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Effect of Twin Boundary Orientation on the Mechanical Properties of Bicrystalline Copper Micropillars

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Document pages: 27 pages

Abstract: Twin boundaries (TBs) constitute a special type of symmetric grain boundary (GB). TBs influence plastic deformation in a complex manner. They not only act as dislocation obstacles but can also accommodate twinning dislocations (TDs) whose motion enables twin boundary migration as an alternative deformation mechanism. Exploiting this dual effect offers interesting perspectives in view of designing materials that combine high strength and ductility. In the present work,we propose a model for dislocation-TB interactions in the framework of discrete dislocation dynamics (DDD) simulations, which we use to investigate the mechanical properties of bicrystalline copper micropillars containing a TB. We systematically investigate how the compressive response depends on the orientation of the TB with respect to the micropillar cross section. The simulations show significant strengthening effects for TB orientation angles less than 45º, where the interaction between mixed dislocations and TBs plays an important role.For angles larger than 45º, the interaction between screw dislocations and TB dominates, leading to weak strengthening. At 45º, dislocations on the dominant slip systems glide parallel to the TB and no strengthening is observed.

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