Mesoscale modeling of microstructure evolution influenced by dislocation density gradients

• The presence of grain boundaries in the microstructure of metallic materials has a major influence on the material behavior and not least on macroscopic material properties. The grain boundaries pose obstacles to slip deformation by preventing dislocation motion, resulting in localized dislocation storage and heterogeneous deformation fields within the grains. In the present contribution, the development of heterogeneous dislocation density distributions is approached on the mesoscale by modeling the evolution of distributions of mobile and immobile dislocations in a reaction-diffusion system. A polycrystal model is formulated in a combined finite difference/cellular automaton algorithm and gradient effects are introduced by making the immobilization of dislocations sensitive to the presence of grain boundaries. The result is an efficient hybrid algorithm for mesoscale modeling of the evolution of grain microstructures, influenced by dislocation density gradients. The model provides a homogenized macroscopic yield stress behavior of Hall-Petch type, without explicitly incorporating a yield stress dependence on the grains size. In addition, being employed in a cellular automaton setting, the model conveniently allows simulations of polycrystalline microstructures, evolving due to dynamic recrystallization, confirming that the introduced gradients provide important additions to recrystallization modeling.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering (hsv//eng)

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