Investigation of Sintering Processes by Tomography

Abstract:

Sintering especially of loose particle packings is accompanied by dimensional changes of the specimen. The growth of inter particle contacts under the influence of the Laplace pressure is well understood and described by the two particle model. On the other hand the understanding of other fundamental sintering phenomena i.e. cooperative material transport processes is rather vague. To overcome this limitation for near net-shape production of components by powder metallurgy an improved model of particle rearrangement processes is required. First efforts to obtain necessary experimental data were performed at 1D and 2D models. But recent improvements of high resolution synchrotron computer tomography (SCT) setups allow the acquisition of in-situ data of particle rearrangements. In-situ studies of particle rotations during sintering were conducted at the ESRF in Grenoble. The rotations during free sintering of monocrystalline particles were investigated during continuous heating up to 1050 °C or with frequent interruptions of the heating by 1 hr dwell times every 100 °C. In contrast to 1D specimens measured by Wieters the 3D specimens showed negligible rotations. This must be attributed to the constraints in 3D samples. To obtain a more detailed insight in the rotations the particles of one sample were marked. It is possible to show that the particles perform intrinsic rotations. Therefore a new rotation model is developed. The intrinsic rotations are confirmed by complementary EBSD analyses as well.

• Periodical: Materials Science Forum (Volumes 638-642)
• Pages: 2511-2516
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.638-642.2511
• Online since: January 2010
• Authors: Bernd Kieback, Michael Nöthe, J. Banhart, Rainer Grupp
• Keywords: Fundamental, Sintering, Tomography

References

[1] .E. Geguzin, Physik des Sinterns, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig (1973).

DOI: 10.1002/mawe.19730040818

[2] H.E. Exner, Grundlagen von Sintervorgängen. Berlin/Stuttgart: Gebrüder Borntraeger (1978).

[3] H.E. Exner, T. Kraft, Review on Computer Simulations of Sintering Processes. Proc. PM World Congress, Granada, 278-82 (1998).

[4] W. Schatt, Sintervorgänge, VDI-Verlag (1992).

[5] R.M. German., Powder Metallurgy Science, Metal Powder Industries Federation, Princeton (1984).

[6] P.C. Eloff, F.V. Lenel, The Effects of Mechanical Constrains upon the Early Stages of Sintering, Modern Developments in Powder Metallurgy, 4, 291-302 (1971).

[7] A.P. Sutton, R.W. Balluffi, Interfaces in crystalline materials, Oxford University press (2003).

[8] A. Vagnon, J.P. Rivière, J.M. Missiaen, D. Bellet, M. Di Michiel, C. Josserond, D. Bouvard, 3D statistical analysis of a copper powder sintering observed in situ by synchrotron microtomography, Acta Materialia, 58, 1084-93 (2008).

DOI: 10.1016/j.actamat.2007.11.008

[9] O. Lame, D. Bellet, M. Di Michiel, D. Bouvard, Bulk observation of metal powder sintering by X-ray synchrotron microtomography; Acta Materialia, 52, 977-84 (2004).

DOI: 10.1016/j.actamat.2003.10.032

[10] M. Nöthe, M. Schulze, R. Grupp, B. Kieback, A. Haibel, Investigation of sintering of spherical copper powder by micro focus computed tomography (µCT) and synchrotron tomography, Materials Science Forum, 539-543, 2657-62 (2007).

DOI: 10.4028/www.scientific.net/msf.539-543.2657

[11] F. Sauerwald, L. Holub, Kristallisation zwischen möglichst weitgehend im Strukturgleichgewicht befindlichen Oberflächen; Zeitschrift für Elektrochemie und angewandte physikalische Chemie, 39, 750-53 (1933).

[12] R. Grupp, Thesis, TU Dresden, in submitted.

[13] K.P. Wieters, Korngrenzeneinfluß beim defektaktivierten Festphasensintern, Thesis, TU Dresden (1988).

[14] S. -W. Chan, R.W. Balluffi, Study of Energy vs. Misorientation for Grain Boundaries in Gold by Crystallite Rotation Method - I.

DOI: 10.1016/0001-6160(85)90205-6

[1] Twist Boundaries, Acta Metallurgica, 33, 1113-19 (1985).

[15] T. Aste, M. Saadatfar, T.J. Senden; Geometrical structure of disordered sphere packings; Physical Review E; Vol. 71; 2005; Seite 061302-1 - 061302-15.

DOI: 10.1103/physreve.71.061302

[16] E. Arzt; The Influence of an Increasing Particle Coordination on the Densification of Spherical Powders; Acta Metallurgica; Vol. 30; 1982; Seite 1883 - 1890.

DOI: 10.1016/0001-6160(82)90028-1