High temperature damping behavior of as-deformed Mg matrix influenced by micron and submicron SiCp

In this paper, the high temperature damping behavior of as-deformed micron and submicron SiCp/AZ91 composite was investigated as compared with monolithic AZ91 alloy. The damping mechanism was analyzed and verified with the help of microstructure observation at elevated temperatures. Results show that the damping capacity of AZ91 alloy and its composites intensively depend on the measuring temperature. The micron SiCp/AZ91 composite exhibits the best damping capacity at 25–300 °C, while the AZ91 alloy shows better damping capacity as the temperature exceeds 300 °C. Two peaks are found in the damping-temperature curves. The one occurring at ~150 °C is thought of as a grain boundary peak, while the second one (existing at 300–350 °C) is recognized as a recrystallization peak. Activation energy H of the first peak is calculated. It is found that 10 vol% micron SiCp lowers the H value slightly, while only 1 vol% submicron SiCp can improve the H value obviously and the reasons are analyzed. Stabilized microstructure caused by the pinning effect of submicron SiCp dense zones and micron SiCp is thought to be responsible for the lower Q−1 value of the second peak in AZ91 alloy.