In situ microtomography investigation of metal powder compacts during sintering Olivier Lame a , Daniel Bellet a , Marco Di Michiel b , Didier Bouvard a, * a Laboratoire G enie Physique et M ecanique des Mat eriaux, Institut National Polytechnique de Grenoble, CNRS UMR 5010, BP 46, 38402 Saint Martin dÕH eres Cedex, France b ESRF, BP 220, F-38043 Grenoble Cedex, France Abstract The mechanisms involved in shape changes arising during sintering of complex materials like iron-based systems are still poorly understood. New information can be obtained by use of advanced techniques such as microtomography. In this study, the microstructural evolution of a Distaloy AE powder compact and of loose copper powder is investigated during a thermal cycle at the European Synchrotron in Grenoble (France). Both materials are sintered in a furnace set in front of a high-energy X-ray source in 30–45 keV range. At various steps of sintering, hundreds of radiographs are taken with different orientations of the specimen. From these images the 3D microstructure is reconstructed. This non- destructive method provides the 3D microstructural evolution of the material during sintering. Local and statistical information can be obtained and will be used in the future for modelling the sintering process. Special attention is given to the anisotropy induced by prior compaction and to its evolution through sintering. Ó 2002 Elsevier Science B.V. All rights reserved. PACS: 87.59.F; 81.20.E Keywords: Sintering; Metallic powder; Tomography 1. Introduction Despite a consistent research activity for de- cades, several questions remain open in the field of metal powder sintering, in particular with regard to the processing of industrial powders with complex composition and morphology. Typical examples concern the evolution of defects due to packing faults or to inclusions, the role of particle rear- rangement in the densification process, the causes of anisotropic shrinkage of powder compacts dur- ing sintering. Traditional observation techniques such as scanning electron microscopy, that show images of grinded cross-sections of previously sin- tered specimens, do not provide relevant informa- tion for investigating these types of problems. Significant advances in the understanding of the phenomena occurring during sintering can cer- tainly arise from bulk images of a powder in the course of sintering. This expectation is no longer utopian thanks to the rapid development of non- invasive 3D imaging techniques, such as X-ray to- mography, for application in materials science [1]. The present paper deals with the use of X-ray micro-tomography to investigate sintering of * Corresponding author. E-mail address: didier.bouvard@inpg.fr (D. Bouvard). 0168-583X/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0168-583X(02)01690-7 Nuclear Instruments and Methods in Physics Research B 200 (2003) 287–294 www.elsevier.com/locate/nimb