Tensile Characteristics of Austempered Ductile Cast Iron in the Temperature Regime of 300 K to 693 K

Shieh, C. S.; Lui, Truan-Sheng; Chen, L. H.

doi:10.2320/matertrans1989.36.620

Cited by 7 publications

(7 citation statements)

References 18 publications

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“…It is therefore reasonable to expect that high strain hardening of austenite in ADI is due to the interaction between the dislocations and carbon atoms. This is further supported by the results of Shieh et al, [32] who showed that dynamic strain aging occurs in ADI over a wide temperature range. Analysis of interaction between the misfit strain field of a carbon atom and the strain field of a dislocation gives an expression for solution hardening that is proportional to the square root of the solute concentration.…”

Section: ͓ ␣ C Ys␣ F␣ ␥ C Ys␥ F␥͔supporting

confidence: 81%

Dependence of fracture toughness of austempered ductile iron on austempering temperature

Rao

Putatunda

1998

Metall Mater Trans A

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Ductile cast iron samples were austenitized at 927 ЊC and subsequently austempered for 30 minutes, 1 hour, and 2 hours at 260 ЊC, 288 ЊC, 316 ЊC, 343 ЊC, 371 ЊC, and 399 ЊC. These were subjected to a plane strain fracture toughness test. Fracture toughness was found to initially increase with austempering temperature, reach a maximum, and then decrease with further rise in temperature. The results of the fracture toughness study and fractographic examination were correlated with microstructural features such as bainite morphology, the volume fraction of retained austenite, and its carbon content. It was found that fracture toughness was maximized when the microstructure consisted of lower bainite with about 30 vol pct retained austenite containing more than 1.8 wt pct carbon. A theoretical model was developed, which could explain the observed variation in fracture toughness with austempering temperature in terms of microstructural features such as the width of the ferrite blades and retained austenite content. A plot of against y (X ␥ C ␥ ) 1/2 resulted in a 2 K IC straight line, as predicted by the model.

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Section: ͓ ␣ C Ys␣ F␣ ␥ C Ys␥ F␥͔supporting

confidence: 81%

Dependence of fracture toughness of austempered ductile iron on austempering temperature

Rao

Putatunda

1998

Metall Mater Trans A

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“…These can lead to the formation of elastic strains, which cause: a) heavy microstructural subsurface damage because of the graphite matrix interfaces and debonding, matrix microcracking, and void growth, b) a significant amount of austenite-martensite transformation, and c) decomposition of the reacted stable austenite, due to the localized increase in temperatures. [16][17][18][19][20] The reacted austenite matrix in ausferrite is thermodynamically stable down to liquid nitrogen temperatures. During the heating process, acicular ferrites in bainitic ductile cast iron break and the reacted austenite phase decomposes to carbide and ferrite.…”

Section: B Results Of Thermal Shock Testmentioning

confidence: 99%

Comparison of High-Temperature Properties and Thermal Shock Resistance of Austempered Ductile Irons (ADI) with Those of Pearlitic Ductile Cast Irons

Ajabshiri

Sharafi

Moeini

2011

Metall Mater Trans A

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MEHRDAD AJABSHIRI, SHAHRIAR SHARAFI, and ALIREZA MOEINI High-temperature strength and thermal shock resistance of austempered ductile iron (ADI) in high temperatures because of instability of ausferrite phase has been less interest. The aim of this study is to investigate the tensile properties of ADI and pearlitic ductile cast iron by using the short-time tensile test in high temperatures. Tensile test was conducted in temperatures of 298 K, 673 K, 873 K, and 1073 K (25°C, 400°C, 600°C, and 800°C). Thermal shock test also was conducted by using the molten lead bath at 1273 K (1000°C). In this experiment, samples of pearlitic ductile cast iron and ADI were divided in two groups; that after immersing in the molten lead bath for 25 seconds, one group was cooled in the air and other one was quenched in the water. Results showed that strength and thermal shock resistance of ADI samples are higher than those of the pearlitic ductile cast iron.

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“…Shieh et al 10) presented serrated flow on the "StressStrain" curves of bainitic austempered ductile irons at testing temperatures lower than 280°C, which was attributed to the presence of acicular ferrite in the microstructure. Since higher volume fraction of ferrite contribute to the distinct dynamic strain aging, serrated flow is more apparent on the "Stress-Strain" curves of the material DI 1 than that of the material DI 2.…”

Section: Resultsmentioning

confidence: 99%

“…The tensile strengths of both ductile irons were maintained almost constant up to 400°C and then dropped sharply at higher temperatures. It is reported that, 10) in the temperature ranges where dynamic strain aging occurs, the strength remains constant or increases slightly with increasing temperature due to strengthening effect of strain aging. Above 400°C, decrease of the tensile strength is accompanied by severe decrease of elongation for both ductile irons.…”

Section: Resultsmentioning

confidence: 99%

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High Temperature Tensile and Abrasive Wear Characteristics of As-cast Ductile Irons

et al. 2003

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In this study, tensile and abrasive wear performances of two different quality as-cast ductile irons have been examined at various temperatures between 25 and 600°C. Tensile tests were carried out with a strain rate of 3ϫ10 Ϫ4 /s. Wear tests were performed under a compression stress of 5.7 N/mm 2 , by rubbing samples on 125 mm Al 2 O 3 abrasive grains. In the temperature range of 100-300°C, where serrated flow is observed during tensile testing, tensile strength values of both ductile irons were invariable. Above 400°C, further increase of temperature caused dramatic decrease in tensile strength. As a general trend, abrasive wear resistances of the both ductile irons increased with increasing tensile strength. Exceptionally, maximum resistance to abrasive wear is obtained from both ductile irons at 100°C, probably due to dynamic strain aging.KEY WORDS: abrasive wear; ductile iron; high temperature; strain aging; tensile characteristics. Results and DiscussionTensile test results of the investigated ductile irons are presented in Fig. 3 as "Stress-Strain" curves. Serrated flow, which is the common feature of dynamic strain aging, is apparent in the temperature range between 100-300°C and much more pronounced for the material DI 1 than the material DI 2.Previously, Lui and Chao 9) reported serrated flow during low strain rate (3ϫ10 Ϫ4 /s) tensile testing of a ferritic ductile iron in the temperature interval between 150 and 350°C. Shieh et al. 10) presented serrated flow on the "StressStrain" curves of bainitic austempered ductile irons at testing temperatures lower than 280°C, which was attributed to the presence of acicular ferrite in the microstructure. Since higher volume fraction of ferrite contribute to the distinct dynamic strain aging, serrated flow is more apparent on the "Stress-Strain" curves of the material DI 1 than that of the material DI 2.Dynamic strain aging, which leads to inhomogeneous deformation characterised by serrated flow, is mainly relevant to the diffusion of interstitial atoms such as carbon or nitrogen to dislocations in motion. When the temperature and the strain rate are such that, the speed of interstitial atoms is more than that of dislocations, dislocations are pinned by interstitial atoms. Serrations occur due to rapid dislocation multiplication during deformation. In the process of dislocation multiplication stress increases, but once the dislocations are released the stress drops to sustain their movement ISIJ International, Vol. 43 (2003) until interstitial atoms diffuse and pin these mobile dislocations again. [11][12][13] The effect of test temperature on the strength and ductility of the investigated ductile irons is plotted in Figs. 4 and 5, respectively. The material DI 2 exhibited higher tensile strength and lower elongation at fracture values than the material DI 1 at the entire temperature range. The tensile strengths of both ductile irons were maintained almost constant up to 400°C and then dropped sharply at higher temperatures. It is reported that, 10) in the t...

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Tensile Characteristics of Austempered Ductile Cast Iron in the Temperature Regime of 300 K to 693 K

Cited by 7 publications

References 18 publications

Dependence of fracture toughness of austempered ductile iron on austempering temperature

Dependence of fracture toughness of austempered ductile iron on austempering temperature

Comparison of High-Temperature Properties and Thermal Shock Resistance of Austempered Ductile Irons (ADI) with Those of Pearlitic Ductile Cast Irons

High Temperature Tensile and Abrasive Wear Characteristics of As-cast Ductile Irons

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