Abstract
This paper describes the influence of thermal cycling on the damping behaviour of a Mg - 26.0 vol.% Al₂O₃ composite. The composite was prepared by squeeze casting. The logarithmic decrement as the characteristics of the process responsible for the damping behaviour was measured after ten thermal cycles between room temperature and an upper temperature. The upper temperature was varied in the interval from 100 to 450 °C. The strain dependence of the logarithmic decrement can be divided into two regions. A region of strain amplitude independent damping at low strains is followed by a region with amplitude dependent damping at higher strains. The damping level in the strain amplitude independent region depends weakly on the upper temperature of the cycle whereas the values of the logarithmic decrement in the strain amplitude dependent region depend very sensitively on the upper temperature of the cycles. The observed experiment data can be explained considering creation of new dislocations during thermal cycling.

Key words
thermal cycling, Mg - Al₂O₃ composite, logarithmic decrement, damping behaviour

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