Short-range reordering of heavy interstitials in Ta, Nb, and Fe during relaxation and static strain aging

Using isothermic relaxation tests and internal friction, the mechanism of the Snoek type recording of heavy interstitials (oxygen, carbon, nitrogen) in tantalum, niobium, and iron is studied. The kinetics and the amplitude of the stress relaxation conform to the general theory of the inelastic dipole due to Berry and Nowick. In an identical temperature range and on the same solid solutions, the effect of static strain aging is investigated on the yield point effect represented by the parameter Δσ/σ. It is shown that, in accordance with the Schoeck and Seeger model, the first period of aging is due to the reorientation at short distance of the interstitials in the dislocation stress field. In fact the identification of the two phenomena leads to the relation Δσ(t)/σ = αΔ/sub s/(t), with α close to the unity, which is in accordance with experiments. (author)