Dislocation–obstacle interactions: Dynamic experiments to continuum modeling

Abstract

Incorporating the interaction of dislocations with obstacles remains a challenge in the development of predictive large-scale plasticity models. The need is particularly important in the elastic-plastic transition region where these interactions can dominate the behavior. By combining post-mortem analysis with dynamic straining in the transmission electron microscope, the atomic processes governing glissile dislocation reactions and interactions with obstacles has been determined. This information has been incorporated at least phenomenologically in models to assess the macroscopic stress-strain response. Two examples will be presented to demonstrate the methodology. The first example considers the interaction of dislocations with small vacancy Frank loops and the formation of defect-free channels in copper, and the second with the influence of imperfect annealing twin boundaries on the macroscopic stress-strain response in silver. In both examples, the importance of grain and twin boundaries as dislocation sources will be demonstrated.

Impact of localized deformation on IASCC in austenitic stainless steels

“…The formation of dislocation channels involves annihilation of irradiation defects by an array of dislocations [28] which are originated from grain boundary imperfections such as micro-scale ledges [29]. Irradiated microstructure, particularly dislocation loops, contributes most to the formation of dislocation channels.…”

Determining the mechanical constitutive properties of metals as a function of strain rate and temperature: A combined experimental and modeling approach; Progress Report for 2004

“…Additional information can be found in ref. 15 Following the anneal and prior to quasi-static testing at room temperature the microstructure was a Figure 13. a).…”

“…These observations provide a physical basis for diminishing the importance of the annealing twins as sources and as barriers to deformation as a function of strain. This work was presented in the Dislocation 2004 meeting and a short paper has been accepted for publication in Materials Science and Engineering 15 . A detailed manuscript is being prepared for submission to an archival journal.…”

Dislocation-Radiation Obstacle Interactions: Developing Improved Mechanical Property Constitutive Models

“…annihilated by the interaction with just one dislocation, and that the obstacle strength for any defect is not constant but is variable and depends on the size and type of the defect, location of the intersection of the glide plane on the defect, and that the nature of the dislocation, and the interaction may change the defect from one type to another [12,13]. A crystal plasticity model based on the dispersed-barrier hardening concept was developed that included the effect of decreasing the effective hardness of radiation defects as the mobile dislocations shear them and that the preexisting dislocations do not contribute significantly to the total plasticity [14].…”

“…This stage has a theoretical use temperature of about 1000K, but the stage design is such that the sample is not in Figure 2. Predictions of the stress-strain relation as a function of increasing dose [13,14].…”