The Bainitic Phase Transformation in Aluminium Containing Ductile Irons after Short Time of Austempering

Document Type : Research Paper

Authors

1 Department of Materials Engineering, Sistan & Baluchestan University Zahedan, Iran

2 Department of Materials, University of Leeds, Leeds, UK

Abstract

The influence of aluminium on the microstructure of austempered ductile cast iron (ADI) has been studied. A number of irons of different compositions have been made by green sand casting and gravity die casting of appropriate design to provide the experimental materials. Austenitising was carried out at different temperatures and holding times for a variety of experimental irons to achieve sufficient homogeneity for further isothermal heat treatment. The transformation to a bainitic microstructure during austempering under different conditions was then examined for the most successful of the experimental casts. Austenitising temperature of 920°C, and austempering temperature of 350 °C for 1 minute have been used. Microstructures have been examined by the light and scanning electron microscopy (SEM). The microstructure of austempered ductile cast iron (ADI) consists of nodular graphite which is randomly dispersed in a bainitic matrix consisting of bainitic ferrite and carbon enriched retained austenite. It has been shown that the former austenite grain boundaries are the preferred sites for bainite nucleation and the best sites for nucleation are grain corners.

Keywords

References

R.Elliott: Cast Iron Technology, Butterworths
London, (1988).
[2] I.C.H.Hughes: Ductile Iron, Metals Handbook,
Casting, Vol.15 BCIRA Int. Center for Cast Metals
Tech., Great Britain, Ninth edition, (1988), 647.
[3] R.Rimmer Mater World, 5(1997), 252.
[4] E.S.Davenport and E.C.Bain, Trans. Met. Soc.
AIME, 90(1930), 117.
[5] H.T.Angus, Cast Iron, Physical and Engineering
Properties, Butterworths , London, (1978).
[6] S.M.A.Boutorabi, J.M.Young, V.Kondic and
M.Salehi, Wear, 165(1993a), 19.
[7] H.Bayati and R.Elliott, Mater. Sci. Tech.,
11(1995), 284.
[8] J.Aranzabal, I.Gutierrez, J.M.Rodriguez-Ibabe
and J.J.Urcola, Mater. Sci. Tech., 8(1992), 263.
[9] N.Darwish and R.Elliott, Mater. Sci. Tech.,
9(1993b), 882.
[10] A.Honarbakhsh-Raouf: The Phase Transformation
in Austempered Ductile Iron, Ph.D. Thesis, School of
Materials, The University of Leeds UK.,(1997).
[11] C.Defrancq, J.Van Fegham and A.A.Desy, 36th
International Foundry Congress, Belgrad, (1969).
[12] R.P.Walson, AFS Trans., 85(1977), 51.
[13] R.J.Smickley and K.B.Rundman, AFS Trans.,
89(1981), 205.
[14] A.R.Kiani-Rashid: The Influence of Aluminium
and Heat Treatment Conditions on Austempered
Ductile Irons, Ph.D. Thesis, University of Leeds,
(2000).
[15] D.A.Porter and K.E.Easterling: Phase
Transformation in Metals and Alloys, Van Nostrand
Reinhold, (1981).
[16] H.K.D.H.Bhadeshia: Bainite in Steels, The
Institute of Materials, Cambridge University Press,
(1992).
[17] S.M.A.Boutorabi, J.M.Young and V.Kondic,
Trans. Japan Foundrymen’s Soc., 12, (1993a), 14.
[18] S.M.A.Boutorabi, J.M.Young and V.Kondic,
Int. J. Cast Metals Res. (UK),6(1993b), 170.
[19] J.G.Pearce and K.Bromage: Copper in Cast Iron,
Hutchinson ,London, (1965), 13.
[20] A.R.Kiani-Rashid and D.V.Edmonds, Int. J.
Eng.15 (2002), 261.
[21] S.M.A.Boutorabi: The Austempering Kinetics,
Microstructure and Mechanical Properties of
Spheroidal Graphite Unalloyed Aluminium Cast
Iron, Ph.D. Thesis, University of Birmingham,
(1991).
[22] E.A.Wilson, Metal Sci, 18(1984), 471.
[23] M.Umemoto, T.Furuhara and I.Tamura, Acta
Metall. 34(1986), 2235.
[24] J. Barford and W.S.Owen: JISI., 197(1961),
p 146.
[25] F.B.Pikering: The Structure and Properties of
Bainite in Steels, Climax Mo Co of Michigan,
(1967), 109.
International Journal of Iron & Steel Society of Iran
Volume 1, Issue 1 - Serial Number 1
December 2004
Pages 8-14

Files

Share

How to cite

Statistics