Nature of the internal friction peak in cold-worked dilute aluminum alloys

The origin of the internal friction peak observed for cold-worked aluminum alloys has been studied by the low-frequency torsion pendulum technique. In ternal friction has been measured for pure aluminum of various grades and d ilute alloys containing Li, Mg, Si, Fe, Ga or Ge. The peak appears at 210 K (for similar to 1 Hz) for unalloyed materials, as well as for the alloys, among which the peak is the largest for those with Si. The peak observed fo r "pure" aluminum is probably due to interaction between dislocations and i mpurities, such as Si. The peak exhibits asymmetrical shape when measured a s a function of temperature (sharper on the low temperature side), and the activation energy and the preexponential factor of the relaxation rate tau( -1) are anomalously large. These features are discussed in the light of phe nomenological models of anelastic relaxation for systems where anelastic el ements interact strongly with each other.