Application of X-Ray Microtomography to Quantify the Liquid Fraction of M2 Steel for Semi-Solid Forming Process

Abstract:

Thixoforging, one variant of semi-solid metal processing in which the metallic alloys are processed at low liquid fraction (0.1< Fl < 0.3), is used to produce complex parts with high mechanical properties. Steel thixoforging faces more challenges as compared to that of low melting point materials due to high processing temperature and lack of understanding of the thermomechanical behavior of materials in the given conditions. It is crucial to study the microstructure at the semi-solid state to improve the understanding of the thixoforging process since the material behavior strongly depends on main parameters: the liquid fraction, its distribution as well as the coherence of the solid skeleton. The microstructure has a great influence on the viscosity of the material, on the flows and finally on the final shape and mechanical properties of the thixoforged parts. Here, the characterization of the volume percentage and distribution of liquid fraction at the semi-solid state with high energy 3D X-ray microtomography was investigated on M2 steel grade as a ‘model’ alloy. The obtained results have been compared to 2D observations using EDS technique in SEM on heated and quenched specimens. They showed a good correlation making both approaches very efficient for the study of the liquid zones at the semi-solid state.

• Periodical: Key Engineering Materials (Volumes 554-557)
• Pages: 547-552
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.554-557.547
• Online since: June 2013
• Authors: Guo Chao Gu, Raphaël Pesci, Eric Becker, Laurent Langlois, Régis Bigot
• Keywords: SEM-EDS, Semi-Solid, Steel, X-Ray Microtomography

References

[1] R. Bigot, V. Favier, C. Rouff. Characterisation of semi-solid material mechanical behavior by indentation test. J. Mater. Process Tech. 160 (2005) 43-53.

DOI: 10.1016/j.jmatprotec.2004.03.016

[2] E. Becker, V. Favier, R. Bigot, P. Cezard, L. Langlois. Impact of experimental conditions on material response during forming of steel in semi-solid state. J. Mater. Process. Tech. 210 (2010) 1482-1492.

DOI: 10.1016/j.jmatprotec.2010.04.006

[3] L.S. Turng, K.K. Wang. Rheological behavior and modeling of semi-solid Sn-15% Pb alloy. J. Mater. Sci. 26 (1991) 2173-2183.

DOI: 10.1007/bf00549185

[4] S.J. Qu, A.H. Feng, L. Geng, Z.Y. Ma, J.C. Han. DSC analysis of liquid volume fraction and compressive behavior of the semi-solid Si3N4w/Al-Si composite. Scripta Mater. 56 (2007) 951-954.

DOI: 10.1016/j.scriptamat.2007.02.011

[5] M.Z. Omar, E.J. Palmiere, A.A. Howe, H.V. Atkinson, P. Kapranos. Thixoforming of a high performance HP9/4/30 steel. Mater. Sci. Eng., A. 395 (2005) 53-61.

DOI: 10.1016/j.msea.2004.12.013

[6] A. Neag, V. Favier, R. Bigot, M. Pop. Microstructure and flow behavior during backward extrusion of semi-solid 7075 aluminium alloy. J. Mater. Process. Technol. 212 (2012) 1472-1480.

DOI: 10.1016/j.jmatprotec.2012.02.003

[7] D.J. Rowenhorst, A. Gupta, C.R. Feng, G. Spanos, 3D crystallographic and morphological analysis of coarse martensite: Combining EBSD and serial sectioning, Scripta Mater. 55 (2006) 11-16.

DOI: 10.1016/j.scriptamat.2005.12.061

[8] M.Z. Omar, A. Alfan, J. Syarif, H.V. Atkinson. Microstructural investigations of XW-42 and M2 tool steels in semi-solid zones via direct partial remelting route. J. Mater. Sci. 46 (2011) 7696-7705.

DOI: 10.1007/s10853-011-5749-4

[9] G.C. Gu, R. Pesci, E. Becker, L. Langlois, R. Bigot, M. Scheel. Quantification and localization of the liquid zone of partially remelted M2 tool steel using X-ray microtomography and scanning electron microscopy. Acta. Mater. 60 (2012) 948-957.

DOI: 10.1016/j.actamat.2011.10.039

[10] M.Z. Omar, H.V. Atkinson, A.A. Howe, E.J. Palmiere, P. Kapranos, M.J. Ghazali. Solid-liquid structural break-up in M2 tool steel for semi-solid metal processing. J. Materi. Sci. 44 (2009) 869-874.

DOI: 10.1007/s10853-008-3181-1