Abstract
Ultrafine-grained magnesium (UFG-Mg) samples were prepared by milling of powder in an inert atmosphere and subsequent compacted and hot extruded. The linear grain size estimated by X-ray line profile analysis was between 100 and 150 nm.
Two developed peaks in the internal friction spectrum were obtained at temperatures about 375 K and about 631 K (1 Hz). The low temperature peak has dislocation origin, while the high temperature peak is conditioned by the grain boundary sliding.
Compression tests were performed between room temperature and 300 degrees C. The yield stress as well as the maximum stress decreases with increasing temperature.
The dislocation substructure of deformed samples was investigated by the high resolution X-ray diffraction peak profile analysis. The influence of cyclic bending on the damping behaviour of UFG-Mg was determined at room temperature.
Nucleation and growth of cracks were manifested by a rapid increase of damping with increasing number of cycles.