Documents disponibles écrits par cet auteur

Appearance of dislocation-mediated and twinning-induced plasticity in an engineering-grade FeMnNiCr alloy / D. Geissler in Acta materialia, Vol. 59 N° 20 (Décembre 2011) 

Public ISBD [article]  in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7711–7723 Titre : Appearance of dislocation-mediated and twinning-induced plasticity in an engineering-grade FeMnNiCr alloy Type de document : texte imprimé Auteurs : D. Geissler, Auteur ; J. Freudenberger, Auteur ; A. Kauffmann, Auteur Année de publication : 2012 Article en page(s) : pp. 7711–7723 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : TWIP  Deformation  twinning  Slip  Stacking  fault  Stacking  fault  energy Résumé : By comparing the microstructural and texture evolution with tensile stress–strain response of an Fe–24Mn–7Ni–8Cr (mass%) alloy, a slip-dominated deformation process and, at a later stage of deformation, twinning-induced plasticity are observed. The occurrence of deformation twinning is texture sensitive and occurs only in the 〈1 1 1〉 fibre texture component. Based on these experimental observations, a model is presented, which reflects an orientational and configurational peculiarity of face-centred cubic stacking faults bordered by two Shockley partials. With this model, the onset point of stacking fault growth, i.e. movement of the leading partial and stopping of the trailing partial, is evaluated. This point reflects the formation of twins in the sense that a twin is regarded as an arrangement of stacking faults on every consecutive slip plane. Furthermore, based on the tensile test results, a model-compatible description of the mechanical behaviour is shown and a reasonable stacking fault energy of about 8 mJ m−2 is calculated for the onset of partial dislocation breakaway, i.e. the onset of deformation twinning. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006173 [article] Appearance of dislocation-mediated and twinning-induced plasticity in an engineering-grade FeMnNiCr alloy [texte imprimé] / D. Geissler, Auteur ; J. Freudenberger, Auteur ; A. Kauffmann, Auteur . - 2012 . - pp. 7711–7723. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7711–7723 Mots-clés : TWIP  Deformation  twinning  Slip  Stacking  fault  Stacking  fault  energy Résumé : By comparing the microstructural and texture evolution with tensile stress–strain response of an Fe–24Mn–7Ni–8Cr (mass%) alloy, a slip-dominated deformation process and, at a later stage of deformation, twinning-induced plasticity are observed. The occurrence of deformation twinning is texture sensitive and occurs only in the 〈1 1 1〉 fibre texture component. Based on these experimental observations, a model is presented, which reflects an orientational and configurational peculiarity of face-centred cubic stacking faults bordered by two Shockley partials. With this model, the onset point of stacking fault growth, i.e. movement of the leading partial and stopping of the trailing partial, is evaluated. This point reflects the formation of twins in the sense that a twin is regarded as an arrangement of stacking faults on every consecutive slip plane. Furthermore, based on the tensile test results, a model-compatible description of the mechanical behaviour is shown and a reasonable stacking fault energy of about 8 mJ m−2 is calculated for the onset of partial dislocation breakaway, i.e. the onset of deformation twinning. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006173

Severe deformation twinning in pure copper by cryogenic wire drawing / A. Kauffmann in Acta materialia, Vol. 59 N° 20 (Décembre 2011) 

Public ISBD [article]  in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7816–7823 Titre : Severe deformation twinning in pure copper by cryogenic wire drawing Type de document : texte imprimé Auteurs : A. Kauffmann, Auteur ; J. Freudenberger, Auteur ; D. Geissler, Auteur Année de publication : 2012 Article en page(s) : pp. 7816–7823 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Deformation  twinning  Copper  Low-temperature  deformation  Stress  state  Resolved  shear  stress Résumé : The effect of low-temperature on the active deformation mechanism is studied in pure copper. For this purpose, cryogenic wire drawing at liquid nitrogen temperature (77 K) was performed using molybdenum disulfide lubrication. Microstructural investigation and texture analysis revealed severe twin formation in the cryogenically drawn copper, with a broad twin size distribution. The spacing of the observed deformation twins ranges from below 100 nm, as reported in previous investigations, up to several micrometers. The extent of twin formation, which is significantly higher when compared to other cryo-deformation techniques, is discussed with respect to the state of stress and the texture evolution during wire drawing. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006197 [article] Severe deformation twinning in pure copper by cryogenic wire drawing [texte imprimé] / A. Kauffmann, Auteur ; J. Freudenberger, Auteur ; D. Geissler, Auteur . - 2012 . - pp. 7816–7823. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 59 N° 20 (Décembre 2011) . - pp. 7816–7823 Mots-clés : Deformation  twinning  Copper  Low-temperature  deformation  Stress  state  Resolved  shear  stress Résumé : The effect of low-temperature on the active deformation mechanism is studied in pure copper. For this purpose, cryogenic wire drawing at liquid nitrogen temperature (77 K) was performed using molybdenum disulfide lubrication. Microstructural investigation and texture analysis revealed severe twin formation in the cryogenically drawn copper, with a broad twin size distribution. The spacing of the observed deformation twins ranges from below 100 nm, as reported in previous investigations, up to several micrometers. The extent of twin formation, which is significantly higher when compared to other cryo-deformation techniques, is discussed with respect to the state of stress and the texture evolution during wire drawing. ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645411006197

Studies on recrystallization of single-phase copper alloys by resistance measurements / J. Freudenberger in Acta materialia, Vol. 58 N° 7 (Avril 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 7 (Avril 2010) . - pp. 2324–2329 Titre : Studies on recrystallization of single-phase copper alloys by resistance measurements Type de document : texte imprimé Auteurs : J. Freudenberger, Auteur ; A. Kauffmann, Auteur ; H. Klauß, Auteur Année de publication : 2011 Article en page(s) : pp. 2324–2329 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Recrystallization  Copper  alloys  Low  temperature  deformation Résumé : Copper-based solid solutions with different contents of solute elements (Zn, Al, Ga, Sn, Ge) were deformed at room temperature and at liquid nitrogen temperature. The recrystallization behaviour of these alloys has been investigated by means of dynamic and isothermal measurements of the resistivity (ρ). Variations of dρ/dT from View the MathML source are interpreted in terms of changes in defect densities by recovery and recrystallization. Deviations from a linear temperature dependence of the resistivity increase with increasing solute concentration. This deviation (i.e. Δρrec as determined at room temperature) also depends on the stacking fault energy γ. We observe a 1/γ2-dependency of Δρrec which is also influenced by the deformation temperature. During deformation, γ controls the possibility of storing deformation energy in the form of dislocations and deformation twins. In combination with the general trend of alloying elements to shift recrystallization to higher temperatures, the recrystallization behaviour of single-phase copper alloys has been described qualitatively. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900860X [article] Studies on recrystallization of single-phase copper alloys by resistance measurements [texte imprimé] / J. Freudenberger, Auteur ; A. Kauffmann, Auteur ; H. Klauß, Auteur . - 2011 . - pp. 2324–2329. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 7 (Avril 2010) . - pp. 2324–2329 Mots-clés : Recrystallization  Copper  alloys  Low  temperature  deformation Résumé : Copper-based solid solutions with different contents of solute elements (Zn, Al, Ga, Sn, Ge) were deformed at room temperature and at liquid nitrogen temperature. The recrystallization behaviour of these alloys has been investigated by means of dynamic and isothermal measurements of the resistivity (ρ). Variations of dρ/dT from View the MathML source are interpreted in terms of changes in defect densities by recovery and recrystallization. Deviations from a linear temperature dependence of the resistivity increase with increasing solute concentration. This deviation (i.e. Δρrec as determined at room temperature) also depends on the stacking fault energy γ. We observe a 1/γ2-dependency of Δρrec which is also influenced by the deformation temperature. During deformation, γ controls the possibility of storing deformation energy in the form of dislocations and deformation twins. In combination with the general trend of alloying elements to shift recrystallization to higher temperatures, the recrystallization behaviour of single-phase copper alloys has been described qualitatively. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900860X