Abstract: The internal friction (IF) of Mg-0.6%Zr alloy is measured in the present study and two IF peaks of (P₁ (97℃, 1 Hz) and P₂ (230 ℃, 1 Hz)) are found, respectively. It is shown that the novel P₁ peak is frequency independent and the peak temperature increased with the increase of strain amplitude or heating rate. P₁ peak could be repressed by the reheating-up measurements and represented by heat treatment. The mechanism of P₁ peak is clarified by optical microscope (OM) and transmission electron microscope (TEM) observation, and considered to be caused by the creation and expansion of dislocations during plastic deformation. The P₂ peak is a thermally activated relaxation IF peak, and activation energy is 1.46~eV, which is caused by the relaxation of the grain boundaries in Mg-0.6%Zr alloy.

Key words: Internal friction, Dislocation, Plastic deformation, Grain boundaries relaxation