[SY-I7] Symposium I-7

[SY-I7] Continuum Dislocation Dynamic Based Grain Fragmentation Modeling for Severe Plastic Deformation in FCC Metals

^○Ali Al-Hadi I. Kobaissy¹, Georges Ayoub², Mu'Tasem Shehadeh¹ (1.Department of Mechanical Engineering, American University of Beirut, Lebanon, 2.Department of Industrial and Manufacturing Systems Engineering, University of Michigan-Dearborn, United States of America)

In this work, the mechanical response as well as the microstructural features of face-centered cubic (fcc) metals subjected to severe plastic deformation (SPD) are investigated. A multi-scale framework that couples crystal plasticity (CP) scheme with continuum dislocation dynamics (CDD) model is proposed to mimic the loading conditions during Equal Channel Angular Pressing (ECAP) processes. Several aspects of the deformation process have been considered including texture evolution, the evolution of statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs), and the fragmentation of the grains and its effect on the overall mechanical response. The framework is applied to a reference volume element (RVE) in which the grains are distributed and assigned a position. Within the model, each grain is allowed to split into 1024 new smaller grains which subsequently lead to strain hardening and grain refinement. The latter is modeled by accounting for the grain-grain interaction, for which the concept of the GNDs is incorporated into the mean free path of the dislocations. GNDs are assumed to be induced by grain boundaries that restrict the free deformation of a grain and result in an increase of stresses leading to the grain size reduction. The grain refinement procedure is triggered when the misorientation threshold between subgrains is exceeded. The calibration of the model parameters is performed using torsion test of pure copper material. The simulations results of generated texture and grain size reduction are in very good agreement with experimental data available in the literature.