenation–disproportionation–desorption–recombination processed Nd–Fe–B powder / H. Sepehri-Amin in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1309–1316 Titre : Effect of Ga addition on the microstructure and magnetic properties of hydrogenation–disproportionation–desorption–recombination processed Nd–Fe–B powder Type de document : texte imprimé Auteurs : H. Sepehri-Amin, Auteur ; W.F. Li, Auteur ; T. Ohkubo, Auteur Année de publication : 2011 Article en page(s) : pp. 1309–1316 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Permanent  magnets  Nd–Fe–B  HDDR  Coercivity  Atom  probe  tomography Résumé : Microstructural evolution of hydrogenation–disproportionation–desorption–recombination processed Nd12.5Fe72.8Co8.0B6.5Ga0.2 powder has been investigated in relation to coercivity development during the desorption recombination process. Coercivity increases when residual NdH2 is completely dehydrogenated and the decomposed Nd is segregated at the grain boundaries of the Nd2Fe14B phase. Three-dimensional atom probe (3DAP) analysis indicates the segregation of Ga at the grain boundary. The reason for the enhancement of the coercivity by the trace addition Ga is discussed based on the 3DAP results. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007290 [article] Effect of Ga addition on the microstructure and magnetic properties of hydrogenation–disproportionation–desorption–recombination processed Nd–Fe–B powder [texte imprimé] / H. Sepehri-Amin, Auteur ; W.F. Li, Auteur ; T. Ohkubo, Auteur . - 2011 . - pp. 1309–1316. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1309–1316 Mots-clés : Permanent  magnets  Nd–Fe–B  HDDR  Coercivity  Atom  probe  tomography Résumé : Microstructural evolution of hydrogenation–disproportionation–desorption–recombination processed Nd12.5Fe72.8Co8.0B6.5Ga0.2 powder has been investigated in relation to coercivity development during the desorption recombination process. Coercivity increases when residual NdH2 is completely dehydrogenated and the decomposed Nd is segregated at the grain boundaries of the Nd2Fe14B phase. Three-dimensional atom probe (3DAP) analysis indicates the segregation of Ga at the grain boundary. The reason for the enhancement of the coercivity by the trace addition Ga is discussed based on the 3DAP results. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007290

Observation and modeling of the through-thickness texture gradient in commercial-purity aluminum sheets processed by accumulative roll-bonding / Saiyi Li in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1317–1331 Titre : Observation and modeling of the through-thickness texture gradient in commercial-purity aluminum sheets processed by accumulative roll-bonding Type de document : texte imprimé Auteurs : Saiyi Li, Auteur ; Fengwei Sun, Auteur ; Hao Li, Auteur Année de publication : 2011 Article en page(s) : pp. 1317–1331 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Accumulative  roll-bonding  Texture  Crystal  plasticity  Anisotropy  Severe  plastic  deformation Résumé : The texture evolution in commercial-purity aluminum (AA1070) processed by accumulative roll-bonding (ARB) is investigated with the aid of X-ray diffraction and crystal plasticity modeling. The experimental results indicate strong texture gradients through the sheet thickness, from rolling-type textures with orthorhombic symmetry at the center to shear-type textures with monoclinic symmetry near the surface. The experimental textures are reproduced well by polycrystal plasticity modeling carried out with deformation histories from finite element simulations. The observations of a relatively strong {4 4 11}〈11 11 8〉 component at the center and a {0 0 1}〈1 1 0〉 component at the surface are attributed to their higher orientation stability than the other rolling- and shear-type orientations. Examination of the average through-thickness textures suggests that the ARB technique may not be an effective means to develop apparent {1 1 1}〈u v w〉 components and thus to enhance the normal anisotropy of plasticity of the bulk sheet materials. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007307 [article] Observation and modeling of the through-thickness texture gradient in commercial-purity aluminum sheets processed by accumulative roll-bonding [texte imprimé] / Saiyi Li, Auteur ; Fengwei Sun, Auteur ; Hao Li, Auteur . - 2011 . - pp. 1317–1331. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1317–1331 Mots-clés : Accumulative  roll-bonding  Texture  Crystal  plasticity  Anisotropy  Severe  plastic  deformation Résumé : The texture evolution in commercial-purity aluminum (AA1070) processed by accumulative roll-bonding (ARB) is investigated with the aid of X-ray diffraction and crystal plasticity modeling. The experimental results indicate strong texture gradients through the sheet thickness, from rolling-type textures with orthorhombic symmetry at the center to shear-type textures with monoclinic symmetry near the surface. The experimental textures are reproduced well by polycrystal plasticity modeling carried out with deformation histories from finite element simulations. The observations of a relatively strong {4 4 11}〈11 11 8〉 component at the center and a {0 0 1}〈1 1 0〉 component at the surface are attributed to their higher orientation stability than the other rolling- and shear-type orientations. Examination of the average through-thickness textures suggests that the ARB technique may not be an effective means to develop apparent {1 1 1}〈u v w〉 components and thus to enhance the normal anisotropy of plasticity of the bulk sheet materials. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007307

Diffusional solidification phenomena in clad aluminum automotive braze sheet / D.M. Turriff in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1332–1341 Titre : Diffusional solidification phenomena in clad aluminum automotive braze sheet Type de document : texte imprimé Auteurs : D.M. Turriff, Auteur ; S.F. Corbin, Auteur ; M. Kozdras, Auteur Année de publication : 2011 Article en page(s) : pp. 1332–1341 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Aluminum  Brazing  DSC  Diffusion  Solidification Résumé : Differential scanning calorimetry (DSC) was used to investigate clad/core interactions and the evolving microstructure during simulated brazing of aluminum brazing sheet alloy No. 12, which consists of an AA3003 core with AA4343 cladding layers on either side. During the brazing operation the clad layers can alloy with the core as a result of Si diffusion before and after clad melting (i.e. in the solid-state and the solid/liquid state). This interaction affects the amount of liquid formed and its duration, which will impact on joint formation and mechanical performance. Metallographic data and DSC liquid fraction measurements show that solid-state interdiffusion prior to melting is responsible for some initial liquid suppression, but the amount of liquid present during the brazing cycle decreases rapidly as a result of isothermal, or diffusional, solidification. The liquid phase can be completely removed via diffusional solidification at the brazing temperature prior to cooling, leaving behind a significantly coarsened clad structure. Using this novel and practical DSC technique, experimental insight regarding Si diffusion into the core can be obtained as well as the evolving clad/core solidification structure. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007393 [article] Diffusional solidification phenomena in clad aluminum automotive braze sheet [texte imprimé] / D.M. Turriff, Auteur ; S.F. Corbin, Auteur ; M. Kozdras, Auteur . - 2011 . - pp. 1332–1341. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1332–1341 Mots-clés : Aluminum  Brazing  DSC  Diffusion  Solidification Résumé : Differential scanning calorimetry (DSC) was used to investigate clad/core interactions and the evolving microstructure during simulated brazing of aluminum brazing sheet alloy No. 12, which consists of an AA3003 core with AA4343 cladding layers on either side. During the brazing operation the clad layers can alloy with the core as a result of Si diffusion before and after clad melting (i.e. in the solid-state and the solid/liquid state). This interaction affects the amount of liquid formed and its duration, which will impact on joint formation and mechanical performance. Metallographic data and DSC liquid fraction measurements show that solid-state interdiffusion prior to melting is responsible for some initial liquid suppression, but the amount of liquid present during the brazing cycle decreases rapidly as a result of isothermal, or diffusional, solidification. The liquid phase can be completely removed via diffusional solidification at the brazing temperature prior to cooling, leaving behind a significantly coarsened clad structure. Using this novel and practical DSC technique, experimental insight regarding Si diffusion into the core can be obtained as well as the evolving clad/core solidification structure. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007393

Crossover from continuous to discontinuous propagation in the Portevin–Le Chatelier effect / H. Ait-Amokhtar in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1342–1349 Titre : Crossover from continuous to discontinuous propagation in the Portevin–Le Chatelier effect Type de document : texte imprimé Auteurs : H. Ait-Amokhtar, Auteur ; C. Fressengeas, Auteur Année de publication : 2011 Article en page(s) : pp. 1342–1349 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Portevin–Le  Chatelier  effect  Dynamic  strain  aging  Unsteadiness  Digital  image  correlation  Infrared  thermography Résumé : The Portevin–Le Chatelier (PLC) effect in an Al–3.2%Mg alloy is investigated using velocity-driven tensile tests at room temperature, in a strain rate range where the crossover from continuous (type A bands) to discontinuous propagation (type B bands) occurs. Digital image correlation and infrared thermography techniques are used to render the strain, strain rate and temperature fields. Particular interest is paid to the critical tests where type A and type B bands are met sequentially. Attention is focused on the unsteadiness and anisotropy of the field variables and their consequences on the instability. It is shown that the decrease of strain rate at large strain and the elevation in temperature occurring at large driving velocity favor dynamic strain aging, reduce strain rate sensitivity and enhance strain localization. Interpretation for the crossover from type A to type B in a single test is provided accordingly. The effects of strain rate and temperature unsteadiness on the extent of the range of PLC effect, the type of instability and the critical plastic strain for the onset of serrations are discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007411 [article] Crossover from continuous to discontinuous propagation in the Portevin–Le Chatelier effect [texte imprimé] / H. Ait-Amokhtar, Auteur ; C. Fressengeas, Auteur . - 2011 . - pp. 1342–1349. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1342–1349 Mots-clés : Portevin–Le  Chatelier  effect  Dynamic  strain  aging  Unsteadiness  Digital  image  correlation  Infrared  thermography Résumé : The Portevin–Le Chatelier (PLC) effect in an Al–3.2%Mg alloy is investigated using velocity-driven tensile tests at room temperature, in a strain rate range where the crossover from continuous (type A bands) to discontinuous propagation (type B bands) occurs. Digital image correlation and infrared thermography techniques are used to render the strain, strain rate and temperature fields. Particular interest is paid to the critical tests where type A and type B bands are met sequentially. Attention is focused on the unsteadiness and anisotropy of the field variables and their consequences on the instability. It is shown that the decrease of strain rate at large strain and the elevation in temperature occurring at large driving velocity favor dynamic strain aging, reduce strain rate sensitivity and enhance strain localization. Interpretation for the crossover from type A to type B in a single test is provided accordingly. The effects of strain rate and temperature unsteadiness on the extent of the range of PLC effect, the type of instability and the critical plastic strain for the onset of serrations are discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007411

Wetting phenomena of Al–Cu alloys on sapphire below 800 °C / Andreas J. Klinter in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1350–1360 Titre : Wetting phenomena of Al–Cu alloys on sapphire below 800 °C Type de document : texte imprimé Auteurs : Andreas J. Klinter, Auteur ; Carlos A. Leon-Patiño, Auteur ; Robin A.L. Drew, Auteur Année de publication : 2011 Article en page(s) : pp. 1350–1360 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Wetting  Al–Cu  alloys  Sapphire  Thermodynamic  modeling  Interfaces Résumé : Using a modified dispensed drop method, a decrease in contact angle on sapphire from pure aluminum to low-copper-containing Al alloys (7–12 wt.%) was found; with higher copper additions θ transitions to the non-wetting regime. Atomic force microscopy on long-term samples showed a significantly increased surface roughness beneath the drop. Using high-resolution transmission electron microscopy, the reaction product at the interface was identified as CuAl2O4 for Al–7Cu and Al2O3 for an Al–99.99 drop. X-ray photoelectron spectroscopy further confirmed the formation of CuAl2O4 under CuAl2 drops. Spinel formation is caused by reaction of the alloy with residual oxygen in the furnace that is transported along the interface as modeled by thermodynamic simulations. The formation of CuAl2O4 causes the reduced σsl and hence the improved wettability of sapphire by low-copper-containing alloys compared to pure aluminum. The main reason for the increase in θ with higher copper contents is the increasing σlv of the alloy. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007435 [article] Wetting phenomena of Al–Cu alloys on sapphire below 800 °C [texte imprimé] / Andreas J. Klinter, Auteur ; Carlos A. Leon-Patiño, Auteur ; Robin A.L. Drew, Auteur . - 2011 . - pp. 1350–1360. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1350–1360 Mots-clés : Wetting  Al–Cu  alloys  Sapphire  Thermodynamic  modeling  Interfaces Résumé : Using a modified dispensed drop method, a decrease in contact angle on sapphire from pure aluminum to low-copper-containing Al alloys (7–12 wt.%) was found; with higher copper additions θ transitions to the non-wetting regime. Atomic force microscopy on long-term samples showed a significantly increased surface roughness beneath the drop. Using high-resolution transmission electron microscopy, the reaction product at the interface was identified as CuAl2O4 for Al–7Cu and Al2O3 for an Al–99.99 drop. X-ray photoelectron spectroscopy further confirmed the formation of CuAl2O4 under CuAl2 drops. Spinel formation is caused by reaction of the alloy with residual oxygen in the furnace that is transported along the interface as modeled by thermodynamic simulations. The formation of CuAl2O4 causes the reduced σsl and hence the improved wettability of sapphire by low-copper-containing alloys compared to pure aluminum. The main reason for the increase in θ with higher copper contents is the increasing σlv of the alloy. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007435

Fabrication, structure and mechanical properties of indium nanopillars / Gyuhyon Lee in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1361–1368 Titre : Fabrication, structure and mechanical properties of indium nanopillars Type de document : texte imprimé Auteurs : Gyuhyon Lee, Auteur ; Ju-Young Kim, Auteur ; Arief Suriadi Budiman, Auteur Année de publication : 2011 Article en page(s) : pp. 1361–1368 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Plastic  deformation  X-ray  diffraction  Compression  test  Electroplating  Yield  phenomena Résumé : Solid and hollow cylindrical indium pillars with nanoscale diameters were prepared using electron beam lithography followed by the electroplating fabrication method. The microstructure of the solid-core indium pillars was characterized by scanning micro-X-ray diffraction, which shows that the indium pillars were annealed at room temperature with very few dislocations remaining in the samples. The mechanical properties of the solid pillars were characterized using a uniaxial microcompression technique, which demonstrated that the engineering yield stress is ∼9 times greater than bulk and is ∼1/28 of the indium shear modulus, suggesting that the attained stresses are close to theoretical strength. Microcompression of hollow indium nanopillars showed evidence of brittle fracture. This may suggest that the failure mode for one of the most ductile metals can become brittle when the feature size is sufficiently small. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007459 [article] Fabrication, structure and mechanical properties of indium nanopillars [texte imprimé] / Gyuhyon Lee, Auteur ; Ju-Young Kim, Auteur ; Arief Suriadi Budiman, Auteur . - 2011 . - pp. 1361–1368. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1361–1368 Mots-clés : Plastic  deformation  X-ray  diffraction  Compression  test  Electroplating  Yield  phenomena Résumé : Solid and hollow cylindrical indium pillars with nanoscale diameters were prepared using electron beam lithography followed by the electroplating fabrication method. The microstructure of the solid-core indium pillars was characterized by scanning micro-X-ray diffraction, which shows that the indium pillars were annealed at room temperature with very few dislocations remaining in the samples. The mechanical properties of the solid pillars were characterized using a uniaxial microcompression technique, which demonstrated that the engineering yield stress is ∼9 times greater than bulk and is ∼1/28 of the indium shear modulus, suggesting that the attained stresses are close to theoretical strength. Microcompression of hollow indium nanopillars showed evidence of brittle fracture. This may suggest that the failure mode for one of the most ductile metals can become brittle when the feature size is sufficiently small. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007459

In situ observation of the formation of intragranular acicular ferrite at non-metallic inclusions in C–Mn steel / Di Zhang in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1369–1378 Titre : In situ observation of the formation of intragranular acicular ferrite at non-metallic inclusions in C–Mn steel Type de document : texte imprimé Auteurs : Di Zhang, Auteur ; Hidenori Terasaki, Auteur ; Yu-ichi Komizo, Auteur Année de publication : 2011 Article en page(s) : pp. 1369–1378 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : In  situ  observation  Nucleation  and  growth  Intragranular  acicular  ferrite  Phase  transformation  Steels Résumé : Intragranular acicular ferrite is regarded as a most desirable microstructure feature, in view of its strength and toughness, both in weld metals and in the heat-affected zone. This paper systematically investigated the effect of Ti addition on the evolution of intragranular acicular ferrite in the heat-affected zone of C–Mn steel. We also systematically studied the effects of austenite grain size, alloy content and the characteristic of inclusions on the formation of intragranular acicular ferrite. The nucleation and growth of intragranular acicular ferrite was directly observed by laser scanning confocal microscopy. Subsequently, microscopy analysis was used to quantitatively determine and distinguish the potent and inactive inclusions with respect to the nucleation of intragranular acicular ferrite. Finally, some possible reasons are given to explain the formation of intragranular acicular ferrite in the C–Mn steel. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007460#cor1 [article] In situ observation of the formation of intragranular acicular ferrite at non-metallic inclusions in C–Mn steel [texte imprimé] / Di Zhang, Auteur ; Hidenori Terasaki, Auteur ; Yu-ichi Komizo, Auteur . - 2011 . - pp. 1369–1378. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1369–1378 Mots-clés : In  situ  observation  Nucleation  and  growth  Intragranular  acicular  ferrite  Phase  transformation  Steels Résumé : Intragranular acicular ferrite is regarded as a most desirable microstructure feature, in view of its strength and toughness, both in weld metals and in the heat-affected zone. This paper systematically investigated the effect of Ti addition on the evolution of intragranular acicular ferrite in the heat-affected zone of C–Mn steel. We also systematically studied the effects of austenite grain size, alloy content and the characteristic of inclusions on the formation of intragranular acicular ferrite. The nucleation and growth of intragranular acicular ferrite was directly observed by laser scanning confocal microscopy. Subsequently, microscopy analysis was used to quantitatively determine and distinguish the potent and inactive inclusions with respect to the nucleation of intragranular acicular ferrite. Finally, some possible reasons are given to explain the formation of intragranular acicular ferrite in the C–Mn steel. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007460#cor1

Principles of ECAP–Conform as a continuous process for achieving grain refinement / Cheng Xu in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1379–1386 Titre : Principles of ECAP–Conform as a continuous process for achieving grain refinement : Application to an aluminum alloy Type de document : texte imprimé Auteurs : Cheng Xu, Auteur ; Steven Schroeder, Auteur ; Patrick B. Berbon, Auteur Année de publication : 2011 Article en page(s) : pp. 1379–1386 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Conform  Equal-channel  angular  pressing  Hardness  Homogeneity  Plastic  anisotropy Résumé : Equal-channel angular pressing (ECAP) combined with the Conform process provides a solution for the continuous production of ultrafine-grained materials. Rods of a commercial Al-6061 alloy were processed by ECAP–Conform at room temperature for up to a total of four passes. Microstructural observations showed significant grain refinement but with elongated grains after four passes with average widths of ∼150 nm and lengths of ∼1.2 μm when viewed on the longitudinal planes. Microhardness measurements after a single pass revealed inhomogeneities both on the cross-sectional planes and along the rod. After processing through four passes there was reasonable homogeneity throughout the rod. Measurements of the shear strengths in two orthogonal directions perpendicular to the extrusion axis showed significant strengthening after ECAP–Conform and there was no evidence for any plastic anisotropy after processing through four passes. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007472 [article] Principles of ECAP–Conform as a continuous process for achieving grain refinement : Application to an aluminum alloy [texte imprimé] / Cheng Xu, Auteur ; Steven Schroeder, Auteur ; Patrick B. Berbon, Auteur . - 2011 . - pp. 1379–1386. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1379–1386 Mots-clés : Conform  Equal-channel  angular  pressing  Hardness  Homogeneity  Plastic  anisotropy Résumé : Equal-channel angular pressing (ECAP) combined with the Conform process provides a solution for the continuous production of ultrafine-grained materials. Rods of a commercial Al-6061 alloy were processed by ECAP–Conform at room temperature for up to a total of four passes. Microstructural observations showed significant grain refinement but with elongated grains after four passes with average widths of ∼150 nm and lengths of ∼1.2 μm when viewed on the longitudinal planes. Microhardness measurements after a single pass revealed inhomogeneities both on the cross-sectional planes and along the rod. After processing through four passes there was reasonable homogeneity throughout the rod. Measurements of the shear strengths in two orthogonal directions perpendicular to the extrusion axis showed significant strengthening after ECAP–Conform and there was no evidence for any plastic anisotropy after processing through four passes. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007472

Electrical resistivity and hydrogen solubility of PdHc thin films / Stefan Wagner in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1387–1394 Titre : Electrical resistivity and hydrogen solubility of PdHc thin films Type de document : texte imprimé Auteurs : Stefan Wagner, Auteur ; Astrid Pundt, Auteur Année de publication : 2011 Article en page(s) : pp. 1387–1394 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Hydrogen  Pd  thin  films  Resistivity  Stress  Buckling Résumé : During hydrogen gas loading, Pd thin films exhibit an anomalous reduction of resistivity change with decreasing film thickness. In this paper we show that this effect can mainly be attributed to a stress-dependent reduction of hydrogen solubility at a given hydrogen pressure. Different stress states of the thin films result from different bonding to a rigid substrate. Strongly buckled thin films show bulk-like pressure–resistivity isotherms. The resistivity changes as a function of hydrogen concentration appear to be independent of film thickness. The apparent Sieverts’ constant seems to be larger for thin films compared to bulk, and increases with cycling of the thin films. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007484 [article] Electrical resistivity and hydrogen solubility of PdHc thin films [texte imprimé] / Stefan Wagner, Auteur ; Astrid Pundt, Auteur . - 2011 . - pp. 1387–1394. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1387–1394 Mots-clés : Hydrogen  Pd  thin  films  Resistivity  Stress  Buckling Résumé : During hydrogen gas loading, Pd thin films exhibit an anomalous reduction of resistivity change with decreasing film thickness. In this paper we show that this effect can mainly be attributed to a stress-dependent reduction of hydrogen solubility at a given hydrogen pressure. Different stress states of the thin films result from different bonding to a rigid substrate. Strongly buckled thin films show bulk-like pressure–resistivity isotherms. The resistivity changes as a function of hydrogen concentration appear to be independent of film thickness. The apparent Sieverts’ constant seems to be larger for thin films compared to bulk, and increases with cycling of the thin films. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007484

The mechanisms of the fcc–bcc martensitic transformation revealed by pole figures / Cyril Cayron in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1395–1402 Titre : The mechanisms of the fcc–bcc martensitic transformation revealed by pole figures Type de document : texte imprimé Auteurs : Cyril Cayron, Auteur ; Françoise Barcelo, Auteur ; Yann De Carlan, Auteur Année de publication : 2011 Article en page(s) : pp. 1395–1402 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : EBSD  Martensitic  phase  transformation  Pole  figure Résumé : Face-centered cubic (fcc) to body-centered cubic (bcc) martensitic transformations occur in many materials, such as steels, FeNi meteorites or brass. The phenomenological theory has been the accepted theory for these transformations for more than half a century. However, it cannot explain the continuous singular features in the experimental electron backscatter diffraction or X-ray diffraction pole figures. Here we show that such patterns can be simulated by one discrete orientation relationship and two continuous rotations that correspond to a trace of the transformation mechanisms. A new theory of martensite transformation that is in full agreement with the experimental pole figures is proposed. In this theory, the fcc–bcc transformation results from a fcc–hexagonal close-packed (hcp) step followed by an hcp–bcc step. The advantages of this two-step theory over the phenomenological theory are discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007496 [article] The mechanisms of the fcc–bcc martensitic transformation revealed by pole figures [texte imprimé] / Cyril Cayron, Auteur ; Françoise Barcelo, Auteur ; Yann De Carlan, Auteur . - 2011 . - pp. 1395–1402. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1395–1402 Mots-clés : EBSD  Martensitic  phase  transformation  Pole  figure Résumé : Face-centered cubic (fcc) to body-centered cubic (bcc) martensitic transformations occur in many materials, such as steels, FeNi meteorites or brass. The phenomenological theory has been the accepted theory for these transformations for more than half a century. However, it cannot explain the continuous singular features in the experimental electron backscatter diffraction or X-ray diffraction pole figures. Here we show that such patterns can be simulated by one discrete orientation relationship and two continuous rotations that correspond to a trace of the transformation mechanisms. A new theory of martensite transformation that is in full agreement with the experimental pole figures is proposed. In this theory, the fcc–bcc transformation results from a fcc–hexagonal close-packed (hcp) step followed by an hcp–bcc step. The advantages of this two-step theory over the phenomenological theory are discussed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007496

Morphological instabilities and alignment of lamellar eutectics during directional solidification under a strong magnetic field / Xi Li in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1403–1417 Titre : Morphological instabilities and alignment of lamellar eutectics during directional solidification under a strong magnetic field Type de document : texte imprimé Auteurs : Xi Li, Auteur ; Zhongming Ren, Auteur ; Yves Fautrelle, Auteur Année de publication : 2011 Article en page(s) : pp. 1403–1417 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Lamellar  eutectics  Morphological  instabilities  Strong  magnetic  field  Alignment  Directional  solidification Résumé : The effects of a strong magnetic field on Al–Al2Cu and Pb–Sn lamellar eutectics during directional solidification have been investigated experimentally. The results show that the application of a strong magnetic field caused “tilting and oscillatory” morphological instabilities and deformation of the eutectic lamellae. Moreover, it was found that the Al–Al2Cu eutectic grain became aligned under a strong magnetic field and that with an increase in the magnetic field intensity this alignment was gradually enhanced. Further, the stresses caused by the magnetization force and the thermoelectric magnetic force during directional solidification under a strong magnetic field were analyzed and it was found that they are likely responsible for the “tilting and oscillatory” morphological instabilities and deformation. This is experimental evidence that the stresses imposed on a solid are capable of inducing the morphological instabilities of lamellar eutectics. The magnetic crystalline anisotropy of the Al2Cu phases and the growth relationship between the primary Al2Cu phase and the eutectic phases was investigated and it was found that the Al2Cu phase had a remarkable magnetic crystalline anisotropy which determined the growth of the Al–Al2Cu eutectic grain. Thus, alignment of the Al–Al2Cu eutectic grain under a strong magnetic field may be attributed to the magnetic crystalline anisotropy of the Al2Cu phase. Based on the growth behaviour of Al–Al2Cu and Pb–Sn lamellar eutectics under a strong magnetic field, an alignment model of lamellar eutectics during directional solidification under a strong magnetic field is proposed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007514 [article] Morphological instabilities and alignment of lamellar eutectics during directional solidification under a strong magnetic field [texte imprimé] / Xi Li, Auteur ; Zhongming Ren, Auteur ; Yves Fautrelle, Auteur . - 2011 . - pp. 1403–1417. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1403–1417 Mots-clés : Lamellar  eutectics  Morphological  instabilities  Strong  magnetic  field  Alignment  Directional  solidification Résumé : The effects of a strong magnetic field on Al–Al2Cu and Pb–Sn lamellar eutectics during directional solidification have been investigated experimentally. The results show that the application of a strong magnetic field caused “tilting and oscillatory” morphological instabilities and deformation of the eutectic lamellae. Moreover, it was found that the Al–Al2Cu eutectic grain became aligned under a strong magnetic field and that with an increase in the magnetic field intensity this alignment was gradually enhanced. Further, the stresses caused by the magnetization force and the thermoelectric magnetic force during directional solidification under a strong magnetic field were analyzed and it was found that they are likely responsible for the “tilting and oscillatory” morphological instabilities and deformation. This is experimental evidence that the stresses imposed on a solid are capable of inducing the morphological instabilities of lamellar eutectics. The magnetic crystalline anisotropy of the Al2Cu phases and the growth relationship between the primary Al2Cu phase and the eutectic phases was investigated and it was found that the Al2Cu phase had a remarkable magnetic crystalline anisotropy which determined the growth of the Al–Al2Cu eutectic grain. Thus, alignment of the Al–Al2Cu eutectic grain under a strong magnetic field may be attributed to the magnetic crystalline anisotropy of the Al2Cu phase. Based on the growth behaviour of Al–Al2Cu and Pb–Sn lamellar eutectics under a strong magnetic field, an alignment model of lamellar eutectics during directional solidification under a strong magnetic field is proposed. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007514

Plasticity of indium antimonide between −176 and 400 °C under hydrostatic pressure / B. Kedjar in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1418–1425 Titre : Plasticity of indium antimonide between −176 and 400 °C under hydrostatic pressure : Part I: Macroscopic aspects of the deformation Type de document : texte imprimé Auteurs : B. Kedjar, Auteur ; L. Thilly, Auteur ; J.-L. Demenet, Auteur Année de publication : 2011 Article en page(s) : pp. 1418–1425 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Semiconductor  Indium  antimonide  Brittle-to-ductile  transition  Compression  Indentation Résumé : Indium antimonide (InSb) single crystals have been plastically deformed between −176 and 400 °C, i.e. below and above the brittle-to-ductile transition temperature situated around 150–160 °C, via the use of microindentation below room temperature (RT) and the Paterson press (compression under gaseous pressure) above RT. The evolution of the macroscopic mechanical data (hardness and critical resolved shear stress) with temperature suggests the existence of three deformation regimes with transitions at Ttr1 = 150 °C and Ttr2 = 20 °C. Ttr1 coincides with the brittle-to-ductile temperature, while Ttr2 may coincide with a transition in the nature of dislocations with dislocations propagating in the glide set above Ttr2 while moving in the shuffle set below Ttr2. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007538 [article] Plasticity of indium antimonide between −176 and 400 °C under hydrostatic pressure : Part I: Macroscopic aspects of the deformation [texte imprimé] / B. Kedjar, Auteur ; L. Thilly, Auteur ; J.-L. Demenet, Auteur . - 2011 . - pp. 1418–1425. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1418–1425 Mots-clés : Semiconductor  Indium  antimonide  Brittle-to-ductile  transition  Compression  Indentation Résumé : Indium antimonide (InSb) single crystals have been plastically deformed between −176 and 400 °C, i.e. below and above the brittle-to-ductile transition temperature situated around 150–160 °C, via the use of microindentation below room temperature (RT) and the Paterson press (compression under gaseous pressure) above RT. The evolution of the macroscopic mechanical data (hardness and critical resolved shear stress) with temperature suggests the existence of three deformation regimes with transitions at Ttr1 = 150 °C and Ttr2 = 20 °C. Ttr1 coincides with the brittle-to-ductile temperature, while Ttr2 may coincide with a transition in the nature of dislocations with dislocations propagating in the glide set above Ttr2 while moving in the shuffle set below Ttr2. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007538

Plasticity of indium antimonide between −176 °C and 400 °C under hydrostatic pressure / B. Kedjar in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1426–1440 Titre : Plasticity of indium antimonide between −176 °C and 400 °C under hydrostatic pressure : Part II: Microscopic aspects of the deformation Type de document : texte imprimé Auteurs : B. Kedjar, Auteur ; L. Thilly, Auteur ; J.-L. Demenet, Auteur Année de publication : 2011 Article en page(s) : pp. 1426–1440 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Semiconductor  Indium  antimonide  Brittle-to-ductile  transition  Transmission  electron  microscopy  Dislocations Résumé : Indium antimonide (InSb) has been plastically deformed over a wide temperature range, from 400 down to −176 °C (see the companion paper: Kedjar B, Thilly L, Demenet JL, Rabier J. Acta Mater 2009) and transmission electron microscopy was used to characterize the deformation microstructures. In the ductile regime, i.e. T > Ttr1 ≈ 150 °C, the crystal deforms via the nucleation and motion of perfect dislocations belonging to the glide set. In the brittle domain, i.e. for T < Ttr1 ≈ 150 °C, two regimes are observed: for Ttr2 ≈ 20 °C < T < Ttr1 ≈ 150 °C, the crystal deformation takes place via the nucleation and glide of dissociated perfect dislocations or only leading partials, while for T < Ttr2 ≈ 20 °C, the crystal deformation proceeds via the nucleation and motion of perfect dislocations belonging to the shuffle set. In view of these observations, the brittle-to-ductile transition (at Ttr1) is confirmed to correspond to a change in the dislocation nature in the glide set, from partial-mediated plasticity at low temperature to perfect-mediated plasticity at high temperature. Another transition is observed at Ttr2 and corresponds to the glide-to-shuffle transition which is observed experimentally for the first time in a III–V compound semiconductor. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007551 [article] Plasticity of indium antimonide between −176 °C and 400 °C under hydrostatic pressure : Part II: Microscopic aspects of the deformation [texte imprimé] / B. Kedjar, Auteur ; L. Thilly, Auteur ; J.-L. Demenet, Auteur . - 2011 . - pp. 1426–1440. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1426–1440 Mots-clés : Semiconductor  Indium  antimonide  Brittle-to-ductile  transition  Transmission  electron  microscopy  Dislocations Résumé : Indium antimonide (InSb) has been plastically deformed over a wide temperature range, from 400 down to −176 °C (see the companion paper: Kedjar B, Thilly L, Demenet JL, Rabier J. Acta Mater 2009) and transmission electron microscopy was used to characterize the deformation microstructures. In the ductile regime, i.e. T > Ttr1 ≈ 150 °C, the crystal deforms via the nucleation and motion of perfect dislocations belonging to the glide set. In the brittle domain, i.e. for T < Ttr1 ≈ 150 °C, two regimes are observed: for Ttr2 ≈ 20 °C < T < Ttr1 ≈ 150 °C, the crystal deformation takes place via the nucleation and glide of dissociated perfect dislocations or only leading partials, while for T < Ttr2 ≈ 20 °C, the crystal deformation proceeds via the nucleation and motion of perfect dislocations belonging to the shuffle set. In view of these observations, the brittle-to-ductile transition (at Ttr1) is confirmed to correspond to a change in the dislocation nature in the glide set, from partial-mediated plasticity at low temperature to perfect-mediated plasticity at high temperature. Another transition is observed at Ttr2 and corresponds to the glide-to-shuffle transition which is observed experimentally for the first time in a III–V compound semiconductor. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007551

Origin of stray grain formation in single-crystal superalloy weld pools from heat transfer and fluid flow modeling / T. D. Anderson in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1441–1454 Titre : Origin of stray grain formation in single-crystal superalloy weld pools from heat transfer and fluid flow modeling Type de document : texte imprimé Auteurs : T. D. Anderson, Auteur ; J.N. DuPont, Auteur ; T. DebRoy, Auteur Année de publication : 2011 Article en page(s) : pp. 1441–1454 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Single  crystal  Weld  repair  Constitutional  supercooling  Stray  grain  formation Résumé : Stray grain formation in laser and electron beam welds on single-crystal alloy CMSX-4 was investigated through heat transfer and fluid flow simulations. The results were combined with a single-crystal growth model and stray grain calculations to investigate the influence of welding parameters on stray grain formation. Stray grain contents were also experimentally measured on laser and electron beam welds prepared over a wide range of parameters. The experimental and simulation results each demonstrate that stray grain content initially increases and then decreases with increasing travel speed. Increases in beam power produce an increase in the stray grain content. The results also demonstrate that restriction of growth along 〈1 0 0〉 directions decreases the magnitude of the temperature gradient and increases the growth rate along the dendrite growth direction (relative to the solidification interface normal). This effect promotes stray grain formation in the pool by increasing the extent of constitutional supercooling. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900754X [article] Origin of stray grain formation in single-crystal superalloy weld pools from heat transfer and fluid flow modeling [texte imprimé] / T. D. Anderson, Auteur ; J.N. DuPont, Auteur ; T. DebRoy, Auteur . - 2011 . - pp. 1441–1454. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1441–1454 Mots-clés : Single  crystal  Weld  repair  Constitutional  supercooling  Stray  grain  formation Résumé : Stray grain formation in laser and electron beam welds on single-crystal alloy CMSX-4 was investigated through heat transfer and fluid flow simulations. The results were combined with a single-crystal growth model and stray grain calculations to investigate the influence of welding parameters on stray grain formation. Stray grain contents were also experimentally measured on laser and electron beam welds prepared over a wide range of parameters. The experimental and simulation results each demonstrate that stray grain content initially increases and then decreases with increasing travel speed. Increases in beam power produce an increase in the stray grain content. The results also demonstrate that restriction of growth along 〈1 0 0〉 directions decreases the magnitude of the temperature gradient and increases the growth rate along the dendrite growth direction (relative to the solidification interface normal). This effect promotes stray grain formation in the pool by increasing the extent of constitutional supercooling. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900754X

Dendrite growth simulation during solidification in the LENS process / H. Yin in Acta materialia, Vol. 58 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1455–1465 Titre : Dendrite growth simulation during solidification in the LENS process Type de document : texte imprimé Auteurs : H. Yin, Auteur ; S.D. Felicelli, Auteur Année de publication : 2011 Article en page(s) : pp. 1455–1465 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Dendrite  growth  LENS  Cellular  automaton  Solidification Résumé : A two-dimensional model combining the finite element method and the cellular automaton technique was developed to simulate dendritic growth occurring in the molten pool during the laser-engineered net shaping (LENS) process. Based on the simulation results and previously published experimental data, empirical expressions describing the relationship between the cooling rate and the dendrite arm spacing (DAS) were proposed. In addition, the influence of LENS process parameters, such as the moving speed of the laser beam, the layer thickness and the substrate size, on the DAS was also discussed. Finally, different dendrite morphologies calculated at different locations were explained based on local solidification conditions. The simulation results showed good agreement with previously published experiments. This work contributes to the understanding of microstructure formation and the resulting mechanical properties of LENS-built parts as well as providing a fundamental basis for optimization of the LENS process. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007563 [article] Dendrite growth simulation during solidification in the LENS process [texte imprimé] / H. Yin, Auteur ; S.D. Felicelli, Auteur . - 2011 . - pp. 1455–1465. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 4 (Fevrier 2010) . - pp. 1455–1465 Mots-clés : Dendrite  growth  LENS  Cellular  automaton  Solidification Résumé : A two-dimensional model combining the finite element method and the cellular automaton technique was developed to simulate dendritic growth occurring in the molten pool during the laser-engineered net shaping (LENS) process. Based on the simulation results and previously published experimental data, empirical expressions describing the relationship between the cooling rate and the dendrite arm spacing (DAS) were proposed. In addition, the influence of LENS process parameters, such as the moving speed of the laser beam, the layer thickness and the substrate size, on the DAS was also discussed. Finally, different dendrite morphologies calculated at different locations were explained based on local solidification conditions. The simulation results showed good agreement with previously published experiments. This work contributes to the understanding of microstructure formation and the resulting mechanical properties of LENS-built parts as well as providing a fundamental basis for optimization of the LENS process. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007563

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse