Low-Temperature Internal Friction in Face-Centered Cubic and Body-Centered Cubic Metals

Abstract

Data on the anelasticity produced by plastic deformation in various face-centered cubic and body-centered cubic pure metals and alloys are reported. Fcc materials studied at temperatures from 4.2\ifmmode^\circ\else\textdegree\fi{}K to 300\ifmmode^\circ\else\textdegree\fi{}K include Cu, Al, and Al-0.25 at.% Cu. Bcc systems are Fe, Nb, and $\ensuremath{\beta}$ brass. Bordoni peaks are observed in Cu and Al in agreement with previous work, but are not found in either strain aged Al-Cu alloys or pure Fe. A peak observed in Nb at 173\ifmmode^\circ\else\textdegree\fi{}K is not believed to be a Bordoni type. Unexplained low-temperature internal friction peaks are also observed in $\ensuremath{\beta}$ brass. A new mechanism is proposed for dislocation relaxation in which the essential feature is the thermally activated motion of paired partial dislocations between vacancy pinning points. It is in general qualitative accord with experiment, and permits semiquantitative evaluation of all essential parameters.