Low-frequency damping behavior of foamed commercially pure aluminum

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2003-01, Vol.332 (1-2), p.375-381
• Main Authors: Wei, J N, Gong, C L, Cheng, H F, Zhou, Z C, Li, Z B, Shui, J P, Han, F S
• Format: Article
• Language: English
• ISSN: 0921-5093

Experiments have been carried out to investigate the damping behavior of foamed commercially pure aluminum (FA). The FA specimens were prepared using a pressure infiltration process. The damping characterization was conducted on a multifunction internal friction apparatus (MFIFA). The internal friction (IF), as well as the relative dynamic modulus, was measured at frequencies of 0.5, 1.0 and 3.0 Hz over the temperature range of 20-400 deg C. The size of macroscopic pores is on the order of a millimeter (1.0 mm) and in large proportions, typically up to 69 vol. percent. The measured IF shows that FA has a damping capacity that is enhanced in comparison with bulk commercially pure aluminum. In particular, an IF peak was found, corresponding to a rapid drop of relative dynamic modulus (vs. temperature) in the FA specimen. The average value of the activation energy of the IF peak is approximately 1.39 plus/minus 0.03 eV. Microstructural analysis was performed using transmission electron microscopy (TEM). TEM observations showed that dislocation substructures exist near the grain boundaries. Accordingly, one can propose that such substructures, intersecting and interacting with the grain boundaries, are dragged along with the grain boundary during the viscous sliding of the boundary, so that the sliding process is limited to the appearance of this IF peak. Finally, a four-parameter mechanical model used to describe the operative damping mechanism of the IF peak in the FA is discussed in light of IF measurements and microstructural studies.