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Author: Publisher: ISBN: Category : Iron Languages : en Pages : 288
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: Publisher: ISBN: Category : Iron Languages : en Pages : 288
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: Deepak Joshi Publisher: ISBN: Category : Materials science Languages : en Pages : 0
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: J. T. M. De Hosson Publisher: WIT Press ISBN: 1845645308 Category : Technology & Engineering Languages : en Pages : 321
Book Description
Contact mechanics and surface effects, as well as their interaction, are important in modern engineering. The life and performance of structural components is affected by surface conditions such as wear, corrosion and, high cycle fatigue. Surface treatments that address contact conditions can reduce costs by extending the life of components. These are the subjects of a biennial conference first held in 1993, the papers from the latest of which are collected in this volume. The book discusses Computer simulation; Surface modification; Surface treatments; Surface problems in contact mechanics; Contact mechanics; Applications and case studies; Indentation and hardness; Thick and thin coatings; Corrosion problems; Nano-characterisation; Test methodology; Multiscale experiments and modelling; and Fracture fatigue and mechanics.
Author: O. Vázquez-Gómez Publisher: ISBN: Category : Ductile iron Languages : en Pages : 14
Book Description
Austempering of ductile iron is a heat treating process designed to improve the mechanical properties of ductile iron: Increasing its strength and wear resistance while maintaining the tenacity and ductility associated with the untreated condition. This task is achieved by rapidly cooling the part from the austenitizing temperature to the austempering temperature and holding it during a specific time. Austempering promotes the formation of an ausferrite matrix, i.e., a mixture of bainitic ferrite and retained austenite, along with graphite nodules. In order to achieve the required microstructural control, a detailed knowledge of the phase transformation evolution coupled with a heat transfer analysis is required. Thus a thermostructural model has been developed to simulate the phase transformations during austempering of a ductile iron cylindrical probe. The thermal and microstructural submodels were coupled within the Abaqus software. The predictions were validated by austempering ductile iron probes from an austenitizing temperature of 920°C to an austempering temperature of 300°C in a molten salt bath and comparing predictions versus experimental data. It was concluded that the model is suitable to predict the thermal behavior and the final microstructure of the austempered ductile iron.
Author: Mohammad Jawaid Publisher: Woodhead Publishing ISBN: 0081023006 Category : Technology & Engineering Languages : en Pages : 480
Book Description
Mechanical and Physical Testing of Biocomposites, Fibre-Reinforced Composites and Hybrid Composites covers key aspects of fracture and failure in natural/synthetic fiber reinforced polymer based composite materials, ranging from crack propagation, to crack growth, and from notch-size effect, to damage-tolerant design. Topics of interest include mechanical properties, such as tensile, flexural, compression, shear, impact, fracture toughness, low and high velocity impact, and anti-ballistic properties of natural fiber, synthetic fibers and hybrid composites materials. It also covers physical properties, such as density, water absorption, thickness swelling, and void content of composite materials fabricated from natural or synthetic materials. Written by leading experts in the field, and covering composite materials developed from different natural fibers and their hybridization with synthetic fibers, the book's chapters provide cutting-edge, up-to-date research on the characterization, analysis and modelling of composite materials. - Contains contributions from leading experts in the field - Discusses recent progress on failure analysis, SHM, durability, life prediction and the modelling of damage in natural fiber-based composite materials - Covers experimental, analytical and numerical analysis - Provides detailed and comprehensive information on mechanical properties, testing methods and modelling techniques
Author: Ranjit Kumar Panda Publisher: LAP Lambert Academic Publishing ISBN: 9783659697043 Category : Languages : en Pages : 124
Book Description
Even since its discovery in 1948, the use of ductile iron is increasing continuously, this is due to the combination of its various excellent mechanical properties. Excessive amount of research is being carried out to develop even better properties. Austempererd ductile iron is the most recent development in the area of ductile iron or S.G. iron. This is formed by an isothermal heat treatment of the ductile iron. The newly developed austempered ductile iron is now replacing steel in many fields so it has becoming very important to various aspects of this material. In the present work the effect of copper along with the process variables (austempering temperature and austempering time) on the properties (Hardness, Tensile strength and Elongation) and microstructure of ductile iron is studied. With increasing austempering time hardness, tensile strength and elongation are increasing but with increasing austempering temperature hardness and tensile strength are decreasing and elongation increasing. Austempered ductile iron with copper is showing some higher strength, hardness and lower elongation than the austempered ductile iron without copper. In microstructure ferrite is increasing
Author: Publisher: ISBN: Category : Cast-iron Languages : en Pages : 122
Book Description
Gray cast iron and ductile cast iron are typical cast irons. The low cost and mechanical properties of good ductility, excellent toughness and high strength made these two types of materials become widely used in many industries. In this research, heat treatment was applied on gray iron and ductile iron. Two different heat-treatment processes: austempering and quench-tempering were considered. The effects of different heat treatment and different austempering and quench-tempering temperature were investigated by discussing the microstructures. Hardness measurements and matallurgical evaluation were also completed. Shot-peening treatment is one of the most effective methods to achieve surface strengthening on metals. Shot-peening treatment was used to investigate how it can have an effective influence on the material surface strengthening. X-ray diffraction was used to test residual stress on the material surface and subsurface. Ball-on-disk reciprocating sliding wear tests were carried on the samples after heat treatment and shot-peening treatment. Wear volumes were compared after wear tests between austempered samples and quench-tempered samples. And also, the comparison of wear resistance of shot-peened samples and unshot-peened samples were carried out. Morphology of wear tracks in shot-peened gray iron and ductile iron samples was studied after wear tests by scanning electrical microscopy.
Author: Ann Zammit Publisher: ISBN: Category : Technology Languages : en Pages :
Book Description
Austempered ductile iron (ADI) is a type of heat-treated cast iron, which offers numerous positive advantages including: good combination of mechanical properties and damping characteristics, lower density than steel and the possibility of casting components into near-net shape. However, surface engineering techniques are necessary to extend the use and prolong the lifetime of ADI engineering components. One such treatment for improving the bending fatigue strength of ADI is shot peening. This treatment creates compressive residual stresses and high dislocation densities at the surface of the treated components. However, the shot peening process is not always beneficial in improving the tribological characteristics of ADI. Its behaviour depends on the type of wear mechanism, applied loads, lubrication, heat treatment process parameters and the resulting surface finish of the components. This chapter will look into the effect of shot peening on ADI in more detail and will delve into a case study, which was carried out to analyse the bending fatigue resistance and tribological characteristics of Cu-Ni-alloyed ADI.
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Author: Deepak Joshi
Author: J. T. M. De Hosson
Author: O. Vázquez-Gómez
Author: Mohammad Jawaid
Author: Ranjit Kumar Panda
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Author: Eduard Dorazil
Author: 
Author: Ann Zammit