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Understanding Grain Boundary And Stress Concentration Effects On Strengthening Mechanisms In Nanotwinned Metals, Qiongjiali Fang
Understanding Grain Boundary And Stress Concentration Effects On Strengthening Mechanisms In Nanotwinned Metals, Qiongjiali Fang
Graduate College Dissertations and Theses
The superior strength and large tensile plasticity of nanotwinned (nt) face-centered-cubic metals have been explained by different twin size-dependent dislocation mechanisms and their inherent strengthening/softening effects. Grain boundary (GB) plasticity generally induces softening in nanocrystalline metals; however, our current understanding of the role of GBs in plasticity of nt metals remains limited. Contradicting reports exist in literature on how twin size influences stress concentration at GB – twin boundary (TB) intersections, which facilitates dislocation nucleation. In this thesis, molecular dynamics (MD) simulations and finite element analysis (FEA) were used to study the effects of GB plasticity and stress concentrations, on …
The Interaction Mechanisms Of A Screw Dislocation With A Defective Coherent Twin Boundary In Copper, Qiongjiali Fang
The Interaction Mechanisms Of A Screw Dislocation With A Defective Coherent Twin Boundary In Copper, Qiongjiali Fang
Graduate College Dissertations and Theses
Σ3{111} coherent twin boundary (CTB) in face-centered-cubic (FCC) metals and alloys have been regarded as an efficient way to simultaneously increase strength and ductility at the nanoscale. Extensive study of dislocation-CTB interaction has been carried out by a combination of computer simulations, experiments and continuum theory. Most of them, however, are based on the perfect CTB assumption. A recent study [Wang YM, Sansoz F, LaGrange T, et al. Defective twin boundaries in nanotwinned metals. Nat Mater. 2013;12(8):697-702.] has revealed the existence of intrinsic kink-like defects in CTBs of nanotwinned copper through nanodiffraction mapping technique, and has confirmed the effect of …