Abstract
Plastic deformation of crystalline materials is governed by the features of stress-driven motion of dislocations. In the case of irradiated steels subject to applied stresses, small dislocation loops as well as precipitates are known to interfere with the dislocation motion, leading to an increased yield stress as compared to pure crystals. We study the combined effect of precipitates and interstitial glissile frac{{bf{1}}}{{bf{2}}}langle {bf{111}}rangle dislocation loops on the yield stress of iron, using large-scale three-dimensional discrete dislocation dynamics simulations. Precipitates are included in the simulations using our recent multi-scale implementation [A. Lehtinen et al., Phys. Rev. E 93 (2016) 013309], where the strengths and pinning mechanisms of the precipitates are determined from molecular dynamics simulations. In the simulations we observe dislocations overcoming precipitates with an atypical Orowan mechanism which results from pencil-glide of screw segments in iron. Even if the interaction mechanisms with dislocations are quite different, our results suggest that in relative terms, precipitates and loops of similar sizes contribute equally to the yield stress in multi-slip conditions.
Highlights
Dislocation loops on the yield stress of iron, using large-scale three-dimensional discrete dislocation dynamics simulations
Experimental studies on pristine and irradiated metals have shown complex micro- and nanostructure which in addition to dislocations include voids[1,2,3], bubbles[4], interstitial clusters[3,5], precipitates[4,6,7,8,9,10] and dislocation loops[1,2,4,11]. These different defects serve as obstacles for dislocation motion, and mechanical tests on irradiated steel samples have shown that irradiation will increase the yield strength, but at the same time the yield drop becomes larger in magnitude[5,12]
Our interest is in the yielding process of BCC iron at elevated temperatures, and for this reason dislocation mobility parameters and the elastic constants were taken from molecular dynamics (MD) simulations at the temperature of 750 K, i.e., close to the typical operating temperatures of nuclear reactors
Summary
Dislocation loops on the yield stress of iron, using large-scale three-dimensional discrete dislocation dynamics simulations. Experimental studies on pristine and irradiated metals have shown complex micro- and nanostructure which in addition to dislocations include voids[1,2,3], bubbles[4], interstitial clusters[3,5], precipitates[4,6,7,8,9,10] and dislocation loops[1,2,4,11] These different defects serve as obstacles for dislocation motion, and mechanical tests on irradiated steel samples have shown that irradiation will increase the yield strength, but at the same time the yield drop becomes larger in magnitude[5,12]. These simulations show dislocations bypassing these strong obstacles with www.nature.com/scientificreports/
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