Mechanical loss internal friction experiments were performed on monocrystalline and polycrystalline samples, containing incoherent Si particles of various sizes and spacings, as a function of the pre-strain. The resultant internal function spectra were correlated with microstructural observations. A loss maximum at about 450K (and a frequency of 1Hz), and especially its activation enthalpy of 1.14eV, could be explained by a dislocation model which considered an enhanced transverse diffusivity of solute atoms in the vicinity of the dislocation core. The model was also shown to be in agreement with published data on Al-Si, Al-Mg, Cu-Si and Cu-Al alloys. It was proposed that, in many cases, the internal friction maxima (even when characterized by a so-called low activation enthalpy) was not necessarily due to grain boundary or particle effects, but could be explained by core diffusion effects upon the solute drag which impeded dislocation motion.

A.Pichler, M.Weller, E.Arzt: Acta Metallurgica et Materialia, 1994, 42[11], 3801-9