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1
Lu, Yu 1977. "Effect of boron on microstructure and mechanical properties of low carbon microalloyed steels." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112575.
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Low carbon bainitic steels microalloyed with Nb, Ti and V are widely used for the pipeline, construction and automobile industries because of their excellent combination of strength, toughness and weldability. Boron as another major alloying element has been also frequently used in this type of steels since the 1970s. The purpose of adding boron is to improve the hardenability of the steel by promoting bainite formation.It has been realized that Boron can only be effective as a strengthening element when it is prevented from forming BN and/or Fe23(C, B) 6 precipitates. Therefore, Boron is always added together with other alloying elements which are stronger Nitride or Carbide formers, such as Ti and Nb. However, the formation of complex bainitic structures and the interaction with precipitates at industrial coiling temperature are not adequately understood.
In this study, the effect of boron on the microstructure and mechanical properties of a low carbon Nb-B steel was studied by a hot compression test (50% reduction at 850°C) followed by quenching samples into a salt bath. The microstructures of the tested samples were examined through optical microscopy and SEM; and the mechanical properties of these samples were investigated by micro-hardness and shear punch tests.
The results indicate that during thermo-mechanical controlled rolling (TCR), the final properties of the products not only depend on the applied deformation but also depend on the coiling temperature where phase transformation takes place. According to the investigation, two strengthening mechanisms are responsible for the strength of the steel at the coiling temperature: phase transformation and precipitation. Under optical microscopy, the microstructures of all specimens appear to be bainite in a temperature range from 350°C to 600°C without distinct differences. However, the SEM micrographs revealed that the microstructures at 550°C are very different from the microstructures transformed at the other holding temperatures.
Two strength peaks were observed at 350°C and 550°C in the temperature range studied. It is believed that the NbC precipitates are the main contributor to the peak strength observed at 550°C because the kinetics of NbC is quite rapid at this temperature. The strength peak at 350°C is mainly due to the harder bainitic phase, which formed at relatively lower temperature.
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Reck, Victor. "Mechanical and microstructural properties of ultra-low carbon bainitic steel weld metal." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA302955.
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Sierra, Robinson. "Investigation of the mechanical behaviour of TRIP steels using FEM." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99793.
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The need to develop light-weight and high strength materials for car frames which improve fuel efficiency and provide increased passenger safety during dynamic events such as automobile crashes has been the focus of the steel and automobile industries for the past 30 years. In recent years, the development of high strength steels such as multi-phase TRIP (Transformation-Induced Plasticity)-aided steels have shown great promise due to their excellent combination of high strength and ductility. The savings in automobile weight is provided by the inherent strength of TRIP steels which allows for the use of thinner sections. The TRIP effect is characterized by the phenomenon known as strain-induced martensitic transformation (SIMT) which enhances the work hardenability of such steels as the austenite phase transforms to the much harder martensite phase during plastic straining. This results in a resistance to local necking which subsequently enhances the strength, ductility, and formability of such steels. However, various factors exist which affect the mechanical behaviour of TRIP steels. This study will aim, through the use of finite element models, to investigate the role and influence of each of these factors on the TRIP effect in type 304 austenitic and multi-phase TRIP steels. These factors include the rate at which the martensitic transformation proceeds, the state of stress to which the material is subjected to, the interaction between the surrounding matrix and embedded retained austenite islands in multi-phase TRIP steels, and the volume fraction and morphology of the retained austenite islands. Investigation of these factors will provide further insight on each of their contributions to the TRIP effect in order to exploit the potential benefits offered by these steels.
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Butler, Daniel E. "The quantitative microstructural characterization of multipass TIG ultra low carbon bainitic steel weldments and correlation with mechanical properties." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA275169.
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Debray, Bruno. "Microstructure and mechanical properties of an as-hot rolled carbon manganese ferrite-bainite sheet steel." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69713.
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By means of torsion testing, the microstructures and mechanical properties produced in a 0.14%C-1.18%Mn steel were investigated over a wide range of hot rolling conditions, cooling rates and coiling temperatures. The reheating temperature was varied between 800$ sp circ$C and 1050$ sp circ$C, and strains between 0 and 0.8 were applied. This led to austenite grain sizes ranging from 10 to 150$ mu$m. Two cooling rates, 55$ sp circ$C/s and 90$ sp circ$C/s, were applied and cooling was interrupted at coiling temperatures ranging from 550$ sp circ$C to 300$ sp circ$C.Optical microscopy and TEM were used to study the microstructures. The mechanical properties were studied by means of tensile testing. A method developed by IRSID for deducing the transformation kinetics from the cooling data was adapted to the present context and used successfully to interpret the observed influence of the process parameters. (Abstract shortened by UMI.)
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Ranieri, Arus. "Efeitos das microestruturas bainíticas e multifásicas nas propriedades mecânicas de um aço AISI 4340 /." Guaratinguetá : [s.n.], 2005. http://hdl.handle.net/11449/97120.
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Resumo: Os principais objetivos deste trabalho foram desenvolver estruturas bainíticas e multifásicas através de diversas rotas de tratamentos térmicos, visando as melhores combinações de propriedades mecânicas, fornecendo subsídios científicos/tecnológicos para as indústrias brasileiras. Em certos componentes de veículos aeroespaciais tem sido usado aço de baixa liga e ultra-alta resistência temperados e revenidos com elevada resistência devida a estrutura martensítica mas com baixa tenacidade. Uma melhoria na tenacidade é conseguida com redução controlada de resistência através do revenimento. O novo conceito, para aços avançados que combinam alta resistência com boa tenacidade, está simbolizado pelas microestruturas bainíticas e multifásicas. Neste projeto foi feito um estudo do efeito das microestruturas nas propriedades mecânicas de um aço AISI 4340. Foram analisadas diversas microestruturas, desde aquelas inteiramente bainíticas até microestruturas multifásicas com teores variados de ferrita, bainita, martensita e austenita retida. Os resultados foram comparados com aqueles obtidos por têmpera por resfriamento continuo e com as diversas rotas de transformação isotérmica. As combinações de propriedades mecânicas estão relacionadas com as frações volumétricas das fases e a bainita melhora significativamente a ductilidade do aço, mantendo a resistência elevada e melhorando a combinação resistência/ductilidade. O aço possui baixo coeficiente de encruamento e é possível conseguir resistências entre 1000 MPa e 1400 MPa com alongamento entre 13% e 25%, combinação esta superior aquelas encontradas para o mesmo aço quando temperado e revenido em óleo.Abstract: The main goals of this study were to develop bainitic and multiphasic structures through several routes of heat treatment, in order to reach the better combination of mechanical properties, providing scientific/technological subsidies to Brazilian industries. In some of aerospatial vehicles components have been used quenched and tempered ultra-high-strength low-alloy steel where the martensitic structure is responsible for the high-strength and low toughness levels. Toughness improvements can be achieved by strength reduction control during tempering. The new concept for advanced steels, that combine high-strength and good toughness, is correlated with the bainitic and multiphasic microstructures. In this work the effect of microstructures on the mechanical properties of AISI 4340 steel. Has been analysed several microstructures, from those totally bainitic until multiphasics microstructures with various ferrite, bainite, martensite and retained austenite content. The results were compared with those obtained by quenching through continuous cooling transformation and several routes of isothermal transformation. The combinations of mechanical properties are related with volume fraction of present phases and the bainite improved significantly the toughness steel., keeping the high strength and improving the strength/toughness combination. This steel has low coefficient of hardness and is possible to achieve strengths between 1000 MPa e 1400 MPa with percentual elongation between 13% e 25%, this combination is better than that found to the same steel when quenched and tempered in oil.
Orientador: Tomaz Manabu Hashimoto
Coorientador: Antonio Jorge Abdalla
Banca: Marcelo dos Santos Pereira
Banca: Jorge Otubo
Mestre
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Hausmann, Katharina [Verfasser], Ewald [Akademischer Betreuer] Werner, and Wolfgang [Akademischer Betreuer] Bleck. "TRIP-assisted Thin Sheet Steel with a Bainitic and/or Martensitic Matrix : Effects of Alloying Elements and Heat Treatment on Phase Transformations, Microstructures, and Mechanical Properties / Katharina Hausmann. Gutachter: Wolfgang Bleck ; Ewald Werner. Betreuer: Ewald Werner." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/107165148X/34.
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Hausmann, Katharina Verfasser], Ewald [Akademischer Betreuer] [Werner, and Wolfgang [Akademischer Betreuer] Bleck. "TRIP-assisted Thin Sheet Steel with a Bainitic and/or Martensitic Matrix : Effects of Alloying Elements and Heat Treatment on Phase Transformations, Microstructures, and Mechanical Properties / Katharina Hausmann. Gutachter: Wolfgang Bleck ; Ewald Werner. Betreuer: Ewald Werner." München : Universitätsbibliothek der TU München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20150430-1232002-1-0.
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Wei, Lingyun. "Investigate Correlations of Microstructures, Mechanical Properties and FSW Process Variables in Friction Stir Welded High Strength Low Alloy 65 Steel." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2032.
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The present study focuses on developing a relationship between process variables, mechanical properties and post weld microstructure in Friction Stir Welded HSLA 65 steel. Fully consolidated welds can be produced in HSLA 65 steel by PCBN Convex-Scrolled-Shoulder-Step-Spiral (CS4) tool over a wide range of parameters. Microstructures in the nugget center (NC) are dominated by lath bainite and a few polygonal/allotriomorphic grain boundary ferrites. FSW dependent variables are related to FSW independent variables by non-linear relationship. Heat input is identified to be the best parameter index to correlate with microstructures. With increasing heat input, the volume of bainite is reduced, the shape of bainite is more curved and grain/lath size become coarser. A linear relationship was established between heat input and semi-quantitative post-weld microstructures based on the optical microstructures. Further analysis has been applied on the NC to obtain more fundamental understanding of FSW. The new approach via Orientation Imaging Microscopy (OIM) was developed to acquire quantitative microstructural data including bainite lath/packet and prior austenite grain size (PAG). A linear relationship between heat input and quantitative microstructural features in the NC have been established. Mechanical properties exhibits linear relationship with heat input. These correlations can be utilized to determine FSW weld parameter to get desired mechanical properties welds.
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Ranieri, Arus [UNESP]. "Efeitos das microestruturas bainíticas e multifásicas nas propriedades mecânicas de um aço AISI 4340." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/97120.
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Universidade Estadual Paulista (UNESP)
Os principais objetivos deste trabalho foram desenvolver estruturas bainíticas e multifásicas através de diversas rotas de tratamentos térmicos, visando as melhores combinações de propriedades mecânicas, fornecendo subsídios científicos/tecnológicos para as indústrias brasileiras. Em certos componentes de veículos aeroespaciais tem sido usado aço de baixa liga e ultra-alta resistência temperados e revenidos com elevada resistência devida a estrutura martensítica mas com baixa tenacidade. Uma melhoria na tenacidade é conseguida com redução controlada de resistência através do revenimento. O novo conceito, para aços avançados que combinam alta resistência com boa tenacidade, está simbolizado pelas microestruturas bainíticas e multifásicas. Neste projeto foi feito um estudo do efeito das microestruturas nas propriedades mecânicas de um aço AISI 4340. Foram analisadas diversas microestruturas, desde aquelas inteiramente bainíticas até microestruturas multifásicas com teores variados de ferrita, bainita, martensita e austenita retida. Os resultados foram comparados com aqueles obtidos por têmpera por resfriamento continuo e com as diversas rotas de transformação isotérmica. As combinações de propriedades mecânicas estão relacionadas com as frações volumétricas das fases e a bainita melhora significativamente a ductilidade do aço, mantendo a resistência elevada e melhorando a combinação resistência/ductilidade. O aço possui baixo coeficiente de encruamento e é possível conseguir resistências entre 1000 MPa e 1400 MPa com alongamento entre 13% e 25%, combinação esta superior aquelas encontradas para o mesmo aço quando temperado e revenido em óleo.
The main goals of this study were to develop bainitic and multiphasic structures through several routes of heat treatment, in order to reach the better combination of mechanical properties, providing scientific/technological subsidies to Brazilian industries. In some of aerospatial vehicles components have been used quenched and tempered ultra-high-strength low-alloy steel where the martensitic structure is responsible for the high-strength and low toughness levels. Toughness improvements can be achieved by strength reduction control during tempering. The new concept for advanced steels, that combine high-strength and good toughness, is correlated with the bainitic and multiphasic microstructures. In this work the effect of microstructures on the mechanical properties of AISI 4340 steel. Has been analysed several microstructures, from those totally bainitic until multiphasics microstructures with various ferrite, bainite, martensite and retained austenite content. The results were compared with those obtained by quenching through continuous cooling transformation and several routes of isothermal transformation. The combinations of mechanical properties are related with volume fraction of present phases and the bainite improved significantly the toughness steel., keeping the high strength and improving the strength/toughness combination. This steel has low coefficient of hardness and is possible to achieve strengths between 1000 MPa e 1400 MPa with percentual elongation between 13% e 25%, this combination is better than that found to the same steel when quenched and tempered in oil.
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Soliman, Mohamed A. "Phase transformations and mechanical properties of new austenite-stabilised bainite steels." Clausthal-Zellerfeld Pieper, 2007. http://d-nb.info/989405060/04.
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Linares, Arregui Irene. "Mechanical behaviour of a bainitic high strength roller bearing steel." Licentiate thesis, KTH, Hållfasthetslära (Avd.), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25423.
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Soliman, Mohamed A. [Verfasser]. "Phase transformations and mechanical properties of new austenite stabilised bainite steels / Mohamed Soliman." Clausthal-Zellerfeld : Pieper, 2008. http://d-nb.info/989028798/34.
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Dimitriu, Radu. "Complex mechanical properties of steel." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/218319.
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Whereas considerable progress has been reported on the quantitative estimation of the microstructure of steels as a function of most of the important determining variables, it remains the case that it is impossible to calculate all but the simplest of mechanical properties given a comprehensive description of the structure at all conceivable scales. Properties which are important but fall into this category are impact toughness, fatigue, creep and combinations of these phenomena. The work presented in this thesis is an attempt to progress in this area of complex mechanical properties in the context of steels, although the outcomes may be more widely applied. The approach used relies on the creation of physically meaningful models based on the neural network and genetic programming techniques. It appears that the hot-strength, of ferritic steels used in the powerplant industry, diminishes in concert with the dependence of solid solution strengthening on temperature, until a critical temperature is reached where it is believed that climb processes begin to contribute. It is demonstrated that in this latter regime, the slope of the hot-strength versus temperature plot is identical to that of creep rupture-strength versus temperature. This significant outcome can help dramatically reduce the requirement for expensive creep testing. Similarly, a model created to estimate the fatigue crack growth rates for a wide range of ferritic and austenitic steels on the basis of static mechanical data has the remarkable outcome that it applies without modification to nickel based superalloys and titanium alloys. It has therefore been possible to estimate blindly the fatigue performance of alloys whose chemical composition is not known. Residual stress is a very complex phenomenon especially in bearings due to the Hertzian contact which takes place. A model has been developed that is able to quantify the residual stress distribution, under the raceway of martensitic ball bearings, using the running conditions. It is evident that a well-formulated neural network model can not only be extrapolated even beyond material type, but can reveal physical relationships which are found to be informative and useful in practice.
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Peacock, Simon. "Mechanical properties of rotary forged sintered steel compacts." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319953.
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Mattes, Victor R. "Microstructure and mechanical properties of HSLA-100 steel." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242937.
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Thesis (M.S. in Mechanical Engineering and Mechanical Engineer)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Fox, Alan G. "December 1990." Description based on title screen as viewed on April 2. 2010. DTIC Identifier(s): Steel, Microstructure, Mechanical Properties, Copper, Quenching, Tempering, Processing, Naval Vessels, HSLA-100 Steel, Theses, Age Hardening, Modulus of Elasticity, Charpy V Notch Tests. Author(s) subject terms: HSLA-100, Mechanical Properties, Copper Precipitation, Carbide. Includes bibliographical references (p. 66-68). Also available in print.
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Clark, Justin Lewis. "Stainless steel hollow sphere foams : processing and properties." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20502.
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Georges, Cédric. "Improvement of the mechanical properties of TRIP-assisted multiphase steels by application of innovative thermal or thermomechanical processes." Université catholique de Louvain, 2008. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-08232008-100716/.
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For ecological reasons, the current main challenge of the automotive industry is to reduce the fuel consumption of vehicles and then emissions of greenhouse gas. In this context, steelmakers and automotive manufacturers decided for some years now to join their efforts to promote the development and use of advanced high strength steels such as TRIP steels. A combination of high strength and large elongation is obtained thanks to the TRansformation Induced Plasticity (TRIP) effect. However, improvement of the mechanical properties is still possible, especially by the refinement of the matrix. In this work, two main ways were followed in order to reach improved properties. The classical way consisting of the annealing of cold-rolled samples and an innovative way consisting of obtaining the desired microstructure by direct hot rolling of the samples. In the classical way, this refinement can be obtained by acting on the chemical composition (with such alloying elements like Cu and Nb). It was observed that complete recrystallisation of the ferrite matrix is quite impossible in presence of Cu precipitates. In addition, if the ferrite recrystallisation is not completed before reaching the eutectoid temperature, the recrystallisation will be slowed down by a large way. An innovative heat treatment consisting in keeping the copper in solid solution in the high-Cu steel was developed. Therefore, ferrite recrystallises quite easily and very fine ferrite grains (~1µm) were obtained. In the innovative way, the effects of hot-rolling conditions on TRIP-assisted multiphase steels are of major importance for industrial practice and could open new dimensions for the TRIP steels (i.e. thanks to precipitation mechanisms leading to additive strengthening). Impressive mechanical properties (true stress at maximum load of 1500 MPa and true strain at uniform elongation of 0.22) were obtained with a relatively easy thermomechanical process, the role played by Nb being essential.
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Fox, Alan G. "Factors influencing the microstructure and mechanical properties of ultra low carbon bainitic 100 tungsten inert gas multipass weldments." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23896.
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Amen, S. A. "Processing, mechanical and wear properties of BT1 high-speed steel." Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355216.
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Medvedeva, Anna. "Tool steel for tool holder applications : microstructure and mechanical properties." Licentiate thesis, Karlstad : Faculty of Technology and Science, Materials Engineering, Karlstads universitet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-2872.
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Wei, Yun. "Microstructural characterization and mechanical properties of super 13% Cr steel." Thesis, University of Sheffield, 2005. http://etheses.whiterose.ac.uk/12826/.
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Super 13% Cr steels are used for offshore applications and have to meet strict tensile strength, yield strength, toughness, elongation, and hardness specifications. The mechanical properties of these steels are strongly dependent on the proportions of retained austenite and martensite, and consequently small changes in heat treatment parameters result in major changes in properties. In this work, a detailed investigation of the effect of heat treatment parameters on microstructural features, hardness and tensile properties of the commercial supermartensitic 13Cr-5Ni-2Mo steels in the asreceived and re-heat treated state were undertaken. The re-heat treatment was performed by re-austenitising the samples at 950 °C for 2 h, air-cooling, and then tempering (single and double temper) in the range of 550-700 °C. The effects of tempering temperature, time, and their combination P (P = (273+T (°C) x (40 + login t (h)) x 1000'1), the Holloman-Jaffe parameter, on retained austenite volume fraction, hardness and tensile properties were investigated. Retained austenite content increased with P to a peak value at P-36.9 and then decreased due to the formation of fresh martensite. However, the second temper increased retained austenite due to the re-transformation of fresh martensite to austenite. This resulted in refined grain size and a high dislocation density. An increase in P gave a decrease in the C and Ni content in austenite on tempering while the austenite grain size increased. The combination of these two effects led to a decrease in the stability of the retained austenite with P, as shown by the increased M. For the first temper at P > 36.9, the austenite present after the second temper was more stable than after the first temper as a result of re-distribution of C and Ni from the martensite to the austenite. 0.2% proof strength and hardness were inversely related to retained austenite content with P. Both hardness and 0.2% proof strength decreased linearly with increase in retained austenite content, but elongation showed the reverse trend. However, the slope of the relationships depended on whether fresh martensite was present or not. The results have shown that retained austenite with volume fraction between 16-30 vol% and size < 208 nm gives the optimum combination of strength, ductility and hardness.
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Sobeih, Mahmoud Omar R. J., and Moazzam Maqsood. "Influence of Hydrogen Charging on Mechanical Properties and Microstructure of Structural Steel S235 & Stainless Steel 316L." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18792.
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The present paper studied the influence of hydrogen on the mechanical properties and microstructure of the materials. This study is done by doing hydrogen charging of steel bar specimens. The two types of steel are used for study, structural steel S235 and stainless steel 316L. The tensile test has been performed to get the data of the charged and uncharged specimens. Different strain rates were used to study the effect of the material after charging. The charging time ranged from 24 hours to 144 hours. The specimens are cylindrical shape. Digital image analysis is performed for the uncharged specimens to correctly analyse the strain field and compare it with the results from tensile test. For DIC analysis a GOM correlate software was used to study the 2D strain analysis of the specimen. The results show that hydrogen influences the mechanical properties of the material and microstructure.
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Jayaraman, Vikram. "Production, characterization and testing of Tempered Martensite Assisted Steels (TMAS) obtained via subcritical annealing of cold rolled TRIP steels." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99769.
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The requirement for lighter, safer and fuel efficient cars has created a major stir in the steel research society to develop advanced automotive steels. Since there is a trade off between strength and ductility, most of the conventional high strength steels do not address the strength-formability combination. With the realization of the TRIP phenomenon first in austenitic stainless steels, a new generation of advanced steels called TRIP steels were realised with an inexpensive and easier to process C-Mn-Si chemistry. TRIP or TRransformation Induced Plasticity is a phenomenon where the timely strain induced transformation of Retained Austenite (RA) to Martensite locally strengthens the steel at the point of plastic instability, causing failure by necking to be postponed and shifted elsewhere along the steel. This phenomenon repeated over and over again allows increased levels of strength and ductility, prior to fracture.In current TRIP grades, the retained austenite particles present have to posses certain characteristics such as, optimum carbon concentration, optimum grain size and morphology etc. in order to account toward mechanical properties. Such limiting characteristics in turn minimize the processing window and make TRIP processing expensive and difficult to control. In this work, it is suggested that Tempered Martensite Assisted Steels (TMAS) obtained from TRIP steels via subcritical annealing of cold rolled TRIP steels may potentially replace TRIP steels. Relationship between the retained austenite volume fractions and mechanical properties was developed for TRIP steels. The effect of variation of retained austenite on tempered martensite volume fraction in TMAS, which in turn affect the mechanical properties was also investigated in depth. Results indicate that tempered martensite particles in TMAS do not have any limiting factors as in the case of RA in TRIP steels, in order to contribute toward enhancement of mechanical properties. Results also indicate that TMAS offers better strength levels compared to TRIP steels for same the level of formability.
Retained austenite volume fractions in TRIP steels were measured through XRD. Cold rolling of the samples was done in a laboratory scale rolling machine. The microstructures were analysed using conventional and color etching techniques. A new color etching technique for viewing all the four major phases in TRIP steel was developed in this work. The mechanical properties of both TRIP and TMAS were assessed by shear punch testing. And finally, the relationship between tempered martensite volume fraction and TMAS properties was developed and was compared to TRIP properties.
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McHale, Paul F. "Factors influencing the microstructural and mechanical properties of ULCB steel weldments." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28206.
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Ajmal, Mohammed. "Thermomechanically processed dual-phase steel : effects on hardenability and mechanical properties." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328761.
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Toledo, García Gustavo A. "High temperature compression testing of hardened steels for plasticity behavior modeling." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16909.
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Muller, Bruce Walter. "Evaluation of the sag properties in a dual stabilized ferritic stainless steel." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5501.
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Includes bibliographical references.The dual stabilised type 441 (DIN 1.4509) ferritic stainless steel is primarily used in the automative industry for catalytic converters. The steel, in addition to oxidation and corrosion resistance, is required to have a certain degree of creep resistance in the operating environment. The customer, by means of a modified creep test known as the sag test, usually specifies this requirement. This requirement is attained in most cases; however, in certain instances the customer places a severe requirement on the material, which exceeds the normal capabilities of type 441 material for sag resistance.
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Elsherief, Ahmed Fathy Abd Elshafi. "The structure, mechanical and corrosion properties of duplex stainless weldments." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303482.
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Mahmoody, Sam. "Micromechancal modeling of dual-phase steel using a rate-dependent crystal plasticity model." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99778.
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Dual-phase (DP) steels consisting of a ferrite matrix with dispersed martensite particles have attracted a significant interest due to their combination of high work hardening and ductility. A great deal of experimental work has been done to obtain a better comprehension of the relation of their mechanical behaviour to their microstructural characteristics. In the present work, a micromechanical study of ferrite-martensite DP steels is conducted. The deformation of ferrite is described by a rate-dependent crystal plasticity theory, which relates the stress-strain field equations on the grain level to the macroscopic behaviour of the material. The crystal plasticity theory assumes that slip is the only deformation mechanism. Martensite, on the other hand, is considered an elastic-plastic isotropic solid. The interfaces of the grains are taken into account through an idealized form of grain boundaries. A FORTRAN program was coupled with the finite element method to solve the stress equations of the crystal plasticity. Including the grain boundaries made it possible to examine the effect of ferrite grain size on the strength of the material. It is shown that by decreasing the grain size, the yield stress increases according to Hall-Petch equation. Additionally, the effects of the volume fraction of martensite (Vm) on the onset strain, i.e. the strain at which martensite deforms plastically, and of the distribution of martensite on the stress are studied. The former showed that the onset strain of the DP steel declines linearly with increasing Vm up to 36%, beyond which the onset strain becomes independent of V m. The latter revealed that when martensite particles are formed as islands in the ferrite grains, the material exhibits higher strength and hardening rate; compared to when martensite is distributed as large blocks among the ferrite grains.
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Qu, Jinbo 1971. "Effect of microstructure on static and dynamic mechanical properties of high strength steels." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103281.
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The high speed deformation behavior of a commercially available dual phase (DP) steel was studied by means of split Hopkinson bar apparatus in shear punch (25m/s) and tension (1000s-1) modes with an emphasis on the influence of microstructure. The cold rolled sheet material was subjected to a variety of heat treatment conditions to produce several different microstructures, namely ferrite plus pearlite, ferrite plus bainite and/or acicular ferrite, ferrite plus bainite and martensite, and ferrite plus different fractions of martensite. Static properties (0.01mm/s for shear punch and 0.001s -1 for tension) of all the microstructures were also measured by an MTS hydraulic machine and compared to the dynamic properties. The effects of low temperature tempering and bake hardening were investigated for some ferrite plus martensite microstructures. In addition, two other materials, composition designed as high strength low alloy (HSLA) steel and transformation induced plasticity (TRIP) steel, were heat treated and tested to study the effect of alloy chemistry on the microstructure and property relationship.A strong effect of microstructure on both static and dynamic properties and on the relationship between static and dynamic properties was observed. According to the variation of dynamic factor with static strength, three groups of microstructures with three distinct behaviors were identified, i.e. classic dual phase (ferrite plus less than 50% martensite), martensite-matrix dual phase (ferrite plus more than 50% martensite), and non-dual phase (ferrite plus non-martensite). Under the same static strength level, the dual phase microstructure was found to absorb more dynamic energy than other microstructures. It was also observed that the general dependence of microstructure on static and dynamic property relationship was not strongly influenced by chemical composition, except the ferrite plus martensite microstructures generated by the TRIP chemistry, which exhibited much better dynamic factor values. This may suggest that solid solution strengthening should be more utilized in the design of crashworthy dual phase steels.
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Vara, Amit Rashiklal. "Determination of material properties of mild steel at different temperatures and strain rates." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5458.
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Includes abstract.Includes bibliographical references.
Quantification of material properties through physical experiments is of significant importance. Test data from such experiments aid in the understanding of the material behaviour when exposed to a variety of loading conditions. Such data also help in the formulation of empirical and constitutive relations that can be applied in numerical simulations. This project dealt with the determination of the variation of the yield stress of mild steel with temperature and strain rate. This was achieved by carrying out high temperature tensile tests at different strain rates on mild steel specimens. These experiments also helped set a methodology for carrying out high temperature tensile tests using a servohydraulic universal tester. Results from the tests indicated that increases in temperature tended to decrease the yield stress, whereas increases in strain rate had the opposite effect. This was found to be consistent with data found in literature. It was also noted that the temperature effect was more dominant than the strain rate effect over quasi-static strain rates.
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Dollman, Michael J. "The influence of microstructure on the creep properties of 441 ferritic stainless steel." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/5575.
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Includes bibliographical references.The objectives of this report were to determine the influence of microstructure on the creep properties of 441 stainless steel. Of particular interest was the effect of grain size and of the niobium content. A further requirement of this investigation was to design and manufacture two lever-arm type, constant load creep rigs in response to the need for a high quality creep test facility. These rigs were to be used to satisfy the initial objective and to evaluate an industry benchmark test used for determining the creep resistance of a particular alloy, known as the sag test.
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Lu, Miao. "Mechanical and acoustic properties of porous steel manufactured by lost carbonate sintering." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569586.
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Over the last few decades, porous metals have received a large amount of interest in industry due to the rapid advancement in manufacturing techniques, design and possible applications. Their unique properties and multi-functionality allow them to be utilized in many different applications throughout different industrial sectors. This thesis manufactured porous steel using the Lost Carbonate Sintering (LCS) method and studied their mechanical and sound absorption properties. The dissolution, decomposition and re-sintering routes were studied and compared. The mechanical properties of the specimens manufactured by LCS via the dissolution and decomposition routes were measured by compression and three-point bending tests. The compression strength, elastic modulus and flexural strength of the porous steel specimens manufactured with both routes increased with increasing relative density, pore size and compaction pressure. Increasing the sintering temperature and time in the decomposition route served to increase the compression strength, elastic modulus and flexural strength. The advantages and disadvantages of the dissolution and decomposition routes were analyzed. The porous steel specimens manufactured by the decomposition route had better mechanical properties than those manufactured by the dissolution route. The acoustic absorption performance of porous steel manufactured by the LCS process via the dissolution route was assessed using the standing wave impedance tube method. The single layer specimens showed excellent sound absorption properties at high frequencies. Pore size of the porous steel had no significant effect on the sound absorption coefficient. Sound absorption at low frequencies can be improved by increasing the thickness of specimens, or by introducing an air gap behind the absorber. The sound absorption properties of the porous specimens of multi-layer assemblies with different porosities, pore sizes, thicknesses and air-gap depths were assessed. The porosity of the first layer of multi-layer-assembled specimens had a critical effect on the sound absorption coefficient and frequency of peak. Increasing this porosity increased the sound absorption coefficient at all frequencies after the peak. The effects of the porosities of the subsequent layers were smaller. When the first layer had a high porosity, increasing the porosity of the second layer increased the frequency of peak. When the first layer had a low porosity, increasing the porosity of the second layer enhanced the sound absorption coefficient of peak. The effects of pore size were not significant. Increasing the thickness of specimens and the depth of air-gap behind the specimens decreased the frequency and coefficient of the peak in the sound absorption curve.
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Fager, Fredrick, and Serg Chanouian. "Nuclear Waste Canister : Evaluating the mechanical properties of cassette steel after casting." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209803.
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Företaget Svensk Kärnbränslehantering AB (SKB) håller på att utveckla en slutförvaringskapsel som kommer innehålla avfall från den svenska kärnkraften. Det är dock fortfarande en process under utveckling och därför undersöks olika typer av metoder och kapselmaterial för att kunna tillverka en hållbar och säker kapsel. Kapseln består av ett hölje av kopparrör med svetsad botten och lock och en insats med stållock. Insatsen är en cylindrisk konstruktion av segjärn och innehåller en svetsad stålkassett för att skapa utrymmen till det använda kärnbränslet. Insatsen innehåller bland annat stålrör som under tillverkning får utstå en gjutprocess med segjärn och erhåller efter det icke homogena egenskaper. Målet med undersökningen är hur stor påverkan gjutningen har på stålets kemiska sammansättning samt mikrostrukturer. Det som orsakar de inhomogena egenskaperna är främst värmebehandlingen som driver diffusionen av kol från gjutjärnet till stålet, som då ger ett hårdare men sprödare material. Med hjälp av experiment och simuleringar upptäcks hur mycket kol som diffunderar in i stålet samt ändringar i den kemiska sammansättningen i de påverkade zonerna. Identifiering av fasomvandlingar, diffusion och ändringar i mikrostrukturer är stora faktorer som i sin tur ändrar de mekaniska egenskaperna i stålet.The Swedish Nuclear Fuel and Waste Management Company (SKB) have developed a final storage canister that will contain waste from the Swedish nuclear power plants. However, it is still in a development phase and therefore different types of methods and canister materials are investigated to produce the most durable and safe canister. The canister is made of a copper tube with a welded bottom and lid with an insert. The insert is a cylindrical construction of nodular cast iron that contains a welded steel cassette, to make space for the spent fuel, and a steel lid. The steel tubes showed inhomogeneous properties after being exposed to a casting around them. The aim of this investigation is to clarify the impact of casting on the chemical composition of the steel as well as the microstructure. The cause to the inhomogeneous properties were the diffusion of carbon from the cast iron to the steel, which then produced a harder and more brittle material. Experiments and simulations were used to see the carbon diffusion into the steel as well as what happens with the chemical composition in the affected zones. Identification of phase changes, diffusion and microstructures contributed to changes of mechanical properties in the steel.
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Keehan, Enda. "Effect of microstructure on mechanical properties of high strength steel weld metals." Thesis, University of Cambridge, 2004. https://www.repository.cam.ac.uk/handle/1810/218395.
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The effects of variations in alloying content on the microstructure and mechanical properties of high strength steel weld metals have been studied. Based on neural network modelling, weld metals were produced using shielded metal arc welding with nickel at 7 or 9 wt. %, manganese at 2 or 0.5 wt. % while carbon was varied between 0.03 and 0.11 wt. %. From mechanical testing, it was confirmed that a large gain in impact toughness could be achieved by reducing the manganese content. Carbon additions were found to increase strength with only a minor loss to impact toughness as predicted by the modelling. The highest yield strength (912 MPa) in combination with good impact toughness (over 60 J at -100 °C) was achieved with an alloying content of 7 wt. % nickel, 0.5 wt. % manganese and 0.11 wt. % carbon. Based on thermodynamic calculations and observed segregation behaviour it was concluded that the weld metals solidify as austenite. The microstructure was characterised using optical, transmission electron and high resolution scanning electron microscopy. At interdendritic regions mainly martensite was found. In dendrite core regions of the low carbon weld metals a mixture of upper bainite, lower bainite and a novel constituent - coalesced bainite - formed. Coalesced bainite was characterised by large bainitic ferrite grains with cementite precipitates and is believed to form when the bainite and martensite start temperatures are close to each other. Carbon additions were found to promote a more martensitic microstructure throughout the dendrites. Mechanical properties could be rationalised in terms of microstructural constituents and a constitutional diagram was constructed summarising microstructure as a function of manganese and nickel contents.
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Cantergiani, Elisa. "Mechanical Properties of Functionally Graded Materials: Carbon Gradient inside Interstitial Free Steel." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34314.
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In the last decade aluminium started to be considered as an alternative to steel to produce car body panels, especially considering the strict demands to decrease fuel consumption which require vehicle weight reduction. In order to keep their leading role, steel companies have to produce stronger materials to reduce the thickness of steel sheets used in cars and are now considering non-conventional steel making processes.
The purpose of this PhD research was to investigate the possibility of strengthening thin sheets of interstitial free steel (IF steel) by using carbon rich films deposited on the steel surface using Physical Vapour Deposition (PVD). These films then act as a carbon reservoir which upon heat treatment release carbon in the IF steel and strengthen it.
Coated tensile coupons 200 μm thick were annealed at different temperatures under high vacuum. Tensile tests show that a 100 MPa increase in yield stress can be obtained after annealing at 430 ˚C for 1h in high vacuum. The effects of annealing environment, film thickness and prestrain on carbon diffusion were also investigated. It was shown that carbon diffusion from the film to the IF steel substrate is limited by the film transformation into cementite at temperatures equal or higher than 530 ˚C.
All tensile curves showed a plastic instability known as Lüders plateau, which is undesirable as it results in surface markings on the deformed part. FEM analyses were performed to find ways to suppress the Lüders plateau, proving that increasing strain-hardening or having a graded instead of uniform carbon content through thickness can suppress or limit Lüdering.
The possibility of creating a through thickness gradient of microstructure was investigated as it could suppress Lüdering and result in higher strength. For these tests, FeC coated coupons were induction heated to 820 ˚C followed by water quenching. After only 2 minutes of heat treatment the yield stress was increased by 250 MPa and the ultimate tensile strength reached 400 MPa. With an annealing of 4 minutes, the Lüders plateau was fully suppressed and the microstructure consisted in ferrite grains and TiC nanocarbides. This work demonstrates that FeC films can be effectively used to diffuse carbon into steel and that a significant increase in mechanical properties can be obtained after a heat treatment of only a few minutes.
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Shendye, Sanjay B. "Effect of long term elevated temperature exposure on the mechanical properties and weldability of cast duplex stainless steels /." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,115.
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Kasonde, Maweja. "Optimising the mechanical properties and microstructure of armoured steel plate in the quenched and tempered condition." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-11022006-192139.
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Maréchal, David. "Linkage between mechanical properties and phase transformations in a 301LN austenitic stainless steel." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/34005.
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In this work, the deformation mechanisms of an austenitic stainless steel (grade 301LN) have been investigated with particular attention on the strain-induced phase transformations from austenite to ε and α’ martensites.
The average grain size of this alloy was varied in the range 0.5-28 µm, and two strain paths, namely uniaxial tension and simple shear, were analyzed. At the macroscopic level, the work-hardening response was examined in relation to the formation of ε and α’ martensites, followed by X-ray phase quantification and Feritscope measurements. At a microscopic level, the microstructures after deformation were investigated using electron back-scatter diffraction, energy-dispersive X-ray spectroscopy and transmission electron microscopy.
It was found that the grain size refinement was responsible of a change in nucleation mechanisms of α’-martensite, thereby affecting the macroscopic volume fraction of α’-martensite.
The switch from tension to shear was not found to affect the mechanisms of formation of ε and α’ martensites, but significantly reduced the work-hardening, an effect too large to be attributed to the slight reduction of the kinetics of α’ volume fraction.
The stresses borne in the α’-martensite were quantified using a novel method based on the magnetomechanical effect. These stresses, together with the determination of the intrinsic constitutive laws of austenite and α’-martensite, were used to design a one-dimensional physically-based model of the work-hardening in this alloy. This model, based on the “dynamic composite" effect of the formation of fresh α’-martensite in austenite, successfully predicted the measured stress-strain behaviour in tension, as well as the tensile instabilities encountered in this class of materials.
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Nex, Christopher Paul. "The effect of joining technique on the mechanical properties of stainless steel structures." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284383.
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Hsiao, Yu-Hsian. "Factors affecting creep damage accumulation and mechanical properties of 316 stainless steel weldments /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487849377292843.
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Lawson, Benjamin James. "Compositional Optimization, Mechanical Properties, and Tempering Response in Type 410 Stainless Steel Welds." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557201840078564.
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Li, Xuan. "Hydrogen Effects on X80 Steel Mechanical Properties Measured by Tensile and Impact Testing." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6110.
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The effect of hydrogen charging current density and tensile strain rate on the mechanical properties of X80 pipeline steel were investigated by slow strain rate test (SSRT), Charpy impact test, and scanning electron microscopy (SEM) in this thesis. The results show that both the ultimate tensile strength and elongation to failure of X80 steel were deteriorated significantly after charging with hydrogen. With a strain rate of 5 x 10-5 s-1, the relative tensile strength and plasticity loss of X80 steel had no significant change within the range of assumed hydrogen partial pressures at room temperature. At room temperature, X80 steel had no apparent variation in ultimate tensile strength and elongation, except at the strain rate of 10-6 s-1. Specimens obtained the greatest relative tensile strength loss and plasticity loss when strained at 10-6 s-1 with a current density of 4.6 mA/cm2. The fracture morphology of two test groups of X80 steel exhibited significant brittle rupture when tested with dynamic hydrogen charging. The impact energy of X80 was not affected by hydrogen charging. Different current density also had no influence on the results of the impact test.
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Paananen, J. (Joni). "Modeling of the microstructure and mechanical properties during welding of low alloyed high strength steel." Master's thesis, University of Oulu, 2017. http://urn.fi/URN:NBN:fi:oulu-201711303218.
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The aim of the work was to create a model to simulate the evolution of the microstructure during welding. The model consists of heat transfer and heat input models, microstructure model and hardness model. The heat transfer and heat input models are used to model the arc welding and the temperature changes in the welded piece. A microstructure model has been coupled with the heat transfer model i.e. the microstructure evolution is modeled simultaneously with the heat transfer model. The microstructure model simulates phase transformations and grain growth. In addition, the model predicts the hardness based on the microstructure. A graphical user interface was also developed to ease the usage of the model. The developed model is numerical and is based on theories presented in the literature. Some parameters for theories have also been defined experimentally using thermomechanical simulator. Real welding experiments were also made to verify the model. The temperature model can predict the temperatures in the heat-affected zone quite reliably. The phase transformation model works also well. The phase fractions from the model correlate with those seen under a microscope and the model predicts the shapes of the heat-affected zone and fusion zone with relatively good accuracy. The grain growth model works well far from fusion line but is not as good near the fusion line. The hardness model is not as reliable as other models but is still able to predict the hardness quite well even though the model is rather simpleTyön tavoitteena oli kehittää malli hitsauksessa tapahtuvien mikrorakennemuutosten simuloimiseen. Malli koostu lämmönsiirto- ja lämmöntuontimallista, mikrorakennemallista sekä kovuusmallista. Lämmönsiirto- ja lämmöntuontimalleilla mallinnetaan kaarihitsausta ja sen aikaansaamia lämpötilamuutoksia teräksessä. Mikrorakennemalli on kytketty lämpötilamalliin eli mikrorakennetta mallinnetaan samanaikaisesti lämpötilojen kanssa. Mikrorakennemalli simuloi faasimuutoksia ja rakeenkasvua. Lisäksi malli pyrkii ennustamaan kovuutta mikrorakenteen perusteella. Malliin luotiin myös graafinen käyttöliittymä helpottamaan käyttöä. Työssä luotu malli on numeerinen ja se perustuu kirjallisuudessa esitettyihin teorioihin. Lisäksi teorioiden vaatimia parametreja on määritetty kokeellisesti termomekaanisella simulaattorilla. Lisäksi työssä tehtiin hitsauskokeita mallin verifioimiseksi. Lämpötilamalli ennustaa muutosvyöhykkeen lämpötilat melko luotettavasti. Faasimuutosmalli toimii myös hyvin. Kokeelliset ja mallinnetut faasiosuudet vastaavat toisiaan. Malli ennustaa myös suhteellisen hyvin sula-alueen ja muutosvyöhykkeen muotoa. Raekokomalli toimii hyvin kauempana sula-alueesta, mutta lähellä sula-aluetta malli ei toimi yhtä hyvin. Kovuusmalli ei ole yhtä luotettava kuin muut mallit, mutta ennustaa silti kovuuksia todella hyvin, vaikka onkin melko yksinkertainen
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Cyril, Nisha S. "Anisotropy and Sulfide Inclusion Effects on Tensile Properties and Fatigue Behavior of Steels." Connect to full text in OhioLINK ETD Center, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1198808409.
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Thesis (M.S.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science Degree in Mechanical Engineering." "A thesis entitled"--at head of title. Bibliography: leaves 204-209.
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Moleejane, Cullen Mayuni. "An experimental investigation of the effect of microstructural features on mechanical properties of EN8 steel." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1254.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2009.Materials in almost all components are subjected to some kind of loading that must be correctly predicted to produce reliable designs. The understanding of a material's properties significantly impacts appropriate selection for a structure. This kind of material characterization is also important in the development of improved or new materials for high strength and novel applications. There are numerous metallurgical variables (composition and process parameters) that influence the physical and mechanical properties of materials. The aim of this work has been to study the influence of microstructure on mechanical properties of steel, specifically the effect of grain sizes within solid phase mixtures. Parameters for simple models of the variation of material properties with grain size can be determined. These models can then be incorporated in the material data sets of Finite Element Analysis programs which will then allow for structural analysis with zones in a material having different grain sizes. The deformation and damage behaviour of EN 8 steel have been stUdied with emphasis on the effects of grain size on the elastic-plastic response of the material. For that purpose, EN 8 specimens with a range of microstructures (grain size and phase) were prepared by heat treatment The microstructural features were carefully characterized using two different experimental surface microscopy techniques; Light Optical Microscope and Scanning Electron Microscope. The deformation and hardness characteristics have been studied with the help of tensile and hardness tests. The mechanical properties were determined as a function of microstructure (grain size and phase). The yield stress followed the classical Hall-Petch relation. The results indicated that tensile strength and hardness increases with decrease in grain size while elongation decreases. The main philosophy behind this research has been the study of the microstructure and information from the iron-carbon phase diagram together with numerical analysis of stress-strain data, in order, to understand the influence of grain size on mechanical behaviour of EN8 steel. This combination was then used to make general conclusions on mechanical behaviour of EN 8 based on heat treatment history.
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Davut, Kemal [Verfasser]. "Relation between microstructure and mechanical properties of a low-alloyed TRIP steel / Kemal Davut." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1038571014/34.
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Chiou, Chuan-Sheng, and 邱傳聖. "The microstructure, phase transformation characteristics and related mechanical properties of an ultra low carbon bainitic steel." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/53500540683010865212.
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博士國立臺灣大學
材料科學與工程學研究所
89
For the purpose of investigating the trend of toughness versus variation of microstructual constituents for an experimental ultra-low carbon bainitic steel, the experiments (with and without prior compressive deformation) have been carried out on a Gleeble 1500 machine. The Charpy impact specimens were prepared from the samples treated by the Gleeble machine. The Charpy impact absorbed energy for toughness was measured, and the corresponding fractographs, optical metallographs and transmission electron micrographs have been examined. The result shows that the prior compressive deformation of austenite promotes the formation of intragranular non-parallel plates of acicular ferrite but stifles the formation of sheaf-like parallel plates of bainitic ferrite. Furthermore, the study emphasizes that the microstructure containing a high volume fraction of acicular ferrite possesses better toughness and strength than the microstructure containing mainly bainite. The effects of high temperature tempering on the microstructure and mechanical property of an ultra-low carbon bainitic (ULCB) steel have been investigated by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) ，micro-hardness measurements and dilatometry. This study aims at the exploration of the observation of the morphological changes of bainite with M/A constituents and precipitation of carbides during the tempering treatment. The sequence of morphological change of bainitic ferrite is the coalescence of bainitic ferrite sub-grain boundary, the recovery, recrystallisation and grain growth of ferrite. As to the aspect of precipitation of carbides, the discontinuous grain type of cementite first forms from the transformation of retained austenite located at the bainitic ferrite sub-grain boundary. Then the Nb(CN) precipitate within the ferritic grain and sub-grain boundary. Both the cementite and Nb(CN) coarsen during the prolonged tempering. Finally, the succession of the morphological changes in the M/A constituents are the transformation of thin-film like retained austenite and the precipitation of cementite within the blocky M/A constituents followed with the disappear of low angle lath boundary. The results of this study elucidate the stability of bainite structure in spite of the nature of non-equilibrium product. The tensile microfracture characteristics of an experimental ultra-low carbon bainitic steel with different cooling rates are examined such that the movement of slip bands, crack initiation and propagation are recorded in situ in a scanning electron microscope. The heat treatments have been carried out on a Gleeble 1500 machine and dilatometer. For the specimen with lower cooling rate, the microstructures consist in granular bainite, allotriomorphic ferrite and coarse blocky M/A constituents. The coarse M/A constituents could deflect effectively the movement of slip bands. The primary cracks nucleate at the interface between M/A constituents and bainitic ferrite. For the specimen with higher cooling rate, the microstructure of specimens is composed of a fine substructured bainitic ferrite matrix with a small amount of uniformly distributed carbon-rich second phase. These carbon-rich second phases, thin-film like M/A constituents, locate among the sheaves of bainitic ferrite. The thin-film like M/A (mainly residual austenite) constituents can hinder the movement of dislocation but cannot prevent effectively the movement of slip bands. The sub-structured boundary between bainitic ferrite belongs to the low angle boundary that hinder only the dislocation from motion. The primary cracks form at the high angle grain boundaries (bainitic packet boundary) eventually and serve as the initiation of fracture. The results in this study show that the tensile strength and ductility of sheaf-like bainitic ferrite prevails over that of granular bainite and allotriomorphic ferrite.
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LIAO, YAN-CONG, and 廖彥璁. "Passivation and Mechanical Properties of Stainless Steel Parts." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/d29bwq.
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碩士國立虎尾科技大學
車輛工程系碩士班
106
This experiment, the martensitic based stainless steel was compared after heat treatment, the difference of mechanical properties of both nitrogen accelerated cooling and oil quenching was investigated. Then, the chemically passivated method A-A-A(alkaline-acid-alkaline) was used as the surface processing, to this stainless steel to find the suitable condition of passivation treatment to improve and enhance the corrosion performance.