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Original Articles

Analysis of temperature and concentration dependence of flow stress in KCl–KBr single crystals with special reference to solute distribution

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Pages 1811-1820 | Received 30 Jun 2006, Accepted 20 Oct 2006, Published online: 12 Mar 2007
 

Abstract

Available data on the temperature and concentration dependence of critical resolved shear stress (CRSS) of KCl–KBr solid-solution crystals containing 9, 17, 27 and 45 mol% KBr in the temperature range 77–230 K have been analyzed within the framework of the kink-pair nucleation model of plastic flow in solid- solution crystals. It is found that CRSS τ decreases with increasing temperature T in accordance with the model relation lnτ = A − BT, where A and B are positive constants. The CRSS τ at a given temperature depends on solute concentration c as τ ∝ cp , where exponent p has a value between 0.33 and 0.57 as temperature T rises from 0 to 230 K. The model parameter W o, i.e. binding energy between the edge-dislocation segment L o involved in the unit activation process and the solute atoms close to it (T → 0 K), which is inversely proportional to B, increases with solute concentration c monotonically as W o ∝ c 0.33 up to a critical value c m = 35 mol% KBr, which is in reasonable agreement with the model prediction W o ∝ c 0.25. However, W o decreases with an increase in c beyond c m, which indicates somewhat ordered distribution of solute in the host lattice of concentrated KCl–KBr solid solutions with c > c m.

Acknowledgement

One of us (M. Z. Butt) is grateful to the Pakistan Council for Science and Technology, Government of Pakistan, Islamabad for financial assistance under the Research Productivity Allowance Scheme.

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