Transient solute drag and strain aging of dislocations

• Published in: Acta materialia Vol. 193; no. C; pp. 182 - 190
• Main Authors: Epperly, E.N., Sills, R.B.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01-07-2020; Elsevier
• Subjects: Cottrell atmospheres; Dislocation dynamics; MATERIALS SCIENCE; Solute strengthening; Dislocation dynamics; Solute strengthening; Cottrell atmospheres
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2020.03.031

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The transient drag force exerted by mobile solutes on a moving dislocation is computed using continuum theory. These mobile solutes form so-called Cottrell atmospheres around dislocations during static and dynamic strain aging. We evaluate the evolution of the drag force exerted by the atmosphere under two velocity time-histories: impulsive acceleration to a chosen velocity and a constant acceleration rate. A particular focus is on the conditions under which the stationary limit assumed by theories of dynamic strain aging is obeyed. According to our results, two conditions—one on the dislocation velocity and one on the acceleration rate—must be satisfied for the stationary limit to hold. Using the Orowan relation and a line tension model, we obtain estimates for the temperature, stress, strain rate, and dislocation density regimes where the stationary limit is valid, and compare these results with experiments for a few material systems.