双晶の組織形成を考慮したHCP結晶に対する転位-結晶塑性モデリングおよびシミュレーション

概要

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In this study, a dislocation-based crystal plasticity model for HCP crystals considering evolution of twin-microstructure is newly developed. In order to represent an anisotropic glide of dislocation in HCP crystals, a conventional dislocation-crystal plasticity model for FCC crystals is extended to that for HCP one. Additionally, a new deformation twining model based on the phase-field theory is coupled with the above model through an order parameter and resolved shear stress. In this model, elastic strain energy on twin plane and anisotropic interfacial energy between matrix and twinned region are adopted in the Ginzburg-Landau free energy as the bulk energy and the gradient energy, respectively. Using the above models, uniaxial compression tests under plane strain condition for Mg single crystal with different crystal orientations are demonstrated by means of FEM for dislocation-based crystal plasticity analyses coupling with FDM for phase-field one. From the results of the present simulations, it is shown that the present model can reproduce an anisotropic plastic behavior of Mg single crystal. Moreover, lenticular shaped twins as reported in many experimental studies are reproduced by a-axis compression tests.