Temperature damping capacity and microstructure evolution of Mg–Al–Zn–Sn alloy

The temperature damping capacities of Mg-3Al-1Zn-xSn (x=3, 6, 9) alloys were investigated using a Dynamic Mechanical Thermal Analyzer (DMA) under varying loading frequencies and Sn concentrations. The addition of Sn resulted in a leftward shift of the P1 dislocation damping peak around 80 °C and a rightward shift of the P3 peak around 220 °C, which were attributed to the second phases in the vicinity of grain boundaries. By combining the Granato-Lücke model and the Peguin model, the damping curves were analyzed, and the temperature damping mechanism of Mg-3Al-1Zn-xSn alloy was summarized. Before 220 °C, the addition of Sn significantly enhanced the damping capacity at different frequencies, which was attributed to the elevated quantity of point defects and second phase precipitates. The damping mechanism was dominated by microplastic internal friction in the later part of the test. There is a negative correlation between frequency and damping. The observation of microstructures suggested that dynamic recrystallization, twins, and the increasing in Schmid factors values of non-basal slip systems were the sources of the microplastic damping capacity. The dynamic recrystallization mechanism was analyzed and it was identified that the main type of recrystallization at high temperatures is continuous dynamic recrystallization caused by cyclic loading.