Ritter, Yvonne (2012)
Molecular Dynamics Simulations of Structure-Property Relationships in Cu-Zr Metallic Glasses.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
The scope of this thesis is to elucidate structure-property relationships in copper-zirconium amorphous alloys using molecular dynamics simulations. We investigate the plastic deformation of Cu-Zr glasses in the absence of free surfaces or other heterogeneities and show that strain localization is an intrinsic metallic glass property. Tensile tests of metallic glass nanowires reveal that even in samples with a diameter of only 5nm shear banding is the dominant deformation mode and that there is no intrinsic size effect in the plastic deformation of metallic glasses. The structure and properties of shear bands are investigated in a comprehensive study considering chemical short range order, topological short range order and medium range order. Our results suggest that the picture of a structural backbone, which is locally destabilized and causes strain localization, is not a universal concept for describing shear banding in metallic glasses. When subjected to thermal annealing, shear bands recover and, depending on the annealing temperature, collective motion or nearest neighbor jumps in addition to collective motion are the relevant relaxation mechanisms. Linking free volume theory and experimental observations, our results provide an explanation why shear bands do not recover instantaneously at elevated temperatures but rather on time scales in the range of hours. We finally investigate the deformation of nanostructured metallic glasses, namely nanoglasses obtained by powder consolidation. Nanoglasses comprise a network of glass-glass interfaces with a defective short range order, which act as shear band precursors. This leads to a more homogeneous distribution of plastic strain in a pattern of multiple shear bands, wherefore we predict an enhanced ductility for metallic nanoglasses as compared to conventional metallic glasses.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2012 | ||||
Autor(en): | Ritter, Yvonne | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Molecular Dynamics Simulations of Structure-Property Relationships in Cu-Zr Metallic Glasses | ||||
Sprache: | Englisch | ||||
Referenten: | Albe, Prof. Dr. Karsten ; Gerhard, Prof. Dr. Wilde | ||||
Publikationsjahr: | 19 Januar 2012 | ||||
Ort: | Darmstadt | ||||
Datum der mündlichen Prüfung: | 16 Dezember 2011 | ||||
URL / URN: | urn:nbn:de:tuda-tuprints-28685 | ||||
Kurzbeschreibung (Abstract): | The scope of this thesis is to elucidate structure-property relationships in copper-zirconium amorphous alloys using molecular dynamics simulations. We investigate the plastic deformation of Cu-Zr glasses in the absence of free surfaces or other heterogeneities and show that strain localization is an intrinsic metallic glass property. Tensile tests of metallic glass nanowires reveal that even in samples with a diameter of only 5nm shear banding is the dominant deformation mode and that there is no intrinsic size effect in the plastic deformation of metallic glasses. The structure and properties of shear bands are investigated in a comprehensive study considering chemical short range order, topological short range order and medium range order. Our results suggest that the picture of a structural backbone, which is locally destabilized and causes strain localization, is not a universal concept for describing shear banding in metallic glasses. When subjected to thermal annealing, shear bands recover and, depending on the annealing temperature, collective motion or nearest neighbor jumps in addition to collective motion are the relevant relaxation mechanisms. Linking free volume theory and experimental observations, our results provide an explanation why shear bands do not recover instantaneously at elevated temperatures but rather on time scales in the range of hours. We finally investigate the deformation of nanostructured metallic glasses, namely nanoglasses obtained by powder consolidation. Nanoglasses comprise a network of glass-glass interfaces with a defective short range order, which act as shear band precursors. This leads to a more homogeneous distribution of plastic strain in a pattern of multiple shear bands, wherefore we predict an enhanced ductility for metallic nanoglasses as compared to conventional metallic glasses. |
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Alternatives oder übersetztes Abstract: |
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Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 530 Physik 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau |
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Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Materialmodellierung |
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Hinterlegungsdatum: | 24 Jan 2012 09:30 | ||||
Letzte Änderung: | 12 Mai 2015 10:04 | ||||
PPN: | |||||
Referenten: | Albe, Prof. Dr. Karsten ; Gerhard, Prof. Dr. Wilde | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 16 Dezember 2011 | ||||
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