Research report 2004 - Max Planck Institute for Intelligent Systems, Stuttgart site
Structure and Chemical Composition of Internal Interfaces in Different Materials
Gefüge und Grenzflächen (Prof. Dr. Manfred Rühle)
MPI für Metallforschung, Stuttgart
SummaryMost materials used in technical applications are polycrystalline. They consist of small crystallites (grains) which meet at internal interfaces. These two-dimensional defects (internal interfaces) influence strongly many, also technically relevant, properties. Investigations proved that the macroscopic properties of grain boundaries depend strongly on their microstructure. In nanocrystalline materials the volume fraction of atoms at grain boundaries can be up to several percent and, therefore, grain boundaries play a major role in the nanoworld. Subsequently, the results of experimental and theoretical investigations will be reported for α-Al2O3 (corundum). For corundum artificially processed bicrystals were investigated, where the interface plane as well as the misorientation between the two crystals meeting at the interface were predetermined. Results of experimental observations will be compared to results of theoretical analyses. In addition, investigations of "real" sintered materials consisting of polycrystalline α-Al2O3 were performed. The results can be used for an explanation of grain growth in α-Al2O3. Furthermore, results from studies of the Cu/α-Al2O3 interface will be reported. This heterophase boundary plays an important role in technical applications of electronic as well as structural materials.