Auswirkungen der Prozessparameter auf Eigenspannungen und innere Lastübertragung in Metallmatrix-Verbundwerkstoffen
Final Report Abstract
Systematic study of the effect of the processing parameters and preform morphology on the thermo-mechanical properties of interpenetrating metal/ceramic composites was carried out in this project. Main conclusions from the project are summarized below: A novel processing route was developed to fabricate open porous silicon carbide preforms with easily tailorable microstructure. Thorough study of the influence of the preform structure on preform elastic properties was carried out and a processing parameter – elastic anisotropy map was proposed. Fabricated alumina and silicon carbide preforms were infiltrated under inert gas pressure. Additional composites fabricated infiltrated both squeeze-casting and die-casting and having various phase morphologies were also studied. While stiffness of the composites was independent of preform morphology and employed infiltration technique; compressive strength depended on preform morphology. Composites with a finer preform structure displayed higher compressive strength. Thermal expansion of composites having similar preform structure and density, but fabricated using different infiltration techniques showed different behavior. This difference can probably be attributed to the presence of residual porosity in the composite samples. At a constant ceramic content, the evolution of expansion coefficient with temperature displays a distinct anisotropy, with the coefficient along the preform press direction being significantly higher than the coefficients along the two other orthogonal directions. This anisotropy in the thermal expansion behavior has been discussed in terms of the elastic anisotropy present in the preforms and the composite material. In-situ compression test with energy dispersive synchrotron X-ray diffraction shows that load transfer occurs from the softer and more compliant aluminium solid solution phase to the stiffer and stronger alumina phase. The extent of load transfer however was very different in the studied samples. This has been attributed to different ceramic contents inside the diffraction gauge volume in individual samples, resulting from a combination of the inhomogeneous composite microstructure and very small size of the gauge volume in the employed diffraction technique. Neutron diffraction, with a much larger gauge volume, is a potential technique to overcome this problem.
Publications
- Internal load transfer and damage evolution in a 3D interpenetrating metal/ceramic composite, Materials Science and Engineering A, A551, 272-279, 2012
S. Roy, J. Gibmeier, V. Kostov, K. A. Weidenmann, A. Nagel, A. Wanner
(See online at https://doi.org/10.1016/j.msea.2012.05.016) - Processing and elastic property characterisation of porous SiC preform for interpenetrating metal/ceramic composites, Journal of The American Ceramic Society, 95, 3078-3083, 2012
S. Roy, K. G. Schell, C. Bucharsky, P. Hettich, S. Dietrich, K. A. Weidenmann, A. Wanner, M. J. Hoffmann
(See online at https://doi.org/10.1111/j.1551-2916.2012.05347.x) - Processing and non-destructive characterisation of porous silicon carbide preforms for metal/ceramic composite fabrication, Proceedings of CELLMAT 2012, Dresden, Nov. 7-9, 2012
S. Roy, K. G. Schell, C. Bucharsky, P. Hettich, S. Dietrich, K. A. Weidenmann, A. Wanner, M. J. Hoffmann
