Investigation of interaction between a dislocation and a Cl − or I − ion in NaBr single crystals

Abstract

Strain rate cycling tests were carried out under superimposition of oscillatory stress for NaBr single crystals doped with Cl − or I −. The relationship between strain rate sensitivity (SRS) of flow stress and stress decrement Δ τ due to superimposition of oscillatory stress is stair-like and consists of three regions, i.e. two plateau regions at low and high Δ τ and a middle region where the SRS decreases with increasing Δ τ. The stress τ p at the first bending point between the first plateau region and the middle one, which is considered to be the effective stress due to Cl − or I −, decreases with increasing temperature. The difference (SRS p) between the SRS at the first and second plateau regions decreases with temperature. The SRS p is attributed to Cl − or I −. The interaction energies between a dislocation and a Cl − or I − are 0.40 or 0.47 eV in NaBr assuming that the force–distance profile is expressed by the Cottrell–Bilby relation. The force–distance profile is different from that for KCl:Br −.