Study Of Damping Capacities In Silicon Carbon Whisker Reinforced Magnesium Matrix Composite

Commercial pure Mg, AZ91D and Mg-1%Si were chosen as the matrix alloys, the silicon carbon whisker was used as the reinforcement, 20%-SiCw/Mg,20%SiCw/Mg-Si,20%SiCw/AZ91D and 30%SiCw/Mg-Si were fabricated by squeeze cast method; 20%SiCw/Mg-Si and 20%SiCw/AZ91D were extruded at the temperature of 648K. The mechanical properties were tested by tensile test, the damping capacities were measured by dynamic mechanical analyzer (DMA) Q-800 type, the microstructures of the matrix alloys were observed by Optical Micrograph (OM), the distribution of the whiskers before and after hot extrusion and the tensile fracture were observed by Scanner Electron Microscope (SEM), the microstructure of the reinforcement/matrix interface and the configuration of dislocations in the composites were investigated by Transmission Electron Microscope (TEM) observation.The results showed that the reinforcement/matrix interfaces of the composites were similar. The mechanical properties of the composites were depended on the mechanical and casting properties of the matrix alloys. The hot extrusion resulted in that the distribution of the whiskers was along the hot extrusion direction, and the mechanical properties of the materials were improved.The investigation of the strain amplitude dependent damping capacity indicated that the curve showed strain amplitude dependent and independent regions. The curves were well interpreted by G-L dislocation model. The investigation of the temperature dependent damping capacity showed that the damping capacity increased when the temperature increased or the frequency decreased. Two peaks were found at 120oC,220oC respectively, and we concluded that the first peak was resulted from the movements of the dislocation on the base-face, and the second peak was induced by the micro-slide of the reinforcement/matrix interface.The study of the damping capacity after the hot extrusion showed that the relationships between the damping capacity and the strain amplitude, temperature, frequency had no change. The damping capacity was decreased at the room...