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April 4 @ 14:00 - 15:00
Thursday, 4.4. 2019, 14.00,
Lecture room F2 (1st floor), MFF UK, Ke Karlovu 5
Institute of Materials Science, Technical University Bergakademie Freiberg, Freiberg, Germany
Boon and bane of internal interfaces and microstructure defects
A high density of internal interfaces is a common characteristics of the nanocrystalline materials and nanocomposites, in which the interface-related phenomena are used to manipulate the materials properties. On the example of hard (Ti,Al)N, (Cr,Al)N, (Zr,Al)N and BN nanocomposites, it will be illustrated, how the presence of local strain fields at the phase boundaries, as a particular case of the internal interfaces, affects the hardness of the nanocomposites.
For titanium nitride coatings alloyed with aluminum, it will be shown, how the partially coherent interfaces between adjacent crystallites with different crystal structures can be formed in a deposition process and how the presence of such interfaces stabilizes metastable fcc-(Ti,Al)N with a high aluminum content. In this context, the role of the lattice misfit at the internal interfaces and the role of the microstructure defects like dislocations and stacking faults will be discussed. For the fcc-(Ti,Al)N/fcc-(Al,Ti)N multilayers with partially coherent interfaces, the competition between the Gibbs energy and the strain energy will be shown to be a crucial factor influencing the thermodynamic stability of metastable phases. Finally, the ‘goodness’ and ‘badness’ of the microstructure defects will be discussed for selected compounds.