{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/80511"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/80511","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Mechanism for Gamma-Precipitation in Aluminum-Silver Alloys and Self-Assembly of Polyelectrolytes: Modeling of Complex Layered Materials","abstract":"In fcc Al, stacking fault energy (SFE) is high at ∼150 mJ/m 2, inhibiting stacking fault (SF) formation and dislocation motion. Yet hcp precipitates form rapidly in Al-rich face centered cubic (fcc) Al-Ag, even as the energy difference DeltaEhcp-fcc between hcp and fcc solid solution increases with Ag content. Using ab initio methods, based on electron density functional theory (DFT), I have calculated SFE versus distance of a Ag (111) plane from intrinsic (isf), extrinsic (esf) and twin (tsf) defects. I have found that Ag solute adjacent to (111) shear planes greatly reduces the ideal shear strength in fcc Al-Ag solid solution. Now with an inhomogeneous distribution of solute, SF formation is favorable, especially when a Tungsten-Carbide-like structure of alternating AlAg hcp decorates defects. I have found that solute position relative to defect plane, i.e. lattice symmetry, combined with favorable solute mixing, i.e. alloy chemistry, significantly lower SFE. My results indicate that commonly quoted arguments relating gammaesf ∼ gammaisf ∼ 2gamma tsf ∼ DeltaEhcp-fcc hold only in cases that maintain symmetry of the underlying Bravais lattice, such as elemental metals and homogeneous solid-solution. I then provide a generalization of the relation that is applicable to more realistic systems. I show that this defect/solute-mediated, low energy pathway provides a local mechanism in inhomogeneous solid solutions for rapid hcp precipitation as observed in Al-rich fcc Al-Ag. I have used approximate unit cells with DFT calculation to estimate hcp precipitate/fcc interface energy in Al-Ag and found that classical nucleation theory in combination with dendritic growth of secondary, nucleating edge structures gives √t increase in hcp precipitate width-to-thickness aspect ratio with time t. My aspect-ratio model is the first theory of which I am aware that accurately predicts an increasing aspect ratio for Al-Ag hcp precipitates, as observed.","abstract_html":"In fcc Al, stacking fault energy (SFE) is high at ∼150 mJ/m 2, inhibiting stacking fault (SF) formation and dislocation motion. Yet hcp precipitates form rapidly in Al-rich face centered cubic (fcc) Al-Ag, even as the energy difference DeltaEhcp-fcc between hcp and fcc solid solution increases with Ag content. Using ab initio methods, based on electron density functional theory (DFT), I have calculated SFE versus distance of a Ag (111) plane from intrinsic (isf), extrinsic (esf) and twin (tsf) defects. I have found that Ag solute adjacent to (111) shear planes greatly reduces the ideal shear strength in fcc Al-Ag solid solution. Now with an inhomogeneous distribution of solute, SF formation is favorable, especially when a Tungsten-Carbide-like structure of alternating AlAg hcp decorates defects. I have found that solute position relative to defect plane, i.e. lattice symmetry, combined with favorable solute mixing, i.e. alloy chemistry, significantly lower SFE. My results indicate that commonly quoted arguments relating gammaesf ∼ gammaisf ∼ 2gamma tsf ∼ DeltaEhcp-fcc hold only in cases that maintain symmetry of the underlying Bravais lattice, such as elemental metals and homogeneous solid-solution. I then provide a generalization of the relation that is applicable to more realistic systems. I show that this defect/solute-mediated, low energy pathway provides a local mechanism in inhomogeneous solid solutions for rapid hcp precipitation as observed in Al-rich fcc Al-Ag. I have used approximate unit cells with DFT calculation to estimate hcp precipitate/fcc interface energy in Al-Ag and found that classical nucleation theory in combination with dendritic growth of secondary, nucleating edge structures gives √t increase in hcp precipitate width-to-thickness aspect ratio with time t. My aspect-ratio model is the first theory of which I am aware that accurately predicts an increasing aspect ratio for Al-Ag hcp precipitates, as observed.","abstract_has_math":false,"creators":["Finkenstadt, Daniel Kris"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Johnson, Duane D."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-25T20:02:50Z","date_published":"2015-09-25T20:02:50Z","updated_at":"2026-07-22T22:26:14Z","subjects":["Engineering, Materials Science"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI3182263"],"render_values":[{"text":"(MiAaPQ)AAI3182263","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/80511","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Johnson, Duane D."]},{"key":"dc:creator","label":"Author","values":["Finkenstadt, Daniel Kris"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-25T20:02:50Z","10000-01-01","2005"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Engineering, Materials Science"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/80511","(MiAaPQ)AAI3182263"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["In fcc Al, stacking fault energy (SFE) is high at ∼150 mJ/m 2, inhibiting stacking fault (SF) formation and dislocation motion. Yet hcp precipitates form rapidly in Al-rich face centered cubic (fcc) Al-Ag, even as the energy difference DeltaEhcp-fcc between hcp and fcc solid solution increases with Ag content. Using ab initio methods, based on electron density functional theory (DFT), I have calculated SFE versus distance of a Ag (111) plane from intrinsic (isf), extrinsic (esf) and twin (tsf) defects. I have found that Ag solute adjacent to (111) shear planes greatly reduces the ideal shear strength in fcc Al-Ag solid solution. Now with an inhomogeneous distribution of solute, SF formation is favorable, especially when a Tungsten-Carbide-like structure of alternating AlAg hcp decorates defects. I have found that solute position relative to defect plane, i.e. lattice symmetry, combined with favorable solute mixing, i.e. alloy chemistry, significantly lower SFE. My results indicate that commonly quoted arguments relating gammaesf ∼ gammaisf ∼ 2gamma tsf ∼ DeltaEhcp-fcc hold only in cases that maintain symmetry of the underlying Bravais lattice, such as elemental metals and homogeneous solid-solution. I then provide a generalization of the relation that is applicable to more realistic systems. I show that this defect/solute-mediated, low energy pathway provides a local mechanism in inhomogeneous solid solutions for rapid hcp precipitation as observed in Al-rich fcc Al-Ag. I have used approximate unit cells with DFT calculation to estimate hcp precipitate/fcc interface energy in Al-Ag and found that classical nucleation theory in combination with dendritic growth of secondary, nucleating edge structures gives √t increase in hcp precipitate width-to-thickness aspect ratio with time t. My aspect-ratio model is the first theory of which I am aware that accurately predicts an increasing aspect ratio for Al-Ag hcp precipitates, as observed.","Made available in DSpace on 2015-09-25T20:02:50Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3182263.pdf: 3429940 bytes, checksum: 31a7e0770c13a037449e31a2ebf799e3 (MD5) Previous issue date: 2005","Embargo set by: Seth Robbins for item 81793 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","131 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005."]},{"key":"dc:title","label":"Title","values":["Mechanism for Gamma-Precipitation in Aluminum-Silver Alloys and Self-Assembly of Polyelectrolytes: Modeling of Complex Layered Materials"]}]}],"canonical_facts":{"dc:contributor":["Johnson, Duane D."],"dc:creator":["Finkenstadt, Daniel Kris"],"dc:date":["2015-09-25T20:02:50Z","10000-01-01","2005"],"dc:description":["In fcc Al, stacking fault energy (SFE) is high at ∼150 mJ/m 2, inhibiting stacking fault (SF) formation and dislocation motion. Yet hcp precipitates form rapidly in Al-rich face centered cubic (fcc) Al-Ag, even as the energy difference DeltaEhcp-fcc between hcp and fcc solid solution increases with Ag content. Using ab initio methods, based on electron density functional theory (DFT), I have calculated SFE versus distance of a Ag (111) plane from intrinsic (isf), extrinsic (esf) and twin (tsf) defects. I have found that Ag solute adjacent to (111) shear planes greatly reduces the ideal shear strength in fcc Al-Ag solid solution. Now with an inhomogeneous distribution of solute, SF formation is favorable, especially when a Tungsten-Carbide-like structure of alternating AlAg hcp decorates defects. I have found that solute position relative to defect plane, i.e. lattice symmetry, combined with favorable solute mixing, i.e. alloy chemistry, significantly lower SFE. My results indicate that commonly quoted arguments relating gammaesf ∼ gammaisf ∼ 2gamma tsf ∼ DeltaEhcp-fcc hold only in cases that maintain symmetry of the underlying Bravais lattice, such as elemental metals and homogeneous solid-solution. I then provide a generalization of the relation that is applicable to more realistic systems. I show that this defect/solute-mediated, low energy pathway provides a local mechanism in inhomogeneous solid solutions for rapid hcp precipitation as observed in Al-rich fcc Al-Ag. I have used approximate unit cells with DFT calculation to estimate hcp precipitate/fcc interface energy in Al-Ag and found that classical nucleation theory in combination with dendritic growth of secondary, nucleating edge structures gives √t increase in hcp precipitate width-to-thickness aspect ratio with time t. My aspect-ratio model is the first theory of which I am aware that accurately predicts an increasing aspect ratio for Al-Ag hcp precipitates, as observed.","Made available in DSpace on 2015-09-25T20:02:50Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3182263.pdf: 3429940 bytes, checksum: 31a7e0770c13a037449e31a2ebf799e3 (MD5) Previous issue date: 2005","Embargo set by: Seth Robbins for item 81793 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","131 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005."],"dc:identifier":["http://hdl.handle.net/2142/80511","(MiAaPQ)AAI3182263"],"dc:language":["eng"],"dc:subject":["Engineering, Materials Science"],"dc:title":["Mechanism for Gamma-Precipitation in Aluminum-Silver Alloys and Self-Assembly of Polyelectrolytes: Modeling of Complex Layered Materials"],"dc:type":["text"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:14Z"}