Vol.60, Nos. 2-3 - Indira Gandhi Centre for Atomic Research

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Trans. Indian Inst. Met. Vol.60, Nos. 2-3, April-June 2007, pp. 273-276 TP 2138 Stereological Characterization of Solidification Microstructure Asim Tewari Staff Researcher, General Motors R&D India Science Lab, Bangalore, India E-mail: asim.tewari@gm.com (Received 30 June 2006 ; in revised form 20 November 2006 ) ABSTRACT Formation and evolution of microstructure during solidification involves nucleation and growth of different phases from a liquid melt. In general these solidifying phases have complex shapes and orientations depending on their crystal structure and thermal & compositional gradients. In order to develop a solidification micro-model one needs to be able to mathematically describe these complex microstructures and provide a quantitative description. This paper presents a set of stereological techniques based on differential-geometry formulation, which provide the necessary framework for such analysis. Particular emphasis is given to curvature measurements and application of concepts of spherical image. Trans. Indian Inst. Met. Vol.60, Nos. 2-3, April-June 2007, pp. 277-280 TP 2139 Effect of Brownian Motion on Microstructure of Al-Sn Alloy P. Padhi, Debasis Kar, Sudipto Ghosh and S.C. Panigrahi Department of Metallurgical and Materials Engineering Indian Institute of Technology, Kharagpur, India E-mail: scp@metal.iitkgp.ernet.in (Received 30 June 2006 ; in revised form 20 November 2006 ) ABSTRACT CA based models coupled with CFD methods have been extensively used for prediction of cast microstructure. In the present work, the approach has been tested for Al-22Sn alloy. However, the CA based model was enhanced by incorporating the movements of newly formed nuclei due to Brownian movement. The average grain size predicted by the model incorporating Brownian motion was higher than the experimentally determined value and the model without incorporating the Brownian motion under predicted the average grain size. The grain size distributions obtained experimentally and by simulation suggests that further improvement in CA based model is required to bring the predictions closer to the experimental data. However, the present work establishes that Brownian motion significantly modifies the grain size distribution for Al-22Sn alloy and thus can not be ignored.
Trans. Indian Inst. Met. Vol.60, Nos. 2-3, April-June 2007, pp. 281-286 TP 2140 In situ Synchrotron X-ray Imaging of the Solidification Progress in Metallic Alloys Joseph Gastaldi 1 , Bernard Billia 2 , Henri Nguyen-Thi 2 , Thomas Schenk 3 , Guillaume Reinhart 2 , Nathalie Mangelinck 2 , Holger Klein 4 , Jürgen Härtwig 5 , Jose Baruchel 5 1 CRMCN, UPR CNRS 7251, Campus Luminy, Case 913, 13288 Marseille Cedex 9, France 2 L2MP, UMR CNRS 6137, Université Paul Cézanne Aix-Marseille III, Faculté des Sciences de Saint-Jérôme, Case 142, 13397 Marseille Cedex 20, France 3 Laboratoire de Physique des Matériaux, UMR CNRS 7556, Ecole des Mines de Nancy, Parc de Saurupt, 54 042 Nancy Cedex, France 4 Laboratoire de Cristallographie,UPR CNRS 5031, CNRS, BP 166, 38402 Grenoble Cedex 9, France 5 ESRF, BP 220, 38043 Grenoble Cedex, France E-mail: gastaldi@crmcn.univ-mrs.fr (Received 30 June 2006 ; in revised form 20 November 2006 ) ABSTRACT In situ X-ray imaging of the solidification progress can be carried out, nowadays, in front of the synchrotron sources, by combining X-ray radiography with X-ray topography. Thereby it is possible to obtain information directly, on the one hand on the shape and the velocity of the growing interface by means of X-ray radiography, and on the other hand, thanks to X-ray topography, on the strains and the defects generated at the moving interface by the growth process as well as in the grain volume by internal stress centres and external thermomechanical stresses. In addition, the interaction of strains and defects, contributing to the formation of the solidification microstructure observed after cooling, can also be followed during this combined imaging. Some of these feasibilities are highlighted by presenting various examples of the solidification of opaque alloys, displaying facetted or dendritic growth, we have studied with the apparatus we have developed to perform such experiments at the ID 19 ESRF (European Synchrotron Radiation Facility – Grenoble - France) beamline. Trans. Indian Inst. Met. Vol.60, Nos. 2-3, April-June 2007, pp. 287-291 TP 2141 Growth Structures, Interface Dynamics and Stresses in Metallic Alloy Solidification: In situ Synchrotron X-ray Characterisation B. Billia 1 , J. Gastaldi 2 , H. Nguyen-Thi 1 , T. Schenk 3 , G. Reinhart 1 , N. Mangelinck 1 , B. Grushko 4 , H. Klein 5 , J. Härtwig 6 and J. Baruchel 6 1 L2MP, UMR CNRS 6137, Université Paul Cézanne Aix-Marseille III, Marseille, France 2 CRMCN, UPR CNRS 7251, Campus Luminy, Marseille, France 3 Laboratoire de Physique des Matériaux, UMR CNRS 7556, Ecole des Mines de Nancy, Nancy, France 4 IFF, Forschungszentrum Juelich GmbH, Juelich, Germany 5 Laboratoire de Cristallographie,UPR CNRS 5031, CNRS, Grenoble, France 6 ESRF, Grenoble, France E-Mail: bernard.billia@L2MP.fr (Received 30 June 2006 ; in revised form 20 November 2006 ) ABSTRACT In solidification processing, the physical properties are primarily controlled by the microstructure built in the solid. Thus, materials engineering requires detailed understanding of microstructure formation dynamics. Using in situ and real-time synchrotron X-ray imaging at the European Synchrotron Radiation Facility, the solidification progress in thin metallic alloys is characterized. On Al - 3.5 wt% Ni alloys, disorienting induced by stress accumulation with the development of columnar dendrites is observed. In particular, X-ray radiography shows bending of secondary dendrite arms which, in the columnar to equiaxed transition, can be furthermore precipitated by equiaxed crystal sedimentation. Ledge growth and facetted solid-melt interface are found on AlPdMn quasicrystals. Increasing the solidification rate, the kinetic undercooling becomes sufficient for nucleation and growth of new grains ahead of the columnar grains.
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Vol.60, Nos. 2-3 - Indira Gandhi Centre for Atomic Research

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