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Susil K Putatunda - One of the best experts on this subject based on the ideXlab platform.
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INFLUENCE OF STEP-DOWN Austempering PROCESS ON THE FRACTURE TOUGHNESS OF AUSTEMPERED DUCTILE IRON
2020Co-Authors: Susil K Putatunda, Gowtham A. BingiAbstract:Austempered ductile cast iron (ADI) has emerged as a major engineering material in recent years because of its many attractive properties. In this investigation, the influence of a step-down Austempering process on the microstructure and mechanical properties including fracture toughness of an unalloyed ductile cast iron was examined. Compact tension and cylindrical tensile specimens were prepared from unalloyed nodular cast iron as per ASTM standards and were subjected to conventional as well as step-down Austempering process at three different Austempering temperatures. The microstructure and mechanical properties of these samples were evaluated and compared. Test results show that both the step-down and conventional Austempering process resulted in very similar microstructure and mechanical properties in unalloyed ADI. The fracture toughness of the material was found to be influenced by both ferritic cell size (d) and the austenitic carbon ( ). . γ
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influence of intercritical Austempering on the microstructure and mechanical properties of austempered ductile cast iron adi
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Saranya Panneerselvam, Susil K Putatunda, Richard Gundlach, James BoileauAbstract:Abstract The focus of this investigation was to examine the influence of intercritical Austempering process on the microstructure and mechanical properties of low-alloyed austempered ductile cast iron (ADI). The investigation also examined the influence of intercritical Austempering process on the plane strain fracture toughness of the material. The effect of both austenitization and Austempering temperature on the microstructure and mechanical properties was examined. The microstructural analysis was carried out using optical microscopy, scanning electron microscopy and X-ray diffraction. The test results indicate that by intercritical Austempering it is possible to produce proeutectoid ferrite in the matrix microstructure. Lower austenitizing temperature produces more proeutectoid ferrite in the matrix. Furthermore, the yield, tensile strength and the fracture toughness of the ADI decreases with decrease in austenitizing temperature. A considerable increase in ductility was observed in the samples with higher proeutectoid ferrite content. The fracture surfaces of the ADI samples revealed that dimple ductile fracture produced higher fracture toughness of 60±5 MPa√m in this intercritically austempered ADI.
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influence of Austempering temperature on the mechanical properties of a low carbon low alloy steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Susil K Putatunda, Codrick J Martis, James BoileauAbstract:Abstract In this investigation, a new low alloy and low carbon steel with exceptionally high strength and high fracture toughness has been developed. The effect of Austempering temperature on the microstructure and mechanical properties of this new steel was examined. The influence of the microstructure on the mechanical properties and the fracture toughness of this steel was also studied. Test results show that the Austempering produces a unique microstructure consisting of bainitic ferrite and austenite in this steel. There were significant improvement in mechanical properties and fracture toughness as a result of Austempering heat treatments. The mechanical properties as well as the fracture toughness were found to decrease as the Austempering temperature increases. On the other hand, the strain hardening rate of steel increases at higher Austempering temperature. A linear relationship was observed between strain hardening exponent and the austenitic carbon content.
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comparison of the mechanical properties of austempered ductile cast iron adi processed by conventional and step down Austempering process
Materials and Manufacturing Processes, 2010Co-Authors: Susil K PutatundaAbstract:An investigation was carried out to examine the influence of step-down Austempering process on the mechanical properties of austempered ductile cast iron (ADI). Compact tension and cylindrical tensile specimens were prepared from nodular cast iron as per ASTM standards and were subjected to two different Austempering heat treatments; that is, conventional and step-down Austempering in the upper bainitic temperature range. The specimens were austempered at four different temperatures; that is, 343, 357, 371, and 385°C. The influence of these Austempering processes on the microstructure and the mechanical properties of the material was examined at room temperature and ambient atmosphere. The influence of these Austempering processes on the plane strain fracture toughness of the material was also investigated. The present test results indicate no significant difference in the mechanical properties and fracture toughness in ADI processed by conventional as well as step-down Austempering process at the same au...
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effect of microstructure on abrasion wear behavior of austempered ductile cast iron adi processed by a novel two step Austempering process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Jianghuai Yang, Susil K PutatundaAbstract:Abstract An investigation was carried out to examine the influence of a novel two-step Austempering process on microstructural parameters and the abrasion wear resistance of austempered ductile cast iron (ADI). Two batches of cylindrical pin specimens were prepared from an alloyed nodular ductile cast iron and were initially austenitized at 927 °C (1700 °F) for 2 h. The first batch of samples was austempered by the conventional single-step Austempering process at five different temperatures, e.g., 288 °C (550 °F), 316 °C (600 °F), 343 °C (650 °F), 371 °C (700 °F), and 385 °C (725 °F) for 2 h, whereas the second batch of samples were processed by the two-step Austempering process. These samples were initially quenched in a salt bath maintained at 260 °C (500 °F) and then the temperature of the salt bath was raised to interfacial Austempering temperatures316 °C, 343 °C, 371 °C and 385 °C. These samples were austempered at these temperatures for 2 h. The test results show that this two-step Austempering process has resulted in significant improvement in microstructural parameters (such as higher volume fraction of austenite, X γ , higher carbon content in austenite, C γ , finer ferritic cell size, d , as well as higher total carbon in the matrix, X γ C γ ). Two-step process has also resulted in significant improvement in abrasion wear resistance in ADI, compared to the conventional single-step Austempering process.
R Elliott - One of the best experts on this subject based on the ideXlab platform.
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influence of molybdenum on Austempering behaviour of ductile iron part 1 Austempering kinetics and mechanical properties of ductile iron containing 0 13 mo
Materials Science and Technology, 1999Co-Authors: S. Yazdani, R ElliottAbstract:AbstractMeasurements of the Austempering kinetics and mechanical properties are presented for a ductile iron of composition Fe–3·51C– 2·81Si–0·25Mn–0·39Cu–0·13Mo–0·04Mg (wt-%) for Austempering temperatures of 285, 320, 375, and 400°C after austenitising at 870°C for 120 min. The kinetic studies show that the alloying level is insufficient to cause a significant delay in ausferrite formation in the intercellular boundaries. This implies that the heat treatment processing window is open for all Austempering conditions studied. The mechanical property measurements show that with the correct selection of Austempering temperature all the grades of the ASTM Standard 897M : 1990 and BS EN 1564 : 1997 can be satisfied. The hardenability of the present iron is limited and it is therefore unlikely that these standards will be achieved in thicker section components.
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use of austenitising temperature in control of Austempering of an mn mo cu alloyed ductile iron
Materials Science and Technology, 1997Co-Authors: R Kazerooni, A Nazarboland, R ElliottAbstract:Abstract Measurements of ultimate tensile strength, 0.2% proof strength, elongation, unnotched Charpy impact energy, and Austempering kinetics are presented as a function of Austempering time over the range 1–4320 min and for an Austempering temperature of 375°C after austenitising at 950, 920, 870, 840, and 800°C for a ductile iron of composition Fe-3.39C-2.56Si-0.37Mn-0.25 Mo-0.29Cu-0.04Mg. These measurements are analysed to relate microstructure and mechanical properties, and to define processing windows for the different austenitising temperatures. It is shown that decreasing the austenitising temperature accelerates the stage I reaction and can be used to open a processing window that is closed at a higher austenitising temperature. The introduction of ferrite into the austempered structure, through control of the austenitising temperature, can be used to influence the mechanical properties of the austempered iron. Decreasing the austenitising temperature reduces the iron hardenability.
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The Austempering kinetics and mechanical properties of an austempered Cu–Ni–Mo–Mn alloyed ductile iron
Journal of Materials Science, 1997Co-Authors: M Bahmani, R Elliott, N VarahramAbstract:Measurements of Austempering kinetics and mechanical properties are presented as a function of Austempering time over the range 1–4320 min for different combinations of Austempering temperature (275, 315, 370 and 400 °C) and austenitizing temperature (870, 900 and 950 °C) for a ductile iron of composition 3.5% C, 2.6% Si, 0.48% Cu, 0.96% Ni, 0.27% Mo and 0.25% Mn. The Austempering kinetics are used to calculate processing windows for the three austenitizing temperatures. The mechanical properties are analysed to show that the processing windows accurately predict the Austempering times over which the mechanical properties satisfy the ASTM standard. The analysis shows the role of austenitizing temperature, Austempering temperature and time in optimizing the mechanical properties.
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Role of austenite in promoting ductility in an austempered ductile iron
Materials Science and Technology, 1997Co-Authors: H. Bayati, R ElliottAbstract:AbstractMeasurements of the Austempering kinetics and mechanical properties of an alloy ductile iron after single and stepped Austempering treatments following austenitising at 920°C are presented. The kinetic and tensile data are analysed to show how the thermal and mechanical stability of the austenite phase vary with Austempering treatment. Both the thermal and mechanical instability of the austenite phase are shown to limit the ductility achieved in single Austempering treatments at 375 and 400°C to such an extent that the Charpy impact energy fails to satisfy the ASTM standard A897M: 1990. Stepped Austempering treatment improves both the thermal and mechanical stability of the austenite phase and increases the impact energy to such an extent that the ASTM standard is satisfied over a wide range of Austempering conditions. A well defined relationship is shown to exist between impact energy and the austenite carbon content for different Austempering treatments after austenitising at 920°C.
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influence of heat treatment parameters on stepped Austempering of 0 37 mn mo cu ductile iron
Materials Science and Technology, 1997Co-Authors: A Nazarbol, R ElliottAbstract:AbstractMeasurements of the average austenite carbon content, retained austenite content, unreacted austenite content, and mechanical properties are reportedfor various Austempering heat treatments of an alloyed ductile iron of composition (wt-%) Fe-3.39C-2.56Si-0.37Mn-0.25Mo-0.29Cu-0.04Mg. It is shown that a stepped Austempering treatment can be used to considerably increase the ductility of the alloy compared with a single heat treatment and to extend the Austempering time interval over which the ASTM standard can be satisfied. Decreasing the second step Austempering temperature accelerates the stage I reaction during the second step treatment but produces little change in the mechanical properties of the alloy used in the present work. Decreasing the first step Austempering time to 375°C accelerates the stage I reaction in the second step treatment but slightly decreases the maximum impact energy and increases the Austempering time at which it is achieved.
Jianghuai Yang - One of the best experts on this subject based on the ideXlab platform.
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effect of microstructure on abrasion wear behavior of austempered ductile cast iron adi processed by a novel two step Austempering process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Jianghuai Yang, Susil K PutatundaAbstract:Abstract An investigation was carried out to examine the influence of a novel two-step Austempering process on microstructural parameters and the abrasion wear resistance of austempered ductile cast iron (ADI). Two batches of cylindrical pin specimens were prepared from an alloyed nodular ductile cast iron and were initially austenitized at 927 °C (1700 °F) for 2 h. The first batch of samples was austempered by the conventional single-step Austempering process at five different temperatures, e.g., 288 °C (550 °F), 316 °C (600 °F), 343 °C (650 °F), 371 °C (700 °F), and 385 °C (725 °F) for 2 h, whereas the second batch of samples were processed by the two-step Austempering process. These samples were initially quenched in a salt bath maintained at 260 °C (500 °F) and then the temperature of the salt bath was raised to interfacial Austempering temperatures316 °C, 343 °C, 371 °C and 385 °C. These samples were austempered at these temperatures for 2 h. The test results show that this two-step Austempering process has resulted in significant improvement in microstructural parameters (such as higher volume fraction of austenite, X γ , higher carbon content in austenite, C γ , finer ferritic cell size, d , as well as higher total carbon in the matrix, X γ C γ ). Two-step process has also resulted in significant improvement in abrasion wear resistance in ADI, compared to the conventional single-step Austempering process.
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near threshold fatigue crack growth behavior of austempered ductile cast iron adi processed by a novel two step Austempering process
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Jianghuai Yang, Susil K PutatundaAbstract:Abstract The influence of a novel two-step Austempering process on the microstructure and the near threshold fatigue crack growth behavior of austempered ductile cast iron (ADI) were investigated. Cylindrical tensile and compact tension (CT) specimens (for fatigue threshold tests) were prepared from an alloyed nodular ductile cast iron as per ASTM standards and were austempered by both the conventional single-step and the novel two-step Austempering processes at four different temperatures. The near threshold fatigue crack growth behavior of these samples was examined in room temperature and ambient atmosphere. Tests results indicate this two-step Austempering process has resulted in higher hardness, higher yield and tensile strengths for ADI but higher near threshold fatigue crack growth rate and lower fatigue threshold, as compared to the conventional single-step Austempering process. Results also demonstrate that fatigue crack growth behavior of ADI in the near threshold region is influenced by microstructural parameters, such as volume fraction of austenite ( X γ ), carbon content in austenite ( C γ ), ferritic cell size ( d ) as well as total austenitic carbon, X γ C γ . SEM fractographs in all samples exhibit a combination of mechanisms, i.e. ductile striation with quasi-cleavage facet around graphite nodules.
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influence of a novel two step Austempering process on the strain hardening behavior of austempered ductile cast iron adi
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Jianghuai Yang, Susil K PutatundaAbstract:Abstract An investigation was carried out to examine the influence of a novel two-step Austempering process on the strain-hardening behavior of austempered ductile cast iron (ADI). Strain-hardening exponent ( n value) of specimens austempered by conventional single-step Austempering process as well as the novel two-step process were determined over the entire plastic deformation regions of the stress–strain curves. Optical microscopy and X-ray diffraction analysis were performed to examine mechanisms of strain-hardening behavior in ADI under monotonic (tensile) loading. Test results show that this novel two-step process has resulted in improved microstructural variables in the ADI matrix, and higher hardness, yield strength and tensile strengths, but lower ductility and strain-hardening exponent values compared to the conventional single-step Austempering process. Test results also indicate that strain-hardening exponent of ADI is a function of amount and morphology of microstructural constituents and interaction intensities between carbon atoms and dislocations in the matrix.
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improvement in strength and toughness of austempered ductile cast iron by a novel two step Austempering process
Materials & Design, 2004Co-Authors: Jianghuai Yang, Susil K PutatundaAbstract:Austempered ductile cast iron (ADI) has emerged as an important engineering material in recent years because of its excellent mechanical properties. These include high strength with good ductility, good wear resistance, fatigue strength and fracture toughness. It is therefore considered as an economical substitute for wrought or forged steel in several structural applications especially in the automotive industry. In this investigation, a nodular or ductile cast iron with predominantly pearlitic as-cast structure was processed by a novel two-step Austempering process. Two batches of samples were prepared. All the specimens were initially austenitized at 927 °C (1700 °F) for 2 h. The first batch of samples were processed by conventional single-step Austempering process at several temperatures such as 260 °C (500 °F), 273 °C (525 °F), 288 °C (550 °F), 302 °C (575 °F), 316 °C (600 °F), 330 °C (625 °F), 343 °C (650 °F), 357 °C (675 °F), 371 °C (700 °F), 385 °C (725 °F) and 400 °C (750 °F) for 2 h, whereas the second batch of samples were processed by the two-step Austempering process. These samples were initially quenched for 5 min in a salt bath maintained at 260 °C (500 °F) and then austempered for 2 h at several Austempering temperatures. These temperatures were 288 °C (550 °F), 302 °C (575 °F), 316 °C (600 °F), 330 °C (625 °F), 343 °C (650 °F), 357 °C (675 °F), 371 °C (700 °F), 385 °C (725 °F) and 400 °C (750 °F). Influence of this two-step Austempering process on microstructure and mechanical properties of ADI was examined. Test results show that this two-step Austempering process has resulted in significant improvement in yield and tensile strengths and fracture toughness of the material over the conventional single-step Austempering process.
S R Prabhakar - One of the best experts on this subject based on the ideXlab platform.
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Tensile properties of copper alloyed austempered ductile iron: Effect of Austempering parameters
Journal of Materials Engineering and Performance, 2004Co-Authors: Uma Batra, S R PrabhakarAbstract:A ductile iron containing 0.6% copper as the main alloying element was austenitized at 850 °C for 120 min and was subsequently austempered for 60 min at Austempering temperatures of 270, 330, and 380 °C. The samples were also austempered at 330 °C for Austempering times of 30–150 min. The structural parameters for the austempered alloy austenite ( X _ γ ), average carbon content ( C _ γ ), the product X _ γ C _ γ , and the size of the bainitic ferrite needle ( d _ α ) were determined using x-ray diffraction. The effect of Austempering temperature and time has been studied with respect to tensile properties such as 0.2% proof stress, ultimate tensile strength (UTS), percentage of elongation, and quality index. These properties have been correlated with the structural parameters of the austempered ductile iron microstructure. Fracture studies have been carried out on the tensile fracture surfaces of the austempered ductile iron (ADI).
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the influence of nickel and copper on the Austempering of ductile iron
Journal of Materials Engineering and Performance, 2004Co-Authors: Uma Batra, S R PrabhakarAbstract:In the present investigation, the effect of alloying elements on the Austempering process, austempered microstructure, and structural parameters of two austempered ductile irons (ADI) containing 0.6% Cu and 0.6% Cu/1.0% Ni as the main alloying elements was investigated. The optical metallography and x-ray diffraction were used to study the changes in the austempered structure. The effect of alloying additions on the Austempering kinetics was studied using the Avrami equation. Significantly more upper bainite was observed in the austempered Cu-Ni alloyed ADI than in Cu alloyed ADI. The volume fraction of retained austenite (Xγ), the carbon level in the retained austenite (Cγ), and the product XγCγ in an austempered structure of Cu-alloyed ADI are higher than in Cu-Ni-alloyed ADI. The Austempering Kinetics is slowed down by the addition of Ni.
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effect of austenitization on Austempering of copper alloyed ductile iron
Journal of Materials Engineering and Performance, 2003Co-Authors: Uma Batra, S R PrabhakarAbstract:A ductile iron containing 0.6% copper as the main alloying element was austempered at a fixed Austempering temperature of 330 °C for a fixed Austempering time of 60 min after austenitization at 850 °C for different austenitization periods of 60, 90, and 120 min. The Austempering process was repeated after changing austenitization temperature to 900 °C. The effect of austenitization temperature and time was studied on the carbon content and its distribution in the austenite after austenitization. The effect of austenitization parameters was also studied on austempered microstructure, structural parameters like volume fraction of austenite, Xγ, carbon content Cγ, and XγCγ, and bainitic ferrite needle size, dα after Austempering. The average carbon content of austenite increases linearly with austenitization time and reaches a saturation level. Higher austenitization temperature results in higher carbon content of austenite. As regards the austempered structure, the lowering austenitization temperature causes significant refinement and more uniform distribution of austempered structure, and a decrease in the volume fraction of retained austenite.
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Austempering and austempered ductile iron microstructure in copper alloyed ductile iron
Journal of Materials Engineering and Performance, 2003Co-Authors: Uma Batra, S R PrabhakarAbstract:The variation in the austempered microstructure, the volume fraction of retained austenite, Xλ, the average carbon content of retained austenite, Cλ, their product XλCλ and the size of bainitic ferrite needles with Austempering temperature for 0.6% Cu alloyed ductile iron have been investigated for three Austempering temperatures of 270, 330, and 380 °C for 60 min at each temperature after austenitization at 850 °C for 120 min. The Austempering temperature not only affects the morphology of bainitic ferrite but also that of retained austenite. There is an increase in the amount of retained austenite, its carbon content, and size of bainitic ferrite needles with the rise in Austempering temperature. The influence of Austempering time on the structure has been studied on the samples austempered at 330 °C. The increase in the Austempering time increases the amount of retained austenite and its carbon content, which ultimately reaches a plateau.
H. Bayati - One of the best experts on this subject based on the ideXlab platform.
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The influence of cobalt on the Austempering reaction in ductile cast iron
International Journal of Cast Metals Research, 2020Co-Authors: S. Yazdani, H. Bayati, Rachel ElliottAbstract:Austempering kinetic measurements and mechanical property measurements are reported for two Mn ductile irons with and without Co and three Austempering treatments. It is shown that Co accelerates the stage I reaction in each of the irons and for each of the Austempering treatments but has little affect on the stage II reaction. Consequently, the processing window is widened and moves to earlier Austempering times. This can be useful in the Austempering of thicker section components to obtain the higher ductility grades of the ADI standard and to increase process productivity.
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Role of austenite in promoting ductility in an austempered ductile iron
Materials Science and Technology, 1997Co-Authors: H. Bayati, R ElliottAbstract:AbstractMeasurements of the Austempering kinetics and mechanical properties of an alloy ductile iron after single and stepped Austempering treatments following austenitising at 920°C are presented. The kinetic and tensile data are analysed to show how the thermal and mechanical stability of the austenite phase vary with Austempering treatment. Both the thermal and mechanical instability of the austenite phase are shown to limit the ductility achieved in single Austempering treatments at 375 and 400°C to such an extent that the Charpy impact energy fails to satisfy the ASTM standard A897M: 1990. Stepped Austempering treatment improves both the thermal and mechanical stability of the austenite phase and increases the impact energy to such an extent that the ASTM standard is satisfied over a wide range of Austempering conditions. A well defined relationship is shown to exist between impact energy and the austenite carbon content for different Austempering treatments after austenitising at 920°C.
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stepped heat treatment for Austempering of high manganese alloyed ductile iron
Materials Science and Technology, 1995Co-Authors: H. Bayati, R Elliott, G W LorimerAbstract:AbstractA stepped heat treatment is proposed for overcoming the difficulty of obtaining ductility in an austempered alloyed ductile iron. The method is illustratedfor an iron containing 0·67%Mn, 0·25%Mo, and 0·25%Cu, using an austenitising temperature of 920°C, afirst step Austempering temperature of 400°C for 120 min, and a second step Austempering temperature of 285°C. The change in the microstructure and phase characteristics with time during the second Austempering step are described. Related changes in the mechanical properties compared with a single Austempering treatment at 400°C are an increase in the ultimate tensile strength from 770 to 970 MN m−2, an increase in elongation from 2·5 to 7·5%, and an increase in the unnotched Charpy impact energy from 40 to 150 J.MST/3119
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influence of austenitising temperature on Austempering kinetics of high manganese alloyed ductile cast iron
Materials Science and Technology, 1995Co-Authors: H. Bayati, R Elliott, G W LorimerAbstract:AbstractX-ray diffraction, optical microscopy, and hardness measurements were used to determine the austenitising kinetics of an alloyed ductile iron containing 0·67%Mn, 0·25%Mo, and 0·25%Cu, during Austempering at 285 and 375°C after austenitising at 870, 900, and 920°C. The austenitising kinetics show that 120 min is sufficient time to produce afully austenitic matrix. The stage I reaction during Austempering occurs in two distinct steps: first in the eutectic cell and then in the intercellular areas. Decreasing the austenitising temperature is shown to increase the driving force for the stage I reaction but to have only a small effect on the stage II kinetics. Decreasing the austenitising temperature results in a more uniform austempered microstructure and reduces the amount of martensite in the structure. These changes shift the heat treatment processing window for high Mn irons to shorter timesfor Austempering at 285°C and come close to, but do not open the processing window at 375°C.MST/3117
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Austempering process in high manganese alloyed ductile cast iron
Materials Science and Technology, 1995Co-Authors: H. Bayati, R ElliottAbstract:AbstractMicrostructural observations and measurements of the retained austenite content, hardness, austenite C content, and unreacted austenite content are reported during Austempering at 400, 375, 320, and 285°C after austenitising at 920°C for a ductile iron containing 3·52%C, 2·64%Si, 0·67%Mn, 0·007%P, 0·013%S, 0·25%Mo, 0·25%Cu, and 0·04%Mg. The segregation of solute during solidification to the intercellular areas is shown to result in the stage I reactions in the eutectic cell and intercellular areas being separated in Austempering time. Evidence is provided of the occurrence of the stage II reaction before the completion of the stage I reaction. The consequence of this sequence of changes is that the processing window as defined for unalloyed irons and known to correspond to optimum mechanical properties is closed for all Austempering temperatures.MST/3053
