HIGH-TEMPERATURE INTERNAL-FRICTION PEAKS IN DILUTE AL-SN POLYCRYSTALS

Two kinds of internal friction peaks denoted as P1 and P2 located at temperatures higher than that of the grain boundary peak (GBP) are observed in Al–0.008, 0.0135 and 0.067 wt% Sn polycrystalline specimes. The one appearing in Al–0.008 and 0.0135 wt% Sn specimens is found to have a growth‐decline relation with GBP, it will only appear in measurements with descending temperatures and its position and strength are very sensitive to annealing. This peak is thought to be contributed by those grain boundaries preferentially segregated with lots of Sn atoms. However, the one appearing obviously in Al–0.067 wt% Sn specimen only when the annealing temperature is higher than 600 °C shows less relationship with GBP, it ranges at about 480 °C and is unsensitive to the way of measurement (ascending or descending temperatures). This peak seems to be caused by sliding of coarse grain boundaries with AlSn particles. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA