Transformation Kinetics, Microstructure and Mechanical Properties of Un-alloyed and Cu-Ni Austempered Ductile Irons PDF Download
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Author: Nawras Darwish
Publisher:
ISBN:
Category :
Languages : en
Pages : 356
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Author: Nawras Darwish
Publisher:
ISBN:
Category :
Languages : en
Pages : 356
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Author: Duncan Colin Putman
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Austempered ductile iron (ADI) has a microstructure consisting mainly of high carbon austenite, bainitic ferrite and graphite nodules, produced by a two stage austenitisation and austempering heat treatment. The resulting microstructure gives these materials a combination of high strength and toughness, making them attractive for a wide range of applications. To increase surface hardness, ductile iron alloys can also be cast into chilled moulds to induce carbide formation in the required areas of components. These chilled ductile iron alloys can also be subjected to austenitisation and austempering heat treatments, therefore further improving the mechanical properties of the components core, whilst retaining the hard carbides present in the surface layers. This work encompasses three main areas; two are concerned with the production of generic microstructure models, which work in conjunction with thermodynamic modelling software MTDATA, and one relates to high temperature X-ray diffraction experiments. The first modelling section details how a computer program was developed that can be used to investigate how chemical composition influences the chill tendency of ductile iron alloys. The model predictions were shown to be in good agreement with a wide range of experimental measurements. The second modelling section considers ADI alloys. A computer program was developed which, given the chemical composition and austenitisation and austempering temperatures, produces a prediction of the microstructure of the alloy at the end of stage 1 of the austempering heat treatment, taking into account segregation of alloying elements. Experimental segregation profiles produced during this work showed good agreement with the model predictions. Furthermore, predictions of the stage 1 transformation kinetics as a function of alloying element segregation, are also made by the model. Therefore, the local microstructural transformation times during austempering can be predicted. Good agreement has been observed between phase volume fractions, transformation times and mechanical property predictions made using the model and those found in literature, therefore a useful tool for new alloy development has been produced. High temperature X-ray diffraction experiments were also performed as part of this work. Microstructures typical of ADI alloys were produced during these experiments, although small quantities of pearlite were observed in the samples, and care was taken to minimise any effects of decarburisation and/or oxidation. The austenite carbon content was monitored during austenitisation and austempering, enabling comparisons to be made between high temperature and low temperature X-ray diffraction measurements in ADI alloys.
Author: Rafael Colás
Publisher: CRC Press
ISBN: 1000031675
Category : Technology & Engineering
Languages : en
Pages : 3918
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The first of many important works featured in CRC Press’ Metals and Alloys Encyclopedia Collection, the Encyclopedia of Iron, Steel, and Their Alloys covers all the fundamental, theoretical, and application-related aspects of the metallurgical science, engineering, and technology of iron, steel, and their alloys. This Five-Volume Set addresses topics such as extractive metallurgy, powder metallurgy and processing, physical metallurgy, production engineering, corrosion engineering, thermal processing, metalworking, welding, iron- and steelmaking, heat treating, rolling, casting, hot and cold forming, surface finishing and coating, crystallography, metallography, computational metallurgy, metal-matrix composites, intermetallics, nano- and micro-structured metals and alloys, nano- and micro-alloying effects, special steels, and mining. A valuable reference for materials scientists and engineers, chemists, manufacturers, miners, researchers, and students, this must-have encyclopedia: Provides extensive coverage of properties and recommended practices Includes a wealth of helpful charts, nomograms, and figures Contains cross referencing for quick and easy search Each entry is written by a subject-matter expert and reviewed by an international panel of renowned researchers from academia, government, and industry. Also Available Online This Taylor & Francis encyclopedia is also available through online subscription, offering a variety of extra benefits for researchers, students, and librarians, including: Citation tracking and alerts Active reference linking Saved searches and marked lists HTML and PDF format options Contact Taylor and Francis for more information or to inquire about subscription options and print/online combination packages. US: (Tel) 1.888.318.2367; (E-mail)
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Author: Radhakanta Rana
Publisher: Springer Nature
ISBN: 3030538257
Category : Technology & Engineering
Languages : en
Pages : 673
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The current state of understanding of emerging iron alloys and high-alloy ferrous systems, in comparison with some conventional steels, is compiled in this single volume to further their development. While most of the conventional steels are produced routinely today, many advanced high strength steels and iron-based alloys are still in the laboratory stage. The iron-based emerging alloys can yield high levels of mechanical and physical properties due to their new alloy concepts and novel microstructures leading to multiple benefits of their use in terms of sustainability and environmental impact. This book contains introductory chapters that present the requisite background knowledge on thermodynamics, phase diagrams, and processing routes used for the ferrous alloys to enable the readers a smooth understanding of the main chapters. Then, an overview of the conventional microalloyed steels and advanced high strength steels is given to present the benchmark of the existing steels and ferrous alloys manifesting their current state-of-the-art in terms of physical metallurgy and engineering applications. Subsequent chapters detail novel, emerging ferrous alloys and high-alloy ferrous systems. Summarizes the state-of-the-art of emerging iron-based alloys and the new processing and physical metallurgy-related developments of high-alloy iron systems; Explores new iron-based systems driven by the need for new properties, enhanced performance, sustainable processes and educed environmental impact; Compiles cutting-edge research on the progress of materials science of iron-based systems, from physical metallurgy to engineering applications, and possible avenues for future research.
Author:
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Category :
Languages : en
Pages :
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The strong influence of the fine-scale microstructural features on mechanical properties has become increasingly evident during the past decade. This is particularly true for fracture toughness of quenched and tempered alloy steels. Large differences in microstructure can be produced by isothermal, rather than athermal, treatments in the bainite and upper martensite temperature ranges. The kinetics of transformation as well as the kinds and volume fractions of transformation products can be varied over wide ranges by relatively small changes in chemical composition. The effects of the common alloying elements on transformation kinetics, both separately and in various combinations were determined experimentally. The synergistic effects of individual elements added as pairs of elements were not predictable from a knowledge of the effects of the individual elements. Isothermal treatments, coupled with variations in the kinds and amounts of alloying elements, produced different morphologies, compositions, and volume fractions of the transformation products. The effects of such microstructural differences on tensile properties, fracture toughness, and fatigue characteristics were evaluated. Beneficial effects were found, such as substantial increases in fracture toughness, with small changes in alloy content or with heat treatments that differed from those conventionally used.
Author:
Publisher:
ISBN:
Category : Iron
Languages : en
Pages : 288
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Austempered ductile iron (ADI) is a type of ductile iron produced by an isothermal heat treatment process. ADI has been widely used in diverse applications such as automobiles and agricultural tools. The exceptional mechanical properties of high strength-to-weight ration, excellent ductility and toughness, low cost and good machinability compared with traditional iron forgings and castings can be attributed to its unique ausferritic structure including the acicular ferrite and carbon enriched austenite. The properties of ADI are strongly dependent on the specific chemical composition, austempering temperature, holding time and cooling rate in quenching mediums. In this research, the graphite ductile iron with and without nickel (Ni) element was subjected to different austempering temperatures and holding times. The effects of presence of Ni, austempering temperature and holding time on the formation of ausferritic structure were investigated by evaluating the microstructure and analyzing the transformation kinetics. The addition of Ni accelerated the ausferritic transformation for ADI. The lower austempering temperature promoted the nucleation of acicular ferrite. The ferrite platelet became more coarse at either higher austempering temperature or longer holding time. A rolling contact fatigue test was used to evaluate the fatigue resistance of ADI in comparison with conventional quenched and tempered ductile iron. ADI material had better fatigue resistance than that of quenched and tempered ductile iron. The results could be credited to the increase of micro hardness on and near the surface because of the strain induced transformation of retained austenite into martensite. The decrease of percentage of retained austenite on the wear track was detected in X-ray diffraction (XRD) analysis. Then, various tempering cycles with constant low tempering temperature were applied on ADI to study the tempering responses of ADI material. Single or multiple one-hour tempering cycles at 177°C did not alter the overall hardness ofthe ADI. Increased hardness due to part of the retained austenite being converted into new bittle martensite was found to be balanced by the formation of relatively soft tempered martensite from the existing quenched martensite in the matrix. Ball-on-disk rotational sliding tests were utilized to compare the wear resistance between un-tempered ADI and tempered ADI with three tempering cycles. Overall, ADI had significantly higher wear resistance as compared with conventional quenched and tempered ductile iron. Tempered ADI even showed higher wear resistance than that of un-tempered ADI which could be attributed to the enhanced toughness caused by the decrease of retained austenite and formation of tempered martensite in matrix. Finally, the study of the influences of tempering temperatures on the phase transformation and tribological properties of tempered ADI was conducted. The ausferritic structure was gradually decomposed into dispersive cementite particles at high tempering temperatures. There were very few needle-like or feather-like ferrite which still existed at and above the tempering temperature of 538°C. In XRD analysis, no ausferritic structure existed in the matrix after receiving a tempering process at or above 538°C. In addition, the tempered ADI with tempering temperature of 427°C showed lower wear volume loss than quenched and tempered ductile iron due to residual ausferritic structure and tempered martensite in tempered ADI that could provide enhanced toughness which resulted in a lower wear rate. Even when ADI received a high tempering temperature of 538°C, it still outperformed quenched and tempered ductile iron under similar hardness.
Author: Deepak Joshi
Publisher:
ISBN:
Category : Materials science
Languages : en
Pages : 0
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A novel, Two-Step Austenitizing heat treatment process for creation of Austempered Ductile Iron (ADI) with an optimum combination of strength, ductility and fracture toughness was conceived in this investigation. This novel heat treatment process involves heating the ductile iron in the lower intercritical temperature range and then raising the temperature to the fully austenitic temperature range followed by austempering in the bainitic temperature range. This heat treatment was expected to result in a microstructure consisting of proeutectoid ferrite, very fine scale bainitic ferrite, and high-carbon austenite. Tensile and CT test specimens were created and tested to evaluate the effects of several Two-Step Austenitizing heat treatment processes. The effect of the heat treatment parameters on the dislocation density of ADI was also studied. A simple, first-principles approach was taken to model the phase transformation kinetics associated with the phase transformations in the ADI alloy. The mechanical properties of a multiphase crystalline material such as ADI are hypothesized to be dictated by complex and interrelated effects involving microstructural features (such as the ferrite lathe size, retained austenite volume fraction, and carbon content of retained austenite) that are, in turn, strongly influenced by austenitization and austempering times and temperatures. This research study determined that, compared to conventionally processed ADI., one variant of the Two-Step Austenitizing heat treatment process yielded an ADI alloy with superior fracture toughness without significantly compromising the strength and ductility. It was concluded that prior nucleated proeutectoid ferrite was an important factor in this improvement. An analytical model based upon the nucleation of proeutectoid ferrite and graphite nodules during intercritical austenitization was created to explain this physical outcome.
Author: Kiyoshi Funatani
Publisher: ASM International
ISBN: 1615032053
Category : Technology & Engineering
Languages : en
Pages : 1214
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Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 1046
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Author:
Publisher:
ISBN:
Category : Metallurgy
Languages : en
Pages : 1176
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