Authors: Dong Uk Kim, Seong Gyoon Kim, Won Tae Kim, Jae Hyung Cho, Heung Nam Han, Pil Ryung Cha
Abstract: In this presentation, a novel phase field grain growth model combined with a micro-elasticity effect including elastic anisotropy and inhomogeity is presented to demonstrate the effect of micro-elasticity on grain growth and texture evolution. We report on texture evolution and abnormal grain growth induced by external elastic load from the viewpoint of micro-elasticity and first demonstrate that the previous mechanism (macroscopic viewpoint) on the effect of external elastic load on grain growth does not work in strain-controlled system. In contrast to the macro-elastic descriptions, strong localization of strain energy density and inhomogeneous distribution even inside grains are observed. Moreover, elastically soft grains with a higher strain energy density grow at the expense of the elastically hard grains to reduce the total strain energy. It is observed that strong <100>//ND fiber texture was developed in poly-crystalline Cu with initial random texture by biaxial external strain while <111>//ND fiber texture evolved in biaxial external stress condition. Even, grain growth of <100>//ND textured grains is occurred as abnormal grain growth when <100>//ND textured grains are surrounded by <111>//ND fiber textured grains.
1590
Authors: Kyung Jun Ko, Pil Ryung Cha, Jong Tae Park, Jae Kwan Kim, Nong Moon Hwang
Abstract: Phase-field model (PFM) in multiple orientation fields was used to simulate the grain
growth in three-dimensions (3-D) for isotropic and anisotropic grain boundary energy. In the
simulation, the polycrystalline microstructure was described by a set of non-conserved order
parameters and each order parameter describes each orientation of grains. For isotropic grain
boundary energy, the simulation showed the microstructure evolution of normal grain growth. For
anisotropic grain boundary energy, however, the simulation showed that certain grains which share a
high fraction of low energy grain boundaries with other grains have a high probability to grow by
wetting along triple junctions and can grow abnormally with a growth advantage of solid-state
wetting. The PFM simulation shows the realistic microstructural evolution of island and peninsular
grains during abnormal grain growth by solid-state wetting.
1101
Authors: Kyung Jun Ko, Pil Ryung Cha, Jong Tae Park, Jae Kwan Kim, Nong Moon Hwang
Abstract: Abnormal grain growth (AGG) takes place in many metallic systems especially after
recrystallization of deformed polycrystals. A famous example of AGG in metallic system is the Goss
texture in Fe-3%Si steel. During high temperature annealing of Fe-3%Si sheet, a few near Goss {110}
<001> grains grow exclusively fast and consume the matrix grains. Therefore, the grains which have
near Goss orientation have special advantage over other grains. As a new approach to the growth
advantage of AGG, we suggested the solid-state wetting mechanism, where a grain wets or penetrates
the grain boundary or the triple junction of its neighboring grains. The solid-state wetting mechanism
for the evolution of the Goss texture in Fe-3%Si steel was studied experimentally and by phase-field
model (PFM) simulation.
65
Authors: Kyung Soo Kim, Seung Cheol Lee, Kwang Real Lee, Pil Ryung Cha
Abstract: Developments of tetrahedral amorphous carbon (ta-C) films having low residual
compressive stress are essential to extend the applicability of the films. The annealing of the ta-C
films was known to be an effective way for the reduction the stress of the films. However, the effects
of annealing on the atomic structure of ta-C films have not been fully understood. The atomic
structure changes by the annealing were studied using molecular dynamics simulation. The
simulation showed that the annealing caused an increase of the atomic volume of ta-C film, which
explained the stress reduction partially. However, the tendency of the stress reduction was different to
high and low stress films. The annealing substantially reduced the stresses of high stress films
compared to those of low stress films. Atomic structure analysis showed that the reason for the
asymmetric stress reduction resulted from the relaxation of highly distorted bonds that existed in
as-deposited films.
1685
Authors: Jin You Kim, Jong Kyu Yoon, Yoo Chan Kim, Hyunn Kwang Suck, Ki Bae Kim, Pil Ryung Cha
Abstract: We present a phase field model for coherent phase transition and its application to the
self-assembled arrangement of second phase particles in coherent phase transition. The model
developed here is free from the interface instability due to the contribution of chemical free energy
and correctly describes elastically inhomogeneous system. It is observed that coherent misfit strain
and anisotropy of elastic constants induce the interface instability that brings about the particle
splitting and the self-assembled alignment of second phase particles. Their arrangement to the
elastically soft direction occurs only in the system where the elastic contant of the precipitates is larger
than that of the matrix phase.
583
Abstract: We present the linear stability analysis for the epitaxial thin film growth on the vicinal
surface of strained Si and the growth mode diagrams of the epitaxial growth under various operation
conditions. Competition between step-step elastic interactions and the asymmetry of incorporation of
adatoms from the terraces to step edge is considered. Force monopoles at steps and their interaction
lead to it on the vicinal surface while kinetic asymmetry of the adatom incorporation at steps due to
Ehrlich-Schwoebel barrier prevents the step bunching instability. Growth mode on the vicinal surface
is determined by the competition between elastic step-step interactions and Ehrlich-Schwoebel
barrier.
547
Authors: Kyung Jun Ko, Pil Ryung Cha, Nong Moon Hwang
2557
Authors: Jin You Kim, Dong Hee Yeon, Pil Ryung Cha, Jong Kyu Yoon
Abstract: A phase field model for step dynamics on vicinal surface is presented. Using this model, time dependent, collective motions of steps were investigated. Through numerical simulations, morphological step instabilities induced by ES barrier were analyzed, and it is shown that this model could interpret various phenomena during step flow growth such as step bunching and meandering.
3181
Authors: Ki-Ha Hong, Pil Ryung Cha, Jong Kyu Yoon
3463
Authors: Dong Hee Yeon, Pil Ryung Cha, Jong Kyu Yoon
3879