Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties

Tesis Doctoral presentada en Madrid, septiembre de 2015 en la Universidad Complutense de Madrid. Facultad de Ciencias Físicas. Departamento de Física de Materiales

Detalles Bibliográficos
Autor: Alonso de Celada Casero, Carola
Tipo de recurso: tesis doctoral
Fecha de publicación:2015
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/125094
Acceso en línea:http://hdl.handle.net/10261/125094
Access Level:acceso abierto
Palabra clave:Stainless steel
Phase transformations
Characterization
Microstructure
Mechanical Properties
Acero inoxidable
Transformaciones de fase
Caracterización
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dc.title.none.fl_str_mv Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
Transformaciones de Fase en Estado Sólido en un Acero Inoxidable Metaestable: Control Microestructural y Propiedades Mecánicas
title Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
spellingShingle Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
Alonso de Celada Casero, Carola
Stainless steel
Phase transformations
Characterization
Microstructure
Mechanical Properties
Acero inoxidable
Transformaciones de fase
Caracterización
title_short Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
title_full Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
title_fullStr Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
title_full_unstemmed Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
title_sort Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical Properties
dc.creator.none.fl_str_mv Alonso de Celada Casero, Carola
author Alonso de Celada Casero, Carola
author_facet Alonso de Celada Casero, Carola
author_role author
dc.contributor.none.fl_str_mv San Martín Fernández, David
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Stainless steel
Phase transformations
Characterization
Microstructure
Mechanical Properties
Acero inoxidable
Transformaciones de fase
Caracterización
topic Stainless steel
Phase transformations
Characterization
Microstructure
Mechanical Properties
Acero inoxidable
Transformaciones de fase
Caracterización
description Tesis Doctoral presentada en Madrid, septiembre de 2015 en la Universidad Complutense de Madrid. Facultad de Ciencias Físicas. Departamento de Física de Materiales
publishDate 2015
dc.date.none.fl_str_mv 2015
2015
2015
dc.type.none.fl_str_mv info:eu-repo/semantics/doctoralThesis
http://purl.org/coar/resource_type/c_db06
format doctoralThesis
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/125094
url http://hdl.handle.net/10261/125094
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Universidad Complutense de Madrid
CSIC - Centro Nacional de Investigaciones Metalúrgicas (CENIM)
publisher.none.fl_str_mv Universidad Complutense de Madrid
CSIC - Centro Nacional de Investigaciones Metalúrgicas (CENIM)
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
_version_ 1869403370066804736
spelling Solid-Solid Phase Transformations in a Metastable Stainless Steel: Microstructural Control and Mechanical PropertiesTransformaciones de Fase en Estado Sólido en un Acero Inoxidable Metaestable: Control Microestructural y Propiedades MecánicasAlonso de Celada Casero, CarolaStainless steelPhase transformationsCharacterizationMicrostructureMechanical PropertiesAcero inoxidableTransformaciones de faseCaracterizaciónTesis Doctoral presentada en Madrid, septiembre de 2015 en la Universidad Complutense de Madrid. Facultad de Ciencias Físicas. Departamento de Física de MaterialesIn this thesis work the processing-microstructure-mechanical properties relationship has been studied in a cold-rolled semi-austenitic metastable stainless steel of composition: 12Cr-9Ni-4Mo-2Cu-1Ti-0.5Mn-0.4Al (wt. %). Due to its good corrosion resistance, good ductility in the annealed state, high strength in martensitic state and its ability to precipitation harden, this material is especially suitable for complicated designs that still have high requirements on the strength of the final product. However, the complex thermo-mechanical behavior of this steel is difficult to understand and limits its applications. Therefore, and in view of its good properties, it is worth investing time in studying the phase transformations that the material may undergo during the thermo-mechanical processing as well as the interlink microstructure-properties. In this way, it is possible to gain insight about the parameters controlling the thermal and mechanical stability and to propose new processing routes that lead to the adequate final properties depending on the application. The pronounced chemical banding present in the cold-rolled as-received state has turned up to be a thorny and difficult-to-solve problem that influences the stability and the microstructure of the material. The combination of techniques such as transmission electron microscopy (TEM), electron probe microanalysis (EPMA), magnetization measurements, micro-hardness Vickers and thermoelectric power (TEP) measurements have allow to perform a detailed characterization of the α’→γ transformation upon isochronal heating (0.1, 1 and 10 ºC/s). It was found to occur in a wide range of temperatures, in two steps due to the chemical banding, and through an interface-controlled mechanism for all heating rates. The isochronal heating allows the precise control of the microstructure and submicrometer size (0.35-0.41 μm) dual (α’/γ) and austenitic microstructures can be obtained. The mechanical behavior of these microstructures was studied by tensile testing, magnetization measurements and transmission electron microscopy (TEM) and it was found that the ultimate tensile strength (UTS) and elongation can be varied from about 1.20 GPa and 25 % to 2.20 GPa and 3 %, respectively. When the austenite grain size (AGS) is increased to the coarse-grained (CG) scale (~6.50 μm), the yield strength (YS) and UTS can drop to 0.40 and 0.80 GPa, respectively, and the total elongation increase up to 44 %. The main factors affecting the mechanical behavior in this steel are the mechanical stability of the austenite, the balance of austenite/martensite volume fractions, the presence of strengthening second-phase nano-particles and the chemical banding. Due to its metastability, the austenite is susceptible of transforming into strain-induced martensite (SIM) under applied uniaxial tensions (so-called TRIP effect), which results in outstanding work-hardening rates and enhanced mechanical properties. The refinement of the microstructures causes an increase in the critical stress required to initiate the formation of SIM and results in a faster transformation kinetics compared to the CG counterparts. Finally, the ability of precipitation hardening of this steel was thoroughly investigated in the cold-rolled state for aging temperatures of 300-550 ºC and times up to 72 h. The hardening rate during aging has been characterized using hardness and TEP measurements; and nano-precipitates formed have been analyzed by TEM and HRTEM. A semi-empirical model has been used to estimate the activation energy of the process. The mechanical behavior of selected microstructures aged at 400, 450 and 500 ºC has been also characterized and discussed based on the nanometer size of the precipitates, their coarsening and the formation of austenite after long aging treatments.CSIC- beca predoctoral “Junta para la Ampliación de Estudios” (JAE-Pre_2011_01167), cofinanciada por el Fondo Social Europeo.Peer reviewedUniversidad Complutense de MadridCSIC - Centro Nacional de Investigaciones Metalúrgicas (CENIM)San Martín Fernández, DavidConsejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]201520152015info:eu-repo/semantics/doctoralThesishttp://purl.org/coar/resource_type/c_db06http://hdl.handle.net/10261/125094reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)InglésSíinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/1250942026-05-22T06:33:51Z
score 15,811543

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