{"id":{"repo_id":"brazil-uerj","oai_identifier":"oai:pantheon.ufrj.br:11422/6494"},"canonical_url":"https://search.dev.ndltd.org/etd/brazil-uerj/oai:pantheon.ufrj.br:11422/6494","repository":{"repo_id":"brazil-uerj","name":"Brazil UERJ","base_url":"https://pantheon.ufrj.br/oai/request"},"display":{"title":"Influência das rotas de processamento na mesotextura e propriedades mecânicas da superliga de níquel 718","abstract":"The superalloy 718 is a precipitation hardened nickel-base alloy, commonly used for structural components that work under temperatures up to 650˚C and harsh environments, making this alloy widely used for airspace, offshore and nuclear components. This alloy is hardened mainly by precipitation of the phases γ” and γ’. Other phases can also precipitate, as primary carbides and δ phase. The thermomechanical processing may influence the presence and the volumetric fraction of these phases, crystallography of grain boundaries and their size. The grain boundary movement and consequent grain growth can be a limiting factor for applications where a grain size is a prime requisite. The aim of this work is to establish the dependence the processing routes for the control of grain size and, consequently, an increase in the fraction of Σ3n boundaries. Iterative processing routes have been developed combining cold deformation and recrystallization, inducing the formation of “special” low-energy boundaries (Σ<29) and the break of the connectivity of random boundaries (Σ>29). The characterization of the grain boundary character distribution was performed via EBSD analysis. The microstructural development of the alloy, especially the δ phase precipitation was observed by SEM. Tensile tests were performed in order to evaluate the influence of the microstructure on mechanical properties. The results show that a high proportion of Σ3n boundaries (> 60%) was achieved while maintaining a refined microstructure, via controlled precipitation of δ phase during processing. Regarding the mechanical properties, a positive relation of ductility with the amount of special boundaries was observed.","abstract_html":"The superalloy 718 is a precipitation hardened nickel-base alloy, commonly used for structural components that work under temperatures up to 650˚C and harsh environments, making this alloy widely used for airspace, offshore and nuclear components. This alloy is hardened mainly by precipitation of the phases γ” and γ’. Other phases can also precipitate, as primary carbides and δ phase. The thermomechanical processing may influence the presence and the volumetric fraction of these phases, crystallography of grain boundaries and their size. The grain boundary movement and consequent grain growth can be a limiting factor for applications where a grain size is a prime requisite. The aim of this work is to establish the dependence the processing routes for the control of grain size and, consequently, an increase in the fraction of Σ3n boundaries. Iterative processing routes have been developed combining cold deformation and recrystallization, inducing the formation of “special” low-energy boundaries (Σ&lt;29) and the break of the connectivity of random boundaries (Σ&gt;29). The characterization of the grain boundary character distribution was performed via EBSD analysis. The microstructural development of the alloy, especially the δ phase precipitation was observed by SEM. Tensile tests were performed in order to evaluate the influence of the microstructure on mechanical properties. The results show that a high proportion of Σ3n boundaries (&gt; 60%) was achieved while maintaining a refined microstructure, via controlled precipitation of δ phase during processing. Regarding the mechanical properties, a positive relation of ductility with the amount of special boundaries was observed.","abstract_has_math":false,"creators":["Medeiros, Melânea Almeida Ramalho"],"institution":"Universidade Federal do Rio de Janeiro","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Araújo, Leonardo Sales"],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017-05","date_published":"2017-05","updated_at":"2026-07-24T01:16:21Z","subjects":["Engenharia metalúrgica e de materiais","Engenharia de contorno de grão","Tratamento termomecânico"],"languages":["por"],"rights":["Acesso Aberto"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11422/6494","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Araújo, Leonardo Sales"]},{"key":"dc:creator","label":"Author","values":["Medeiros, Melânea Almeida Ramalho"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2019-02-15T15:41:17Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-05-16T03:04:12Z"]},{"key":"dc:date.issued","label":"Date","values":["2017-05"]},{"key":"dc:publisher","label":"Institution","values":["Universidade Federal do Rio de Janeiro"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia"]},{"key":"dc:type","label":"Dc Type","values":["Dissertação"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Engenharia metalúrgica e de materiais","Engenharia de contorno de grão","Tratamento termomecânico"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["por"]},{"key":"dc:rights","label":"Dc Rights","values":["Acesso Aberto"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11422/6494"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The superalloy 718 is a precipitation hardened nickel-base alloy, commonly used for structural components that work under temperatures up to 650˚C and harsh environments, making this alloy widely used for airspace, offshore and nuclear components. This alloy is hardened mainly by precipitation of the phases γ” and γ’. Other phases can also precipitate, as primary carbides and δ phase. The thermomechanical processing may influence the presence and the volumetric fraction of these phases, crystallography of grain boundaries and their size. The grain boundary movement and consequent grain growth can be a limiting factor for applications where a grain size is a prime requisite. The aim of this work is to establish the dependence the processing routes for the control of grain size and, consequently, an increase in the fraction of Σ3n boundaries. Iterative processing routes have been developed combining cold deformation and recrystallization, inducing the formation of “special” low-energy boundaries (Σ<29) and the break of the connectivity of random boundaries (Σ>29). The characterization of the grain boundary character distribution was performed via EBSD analysis. The microstructural development of the alloy, especially the δ phase precipitation was observed by SEM. Tensile tests were performed in order to evaluate the influence of the microstructure on mechanical properties. The results show that a high proportion of Σ3n boundaries (> 60%) was achieved while maintaining a refined microstructure, via controlled precipitation of δ phase during processing. Regarding the mechanical properties, a positive relation of ductility with the amount of special boundaries was observed."]},{"key":"dc:title","label":"Title","values":["Influência das rotas de processamento na mesotextura e propriedades mecânicas da superliga de níquel 718"]}]}],"canonical_facts":{"dc:contributor.advisor":["Araújo, Leonardo Sales"],"dc:creator":["Medeiros, Melânea Almeida Ramalho"],"dc:date.accessioned":["2019-02-15T15:41:17Z"],"dc:date.available":["2026-05-16T03:04:12Z"],"dc:date.issued":["2017-05"],"dc:description.abstract":["The superalloy 718 is a precipitation hardened nickel-base alloy, commonly used for structural components that work under temperatures up to 650˚C and harsh environments, making this alloy widely used for airspace, offshore and nuclear components. This alloy is hardened mainly by precipitation of the phases γ” and γ’. Other phases can also precipitate, as primary carbides and δ phase. The thermomechanical processing may influence the presence and the volumetric fraction of these phases, crystallography of grain boundaries and their size. The grain boundary movement and consequent grain growth can be a limiting factor for applications where a grain size is a prime requisite. The aim of this work is to establish the dependence the processing routes for the control of grain size and, consequently, an increase in the fraction of Σ3n boundaries. Iterative processing routes have been developed combining cold deformation and recrystallization, inducing the formation of “special” low-energy boundaries (Σ<29) and the break of the connectivity of random boundaries (Σ>29). The characterization of the grain boundary character distribution was performed via EBSD analysis. The microstructural development of the alloy, especially the δ phase precipitation was observed by SEM. Tensile tests were performed in order to evaluate the influence of the microstructure on mechanical properties. The results show that a high proportion of Σ3n boundaries (> 60%) was achieved while maintaining a refined microstructure, via controlled precipitation of δ phase during processing. Regarding the mechanical properties, a positive relation of ductility with the amount of special boundaries was observed."],"dc:identifier.uri":["http://hdl.handle.net/11422/6494"],"dc:language":["por"],"dc:publisher":["Universidade Federal do Rio de Janeiro"],"dc:publisher.department":["Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia"],"dc:rights":["Acesso Aberto"],"dc:subject":["Engenharia metalúrgica e de materiais","Engenharia de contorno de grão","Tratamento termomecânico"],"dc:title":["Influência das rotas de processamento na mesotextura e propriedades mecânicas da superliga de níquel 718"],"dc:type":["Dissertação"]},"updated_at":"2026-07-24T01:16:21Z"}