The temperature spectrum of internal friction was studied using a macroscopic graphite-particle reinforced Zn-Al metal-matrix composite. Specimens with up to 51vol% of macroscopic particles (0.8mm in diameter) were prepared by using an air-pressure infiltration process. Internal friction and relative dynamic modulus measurements were performed, for maximum surface shear-strains of 2 x 10-5, by using a multi-functional internal friction apparatus at 0.5, 1.0, 2.0 or 3.0Hz; from room temperature to the equilibrium eutectoid isotherm of 277C. At low frequencies and low temperatures, a distinct internal friction peak was found in the internal friction versus temperature curve. The relative dynamic modulus decreased rapidly at this peak. The peak was a grain-boundary one, and was associated with the diffusive grain boundary of Al/Al. Its activation energy was 1.13eV, and the pre-exponential factor was 10-14s.

Grain Boundary Peak in Macroscopic Graphite Particulates Reinforced Zn-Al Metal Matrix Composite. J.N.Wei, Y.L.Li, S.H.Song, G.C.Ji, M.L.Ma, D.Q.Zhang, F.S.Han: Physica Status Solidi A, 2004, 201[5], 923-8