Design and optimization of stepped austempered ductile iron using characterization techniques

Hernández-Rivera, J.L.; Garay-Reyes, C.G.; Campos-Cambranis, R.E.; Cruz-Rivera, J.J.

doi:10.1016/j.matchar.2013.06.004

Cited by 8 publications

(6 citation statements)

References 12 publications

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“…However, the calculated U plat a values are in the upper range of reported values. [10,22,[27][28][29][30][31][32][33] This is mostly due to differences in alloy composition. In most of these references alloys with a significantly higher amount of austenite stabilizing elements, such as copper, nickel, manganese, and molybdenum are used.…”

Section: A Phase Fractionmentioning

confidence: 99%

“…Moreover, the absolute values of carbon enrichment are up to~0.2 wt pct above our results. [10,22,[27][28][29][30][31][32][33] One reason for this deviation is a systematic error of~0.16 wt pct, which was discovered [12] in most of these publications. The authors mistakenly used Å units in an equation, which was originally proposed by [41] in ''kX units,'' for the calculation of austenite lattice parameters.…”

Section: B Austenite Carbon Contentmentioning

confidence: 99%

“…[4,7,11,12,27,34,49] At the lower austempering temperatures the morphology of the ferrite can be described as acicular (lower ausferrite). It becomes coarser resulting in a blocky morphology of the retained austenite at austempering temperatures around 673 K (400°C) (upper ausferrite).…”

Section: B Austenite Carbon Contentmentioning

confidence: 99%

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In Situ Study of the Influence of Nickel on the Phase Transformation Kinetics in Austempered Ductile Iron

Saal

Meier

et al. 2015

Metall Mater Trans A

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Phase fractions and austenite carbon contents in austempered ductile iron samples with three different nickel contents were determined by in situ neutron diffraction. The samples were austenitized at 1178 K (905°C) for 30 minutes and austempered for 3.5 hours at temperatures between 523 K and 723 K (250°C and 450°C) using a mirror furnace. Based on the in situ neutron diffraction studies, plateau times were derived, which determine the end of stage I reaction. The austenite contents increase for higher austempering temperatures when the austempering times are selected properly, considering the accelerated phase transformation at higher temperature. Appropriate austempering times were derived for austempering temperatures between 523 K and 723 K (250°C and 450°C). Increased nickel contents lead to higher austenite phase fractions. Moreover the retarding effect of nickel on the phase transformation was quantified. The plateau values of phase fraction and the according austempering times were converted to TTT diagrams. The evolution of the austenite carbon content shows a maximum at 623 K (350°C) austempering temperature. This can be explained by temperature-dependent carbide precipitation and carbon diffusion into lattice defects. Fine carbides within the ferrite could be found by preliminary APT analysis.

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Section: A Phase Fractionmentioning

confidence: 99%

Section: B Austenite Carbon Contentmentioning

confidence: 99%

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In Situ Study of the Influence of Nickel on the Phase Transformation Kinetics in Austempered Ductile Iron

Saal

Meier

et al. 2015

Metall Mater Trans A

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“…The former one is classified as sorbitic pearlite, and the latter one is troostitic pearlite, which undoubtedly toughens the materials more than sorbitic pearlite. 20 The scenario of decreasing lamellar spacing could be vindicated by the viewpoint of Marder that the lamellar spacing shows inversely proportional relationship with supercooling degree of eutectoid reaction. 21 As we discussed before, the supercooling degree will gradually increase with the increasing Sn content; therefore, the lamellar spacing of CGI will accordingly decline.…”

Section: Methodsmentioning

confidence: 99%

Effect of tin on microstructure and mechanical properties of compacted graphite iron

Lyu

Sun

Liu

et al. 2015

International Journal of Cast Metals Research

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This experiment investigated the effect of tin in an amount up to 0?121 wt-% on the microstructure and mechanical properties of compacted graphite iron. Graphite and matrix evolution was emphasised with the help of scanning electron microscopy. The results indicate that Sn in experimental range reduces graphite size. Pearlite quantity would increase with the increasing Sn and reaches over 95% when Sn is .0?057 wt-%. Sn helps to narrow the lamellar spacing of pearlite from sorbitic pearlite (320 nm) to troostitic pearlite (83 nm) when Sn increases from 0?003 to 0?057 wt-%. Appropriate Sn addition promotes the tensile strength and impact toughness, and the samples containing 0?057 wt-%Sn perform the highest values of 410?7 MPa and 9?11 J cm 22 respectively. Elongation declines with increasing Sn content because of the emergence of more pearlite. Samples containing excessive Sn experience sharp deterioration in mechanical properties due to brittle cementite. Y. Lyu et al. Effect of tin on properties of CGI International Journal of Cast Metals Research 2015 VOL NO 3 28 5 265 Downloaded by [University of Sussex Library] at 04:48 22 June 2016 4 Energy dispersive spectroscopy analysis of massive phase in sample containing 0.121 wt-%Sn 6 Lamellar spacing of samples containing a 0.003 wt-%Sn and b 0.057 wt-%Sn 5 Energy dispersive spectroscopy analysis of samples containing 0.092 wt-%Sn Y. Lyu et al. Effect of tin on properties of CGI

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“…This complex type of ADI heat treatment has a rich bibliography [19][20][21][22][23][24][25][26][27][28]. The opinion that complex heat treatment does enable better mechanical properties, both R m and A, than those achieved due to standard one-step austempering is established.…”

Section: Introductionmentioning

confidence: 99%

Optimization of mechanical properties of complex, two-stage heat treatment of Cu–Ni (Mn, Mo) austempered ductile iron

Gazda

Warmuzek

Bitka

2018

J Therm Anal Calorim

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The aim of the study was to design and optimize the complex, two-step heat treatment of Cu-Ni (Mn, Mo) ductile iron. A method for the formation and investigation of austempered ductile iron (ADI) by means of complex two-step and as comparative, standard one-step heat treatments has been developed, using quenching dilatometer. Investigations of proceeding phase transformations using differential dilatometric and DSC analysis supported by microstructural observations, hardness and austenite volume measurements have been carried out. An analysis of the temperature sequence of the ausferrite decomposition in the one-step and two-step ADI was performed, which allowed for the separation and identification of the effects responsible for the carbon-enriched austenite decomposition. A quantitative relationship was established between basic dimensional effects revealed on the differential dilatometric curve of ausferrite decomposition, which enables prognosis and optimization of the parameters of complex ADI heat treatment variants. Verification tests were performed on a stand equipped with salt furnaces enabling a quick transfer of samples from one bath to another without changing their initial temperature. Optimization of the two-step ADI heat treatment with the use of quantitative dilatometric analysis of the ausferrite decomposition, allowed to obtain for the temperature step-down heat treatment 390°C/15, 20 min ) 270°C/130 min the excellent mechanical properties, unattainable by means of standard 1-step ADI heat treatment.

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Design and optimization of stepped austempered ductile iron using characterization techniques

Cited by 8 publications

References 12 publications

In Situ Study of the Influence of Nickel on the Phase Transformation Kinetics in Austempered Ductile Iron

In Situ Study of the Influence of Nickel on the Phase Transformation Kinetics in Austempered Ductile Iron

Effect of tin on microstructure and mechanical properties of compacted graphite iron

Optimization of mechanical properties of complex, two-stage heat treatment of Cu–Ni (Mn, Mo) austempered ductile iron

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