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Grain Boundary Peak in a Foamed Zn-Al Eutectoid Alloy

We study experimentally the temperature spectra of internal friction (IF) and relative dynamic modulus (RDM) in a foamed Zn-Al eutectoid alloy. The specimens with macroscopic pores (0.5-1.0 mm) were prepared in an air pressure infiltration process. The damping behaviour of the foamed Zn-Al eutectoid alloy is characterized by IF. The IF and RDM measurements at a maximum surface shear strain of 20×10-6 have been made by using a multi-function internal friction apparatus at frequencies of 0.5, 1.0 and 3.0 Hz from room temperature to the equilibrium eutectoid isotherm of 277 °C, while continuously changing the temperature cycle. At low frequency, an IF peak is observed in the IF temperature curve. The IF peak is of a grain boundary, which is associated with the diffusive flux on a crystalline boundary between the like-phases of Al/Al. Its activation energy has been calculated to be 1.10±0.06 eV and the pre-exponential factor τ0 is 10-14 s in the IF measurements.