Funct. Mater. 2015; 22 (3): 293-298.
Influence of elastic stresses and temperature on the dislocation unpinning from the stoppers in KCl crystals
A. Beketov Kharkiv National University of Urban Economy, 12 Revolution St., 61002 Kharkiv, Ukraine
Impulse echo-method was applied to investigate, in the temperature range from 300 to 430 K at 7.5 MGz frequency, the dislocation absorption αd(σ) in KCl crystals as a function of statistic loading in the quasi-elastic strain range. It has been found that the temperature increase at stresses σ < σt (σt is the yield strength of a crystal) leads to the intensive dislocation unpinning). Consequently, concentration of stoppers, controlling their motion, sharply decreases and the effective length of oscillating dislocation segments increases. As a result of the experimental data processing the energy of the impurity atom binding with dislocation U0 and quantity L characterizing a mean size of the dislocation cell was calculated. The experimental results were discussed within the framework of known dislocation theories.
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