“Conjugate Channeling” Effect in Dislocation Core Diffusion: Carbon Transport in Dislocated BCC Iron

Abstract

Dislocation pipe diffusion seems to be a well-established phenomenon. Here we demonstrate an unexpected effect, that the migration of interstitials such as carbon in iron may be accelerated not in the dislocation line direction , but in a conjugate diffusion direction. This accelerated random walk arises from a simple crystallographic channeling effect. is a function of the Burgers vector b, but not , thus a dislocation loop possesses the same everywhere. Using molecular dynamics and accelerated dynamics simulations, we further show that such dislocation-core-coupled carbon diffusion in iron has temperature-dependent activation enthalpy like a fragile glass. The 71° mixed dislocation is the only case in which we see straightforward pipe diffusion that does not depend on dislocation mobility.

Room Temperature Dynamic Strain Aging in Ultrafine-Grained Titanium

“…However, the activation energy Q p for pipe diffusion in titanium is not available in the literature. Ishii et al [72] simulated the interstitial pipe diffusion in bcc iron by molecular dynamics simulation. The results indicate a largely reduced activation energy for pipe diffusion,…”

“…Q GB is the activation energy for grain boundary diffusion, usually considered to be between one-third and one-half of the bulk diffusion coefficient for highangle grain boundary [72,74] :…”

Mechanism transition and strong temperature dependence of dislocation nucleation from grain boundaries: An accelerated molecular dynamics study

“…Because dislocation nucleation is a thermally activated rate-controlling process at finite temperature and is usually rate sensitive, the temperature and strain-rate sensitivities should be carefully studied at realistic time scales [14,15]. Thus in this study we accelerate the dislocation-nucleation events using adaptive-boost MD (ABMD) [16,17] and study the dislocation nucleation with atomic-level resolution at finite temperature, which offers opportunities for more comprehensive investigation of these processes arising from interfacial defects. Note that while the temperature and strain-rate dependences of dislocation nucle-ation from surfaces have been studied using both atomistic modeling [18] and experiments [4], those of dislocation nucleation from GBs have not been studied yet.…”

Локальная Симметрия Канала Для Транспорта Атомов, Молекул И Его Внутренние Размеры

“…45879.17140 Для переноса инородных атомов (ионов, молекул) в различных телах большую роль играют транспортные каналы, поперечные размеры которых сопоставимы или превышают в разы размеры транспорти-руемых атомов (ионов, молекул) [1][2][3][4][5]. Такими каналами могут быть различные молекулярные структуры в биологии [4], кристаллографи-ческие каналы [5] (каналы с открытым типом кристаллографической структуры, например кварц, вода), треки от заряженных частиц, дис-локации [1][2][3][4][5]. В частности, проникновение с поверхности и пере-мещение атомов гелия в кристаллографических телах обусловлены дислокационно-динамической диффузией [6,7].…”