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Metal Casting Technologies : Whos who September 2011
Based on this study the schematic TTT transformation diagram given in Figure 2 is suggested. The work showed that x phase can be found after holding at temperatures up to at least 900oC which is higher than previously observed and that carbides are not observed after holding at 900oC and above which is lower than the 1050oC reported elsewhere . As part of a wider characterisation study the very fine alloy carbides formed during furnace cooling of the same steel from 1175oC were examined using electron energy loss spectroscopy (EELS) and EDS in a TEM . In this way they were identified as (Cr1.52Fe2.33Mo1.25Ni0.17Si0. 46) C which is close to M6C stoichiometry and this structure was confirmed by electron diffraction. Conclusions During isothermal holding within the temperature range 500 -- 900oC four secondary phases were formed in the cast duplex stainless steel containing 22wt%Cr-3.2wt%Mo-6.2wt%Ni- 0.75wt%Cu-0.19wt%N-0.037wt%C. These were carbide, x-phase, σ-phase and secondary austenite (γ2). These phases and the parent matrix could be readily distinguished by their contrast levels in SEM back scattered electron images in the order of brightness: x > σ > γ1 or γ2 > δ > carbide. No carbides were observed after holding at 900oC and above. ■ Figure 2. Schematic TTT diagram for the duplex stainless steel (solution treated condition) used in this study. References: 1. R.N. Gunn: "Duplex Stainless Steels: Microstructures, properties and applications". 1997, Abington Publishing, Cambridge, England. 2. J.T.H. Pearce: "Stainless Steel Castings: Heat Treatment Stops the Rot", Metal Casting Technologies (2003) June pp.26-32. 3. J.O. Nilsson: "Overview: super duplex stainless steels", Mater.Sci.Technol. 8 (1992) 685-700. 4. Y.J. Kim, L.S. Chumbley and B. Gleeson: "Determination of isothermal transformation diagrams for sigma-phase formation in cast duplex stainless steels CD3MN and CD3MWCuN", Metall. Mat. Trans. A 35A (2004) 3377-3386. 5. I. Calliari, M. Pellizzari and E. Ramous: "Precipitation of secondary phases in super duplex stainless steel ZERON100 isothermally aged", Mater.Sci.Technol. 27 (2011) 928-932. 6. T.H. Chen, K.L. Weng and J.R. Yang: "The effect of high-temperature exposure on the microstructural stability and toughness property in a 2205 duplex stainless steel". Mat. Sci. & Eng. A 338 (2002) 259-270. 7. D. Zou, Y. Han, W. Zhang and G. Fan: "Phase transformation and its effects on mechanical properties and pitting corrosion resistance of 2205 duplex stainless steel", J. Iron & Steel Res. Int. 17 (2010) 67-72. 8. I. Calliari, G. Straffelinii and E. Ramous: "Investigation of secondary phase effect on 2205 DSS fracture toughness", Mater. Sci. Technol. 26 (2010) 81-86. 9. H.Y. Liou, R.I. Hsieh and W. Tsai: "Microstructure and pitting corrosion in simulated heat-affected zones of duplex stainless steels", Mat. Chem. & Phys. 74 (2002) 33-42. 10. S.K. Ghosh and S. Mondal: "High temperature ageing behaviour of a duplex stainless steel", Mat. Characterization 59 (2008) 1776-1783. 11. I. Calliari, K. Brunelli, M. Dabala and E. Ramous: "Measuring secondary phases in duplex stainless steels", JOM 61 (2009) 80-83. 12. D. M. Escriba, E. Materna-Morris, R.L. Plaut and A.F. Padilha: "Chi-phase precipitation in a duplex stainless steel", Mat. Characterization 60 (2009) 1214-1219. 13. S. Kuimalee, J.T.H. Pearce and T. Chairuangsri: "Isothermal Phase Transformation Sequence in Duplex Stainless Steel", Chiang Mai J. Sci. 38 (2011) pp.47-55. 14. H.D, Solomon & T.M. Devine: "Influence of microstructure on the mechanical properties and localized corrosion of a duplex stainless steel" ASTM STP 672 (1979) pp.430-461. 15. S. Kuimalee, T. Chairuangsri, J.T.H. Pearce, D.V. Edmonds. AP. Brown, R.M.D. Brydson: "Quantitative analysis of a complex metal carbide formed during furnace cooling of cast duplex stainless steel using EELS and EDS in the TEM", Micron 41 (2010) pp.423-429. Surasak Kuimalee. In 2002 Surasak Kuimalee graduated with a first class honours B.Sc. degree in Industrial Chemistry from Chiang Mai University. He then obtained his M.Eng, in Energy Engineering at Chiang Mai in 2004 before taking up an interest in Materials while working as a lecturer in Chemistry at Naresuan University in Phayao during 2005. He is just completing his Ph.D. study into Characterisation of Cast Duplex Stainless Steel on the International Post-graduate Program at Chiang Mai University. As part of this work he was a visiting researcher at the Institute for Materials Research, School of Process, Environmental and Materials Engineering, The University of Leeds, Leeds, UK where he concentrated on EELS and EDS analysis in the TEM. He is currently a lecturer in the Dept. of Chemistry in Maejo University. Dr. Torranin Chairuangsri Dr. Torranin Chairuangsri obtained his Ph.D. from the Leeds University, UK for work on transmission electron microscopy of steels. He began his career at Chiang Mai University in 1993 as a lecturer in the Dept. of industrial Chemistry, becoming an assistant professor in 1998, and then in 2006 associate professor of metallurgy and acting head of the Industrial Chemistry Department. 46 www.metals.rala.com.au TECHNICAL FEATURE
Whos who September 2012