Time: 04:00 p.m.
Place: Seminar room IC 04-408
Pavel Lejcek, Department of Functional Materials, Academy of Sciences, Prague, Czech Republic
One of the most dangerous technical failures of materials is intergranular brittle fracture (temper embrittlement) as it proceeds very quickly and its appearance is often hardly predictable. It is known that this phenomenon is closely related to the chemistry (solute segregation) of grain boundaries and free surfaces. To elucidate the effect of individual solutes on embrittlement of various materials such as steels and nickel-base superalloys, grain boundary and surface segregations were extensively studied in many laboratories throughout the world. In this talk our effort in this field is summarized concerning (1) Anisotropy of grain boundary segregation and classification of high angle grain boundaries; (2) Grain boundary segregation diagram; (3) Enthalpy/entropy compensation effect; (4) Prediction of grain boundary segregation; and (5) Segregation volume. Finally, calculated data and experimental results on grain boundary segregation and embrittlement will also be compared and the differences between them will be discussed.