A Novel Two Step Austenitization Process to Produce Austempered Ductile Iron (ADI) with High Strength, Ductility and Fracture Toughness PDF Download
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Author: Deepak Joshi
Publisher:
ISBN:
Category : Materials science
Languages : en
Pages : 0
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Book Description
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: Deepak Joshi
Publisher:
ISBN:
Category : Materials science
Languages : en
Pages : 0
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Book Description
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: Saranya Panneerselvam
Publisher:
ISBN:
Category : Materials science
Languages : en
Pages : 199
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Book Description
Austempered Ductile Cast Iron is emerging as an important engineering materials in recent years because of its excellent combination of mechanical properties such as high strength with good ductility, good fatigue strength and fracture toughness together with excellent wear resistance. These combinations of properties are achieved by the microstructure consisting of acicular ferrite and high carbon austenite. Refining of the ausferritic microstructure will further enhance the mechanical properties of ADI and the presence of proeutectoid ferrite in the microstructure will considerably improve the ductility of the material. Thus, the focus of this investigation was to develop nanostructured austempered ductile cast iron (ADI) consisting of proeutectoid ferrite, bainitic ferrite and high carbon austenite and to determine its microstructure-property relationships. Compact tension and cylindrical tensile test samples were prepared as per ASTM standards, subjected to various heat treatments and the mechanical tests including the tensile tests, plane strain fracture toughness tests, hardness tests were performed as per ASTM standards. Microstructures were characterized by optical metallography, X-ray diffraction, SEM and TEM. Nanostructured ADI was achieved by a unique heat treatment consisting of austenitization at a high temperature and subsequent plastic deformation at the same austenitizing temperature followed by austempering. The investigation also examined the effect of cryogenic treatment, effect of intercritical austenitizing followed by single and two step austempering, effect of high temperature plastic deformation on the microstructure and mechanical properties of the low alloyed ductile cast iron. The mechanical and thermal stability of the austenite was also investigated. An analytical model has been developed to understand the crack growth process associated with the stress induced transformation of retained austenite to martensite.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 61
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Book Description
Austempered ductile irons (ADIs) possess a unique combination of toughness and ductility plus high strength which make them attractive alternatives to other metal castings. ADIs can have tensile strengths up to 230 ksi with a 1% elongation and high hardness for wear resistant applications, or tensile strengths of approximately 150 ksi and elongations of 14% where a large amount of ductility is required. Austempering is a two step process: complete transformation to the austenite ([gamma]) phase; and a quench and hold in the temperature range of 270--420°C for some time followed by cooling to room temperature. This quench must be sufficiently rapid to avoid formation of pearlite or ferrite if the best mechanical properties are to be obtained. This thesis presents the results of a number of experiments aimed at determining the effect of Mn on the length of the Stage 1 reaction. (austenite decomposes into bainitie ferrite and high carbon austenite). A basic knowledge of the effects of Mn will yield a more complete understanding of the austempering process for the normal case and also when microsegregation is present. The onset time for Stage 2 (high carbon austenite decomposes into bainitic ferrite plus carbides) in ductile irons is a critical parameter because of the associated degradation of the mechanical properties which result from carbide formation.
Author: Rafael Colás
Publisher: CRC Press
ISBN: 1000031675
Category : Technology & Engineering
Languages : en
Pages : 3918
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Book Description
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)
[email protected] International: (Tel) +44 (0) 20 7017 6062; (E-mail)
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Author:
Publisher:
ISBN:
Category : Iron
Languages : en
Pages : 288
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Book Description
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: Al Alagarsamy
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 300
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Book Description
Author: B. V. Kovacs
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Novel concepts: selective surface austempering, metal shot as quenching medium, and fluidized bed as quenching equipment.
Author: Karl-Heinrich Grote
Publisher: Springer Science & Business Media
ISBN: 3540491317
Category : Science
Languages : en
Pages : 1588
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Book Description
This resource covers all areas of interest for the practicing engineer as well as for the student at various levels and educational institutions. It features the work of authors from all over the world who have contributed their expertise and support the globally working engineer in finding a solution for today‘s mechanical engineering problems. Each subject is discussed in detail and supported by numerous figures and tables.
Author:
Publisher:
ISBN: 9789811504358
Category : Automobiles
Languages : en
Pages : 342
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Book Description
This book presents a comprehensive study of all important aspects of tribology. It covers issues and their remedies adopted by researchers working on automobile systems. The book is broadly divided in to three sections, viz. (i) new materials for automotive applications, (ii) new lubricants for automotive applications, and (iii) impact of surface morphologies for automotive applications. The rationale for this division is to provide a comprehensive and categorical review of the developments in automotive tribology. The book covers tribological aspects of engines, and also discusses influence of new materials, such as natural fibers, metal foam materials, natural fiber reinforced polymer composites, carbon fiber/silicon nitride polymer composites and aluminium matrix composites. The book also looks at grease lubrication, effectiveness and sustainability of solid/liquid additives in lubrication, and usage of biolubricants. In the last section the book focuses on brake pad materials, shot peening method, surface texturing, magnetic rheological fluid for smart automobile brake and clutch systems, and application of tribology in automobile systems. This book will be of interest to students, researchers, and professionals from the automotive industry.
Author: A. K. Lakshminarayanan
Publisher: Springer
ISBN: 9811317801
Category : Technology & Engineering
Languages : en
Pages : 497
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Book Description
This book presents select proceedings of the International Conference on Engineering Materials, Metallurgy and Manufacturing (ICEMMM 2018), and covers topics regarding both the characterization of materials and their applications across engineering domains. It addresses standard materials such as metals, polymers and composites, as well as nano-, bio- and smart materials. In closing, the book explores energy, the environment and green processes as related to materials engineering. Given its content, it will prove valuable to a broad readership of students, researchers, and professionals alike.
