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Effect of Graphite Inclusions on Mechanical Properties of Austempered Ductile Iron

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Abstract:

Recently, austempered ductile iron (ADI) has emerged as a new class of ferrous materials and represents a major achievement in cast iron technology [1]. The mechanical strength and impact toughness of nodular iron are provided by the precipitation of the graphite phase as spheroids surrounded by ferrite (bull’s-eye structure) in a continuous pearlite matrix. The quality of ductile iron increases with the number of the graphite spheroids. A high spheroids volume fraction, which is mainly controlled by the inoculation process, limits the chemical segregation during solidification and ensures the structural homogeneity of the component. In this work, a lower value of Young modulus was obtained when the graphite phase was taken into account in the self-consistent modelling. For 12% of graphite the theoretical Young modulus agrees with the measured one (mechanical tensile test). The volume fraction of graphite was confirmed independently by micrographic observation (14%). It can be concluded that the macroscopic behaviour of ADI steel can be modelled by the self-consistent approach in which the austeno-ferritic aggregate is represented by an effective matrix, while instead of the graphite spherical empty spaces are introduced. Using such an approach it was shown that in the elasto-plastic range of deformation, presence of graphite phase caused stress relaxation.

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Periodical:

Materials Science Forum (Volumes 490-491)

Pages:

73-78

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.490-491.73

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Online since:

July 2005

Authors:

Florin Serban, Andrzej Baczmanski, E. Labbe, Krzysztof Wierzbanowski, Alain Lodini

Keywords:

Austempered Ductile Iron, Graphite Influence, Self-Consistent Model

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© 2005 Trans Tech Publications Ltd. All Rights Reserved

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