Understanding creep in engineering materials through 2D and 3D discrete dislocation models
Antonin Dlouhy, Academy of Sciences of the Czech Republic, Brno, Czech Republic
Discrete dislocation dynamics (DDD) proved to be a powerful modeling methodology that can contribute to a better understanding of plasticity phenomena on the scale of individual dislocations. While a considerable attention has been given to DDD models that address dislocation processes at low temperatures where dislocation displacements mediated by diffusion can be neglected, an extension of DDD methodology to high temperature domain has been tackled only recently [1-4]. These attempts progressed the DDD modeling in that they fully incorporated dislocation segment dynamics driven by climb forces due either to elastic stress state or over/under saturation of vacancies. Nevertheless, the adopted approach often approximates smooth dislocation lines by chains consisting of only pure screw and pure edge dislocation segments . Therefore, we first employ a thermodynamic extremal principle  in order to describe combined glide and climb motion of general mixed dislocation segments. In a second step, we explain how the interaction of mixed dislocation segments and precipitates can be treated within the framework of DDD methodology when effects due to diffusion must be taken into account. These general concepts are then considered in 2D and 3D DDD models which address high temperature deformation in various engineering materials. A particular focus is on (i) dislocation phenomena observed during creep in gamma/gamma’ microstructures of nickel-base superalloys single crystals and (iii) threshold stresses in precipitation and dispersion strengthened alloys. We demonstrate that the improved DDD methodology can contribute to a more complete understanding of plastic deformation mechanisms in these complex engineering alloys.
Acknowledgement: The development and applications of the model were supported by Czech Science Foundation, project nos. 14-22834S, 202/09/2073 and 106/09/H035. Additional financial support was obtained from MEYS through project CEITEC no. LQ1601. XW and GE acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG) through project A2 of SFB/TR 103.
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Session T1: Tuesday, 26 June 2018