Microstructure and damping properties of ZK60 magnesium alloy sheet after heat treatment were investigated by means of metalloscope and multifunctional internal friction meter. The results reveal that the change of grain size is absent after T5 heat treatment

while it is increased significantly after T4 or T6 heat treatment. In addition

the content of the second phase is increased significantly after T5 and T6 heat treatment. There exist two damping peaks in the temperature-damping spectra of T4 and T6 heat treatment

where P

1

peak is grain boundary internal consumption peak

and P

2

peak is recrystallization damping peak

and P

1

peak is inhibited in rolling state and T5 heat treatment

while P

2

peak is higher than that in T4 and T6 heat treatment because of many substructures. Moreover

the second phase particles have a certain strengthening effect on grain boundary

which leads to the increase of activation energy in grain boundary.