A high-temperature relaxation peak (H.T.P.) has been observed at T(°K) ≥ 0·5 Tm in the damping spectra of pure silver and pure copper, in large-grained wire specimens. The relaxation strength of the peak in copper was ∼ 8 times larger than that for silver, though the incidence of “bamboo” grain boundaries was comparable. The occurrence of the peak was associated with the development of a “bamboo” grain structure and was attributed to the reversible shear or glide of boundaries at high temperatures, coupled with the movement of boundary jogs. Trace impurities rapidly suppressed the peak, this phenomenon being explained in terms of the impurity atoms poisoning the jogs and inhibiting their movement.
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