The effects of aging treatment at 190 degrees C for 6, 12, 18, and 36 h on the microstructure, mechanical properties, and damping properties of multipass rolled Mg-1.2Al-0.4Ca-0.3Mn-0.3Zn magnesium alloy plates were investigated. The results show that after aging treatment, the number of precipitated phases in the Mg-1.2Al-0.4Ca-0.3Mn-0.3Zn alloy increases, which are mainly Al2Mn and Al-Ca phases, and are concentrated at the grain boundaries. The size of the second phase at the grain boundaries grew as the elongation time increased, and some of the second phase underwent reverse dissolution, which reduced the alloy's characteristics. The Mg-1.2Al-0.4Ca-0.3Mn-0.3Zn alloy plates after multipass rolling were aged at 190 degrees C/6 h to obtain the best overall mechanical properties, with tensile strength and elongation of 224.2 MPa and 14.2%. In the low strain amplitude region, the damping of the material mainly comes from the friction between the defects, and there is no significant change in the damping value. In the high strain amplitude region, the Q1 values in the rolled state and aging time of 6, 12, 18, and 36 h at a strain amplitude of 0.1% were 0.01083, 0.01741, 0.01202, 0.01298, and 0.01467. The second phase precipitated by the aging treatment acted as a strong pinning point resulting in dislocations that were not easy to be de-pinned enhanced the damping performance.
