Observation of dislocation dynamics in the electron microscope

Abstract

F re ti c r i c k Sc I t M at c I-i ;i I s Re sea rc h Laboratory , Univcrsity of Illinois at U~-bana-Cliampaign, IJrbana IL 0 I801 ' Materials Science and 'I'czhliology I)i\.ision, La wrcncc L i vel-in ox N ;i I i on ;I 1 Laboi.a t o 1-y , L i v c m ore C' A 04 5 5 0 ABSTRACT Deformation experiments performed iii-situ in the transmission electron microscope have led to an increased understanding of dislocation dynamics. To illustrate the capability of this technique twoexamples will be presented. I n the first cxample, thc processes of work hardening in Mo at room temperature will be presented. These studies have improved our understanding of dislocation mobility, dislocation generation, and dislocation-obstacle interactions. In the second example, the interaction of matrix dislocations with grain boundaries will be described. From such studies predictive criteria for slip transfer through grain boundaries have been developed.

The Portevin–Le Chatelier effect: a review of experimental findings

“…In situ deformation techniques based on TEM can be used to clarify plastic deformation, the dynamics and generation of dislocations, and the interactions of dislocations with obstacles and grain boundaries [143]. From such studies, criteria for slip transfer through grain boundaries can easily be determined [144].…”

Plastic deformation of ferritic grains in presence of ODS particles and irradiation-induced defect clusters: A 3D dislocation dynamics simulation study

“…When the applied loading is switched on, familiar glide characteristics of bcc crystals are rendered by our DD model, including: random cross-slip, pencil glide and edge-screw mobility anisotropy [15,35,36]. Dislocation density increases linearly throughout the simulated time, attaining $10 13 m À2 for e p = 2 Â 10 À4 .…”

Brittle–ductile transitions in polycrystalline tungsten

“…Similar modelling of the BDT in some bcc metals (Fe, V, Mo) has been performed with some success [11,12], but has been hampered by the lack of experimental data on dislocation velocity, which is difficult to measure in bcc metals using conventional etch-pitting techniques such as those successfully adopted for semiconductors (for example Si, Ge [12] and GaAs [13]). In general, the expansion of dislocation loops from crack-tips in bcc metals requires motion of both screw dislocations and edge dislocations, but the dislocation nucleation rate in the general case will be controlled by the rate at which the slower screw dislocations can move away from crack-tip sources [14]. In a study of the BDT in single-crystal tungsten, Gumbsch et al [5] deduced an activation energy for the BDT, E BDT , of approximately 0.2 eV.…”