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 mechanism by which motion grain boundaries (GBs) polycrystalline materials are coupled through motion/reactions at/adjacent to GB triple junctions (TJs). focus on TJs composed a pair coherent twin (CTBs) Σ9 copper. As for all GBs, implies multiple modes/local mechanisms CTB migration possible mode selection is affected nature driving force migration. While we observe (HRTEM MD) pure steps driven chemical potential jump, other experimental observations (and our simulations) show stress-driven occurs disconnections with non-zero Burgers vector; these pure-step twinning-partial mechanisms. Our simulations demonstrate drags its delimiting TJ may GBs meeting at TJ. experiments two types CTBs GB; 107° readily migrates while 70° immobile (experiment, simulation) agreement even though intrinsic mobilities constituent do not depend TJ-type. also be formed (chemical jump/stress driven) GB/free surface (stress-driven).