Abstract: Effect of aging treatment on microstructure, mechanical properties and damping properties of Mg-1.2Al-0.4Ca-0.3Mn-0.3Zn magnesium alloy plates after multi-pass rolling+annealing was investigated by means of optical microscope (OM), dynamic thermal analyzer, X-ray diffractor (XRD), tensile testing machine and scanning electron microscope (SEM). The results show that the average grain size of the annealed alloy is 4.82 μm with a small amount of twin, and the tensile strength and elongation are 212.09 MPa and 9.87%, respectively. When the aging temperature is 150 ℃, the average grain size is 4.95 μm, the tensile strength is 207.84 MPa, and the elongation is 6.58%. When the aging temperature is 190 ℃, the average grain size is 4.05 μm, the grains are fine and uniformly distributed and the second phases such as Al-Mn, Al-Ca and Mg₂Ca appear at the grain boundaries of the alloy, which results in good mechanical properties, with tensile strength of 224.21 MPa and elongation of 14.2%. In the low strain amplitude region (ε≤0.1%), the damping values of the alloy rolled, annealed, 150 ℃ aged and 190 ℃ aged are not significantly different. While, in the high strain amplitude region (ε>0.1%), the damping properties of the 190 ℃ aged alloy is the best. In the low-temperature range of 35-150 ℃, the damping peaks of the alloy in four states are all caused by dislocation slip, but in the high temperature range of 150-375 ℃, the damping peak of the rolled state alloy is the highest, and the damping peaks of the rolled, annealed and 150 ℃ aged alloys are caused by dislocation slip, and the damping peak of the 190 ℃ aged alloy is obtained by the superposition of the dislocation slip and the sliding of the grain boundary.

Key words: aging temperature, microstructure, damping properties, Mg-Al-Ca-Mn-Zn alloy