Hamburg 2001 – wissenschaftliches Programm
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M: Metallphysik
M 36: Nanoskalige Materialien IV
M 36.6: Fachvortrag
Freitag, 30. März 2001, 12:15–12:30, S5.3
Grain boundary phase transitions in the Cu-Bi system — •Boris Straumal1, Wolfgang Gust2, and Eric Mittemeijer2 — 1ISSP RAS, Chernogolovka, Russia — 2MPI Metallforschung, Seestr. 92, 70174 Stuttgart
The grain boundary (GB) properties depend hardly on the GB phase transitions. The GB wetting phase transitions in the two-phase area of bulk phase diagram control the penetration of a liquid phase along GBs. The GB prewetting and/or premelting phase transitions in the one-phase area of the bulk phase diagram where only the solid solution is in equilibrium lead to the formation of an equlibrium layer of a GB phase having a high diffusivity. The GB lines in the Cu-Bi bulk phase diagram are constructed both for GB arrays in polycrystals and individual GBs in bicrystals. The influence of temperature and Bi concentration on the GB segregation and GB energy is determined. It is also experimentally shown that the formation of GB layers in Cu-Bi polycrystals changes drastically their electrical resistivity. Therefore, very sensitive low-temperature measurements of the resistivity of quenched samples can be used for the study of GB phase transitions in various systems. The influence of the GB phase transitions on the properties of nanocrystalline materials are duscussed. The financial support of the INTAS Programme, Deutsche Forschungsgemeinschaft and Alexander von Humboldt Foundation is acknowledged