{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/71803"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/71803","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"High Temperature X-Ray Decomposition Studies of Alpha Phase Nickel-Silicon and Beta Phase Copper-Aluminum-Nickel Alloys","abstract":"In-situ high temperature X-ray diffraction studies have been performed in order to study the transformation mechanisms and associated kinetics regarding the decomposition and precipitation processes of two metallic alloys of commercial significance: Ni-12.5 at% Si and Cu-28.15 at% Al-3.88 at% Ni. Earlier resistivity measurements of the Ni-Si superalloy of the same composition yielded what was thought to be an apparent order-disorder instability temperature, below which formation of an ordered (gamma)' Ni(,3)Si phase occurred by a continuous transformation, and above which precipitation occurred by nucleation and growth processes. The X-ray results, however, have shown that the precipitation is actually dependent upon the thermal history of the specimen. In addition, cyclic heating and cooling of the specimen at elevated temperatures alters the growth rate of the ordered phase, thereby giving reason to believe that, for the particular composition studied, the growth of the ordered phase is simply based upon classical nucleation and growth phenomena.","abstract_html":"In-situ high temperature X-ray diffraction studies have been performed in order to study the transformation mechanisms and associated kinetics regarding the decomposition and precipitation processes of two metallic alloys of commercial significance: Ni-12.5 at% Si and Cu-28.15 at% Al-3.88 at% Ni. Earlier resistivity measurements of the Ni-Si superalloy of the same composition yielded what was thought to be an apparent order-disorder instability temperature, below which formation of an ordered (gamma)' Ni(,3)Si phase occurred by a continuous transformation, and above which precipitation occurred by nucleation and growth processes. The X-ray results, however, have shown that the precipitation is actually dependent upon the thermal history of the specimen. In addition, cyclic heating and cooling of the specimen at elevated temperatures alters the growth rate of the ordered phase, thereby giving reason to believe that, for the particular composition studied, the growth of the ordered phase is simply based upon classical nucleation and growth phenomena.","abstract_has_math":false,"creators":["Dvorack, Michael Albert"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Metallurgical Engineering","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-12-16T20:51:52Z","date_published":"2014-12-16T20:51:52Z","updated_at":"2026-07-22T22:26:05Z","subjects":["Engineering, Metallurgy"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8409766"],"render_values":[{"text":"(UMI)AAI8409766","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/71803","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Dvorack, Michael Albert"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2014-12-16T20:51:52Z","10000-01-01","1984"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Metallurgical Engineering"]},{"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, Metallurgy"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/71803","(UMI)AAI8409766"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["In-situ high temperature X-ray diffraction studies have been performed in order to study the transformation mechanisms and associated kinetics regarding the decomposition and precipitation processes of two metallic alloys of commercial significance: Ni-12.5 at% Si and Cu-28.15 at% Al-3.88 at% Ni. Earlier resistivity measurements of the Ni-Si superalloy of the same composition yielded what was thought to be an apparent order-disorder instability temperature, below which formation of an ordered (gamma)' Ni(,3)Si phase occurred by a continuous transformation, and above which precipitation occurred by nucleation and growth processes. The X-ray results, however, have shown that the precipitation is actually dependent upon the thermal history of the specimen. In addition, cyclic heating and cooling of the specimen at elevated temperatures alters the growth rate of the ordered phase, thereby giving reason to believe that, for the particular composition studied, the growth of the ordered phase is simply based upon classical nucleation and growth phenomena.","The Cu-Al-Ni shape memory alloy was studied with respect to both its thermal diffuse scattering (TDS) and decomposition behavior. It was shown during this study that diffuse streaks observed in diffraction patterns of this alloy are due to the presence of a thermally activated soft phonon TA(,2) mode. Decomposition studies of this alloy have revealed that the (gamma)(,2) brass phase appears from the initial (beta)(,1) phase matrix at a peritectoid transition temperature of 275(DEGREES)C. In addition to the (gamma)(,2) structure, the fcc (alpha) phase and orthorhombic (gamma)' martensite phases also appeared. Of particular interest with regard to the (gamma)(,2) phase is the existence of an unusual reversible behavior of intensity with respect to temperature at certain superlattice reflections. This particular effect is believed to be due to preferential growth of the (gamma)(,2) phase due to the anisotropy of the (beta)(,1) parent phase.","Made available in DSpace on 2014-12-16T20:51:52Z (GMT). No. of bitstreams: 1 8409766.pdf: 5036870 bytes, checksum: 3785d5a6256cf08e5e2f4a3fea06f7f5 (MD5) Previous issue date: 1984","Embargo set by: Seth Robbins for item 71969 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","197 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984."]},{"key":"dc:title","label":"Title","values":["High Temperature X-Ray Decomposition Studies of Alpha Phase Nickel-Silicon and Beta Phase Copper-Aluminum-Nickel Alloys"]}]}],"canonical_facts":{"dc:creator":["Dvorack, Michael Albert"],"dc:date":["2014-12-16T20:51:52Z","10000-01-01","1984"],"dc:description":["In-situ high temperature X-ray diffraction studies have been performed in order to study the transformation mechanisms and associated kinetics regarding the decomposition and precipitation processes of two metallic alloys of commercial significance: Ni-12.5 at% Si and Cu-28.15 at% Al-3.88 at% Ni. Earlier resistivity measurements of the Ni-Si superalloy of the same composition yielded what was thought to be an apparent order-disorder instability temperature, below which formation of an ordered (gamma)' Ni(,3)Si phase occurred by a continuous transformation, and above which precipitation occurred by nucleation and growth processes. The X-ray results, however, have shown that the precipitation is actually dependent upon the thermal history of the specimen. In addition, cyclic heating and cooling of the specimen at elevated temperatures alters the growth rate of the ordered phase, thereby giving reason to believe that, for the particular composition studied, the growth of the ordered phase is simply based upon classical nucleation and growth phenomena.","The Cu-Al-Ni shape memory alloy was studied with respect to both its thermal diffuse scattering (TDS) and decomposition behavior. It was shown during this study that diffuse streaks observed in diffraction patterns of this alloy are due to the presence of a thermally activated soft phonon TA(,2) mode. Decomposition studies of this alloy have revealed that the (gamma)(,2) brass phase appears from the initial (beta)(,1) phase matrix at a peritectoid transition temperature of 275(DEGREES)C. In addition to the (gamma)(,2) structure, the fcc (alpha) phase and orthorhombic (gamma)' martensite phases also appeared. Of particular interest with regard to the (gamma)(,2) phase is the existence of an unusual reversible behavior of intensity with respect to temperature at certain superlattice reflections. This particular effect is believed to be due to preferential growth of the (gamma)(,2) phase due to the anisotropy of the (beta)(,1) parent phase.","Made available in DSpace on 2014-12-16T20:51:52Z (GMT). No. of bitstreams: 1 8409766.pdf: 5036870 bytes, checksum: 3785d5a6256cf08e5e2f4a3fea06f7f5 (MD5) Previous issue date: 1984","Embargo set by: Seth Robbins for item 71969 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","197 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984."],"dc:identifier":["http://hdl.handle.net/2142/71803","(UMI)AAI8409766"],"dc:subject":["Engineering, Metallurgy"],"dc:title":["High Temperature X-Ray Decomposition Studies of Alpha Phase Nickel-Silicon and Beta Phase Copper-Aluminum-Nickel Alloys"],"dc:type":["text"],"thesis:degree_discipline":["Metallurgical Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:05Z"}