Abstract
Dislocations can provide short circuit diffusion paths for atoms resulting in a dislocation climb motion referred to as self-climb. A variational principle is presented for the analysis of problems in which fast dislocation core diffusion is the dominant mechanism for material redistribution. The linear element based self-climb model, developed in our previous work [1] Liu, Cocks and Tarleton (2020 J. Mech. Phys. Solids 135 103783), is significantly accelerated here, by employing a new finite element discretisation method. The speed-up in computation enables us to use the self-climb model as an effective numerical technique to simulate emergent dislocation behaviour involving both self-climb and glide. The formation of prismatic loops from the break-up of different types of edge dislocation dipoles are investigated based on this new method. We demonstrate that edge dipoles sequentially pinch-off prismatic loops, rather than spontaneously breaking-up into a string of loops, to rapidly decrease the total dislocation energy.
Highlights
The diffusion of atoms in crystalline materials is a thermally activated process which is drastically enhanced by lattice defects [2], such as surfaces, grain boundaries [3], and dislocations [4, 5]
Dislocations can provide short circuit diffusion paths for atoms resulting in a dislocation climb motion referred to as self-climb
A variational principle is presented for the analysis of problems in which fast dislocation core diffusion is the dominant mechanism for material redistribution
Summary
The diffusion of atoms in crystalline materials is a thermally activated process which is drastically enhanced by lattice defects [2], such as surfaces, grain boundaries [3], and dislocations [4, 5]. While surface diffusion and grain boundary diffusion have been studied and discussed in detail [6,7,8,9,10,11,12], only limited results are available for pipe diffusion along dislocation networks [13]. At lower temperatures, core diffusion plays a dominant role in mass diffusion, at high stresses. The role of core diffusion on dislocation motion has received little attention and is not well understood
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