Disconnection-Mediated Twin/Twin-Junction Migration in FCC metals

We present the results of novel, time-resolved, in situ HRTEM observations, molecular dynamics (MD) simulations, and disconnection theory that elucidate the mechanism by which the motion of grain boundaries (GBs) in polycrystalline materials are coupled through disconnection motion/reactions at/adja...

Full description

Saved in:
Bibliographic Details
Published inarXiv.org
Main Authors Xu, Mingjie, Chen, Kongtao, Cao, Fan, Leonardo Velasco Estrada, Kaufman, Thomas M, Fan, Ye, Hahn, Horst, Han, Jian, Srolovitz, David J, Pan, Xiaoqing
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 11.01.2022
Subjects
Achievement tests
Burgers vector
Chemical potential
FCC metals
Free surfaces
Grain boundaries
Modal choice
Molecular dynamics
Simulation
Twin boundaries
Online AccessGet full text

Cover

More Information
Summary:We present the results of novel, time-resolved, in situ HRTEM observations, molecular dynamics (MD) simulations, and disconnection theory that elucidate the mechanism by which the motion of grain boundaries (GBs) in polycrystalline materials are coupled through disconnection motion/reactions at/adjacent to GB triple junctions (TJs). We focus on TJs composed of a pair of coherent twin boundaries (CTBs) and a {\Sigma}9 GB. As for all GBs, disconnection theory implies that multiple modes/local mechanisms for CTB migration are possible and that the mode selection is affected by the nature of the driving force for migration. While we observe (HRTEM and MD) CTB migration through the motion of pure steps driven by chemical potential jump, other experimental observations (and our simulations) show that stress-driven CTB migration occurs through the motion of disconnections with a non-zero Burgers vector; these are pure-step and twinning-partial CTB migration mechanisms. Our experimental observations and simulations demonstrate that the motion of a GB drags its delimiting TJ and may force the motion of the other GBs meeting at the TJ. Our experiments and simulations focus on two types of TJs composed of a pair of CTBs and a {\Sigma}9 GB; a 107{\deg} TJ readily migrates while a 70{\deg} TJ is immobile (experiment, simulation) in agreement with our disconnection theory even though the intrinsic mobilities of the constituent GBs do not depend on TJ-type. We also demonstrate that disconnections may be formed at TJs (chemical potential jump/stress driven) and at GB/free surface junctions (stress-driven).
ISSN:2331-8422