Partial dislocations interactions with symmetrical-tilt grain boundaries containing e-structural units: Local stress analysis with molecular dynamics
Mohan, Sivasakthya
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https://hdl.handle.net/2142/101206
Description
Title
Partial dislocations interactions with symmetrical-tilt grain boundaries containing e-structural units: Local stress analysis with molecular dynamics
Author(s)
Mohan, Sivasakthya
Issue Date
2018-04-24
Director of Research (if dissertation) or Advisor (if thesis)
Chew, Huck Beng
Department of Study
Aerospace Engineering
Discipline
Aerospace Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Structural unit model
dislocation interaction
grain boundary
local stress fields
molecular dynamics simulations
Abstract
Grain boundaries containing porous E-structural units (SUs) are known to readily emit dislocations under tension. This work establishes a correlation between the atomic structure, evolution of interfacial stresses and slip transfer mechanisms at grain boundaries containing E-structural units. Using molecular dynamics simulations, we study the interactions between <112>{111} Shockley partial dislocations and <110> symmetrical-tilt Ni grain boundaries containing E-SUs. We show that the incoming Shockley partials can be accommodated by porous E-SUs along the grain boundary. However, the partial-absorption process disrupts the short-range interactions of incipient dislocations along the boundary, which generates high local tensile and compressive stress regimes emanating from the impingement site. For the favored Σ9(221) grain boundary comprising only of E-SUs, Shockley partials originating from E-SUs located within the tensile stress regime are subsequently re-emitted into the neighboring grain. We demonstrate that the critical strength for re-emission of Shockley partials can be delineated into contributions from tensile stress generated by partial-absorption, intrinsic grain boundary tractions, as well as external loading. In the presence of other types of SUs, the incoming Shockley partial can also be transmitted through the boundary or be stably absorbed by the boundary with no subsequent re-emission, depending on the impingement site.
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