Snoek relaxation in a copper-precipitated alloy steel

We studied the effect of thermal embrittlement of a steel containing 1.29 at% copper on the Snoek relaxation. The hardness increased with isothermal aging at 723 K and decreased after showing a maximum. Hardness change is governed by bcc–copper clusters precipitated from the ferrite iron crystal. Using a forced-vibration torsion-pendulum method, we studied the internal-friction spectrum and recovery of the maximum relaxation strength after quenching from 723 K. We observed a broad nonsymmetrical spectrum which apparently consists of three Debye peaks. With higher hardness, the recovery rate increased. We interpreted our results in terms of Nowickʹs theory of interstitial/substitutional-solute interactions. For recovery, we used the Cottrell–Bilby–Harper t2/3 model.