Study Of Damping Capacity And Its Mechanism Of Magnesium Alloys

Magnesium alloys has good casting capacity and damping capacity. But the damping capacity and noise absorption capacity has not been paid enough attention in engineering application. One of the important reasons is that magnesium alloys used in transportation industry is mainly aimed at reducing weight. Further research on the damping capacity of magnesium alloys should be performed to make magnesium alloys widely used in machine manufacture as high damping materials. Experts from inland and overseas have made a lot of research to reveal the mechanism of damping capacity in magnesium alloys and have brought forward different theories. Those damping theories could explain some phenomena of damping in magnesium alloys, but most of them separately researched on the interaction effects between dislocations and point defects and did not consider interaction of the other factors in the alloys. This work try to evaluate the damping capacity of magnesium alloys in application and make further research to reveal the essence of damping in magnesium alloys.Firstly, in order to have a clear understand of damping capacity of magnesium alloys in application, we used the Vibration Mode Analysis method to investigate the dynamic mechanical character of engine tank made of magnesium alloys and aluminum alloys. The comparison revealed that the tank made of magnesium alloy had better rigidity and stability and better shock absorption capacity in appliance.Secondly, based on former research works, we developed a set of damping test apparatus, which could measure the damping capacity of materials at free vibration state. Then, solution heat treatment and aging heat treatment after solution of different time were performed on AZ91D samples .The damping capacity of those samples were measured using the self-developed apparatus and got the Damping-Strain amplitude curves. There was great change on the damping capacity after heat treatment. The microstructure and the ingredients distribution in AZ91D of those samples were investigated to analyze the reasons of those changes.Lastly, we got the Damping-Temperature and Damping-Temperature-Frequency curve of those heat treatment samples and found a damping peak around 155～205℃ and another damping peak around 300～325℃. Activation energy of the damping peak were calculated to analyze possible reasons of the two damping peak.