Author:
Michaelsen Carsten,Wöhlert Stefan,Bormann RÜdiger
Abstract
ABSTRACTThe phase selection which is generally observed in the early stages of solid-state reactions was studied using Ti-Al multilayer films as a model system.Although all Ti-Al intermetallic phases have similar driving forces of about 30 kJ/g-atom, TiAl3 is the only phase which is formed as long as the reactants are not consumed. The critical thickness beyond which a second phase is formed is larger than 100 μm. We found that the formation of TiAl3 takes place by nucleation and growth, demonstrating that the driving force available for first-phase formation is considerably reduced by a preceding formation of solid solutions. Furthermore, we observed that nucleation continues at later stages, indicating that non-equilibrium conditions are maintained which are possibly influenced by grain-boundary diffusion. However, the phase selection is determined by the different growth velocities, being much higher for TiAl3 than for all other phases.
Publisher
Springer Science and Business Media LLC
Cited by
29 articles.
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