Abstract
Internal damping after thermal treatment has been studied in Mg-Nd alloy matrix reinforced by short Saffile fibres. The amplitude dependence of the logarithmic decrement reflects changes in the composite microstructure due to thermal stresses induced by a large difference in thermal expansion coefficient between matrix and reinforcement. These thermal stresses may be accommodated inducing new dislocations in the matrix. The newly created dislocations can interact with solute atoms in the matrix alloy. Precipitation processes occurring at elevated temperatures in the matrix may vary the number of free solute atoms and then also the lengths of dislocation segments that vibrate after passing of sound wave. Estimated experimental results can be explained very well using the Granato and Lucke model including a possibility of thermally activated breakaway of dislocation segments from solute atoms.

Key words
internal damping, composite, magnesium alloy, dislocation, precipitation, logarithmic decrement

Full text not available