| With the development of industrialization, it is more important to reduce noise and vibration, Taking advantage of the damping properties of the high-damping structural materials is the most direct and effective method to reduce noise and vibration. The damping properties of composites could be improved by adding more interfaces and changing their structure and performance. The Al matrix composites prepared by reciprocating extrusion not only have high density, good strength, high hardness and excellent damping capacities, but also with low manufacture costs and broad application prospect. In this study, pure aluminum as the matrix and SiC or Al2O3 powder as the reinforcement were used to fabricate SiC/Al and Al2O3/Al composites with different particles content and extrusion passes by reciprocating extrusion (RE). The relation of damping behavior of the composites with different parameters such as amplitude, frequency, temperature were tested by using the Dynamic Mechanical Analyzer (DMA). The internal friction peaks and their activation energies for the composites were calculated with the experiment results. The damping behaviors of the two composites were compared and damping mechanisms were also investigated. The main conclusions are as following:1. The two Al matrix composites exhibit an excellent damping capacity prepared by RE. At room-temperature, when the strain amplitude is small (ε<2×10-6), all the two composites show high the damping capacities, and the dampiong value are higher than 0.01. The damping behaviors of the composits show distinct strain amplitude dependence. As strain amplitude is less than 0.25×10-6, the damping capacity is influenced by strain amplitude slightly. The damping capacity increases sharply when strain amplitude larger than 0.25×10-6, than it maintains constant. The damping value decreases with the increasing of the frequency, whereas the critical strain amplitude remains unchanged.2. The variety tendency of damping properties with frequency is:when frequency is lower than 3Hz, the damping capacity decrease with the increasing of frequency, which means that the damping capacity is sensitive to the frequency. However, the damping capacity is not affected when the frequency is higher than 3 Hz.3. The damping capacity increases slightly with the increasing of temperature lower than 100℃, then it increases remarkably. One wide internal friction peak appears between 150℃and 300℃for each composite. And the peak moves toward higher temperature with the frequency increase, while the damping value decreases, which indicates that the internal friction peak has the relaxation property.4. The room-temperature damping capacities of the two composites are approximately the same under a low strain amplitude. But at high strain amplitude, the damping capacity and the critical strain amplitude of the SiC/Al composite are higher than Al2O3/Al composite. The peak values of internal friction and temperature for Al2O3/Al composite are higher than that of SiC/Al composite, and the values differences between the composites are respectively 0.011 and 21℃, which indicated that Al2O3/Al composites have higher activation energy.5. At low temperature and small strain amplitude, the inherent damping and dislocation damping which resulted from thermal mismatch strain and dislocation unpinning are responsible for the damping of the composites. While at high temperature and large strain amplitude, the damping of the composites is mainly controlled by damping from dislocation pinning and interface damping which resulted from grain boundary relaxation the micro-sliding of the interface between the reinforcement and the matrix.
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