Review on Production Processes and Mechanical Properties of Dual Phase Austempered Ductile Iron

Basso, Alejandro Daniel; Sikora, Jorge Antonio

doi:10.1007/bf03355473

Cited by 23 publications

(28 citation statements)

References 15 publications

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“…Thus, a combination of high strength and high ductility is not possible to produce in conventionally processed ADI. Therefore, in recent years many researchers [11][12][13][14][15][16][17][18] have used an intercritical austempering process to improve the ductility of ADI.…”

Section: Hcmentioning

confidence: 99%

A Novel Step-Up Austenitization and Austempering Heat Treatment Process for Ductile Cast Iron

Joshi¹,

Putatunda

Boileau

2020

RDMS

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A novel heat treatment process has been conceived for creation of Austempered Ductile Iron (ADI) with combination of high strength and high ductility. The process involves a step up austenitization of ductile cast iron after initial austenitization in the lower intercritical temperature range, then raising the temperature to the fully austenitic region followed by austempering at low bainitic temperatures.In this investigation an unalloyed ductile cast iron with low Carbon Equivalent (CE) was processed by the conceived novel austempering process. The microstructure and the mechanical properties of the material processed by this technique were characterized by optical metallography, Scanning Electron Microscopy (SEM) and X-ray diffraction. The influence of austempering temperature and time on the microstructure and mechanical properties of this material was also examined.The test results show that resulting microstructure of the material processed by this novel technique consists of very fine scale bainitic ferrite, proeutectoid ferrite and high carbon austenite. ADI with high yield strength and good ductility were obtained as a result of this novel heat treatment process. The mechanical properties were comparable to the conventionally processed ADI (austenitized at fully austenitic temperature range and subsequently austempered at the same austempering temperature and time). However, the ductility was significantly higher than the conventionally processed ADI.

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Section: Hcmentioning

confidence: 99%

A Novel Step-Up Austenitization and Austempering Heat Treatment Process for Ductile Cast Iron

Joshi¹,

Putatunda

Boileau

2020

RDMS

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“…The ductile cast iron with this desired ausferrite microstructure displays optimum mechanical properties. 3,4,10,16,39,[47][48][49][50][51] The notable feature of intercritical austenitizing heat treatment comparing conventional austenitizing heat treatment ones is that in the austenite + ferrite region, the austenite volume fraction and its carbon content depends on the ICAT. When the ICAT increases the ausferrite volume fraction and the high carbon austenite volume fraction and its carbon content increases (Figs.…”

Section: Microstructural Examinationsmentioning

confidence: 99%

Effect of Microstructure on Fatigue Strength of Intercritically Austenitized and Austempered Ductile Irons with Dual Matrix Structures

2013

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In the present study the fatigue strength of austempered ductile irons with dual matrix structures (ADI with DMS) has been studied for an unalloyed ductile cast iron. For this purpose, specimens were intercritically austenitized (partially austenitized) in two phase region (α + γ ) at various temperatures (810°C, 820°C and 830°C) for 20 minutes and then quenched into salt bath held at austempering temperature of 315°C and 375°C for 120 minutes and then air cooled to room temperature to obtain various ausferrite volume fractions and their morphologies. Conventionally austempered specimens (austempered from 900°C) with fully ausferritic matrix and unalloyed as cast specimens having ferrit + pearlite structures were also tested for a comparison. Rotating bending fatigue test were carried out an the experimental results showed that, in ADI with DMS, volume fraction of ausferrite and continuity of ausferritic structure along intercellular boundaries play important role in determining fatigue strength. The fatigue strength of these specimens increases with increasing ausferrite volume fraction. The fatigue strength was correlated with the ausferrite volume fraction and high carbon austenite and its carbon content. Conventionally austempered specimens exhibited much greater fatigue strength than ADI with DMS specimens.KEY WORDS: austempered ductile iron; dual matrix structure; fatigue; ausferrite volume fraction.

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“…Intercritical austempered ductile iron (IADI) [1][2][3][4][5] also known as dual-phase austempered ductile iron [6][7][8] is an alloy obtained by submitting ductile iron to a thermal cycle that starts with austenitizing at the intercritical range, i.e., austenitizing in the region where graphite nodules, ferrite and austenite coexist, followed by quenching to a temperature between the bainite start (Bs) and martensite start (Ms) and holding long enough for the bainitic transformation to take place. The result is a microstructure of graphite nodules in a matrix of ferrite and ausferrite (bainitic ferrite plus high-carbon austenite).…”

Section: Introductionmentioning

confidence: 99%

“…The result is a microstructure of graphite nodules in a matrix of ferrite and ausferrite (bainitic ferrite plus high-carbon austenite). [1][2][3][4][5][6][7][8][9][10][11][12][13] The intercritical austenitizing step of the heat treatment has a major effect on the mechanical properties, since it determines the fraction of proeutectoid ferrite and austenite transformation products in the microstructure; thus, understanding the formation of austenite at the intercritical range becomes paramount for further development. Some research about austenite formation can be found for austempered ductile iron where complete austenitization is studied and the holding time is long enough to homogenize the carbon concentration throughout the austenite matrix, and no significant difference is found in the final morphology of the austenite transformation products throughout the matrix.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Starting Microstructure in the Formation of Austenite at the Intercritical Range in Ductile Iron Alloyed with Nickel and Copper

et al. 2020

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Intercritical austenitizing is a key step on the production of dual-phase austempered ductile iron. Therefore, understanding the formation of austenite at the intercritical range should provide critical information for the future development of this family of alloys. In this work, a ductile iron alloyed with copper and nickel (3.4 C, 2.6 Si, 0.9 Ni, 0.6 Cu, wt%) was studied. The as-cast alloy was submitted to ferritic annealing and normalizing in order to obtain fully ferritic and fully pearlitic microstructures, respectively. The effect of microsegregation, initial microstructure (ferrite or pearlite) and nodule count on the formation of austenite in the intercritical range under continuous heating was studied using electron probe micro-analyzer-EPMA-high-resolution dilatometry, optical microscopy and scanning electron microscope-SEM-. The results showed that silicon, copper and nickel segregate around the graphite nodules and manganese segregates to the last freezing zones. Also as nodule count increases the segregation level decreased. Regarding the rate of austenite formation, the results showed that it increases as nodule count increases. Additionally, austenite formation is faster when the starting microstructure is pearlitic and it increases as the pearlite interlaminar spacing decreases. Finally, the results showed that the critical temperatures for austenite formation depend mainly on the starting microstructure (ferrite or pearlite).

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Review on Production Processes and Mechanical Properties of Dual Phase Austempered Ductile Iron

Cited by 23 publications

References 15 publications

A Novel Step-Up Austenitization and Austempering Heat Treatment Process for Ductile Cast Iron

A Novel Step-Up Austenitization and Austempering Heat Treatment Process for Ductile Cast Iron

Effect of Microstructure on Fatigue Strength of Intercritically Austenitized and Austempered Ductile Irons with Dual Matrix Structures

Effect of the Starting Microstructure in the Formation of Austenite at the Intercritical Range in Ductile Iron Alloyed with Nickel and Copper

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