Dislocation patterning in fatigued metals: Labyrinth structures and rotational effects

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The nucleation of persistent slip bands (PSBs) in stressed metals may be interpreted as a cooperative phenomenon for dislocation populations. The competition between their mobility and nonlinear interaction (creation, annihilation, pinning) induces an instability of uniform dislocation distributions vs inhomogeneous ones and leads to the formation and persistence of spatial patterns. In particular, we have shown in preceding publications that the nucleation and coexistence of the layered structure of PSBs and the rodlike structure of the surrounding matrix can be described by a system of coupled partial differential equations of the reaction-diffusion type for immobile and mobile dislocations. Here we consider explicitly the motion and interaction of positive and negative mobile dislocations and derive an expression for their effective diffusivity. Moreover we show how these effects together with secondary slip activity may trigger the formation of walls in different directions in analogy with observations of labyrinth structures. © 1986.

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International Journal of Engineering Science